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freebsd-skq/sys/kern/vfs_cache.c

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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1989, 1993, 1995
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Poul-Henning Kamp of the FreeBSD Project.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)vfs_cache.c 8.5 (Berkeley) 3/22/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/capsicum.h>
#include <sys/counter.h>
#include <sys/filedesc.h>
#include <sys/fnv_hash.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <sys/jail.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/seqc.h>
#include <sys/sdt.h>
#include <sys/smr.h>
#include <sys/smp.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vnode.h>
#include <ck_queue.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <sys/capsicum.h>
#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
#include <vm/uma.h>
static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"Name cache");
SDT_PROVIDER_DECLARE(vfs);
SDT_PROBE_DEFINE3(vfs, namecache, enter, done, "struct vnode *", "char *",
"struct vnode *");
SDT_PROBE_DEFINE3(vfs, namecache, enter, duplicate, "struct vnode *", "char *",
"struct vnode *");
SDT_PROBE_DEFINE2(vfs, namecache, enter_negative, done, "struct vnode *",
"char *");
SDT_PROBE_DEFINE2(vfs, namecache, fullpath_smr, hit, "struct vnode *",
"const char *");
SDT_PROBE_DEFINE4(vfs, namecache, fullpath_smr, miss, "struct vnode *",
"struct namecache *", "int", "int");
SDT_PROBE_DEFINE1(vfs, namecache, fullpath, entry, "struct vnode *");
SDT_PROBE_DEFINE3(vfs, namecache, fullpath, hit, "struct vnode *",
"char *", "struct vnode *");
SDT_PROBE_DEFINE1(vfs, namecache, fullpath, miss, "struct vnode *");
SDT_PROBE_DEFINE3(vfs, namecache, fullpath, return, "int",
"struct vnode *", "char *");
SDT_PROBE_DEFINE3(vfs, namecache, lookup, hit, "struct vnode *", "char *",
"struct vnode *");
SDT_PROBE_DEFINE2(vfs, namecache, lookup, hit__negative,
"struct vnode *", "char *");
SDT_PROBE_DEFINE2(vfs, namecache, lookup, miss, "struct vnode *",
"char *");
SDT_PROBE_DEFINE2(vfs, namecache, removecnp, hit, "struct vnode *",
"struct componentname *");
SDT_PROBE_DEFINE2(vfs, namecache, removecnp, miss, "struct vnode *",
"struct componentname *");
SDT_PROBE_DEFINE1(vfs, namecache, purge, done, "struct vnode *");
SDT_PROBE_DEFINE1(vfs, namecache, purge, batch, "int");
SDT_PROBE_DEFINE1(vfs, namecache, purge_negative, done, "struct vnode *");
SDT_PROBE_DEFINE1(vfs, namecache, purgevfs, done, "struct mount *");
SDT_PROBE_DEFINE3(vfs, namecache, zap, done, "struct vnode *", "char *",
"struct vnode *");
SDT_PROBE_DEFINE2(vfs, namecache, zap_negative, done, "struct vnode *",
"char *");
SDT_PROBE_DEFINE2(vfs, namecache, evict_negative, done, "struct vnode *",
"char *");
SDT_PROBE_DEFINE3(vfs, fplookup, lookup, done, "struct nameidata", "int", "bool");
SDT_PROBE_DECLARE(vfs, namei, lookup, entry);
SDT_PROBE_DECLARE(vfs, namei, lookup, return);
/*
* This structure describes the elements in the cache of recent
* names looked up by namei.
*/
struct negstate {
u_char neg_flag;
u_char neg_hit;
};
_Static_assert(sizeof(struct negstate) <= sizeof(struct vnode *),
"the state must fit in a union with a pointer without growing it");
struct namecache {
LIST_ENTRY(namecache) nc_src; /* source vnode list */
TAILQ_ENTRY(namecache) nc_dst; /* destination vnode list */
CK_SLIST_ENTRY(namecache) nc_hash;/* hash chain */
struct vnode *nc_dvp; /* vnode of parent of name */
union {
struct vnode *nu_vp; /* vnode the name refers to */
struct negstate nu_neg;/* negative entry state */
} n_un;
u_char nc_flag; /* flag bits */
u_char nc_nlen; /* length of name */
char nc_name[0]; /* segment name + nul */
};
/*
* struct namecache_ts repeats struct namecache layout up to the
* nc_nlen member.
* struct namecache_ts is used in place of struct namecache when time(s) need
* to be stored. The nc_dotdottime field is used when a cache entry is mapping
* both a non-dotdot directory name plus dotdot for the directory's
* parent.
*
* See below for alignment requirement.
*/
struct namecache_ts {
struct timespec nc_time; /* timespec provided by fs */
struct timespec nc_dotdottime; /* dotdot timespec provided by fs */
int nc_ticks; /* ticks value when entry was added */
int nc_pad;
struct namecache nc_nc;
};
TAILQ_HEAD(cache_freebatch, namecache);
/*
* At least mips n32 performs 64-bit accesses to timespec as found
* in namecache_ts and requires them to be aligned. Since others
* may be in the same spot suffer a little bit and enforce the
* alignment for everyone. Note this is a nop for 64-bit platforms.
*/
#define CACHE_ZONE_ALIGNMENT UMA_ALIGNOF(time_t)
/*
* TODO: the initial value of CACHE_PATH_CUTOFF was inherited from the
* 4.4 BSD codebase. Later on struct namecache was tweaked to become
* smaller and the value was bumped to retain the total size, but it
* was never re-evaluated for suitability. A simple test counting
* lengths during package building shows that the value of 45 covers
* about 86% of all added entries, reaching 99% at 65.
*
* Regardless of the above, use of dedicated zones instead of malloc may be
* inducing additional waste. This may be hard to address as said zones are
* tied to VFS SMR. Even if retaining them, the current split should be
* re-evaluated.
*/
#ifdef __LP64__
#define CACHE_PATH_CUTOFF 45
#define CACHE_LARGE_PAD 6
#else
#define CACHE_PATH_CUTOFF 41
#define CACHE_LARGE_PAD 2
#endif
#define CACHE_ZONE_SMALL_SIZE (offsetof(struct namecache, nc_name) + CACHE_PATH_CUTOFF + 1)
#define CACHE_ZONE_SMALL_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_SMALL_SIZE)
#define CACHE_ZONE_LARGE_SIZE (offsetof(struct namecache, nc_name) + NAME_MAX + 1 + CACHE_LARGE_PAD)
#define CACHE_ZONE_LARGE_TS_SIZE (offsetof(struct namecache_ts, nc_nc) + CACHE_ZONE_LARGE_SIZE)
_Static_assert((CACHE_ZONE_SMALL_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
_Static_assert((CACHE_ZONE_SMALL_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
_Static_assert((CACHE_ZONE_LARGE_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
_Static_assert((CACHE_ZONE_LARGE_TS_SIZE % (CACHE_ZONE_ALIGNMENT + 1)) == 0, "bad zone size");
#define nc_vp n_un.nu_vp
#define nc_neg n_un.nu_neg
/*
* Flags in namecache.nc_flag
*/
#define NCF_WHITE 0x01
#define NCF_ISDOTDOT 0x02
#define NCF_TS 0x04
#define NCF_DTS 0x08
#define NCF_DVDROP 0x10
#define NCF_NEGATIVE 0x20
#define NCF_INVALID 0x40
#define NCF_WIP 0x80
/*
* Flags in negstate.neg_flag
*/
#define NEG_HOT 0x01
static bool cache_neg_evict_cond(u_long lnumcache);
/*
* Mark an entry as invalid.
*
* This is called before it starts getting deconstructed.
*/
static void
cache_ncp_invalidate(struct namecache *ncp)
{
KASSERT((ncp->nc_flag & NCF_INVALID) == 0,
("%s: entry %p already invalid", __func__, ncp));
atomic_store_char(&ncp->nc_flag, ncp->nc_flag | NCF_INVALID);
atomic_thread_fence_rel();
}
/*
* Check whether the entry can be safely used.
*
* All places which elide locks are supposed to call this after they are
* done with reading from an entry.
*/
#define cache_ncp_canuse(ncp) ({ \
struct namecache *_ncp = (ncp); \
u_char _nc_flag; \
\
atomic_thread_fence_acq(); \
_nc_flag = atomic_load_char(&_ncp->nc_flag); \
__predict_true((_nc_flag & (NCF_INVALID | NCF_WIP)) == 0); \
})
/*
* Name caching works as follows:
*
* Names found by directory scans are retained in a cache
* for future reference. It is managed LRU, so frequently
* used names will hang around. Cache is indexed by hash value
* obtained from (dvp, name) where dvp refers to the directory
* containing name.
*
* If it is a "negative" entry, (i.e. for a name that is known NOT to
* exist) the vnode pointer will be NULL.
*
* Upon reaching the last segment of a path, if the reference
* is for DELETE, or NOCACHE is set (rewrite), and the
* name is located in the cache, it will be dropped.
*
* These locks are used (in the order in which they can be taken):
* NAME TYPE ROLE
* vnodelock mtx vnode lists and v_cache_dd field protection
* bucketlock mtx for access to given set of hash buckets
* neglist mtx negative entry LRU management
*
* It is legal to take multiple vnodelock and bucketlock locks. The locking
* order is lower address first. Both are recursive.
*
* "." lookups are lockless.
*
* ".." and vnode -> name lookups require vnodelock.
*
* name -> vnode lookup requires the relevant bucketlock to be held for reading.
*
* Insertions and removals of entries require involved vnodes and bucketlocks
* to be locked to provide safe operation against other threads modifying the
* cache.
*
* Some lookups result in removal of the found entry (e.g. getting rid of a
* negative entry with the intent to create a positive one), which poses a
* problem when multiple threads reach the state. Similarly, two different
* threads can purge two different vnodes and try to remove the same name.
*
* If the already held vnode lock is lower than the second required lock, we
* can just take the other lock. However, in the opposite case, this could
* deadlock. As such, this is resolved by trylocking and if that fails unlocking
* the first node, locking everything in order and revalidating the state.
*/
VFS_SMR_DECLARE;
static SYSCTL_NODE(_vfs_cache, OID_AUTO, param, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"Name cache parameters");
static u_int __read_mostly ncsize; /* the size as computed on creation or resizing */
SYSCTL_UINT(_vfs_cache_param, OID_AUTO, size, CTLFLAG_RW, &ncsize, 0,
"Total namecache capacity");
u_int ncsizefactor = 2;
SYSCTL_UINT(_vfs_cache_param, OID_AUTO, sizefactor, CTLFLAG_RW, &ncsizefactor, 0,
"Size factor for namecache");
static u_long __read_mostly ncnegfactor = 5; /* ratio of negative entries */
SYSCTL_ULONG(_vfs_cache_param, OID_AUTO, negfactor, CTLFLAG_RW, &ncnegfactor, 0,
"Ratio of negative namecache entries");
/*
* Negative entry % of namecache capacity above which automatic eviction is allowed.
*
* Check cache_neg_evict_cond for details.
*/
static u_int ncnegminpct = 3;
static u_int __read_mostly neg_min; /* the above recomputed against ncsize */
SYSCTL_UINT(_vfs_cache_param, OID_AUTO, negmin, CTLFLAG_RD, &neg_min, 0,
"Negative entry count above which automatic eviction is allowed");
/*
* Structures associated with name caching.
*/
#define NCHHASH(hash) \
(&nchashtbl[(hash) & nchash])
static __read_mostly CK_SLIST_HEAD(nchashhead, namecache) *nchashtbl;/* Hash Table */
static u_long __read_mostly nchash; /* size of hash table */
SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0,
"Size of namecache hash table");
static u_long __exclusive_cache_line numneg; /* number of negative entries allocated */
static u_long __exclusive_cache_line numcache;/* number of cache entries allocated */
struct nchstats nchstats; /* cache effectiveness statistics */
static bool __read_frequently cache_fast_revlookup = true;
SYSCTL_BOOL(_vfs, OID_AUTO, cache_fast_revlookup, CTLFLAG_RW,
&cache_fast_revlookup, 0, "");
static u_int __exclusive_cache_line neg_cycle;
#define ncneghash 3
#define numneglists (ncneghash + 1)
struct neglist {
struct mtx nl_evict_lock;
struct mtx nl_lock __aligned(CACHE_LINE_SIZE);
TAILQ_HEAD(, namecache) nl_list;
TAILQ_HEAD(, namecache) nl_hotlist;
u_long nl_hotnum;
} __aligned(CACHE_LINE_SIZE);
static struct neglist neglists[numneglists];
static inline struct neglist *
NCP2NEGLIST(struct namecache *ncp)
{
return (&neglists[(((uintptr_t)(ncp) >> 8) & ncneghash)]);
}
static inline struct negstate *
NCP2NEGSTATE(struct namecache *ncp)
{
MPASS(ncp->nc_flag & NCF_NEGATIVE);
return (&ncp->nc_neg);
}
#define numbucketlocks (ncbuckethash + 1)
static u_int __read_mostly ncbuckethash;
static struct mtx_padalign __read_mostly *bucketlocks;
#define HASH2BUCKETLOCK(hash) \
((struct mtx *)(&bucketlocks[((hash) & ncbuckethash)]))
#define numvnodelocks (ncvnodehash + 1)
static u_int __read_mostly ncvnodehash;
static struct mtx __read_mostly *vnodelocks;
static inline struct mtx *
VP2VNODELOCK(struct vnode *vp)
{
return (&vnodelocks[(((uintptr_t)(vp) >> 8) & ncvnodehash)]);
}
static void
cache_out_ts(struct namecache *ncp, struct timespec *tsp, int *ticksp)
{
struct namecache_ts *ncp_ts;
KASSERT((ncp->nc_flag & NCF_TS) != 0 ||
(tsp == NULL && ticksp == NULL),
("No NCF_TS"));
if (tsp == NULL)
return;
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
*tsp = ncp_ts->nc_time;
*ticksp = ncp_ts->nc_ticks;
}
#ifdef DEBUG_CACHE
static int __read_mostly doingcache = 1; /* 1 => enable the cache */
SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0,
"VFS namecache enabled");
#endif
/* Export size information to userland */
SYSCTL_INT(_debug_sizeof, OID_AUTO, namecache, CTLFLAG_RD, SYSCTL_NULL_INT_PTR,
sizeof(struct namecache), "sizeof(struct namecache)");
/*
* The new name cache statistics
*/
static SYSCTL_NODE(_vfs_cache, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"Name cache statistics");
#define STATNODE_ULONG(name, varname, descr) \
SYSCTL_ULONG(_vfs_cache_stats, OID_AUTO, name, CTLFLAG_RD, &varname, 0, descr);
#define STATNODE_COUNTER(name, varname, descr) \
static COUNTER_U64_DEFINE_EARLY(varname); \
SYSCTL_COUNTER_U64(_vfs_cache_stats, OID_AUTO, name, CTLFLAG_RD, &varname, \
descr);
STATNODE_ULONG(neg, numneg, "Number of negative cache entries");
STATNODE_ULONG(count, numcache, "Number of cache entries");
STATNODE_COUNTER(heldvnodes, numcachehv, "Number of namecache entries with vnodes held");
STATNODE_COUNTER(drops, numdrops, "Number of dropped entries due to reaching the limit");
STATNODE_COUNTER(dothits, dothits, "Number of '.' hits");
STATNODE_COUNTER(dotdothis, dotdothits, "Number of '..' hits");
STATNODE_COUNTER(miss, nummiss, "Number of cache misses");
STATNODE_COUNTER(misszap, nummisszap, "Number of cache misses we do not want to cache");
STATNODE_COUNTER(posszaps, numposzaps,
"Number of cache hits (positive) we do not want to cache");
STATNODE_COUNTER(poshits, numposhits, "Number of cache hits (positive)");
STATNODE_COUNTER(negzaps, numnegzaps,
"Number of cache hits (negative) we do not want to cache");
STATNODE_COUNTER(neghits, numneghits, "Number of cache hits (negative)");
/* These count for vn_getcwd(), too. */
STATNODE_COUNTER(fullpathcalls, numfullpathcalls, "Number of fullpath search calls");
STATNODE_COUNTER(fullpathfail1, numfullpathfail1, "Number of fullpath search errors (ENOTDIR)");
STATNODE_COUNTER(fullpathfail2, numfullpathfail2,
"Number of fullpath search errors (VOP_VPTOCNP failures)");
STATNODE_COUNTER(fullpathfail4, numfullpathfail4, "Number of fullpath search errors (ENOMEM)");
STATNODE_COUNTER(fullpathfound, numfullpathfound, "Number of successful fullpath calls");
/*
* Debug or developer statistics.
*/
static SYSCTL_NODE(_vfs_cache, OID_AUTO, debug, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"Name cache debugging");
#define DEBUGNODE_ULONG(name, varname, descr) \
SYSCTL_ULONG(_vfs_cache_debug, OID_AUTO, name, CTLFLAG_RD, &varname, 0, descr);
#define DEBUGNODE_COUNTER(name, varname, descr) \
static COUNTER_U64_DEFINE_EARLY(varname); \
SYSCTL_COUNTER_U64(_vfs_cache_debug, OID_AUTO, name, CTLFLAG_RD, &varname, \
descr);
DEBUGNODE_COUNTER(zap_bucket_relock_success, zap_bucket_relock_success,
"Number of successful removals after relocking");
static long zap_bucket_fail;
DEBUGNODE_ULONG(zap_bucket_fail, zap_bucket_fail, "");
static long zap_bucket_fail2;
DEBUGNODE_ULONG(zap_bucket_fail2, zap_bucket_fail2, "");
static long cache_lock_vnodes_cel_3_failures;
DEBUGNODE_ULONG(vnodes_cel_3_failures, cache_lock_vnodes_cel_3_failures,
"Number of times 3-way vnode locking failed");
static void cache_zap_locked(struct namecache *ncp);
static int vn_fullpath_hardlink(struct nameidata *ndp, char **retbuf,
char **freebuf, size_t *buflen);
static int vn_fullpath_any_smr(struct vnode *vp, struct vnode *rdir, char *buf,
char **retbuf, size_t *buflen, size_t addend);
static int vn_fullpath_any(struct vnode *vp, struct vnode *rdir, char *buf,
char **retbuf, size_t *buflen);
static int vn_fullpath_dir(struct vnode *vp, struct vnode *rdir, char *buf,
char **retbuf, size_t *len, size_t addend);
static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
static inline void
cache_assert_vlp_locked(struct mtx *vlp)
{
if (vlp != NULL)
mtx_assert(vlp, MA_OWNED);
}
static inline void
cache_assert_vnode_locked(struct vnode *vp)
{
struct mtx *vlp;
vlp = VP2VNODELOCK(vp);
cache_assert_vlp_locked(vlp);
}
/*
* Directory vnodes with entries are held for two reasons:
* 1. make them less of a target for reclamation in vnlru
* 2. suffer smaller performance penalty in locked lookup as requeieing is avoided
*
* Note this preferably would not be done and it's a hold over from. It will be
* feasible to eliminate altogether if all filesystems start supporting
* lockless lookup.
*/
static void
cache_hold_vnode(struct vnode *vp)
{
cache_assert_vnode_locked(vp);
VNPASS(LIST_EMPTY(&vp->v_cache_src), vp);
vhold(vp);
counter_u64_add(numcachehv, 1);
}
static void
cache_drop_vnode(struct vnode *vp)
{
/*
* Called after all locks are dropped, meaning we can't assert
* on the state of v_cache_src.
*/
vdrop(vp);
counter_u64_add(numcachehv, -1);
}
/*
* UMA zones.
*/
static uma_zone_t __read_mostly cache_zone_small;
static uma_zone_t __read_mostly cache_zone_small_ts;
static uma_zone_t __read_mostly cache_zone_large;
static uma_zone_t __read_mostly cache_zone_large_ts;
static struct namecache *
cache_alloc_uma(int len, bool ts)
{
struct namecache_ts *ncp_ts;
struct namecache *ncp;
if (__predict_false(ts)) {
if (len <= CACHE_PATH_CUTOFF)
ncp_ts = uma_zalloc_smr(cache_zone_small_ts, M_WAITOK);
else
ncp_ts = uma_zalloc_smr(cache_zone_large_ts, M_WAITOK);
ncp = &ncp_ts->nc_nc;
} else {
if (len <= CACHE_PATH_CUTOFF)
ncp = uma_zalloc_smr(cache_zone_small, M_WAITOK);
else
ncp = uma_zalloc_smr(cache_zone_large, M_WAITOK);
}
return (ncp);
}
static void
cache_free_uma(struct namecache *ncp)
{
struct namecache_ts *ncp_ts;
if (__predict_false(ncp->nc_flag & NCF_TS)) {
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
uma_zfree_smr(cache_zone_small_ts, ncp_ts);
else
uma_zfree_smr(cache_zone_large_ts, ncp_ts);
} else {
if (ncp->nc_nlen <= CACHE_PATH_CUTOFF)
uma_zfree_smr(cache_zone_small, ncp);
else
uma_zfree_smr(cache_zone_large, ncp);
}
}
static struct namecache *
cache_alloc(int len, bool ts)
{
u_long lnumcache;
/*
* Avoid blowout in namecache entries.
*
* Bugs:
* 1. filesystems may end up trying to add an already existing entry
* (for example this can happen after a cache miss during concurrent
* lookup), in which case we will call cache_neg_evict despite not
* adding anything.
* 2. the routine may fail to free anything and no provisions are made
* to make it try harder (see the inside for failure modes)
* 3. it only ever looks at negative entries.
*/
lnumcache = atomic_fetchadd_long(&numcache, 1) + 1;
if (cache_neg_evict_cond(lnumcache)) {
lnumcache = atomic_load_long(&numcache);
}
if (__predict_false(lnumcache >= ncsize)) {
atomic_subtract_long(&numcache, 1);
counter_u64_add(numdrops, 1);
return (NULL);
}
return (cache_alloc_uma(len, ts));
}
static void
cache_free(struct namecache *ncp)
{
MPASS(ncp != NULL);
if ((ncp->nc_flag & NCF_DVDROP) != 0) {
cache_drop_vnode(ncp->nc_dvp);
}
cache_free_uma(ncp);
atomic_subtract_long(&numcache, 1);
}
static void
cache_free_batch(struct cache_freebatch *batch)
{
struct namecache *ncp, *nnp;
int i;
i = 0;
if (TAILQ_EMPTY(batch))
goto out;
TAILQ_FOREACH_SAFE(ncp, batch, nc_dst, nnp) {
if ((ncp->nc_flag & NCF_DVDROP) != 0) {
cache_drop_vnode(ncp->nc_dvp);
}
cache_free_uma(ncp);
i++;
}
atomic_subtract_long(&numcache, i);
out:
SDT_PROBE1(vfs, namecache, purge, batch, i);
}
/*
* TODO: With the value stored we can do better than computing the hash based
* on the address. The choice of FNV should also be revisited.
*/
static void
cache_prehash(struct vnode *vp)
{
vp->v_nchash = fnv_32_buf(&vp, sizeof(vp), FNV1_32_INIT);
}
static uint32_t
cache_get_hash(char *name, u_char len, struct vnode *dvp)
{
return (fnv_32_buf(name, len, dvp->v_nchash));
}
static inline struct nchashhead *
NCP2BUCKET(struct namecache *ncp)
{
uint32_t hash;
hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen, ncp->nc_dvp);
return (NCHHASH(hash));
}
static inline struct mtx *
NCP2BUCKETLOCK(struct namecache *ncp)
{
uint32_t hash;
hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen, ncp->nc_dvp);
return (HASH2BUCKETLOCK(hash));
}
#ifdef INVARIANTS
static void
cache_assert_bucket_locked(struct namecache *ncp)
{
struct mtx *blp;
blp = NCP2BUCKETLOCK(ncp);
mtx_assert(blp, MA_OWNED);
}
static void
cache_assert_bucket_unlocked(struct namecache *ncp)
{
struct mtx *blp;
blp = NCP2BUCKETLOCK(ncp);
mtx_assert(blp, MA_NOTOWNED);
}
#else
#define cache_assert_bucket_locked(x) do { } while (0)
#define cache_assert_bucket_unlocked(x) do { } while (0)
#endif
#define cache_sort_vnodes(x, y) _cache_sort_vnodes((void **)(x), (void **)(y))
static void
_cache_sort_vnodes(void **p1, void **p2)
{
void *tmp;
MPASS(*p1 != NULL || *p2 != NULL);
if (*p1 > *p2) {
tmp = *p2;
*p2 = *p1;
*p1 = tmp;
}
}
static void
cache_lock_all_buckets(void)
{
u_int i;
for (i = 0; i < numbucketlocks; i++)
mtx_lock(&bucketlocks[i]);
}
static void
cache_unlock_all_buckets(void)
{
u_int i;
for (i = 0; i < numbucketlocks; i++)
mtx_unlock(&bucketlocks[i]);
}
static void
cache_lock_all_vnodes(void)
{
u_int i;
for (i = 0; i < numvnodelocks; i++)
mtx_lock(&vnodelocks[i]);
}
static void
cache_unlock_all_vnodes(void)
{
u_int i;
for (i = 0; i < numvnodelocks; i++)
mtx_unlock(&vnodelocks[i]);
}
static int
cache_trylock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
{
cache_sort_vnodes(&vlp1, &vlp2);
if (vlp1 != NULL) {
if (!mtx_trylock(vlp1))
return (EAGAIN);
}
if (!mtx_trylock(vlp2)) {
if (vlp1 != NULL)
mtx_unlock(vlp1);
return (EAGAIN);
}
return (0);
}
static void
cache_lock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
{
MPASS(vlp1 != NULL || vlp2 != NULL);
MPASS(vlp1 <= vlp2);
if (vlp1 != NULL)
mtx_lock(vlp1);
if (vlp2 != NULL)
mtx_lock(vlp2);
}
static void
cache_unlock_vnodes(struct mtx *vlp1, struct mtx *vlp2)
{
MPASS(vlp1 != NULL || vlp2 != NULL);
if (vlp1 != NULL)
mtx_unlock(vlp1);
if (vlp2 != NULL)
mtx_unlock(vlp2);
}
static int
sysctl_nchstats(SYSCTL_HANDLER_ARGS)
{
struct nchstats snap;
if (req->oldptr == NULL)
return (SYSCTL_OUT(req, 0, sizeof(snap)));
snap = nchstats;
snap.ncs_goodhits = counter_u64_fetch(numposhits);
snap.ncs_neghits = counter_u64_fetch(numneghits);
snap.ncs_badhits = counter_u64_fetch(numposzaps) +
counter_u64_fetch(numnegzaps);
snap.ncs_miss = counter_u64_fetch(nummisszap) +
counter_u64_fetch(nummiss);
return (SYSCTL_OUT(req, &snap, sizeof(snap)));
}
SYSCTL_PROC(_vfs_cache, OID_AUTO, nchstats, CTLTYPE_OPAQUE | CTLFLAG_RD |
CTLFLAG_MPSAFE, 0, 0, sysctl_nchstats, "LU",
"VFS cache effectiveness statistics");
static void
cache_recalc_neg_min(u_int val)
{
neg_min = (ncsize * val) / 100;
}
static int
sysctl_negminpct(SYSCTL_HANDLER_ARGS)
{
u_int val;
int error;
val = ncnegminpct;
error = sysctl_handle_int(oidp, &val, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
if (val == ncnegminpct)
return (0);
if (val < 0 || val > 99)
return (EINVAL);
ncnegminpct = val;
cache_recalc_neg_min(val);
return (0);
}
SYSCTL_PROC(_vfs_cache_param, OID_AUTO, negminpct,
CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0, sysctl_negminpct,
"I", "Negative entry \% of namecache capacity above which automatic eviction is allowed");
#ifdef DIAGNOSTIC
/*
* Grab an atomic snapshot of the name cache hash chain lengths
*/
static SYSCTL_NODE(_debug, OID_AUTO, hashstat,
CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
"hash table stats");
static int
sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
{
struct nchashhead *ncpp;
struct namecache *ncp;
int i, error, n_nchash, *cntbuf;
retry:
n_nchash = nchash + 1; /* nchash is max index, not count */
if (req->oldptr == NULL)
return SYSCTL_OUT(req, 0, n_nchash * sizeof(int));
cntbuf = malloc(n_nchash * sizeof(int), M_TEMP, M_ZERO | M_WAITOK);
cache_lock_all_buckets();
if (n_nchash != nchash + 1) {
cache_unlock_all_buckets();
free(cntbuf, M_TEMP);
goto retry;
}
/* Scan hash tables counting entries */
for (ncpp = nchashtbl, i = 0; i < n_nchash; ncpp++, i++)
CK_SLIST_FOREACH(ncp, ncpp, nc_hash)
cntbuf[i]++;
cache_unlock_all_buckets();
for (error = 0, i = 0; i < n_nchash; i++)
if ((error = SYSCTL_OUT(req, &cntbuf[i], sizeof(int))) != 0)
break;
free(cntbuf, M_TEMP);
return (error);
}
SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD|
CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_rawnchash, "S,int",
"nchash chain lengths");
static int
sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
{
int error;
struct nchashhead *ncpp;
struct namecache *ncp;
int n_nchash;
int count, maxlength, used, pct;
if (!req->oldptr)
return SYSCTL_OUT(req, 0, 4 * sizeof(int));
cache_lock_all_buckets();
n_nchash = nchash + 1; /* nchash is max index, not count */
used = 0;
maxlength = 0;
/* Scan hash tables for applicable entries */
for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
count = 0;
CK_SLIST_FOREACH(ncp, ncpp, nc_hash) {
count++;
}
if (count)
used++;
if (maxlength < count)
maxlength = count;
}
n_nchash = nchash + 1;
cache_unlock_all_buckets();
pct = (used * 100) / (n_nchash / 100);
error = SYSCTL_OUT(req, &n_nchash, sizeof(n_nchash));
if (error)
return (error);
error = SYSCTL_OUT(req, &used, sizeof(used));
if (error)
return (error);
error = SYSCTL_OUT(req, &maxlength, sizeof(maxlength));
if (error)
return (error);
error = SYSCTL_OUT(req, &pct, sizeof(pct));
if (error)
return (error);
return (0);
}
SYSCTL_PROC(_debug_hashstat, OID_AUTO, nchash, CTLTYPE_INT|CTLFLAG_RD|
CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_nchash, "I",
"nchash statistics (number of total/used buckets, maximum chain length, usage percentage)");
#endif
/*
* Negative entries management
*
* Various workloads create plenty of negative entries and barely use them
* afterwards. Moreover malicious users can keep performing bogus lookups
* adding even more entries. For example "make tinderbox" as of writing this
* comment ends up with 2.6M namecache entries in total, 1.2M of which are
* negative.
*
* As such, a rather aggressive eviction method is needed. The currently
* employed method is a placeholder.
*
* Entries are split over numneglists separate lists, each of which is further
* split into hot and cold entries. Entries get promoted after getting a hit.
* Eviction happens on addition of new entry.
*/
static SYSCTL_NODE(_vfs_cache, OID_AUTO, neg, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"Name cache negative entry statistics");
SYSCTL_ULONG(_vfs_cache_neg, OID_AUTO, count, CTLFLAG_RD, &numneg, 0,
"Number of negative cache entries");
static COUNTER_U64_DEFINE_EARLY(neg_created);
SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, created, CTLFLAG_RD, &neg_created,
"Number of created negative entries");
static COUNTER_U64_DEFINE_EARLY(neg_evicted);
SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evicted, CTLFLAG_RD, &neg_evicted,
"Number of evicted negative entries");
static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_empty);
SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_empty, CTLFLAG_RD,
&neg_evict_skipped_empty,
"Number of times evicting failed due to lack of entries");
static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_missed);
SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_missed, CTLFLAG_RD,
&neg_evict_skipped_missed,
"Number of times evicting failed due to target entry disappearing");
static COUNTER_U64_DEFINE_EARLY(neg_evict_skipped_contended);
SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, evict_skipped_contended, CTLFLAG_RD,
&neg_evict_skipped_contended,
"Number of times evicting failed due to contention");
SYSCTL_COUNTER_U64(_vfs_cache_neg, OID_AUTO, hits, CTLFLAG_RD, &numneghits,
"Number of cache hits (negative)");
static int
sysctl_neg_hot(SYSCTL_HANDLER_ARGS)
{
int i, out;
out = 0;
for (i = 0; i < numneglists; i++)
out += neglists[i].nl_hotnum;
return (SYSCTL_OUT(req, &out, sizeof(out)));
}
SYSCTL_PROC(_vfs_cache_neg, OID_AUTO, hot, CTLTYPE_INT | CTLFLAG_RD |
CTLFLAG_MPSAFE, 0, 0, sysctl_neg_hot, "I",
"Number of hot negative entries");
static void
cache_neg_init(struct namecache *ncp)
{
struct negstate *ns;
ncp->nc_flag |= NCF_NEGATIVE;
ns = NCP2NEGSTATE(ncp);
ns->neg_flag = 0;
ns->neg_hit = 0;
counter_u64_add(neg_created, 1);
}
#define CACHE_NEG_PROMOTION_THRESH 2
static bool
cache_neg_hit_prep(struct namecache *ncp)
{
struct negstate *ns;
u_char n;
ns = NCP2NEGSTATE(ncp);
n = atomic_load_char(&ns->neg_hit);
for (;;) {
if (n >= CACHE_NEG_PROMOTION_THRESH)
return (false);
if (atomic_fcmpset_8(&ns->neg_hit, &n, n + 1))
break;
}
return (n + 1 == CACHE_NEG_PROMOTION_THRESH);
}
/*
* Nothing to do here but it is provided for completeness as some
* cache_neg_hit_prep callers may end up returning without even
* trying to promote.
*/
#define cache_neg_hit_abort(ncp) do { } while (0)
static void
cache_neg_hit_finish(struct namecache *ncp)
{
SDT_PROBE2(vfs, namecache, lookup, hit__negative, ncp->nc_dvp, ncp->nc_name);
counter_u64_add(numneghits, 1);
}
/*
* Move a negative entry to the hot list.
*/
static void
cache_neg_promote_locked(struct namecache *ncp)
{
struct neglist *nl;
struct negstate *ns;
ns = NCP2NEGSTATE(ncp);
nl = NCP2NEGLIST(ncp);
mtx_assert(&nl->nl_lock, MA_OWNED);
if ((ns->neg_flag & NEG_HOT) == 0) {
TAILQ_REMOVE(&nl->nl_list, ncp, nc_dst);
TAILQ_INSERT_TAIL(&nl->nl_hotlist, ncp, nc_dst);
nl->nl_hotnum++;
ns->neg_flag |= NEG_HOT;
}
}
/*
* Move a hot negative entry to the cold list.
*/
static void
cache_neg_demote_locked(struct namecache *ncp)
{
struct neglist *nl;
struct negstate *ns;
ns = NCP2NEGSTATE(ncp);
nl = NCP2NEGLIST(ncp);
mtx_assert(&nl->nl_lock, MA_OWNED);
MPASS(ns->neg_flag & NEG_HOT);
TAILQ_REMOVE(&nl->nl_hotlist, ncp, nc_dst);
TAILQ_INSERT_TAIL(&nl->nl_list, ncp, nc_dst);
nl->nl_hotnum--;
ns->neg_flag &= ~NEG_HOT;
atomic_store_char(&ns->neg_hit, 0);
}
/*
* Move a negative entry to the hot list if it matches the lookup.
*
* We have to take locks, but they may be contended and in the worst
* case we may need to go off CPU. We don't want to spin within the
* smr section and we can't block with it. Exiting the section means
* the found entry could have been evicted. We are going to look it
* up again.
*/
static bool
cache_neg_promote_cond(struct vnode *dvp, struct componentname *cnp,
struct namecache *oncp, uint32_t hash)
{
struct namecache *ncp;
struct neglist *nl;
u_char nc_flag;
nl = NCP2NEGLIST(oncp);
mtx_lock(&nl->nl_lock);
/*
* For hash iteration.
*/
vfs_smr_enter();
/*
* Avoid all surprises by only succeeding if we got the same entry and
* bailing completely otherwise.
* XXX There are no provisions to keep the vnode around, meaning we may
* end up promoting a negative entry for a *new* vnode and returning
* ENOENT on its account. This is the error we want to return anyway
* and promotion is harmless.
*
* In particular at this point there can be a new ncp which matches the
* search but hashes to a different neglist.
*/
CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
if (ncp == oncp)
break;
}
/*
* No match to begin with.
*/
if (__predict_false(ncp == NULL)) {
goto out_abort;
}
/*
* The newly found entry may be something different...
*/
if (!(ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))) {
goto out_abort;
}
/*
* ... and not even negative.
*/
nc_flag = atomic_load_char(&ncp->nc_flag);
if ((nc_flag & NCF_NEGATIVE) == 0) {
goto out_abort;
}
if (!cache_ncp_canuse(ncp)) {
goto out_abort;
}
cache_neg_promote_locked(ncp);
cache_neg_hit_finish(ncp);
vfs_smr_exit();
mtx_unlock(&nl->nl_lock);
return (true);
out_abort:
vfs_smr_exit();
mtx_unlock(&nl->nl_lock);
return (false);
}
static void
cache_neg_promote(struct namecache *ncp)
{
struct neglist *nl;
nl = NCP2NEGLIST(ncp);
mtx_lock(&nl->nl_lock);
cache_neg_promote_locked(ncp);
mtx_unlock(&nl->nl_lock);
}
static void
cache_neg_insert(struct namecache *ncp)
{
struct neglist *nl;
MPASS(ncp->nc_flag & NCF_NEGATIVE);
cache_assert_bucket_locked(ncp);
nl = NCP2NEGLIST(ncp);
mtx_lock(&nl->nl_lock);
TAILQ_INSERT_TAIL(&nl->nl_list, ncp, nc_dst);
mtx_unlock(&nl->nl_lock);
atomic_add_long(&numneg, 1);
}
static void
cache_neg_remove(struct namecache *ncp)
{
struct neglist *nl;
struct negstate *ns;
cache_assert_bucket_locked(ncp);
nl = NCP2NEGLIST(ncp);
ns = NCP2NEGSTATE(ncp);
mtx_lock(&nl->nl_lock);
if ((ns->neg_flag & NEG_HOT) != 0) {
TAILQ_REMOVE(&nl->nl_hotlist, ncp, nc_dst);
nl->nl_hotnum--;
} else {
TAILQ_REMOVE(&nl->nl_list, ncp, nc_dst);
}
mtx_unlock(&nl->nl_lock);
atomic_subtract_long(&numneg, 1);
}
static struct neglist *
cache_neg_evict_select_list(void)
{
struct neglist *nl;
u_int c;
c = atomic_fetchadd_int(&neg_cycle, 1) + 1;
nl = &neglists[c % numneglists];
if (!mtx_trylock(&nl->nl_evict_lock)) {
counter_u64_add(neg_evict_skipped_contended, 1);
return (NULL);
}
return (nl);
}
static struct namecache *
cache_neg_evict_select_entry(struct neglist *nl)
{
struct namecache *ncp, *lncp;
struct negstate *ns, *lns;
int i;
mtx_assert(&nl->nl_evict_lock, MA_OWNED);
mtx_assert(&nl->nl_lock, MA_OWNED);
ncp = TAILQ_FIRST(&nl->nl_list);
if (ncp == NULL)
return (NULL);
lncp = ncp;
lns = NCP2NEGSTATE(lncp);
for (i = 1; i < 4; i++) {
ncp = TAILQ_NEXT(ncp, nc_dst);
if (ncp == NULL)
break;
ns = NCP2NEGSTATE(ncp);
if (ns->neg_hit < lns->neg_hit) {
lncp = ncp;
lns = ns;
}
}
return (lncp);
}
static bool
cache_neg_evict(void)
{
struct namecache *ncp, *ncp2;
struct neglist *nl;
struct vnode *dvp;
struct mtx *dvlp;
struct mtx *blp;
uint32_t hash;
u_char nlen;
bool evicted;
nl = cache_neg_evict_select_list();
if (nl == NULL) {
return (false);
}
mtx_lock(&nl->nl_lock);
ncp = TAILQ_FIRST(&nl->nl_hotlist);
if (ncp != NULL) {
cache_neg_demote_locked(ncp);
}
ncp = cache_neg_evict_select_entry(nl);
if (ncp == NULL) {
counter_u64_add(neg_evict_skipped_empty, 1);
mtx_unlock(&nl->nl_lock);
mtx_unlock(&nl->nl_evict_lock);
return (false);
}
nlen = ncp->nc_nlen;
dvp = ncp->nc_dvp;
hash = cache_get_hash(ncp->nc_name, nlen, dvp);
dvlp = VP2VNODELOCK(dvp);
blp = HASH2BUCKETLOCK(hash);
mtx_unlock(&nl->nl_lock);
mtx_unlock(&nl->nl_evict_lock);
mtx_lock(dvlp);
mtx_lock(blp);
/*
* Note that since all locks were dropped above, the entry may be
* gone or reallocated to be something else.
*/
CK_SLIST_FOREACH(ncp2, (NCHHASH(hash)), nc_hash) {
if (ncp2 == ncp && ncp2->nc_dvp == dvp &&
ncp2->nc_nlen == nlen && (ncp2->nc_flag & NCF_NEGATIVE) != 0)
break;
}
if (ncp2 == NULL) {
counter_u64_add(neg_evict_skipped_missed, 1);
ncp = NULL;
evicted = false;
} else {
MPASS(dvlp == VP2VNODELOCK(ncp->nc_dvp));
MPASS(blp == NCP2BUCKETLOCK(ncp));
SDT_PROBE2(vfs, namecache, evict_negative, done, ncp->nc_dvp,
ncp->nc_name);
cache_zap_locked(ncp);
counter_u64_add(neg_evicted, 1);
evicted = true;
}
mtx_unlock(blp);
mtx_unlock(dvlp);
if (ncp != NULL)
cache_free(ncp);
return (evicted);
}
/*
* Maybe evict a negative entry to create more room.
*
* The ncnegfactor parameter limits what fraction of the total count
* can comprise of negative entries. However, if the cache is just
* warming up this leads to excessive evictions. As such, ncnegminpct
* (recomputed to neg_min) dictates whether the above should be
* applied.
*
* Try evicting if the cache is close to full capacity regardless of
* other considerations.
*/
static bool
cache_neg_evict_cond(u_long lnumcache)
{
u_long lnumneg;
if (ncsize - 1000 < lnumcache)
goto out_evict;
lnumneg = atomic_load_long(&numneg);
if (lnumneg < neg_min)
return (false);
if (lnumneg * ncnegfactor < lnumcache)
return (false);
out_evict:
return (cache_neg_evict());
}
/*
* cache_zap_locked():
*
* Removes a namecache entry from cache, whether it contains an actual
* pointer to a vnode or if it is just a negative cache entry.
*/
static void
cache_zap_locked(struct namecache *ncp)
{
struct nchashhead *ncpp;
if (!(ncp->nc_flag & NCF_NEGATIVE))
cache_assert_vnode_locked(ncp->nc_vp);
cache_assert_vnode_locked(ncp->nc_dvp);
cache_assert_bucket_locked(ncp);
cache_ncp_invalidate(ncp);
ncpp = NCP2BUCKET(ncp);
CK_SLIST_REMOVE(ncpp, ncp, namecache, nc_hash);
if (!(ncp->nc_flag & NCF_NEGATIVE)) {
SDT_PROBE3(vfs, namecache, zap, done, ncp->nc_dvp,
ncp->nc_name, ncp->nc_vp);
TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst);
if (ncp == ncp->nc_vp->v_cache_dd) {
vn_seqc_write_begin_unheld(ncp->nc_vp);
ncp->nc_vp->v_cache_dd = NULL;
vn_seqc_write_end(ncp->nc_vp);
}
} else {
SDT_PROBE2(vfs, namecache, zap_negative, done, ncp->nc_dvp,
ncp->nc_name);
cache_neg_remove(ncp);
}
if (ncp->nc_flag & NCF_ISDOTDOT) {
if (ncp == ncp->nc_dvp->v_cache_dd) {
vn_seqc_write_begin_unheld(ncp->nc_dvp);
ncp->nc_dvp->v_cache_dd = NULL;
vn_seqc_write_end(ncp->nc_dvp);
}
} else {
LIST_REMOVE(ncp, nc_src);
if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
ncp->nc_flag |= NCF_DVDROP;
}
}
}
static void
cache_zap_negative_locked_vnode_kl(struct namecache *ncp, struct vnode *vp)
{
struct mtx *blp;
MPASS(ncp->nc_dvp == vp);
MPASS(ncp->nc_flag & NCF_NEGATIVE);
cache_assert_vnode_locked(vp);
blp = NCP2BUCKETLOCK(ncp);
mtx_lock(blp);
cache_zap_locked(ncp);
mtx_unlock(blp);
}
static bool
cache_zap_locked_vnode_kl2(struct namecache *ncp, struct vnode *vp,
struct mtx **vlpp)
{
struct mtx *pvlp, *vlp1, *vlp2, *to_unlock;
struct mtx *blp;
MPASS(vp == ncp->nc_dvp || vp == ncp->nc_vp);
cache_assert_vnode_locked(vp);
if (ncp->nc_flag & NCF_NEGATIVE) {
if (*vlpp != NULL) {
mtx_unlock(*vlpp);
*vlpp = NULL;
}
cache_zap_negative_locked_vnode_kl(ncp, vp);
return (true);
}
pvlp = VP2VNODELOCK(vp);
blp = NCP2BUCKETLOCK(ncp);
vlp1 = VP2VNODELOCK(ncp->nc_dvp);
vlp2 = VP2VNODELOCK(ncp->nc_vp);
if (*vlpp == vlp1 || *vlpp == vlp2) {
to_unlock = *vlpp;
*vlpp = NULL;
} else {
if (*vlpp != NULL) {
mtx_unlock(*vlpp);
*vlpp = NULL;
}
cache_sort_vnodes(&vlp1, &vlp2);
if (vlp1 == pvlp) {
mtx_lock(vlp2);
to_unlock = vlp2;
} else {
if (!mtx_trylock(vlp1))
goto out_relock;
to_unlock = vlp1;
}
}
mtx_lock(blp);
cache_zap_locked(ncp);
mtx_unlock(blp);
if (to_unlock != NULL)
mtx_unlock(to_unlock);
return (true);
out_relock:
mtx_unlock(vlp2);
mtx_lock(vlp1);
mtx_lock(vlp2);
MPASS(*vlpp == NULL);
*vlpp = vlp1;
return (false);
}
/*
* If trylocking failed we can get here. We know enough to take all needed locks
* in the right order and re-lookup the entry.
*/
static int
cache_zap_unlocked_bucket(struct namecache *ncp, struct componentname *cnp,
struct vnode *dvp, struct mtx *dvlp, struct mtx *vlp, uint32_t hash,
struct mtx *blp)
{
struct namecache *rncp;
cache_assert_bucket_unlocked(ncp);
cache_sort_vnodes(&dvlp, &vlp);
cache_lock_vnodes(dvlp, vlp);
mtx_lock(blp);
CK_SLIST_FOREACH(rncp, (NCHHASH(hash)), nc_hash) {
if (rncp == ncp && rncp->nc_dvp == dvp &&
rncp->nc_nlen == cnp->cn_namelen &&
!bcmp(rncp->nc_name, cnp->cn_nameptr, rncp->nc_nlen))
break;
}
if (rncp != NULL) {
cache_zap_locked(rncp);
mtx_unlock(blp);
cache_unlock_vnodes(dvlp, vlp);
counter_u64_add(zap_bucket_relock_success, 1);
return (0);
}
mtx_unlock(blp);
cache_unlock_vnodes(dvlp, vlp);
return (EAGAIN);
}
static int __noinline
cache_zap_locked_bucket(struct namecache *ncp, struct componentname *cnp,
uint32_t hash, struct mtx *blp)
{
struct mtx *dvlp, *vlp;
struct vnode *dvp;
cache_assert_bucket_locked(ncp);
dvlp = VP2VNODELOCK(ncp->nc_dvp);
vlp = NULL;
if (!(ncp->nc_flag & NCF_NEGATIVE))
vlp = VP2VNODELOCK(ncp->nc_vp);
if (cache_trylock_vnodes(dvlp, vlp) == 0) {
cache_zap_locked(ncp);
mtx_unlock(blp);
cache_unlock_vnodes(dvlp, vlp);
return (0);
}
dvp = ncp->nc_dvp;
mtx_unlock(blp);
return (cache_zap_unlocked_bucket(ncp, cnp, dvp, dvlp, vlp, hash, blp));
}
static __noinline int
cache_remove_cnp(struct vnode *dvp, struct componentname *cnp)
{
struct namecache *ncp;
struct mtx *blp;
struct mtx *dvlp, *dvlp2;
uint32_t hash;
int error;
if (cnp->cn_namelen == 2 &&
cnp->cn_nameptr[0] == '.' && cnp->cn_nameptr[1] == '.') {
dvlp = VP2VNODELOCK(dvp);
dvlp2 = NULL;
mtx_lock(dvlp);
retry_dotdot:
ncp = dvp->v_cache_dd;
if (ncp == NULL) {
mtx_unlock(dvlp);
if (dvlp2 != NULL)
mtx_unlock(dvlp2);
SDT_PROBE2(vfs, namecache, removecnp, miss, dvp, cnp);
return (0);
}
if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
if (!cache_zap_locked_vnode_kl2(ncp, dvp, &dvlp2))
goto retry_dotdot;
MPASS(dvp->v_cache_dd == NULL);
mtx_unlock(dvlp);
if (dvlp2 != NULL)
mtx_unlock(dvlp2);
cache_free(ncp);
} else {
vn_seqc_write_begin(dvp);
dvp->v_cache_dd = NULL;
vn_seqc_write_end(dvp);
mtx_unlock(dvlp);
if (dvlp2 != NULL)
mtx_unlock(dvlp2);
}
SDT_PROBE2(vfs, namecache, removecnp, hit, dvp, cnp);
return (1);
}
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
blp = HASH2BUCKETLOCK(hash);
retry:
if (CK_SLIST_EMPTY(NCHHASH(hash)))
goto out_no_entry;
mtx_lock(blp);
CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
break;
}
if (ncp == NULL) {
mtx_unlock(blp);
goto out_no_entry;
}
error = cache_zap_locked_bucket(ncp, cnp, hash, blp);
if (__predict_false(error != 0)) {
zap_bucket_fail++;
goto retry;
}
counter_u64_add(numposzaps, 1);
SDT_PROBE2(vfs, namecache, removecnp, hit, dvp, cnp);
cache_free(ncp);
return (1);
out_no_entry:
counter_u64_add(nummisszap, 1);
SDT_PROBE2(vfs, namecache, removecnp, miss, dvp, cnp);
return (0);
}
static int __noinline
cache_lookup_dot(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
struct timespec *tsp, int *ticksp)
{
int ltype;
*vpp = dvp;
counter_u64_add(dothits, 1);
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ".", *vpp);
if (tsp != NULL)
timespecclear(tsp);
if (ticksp != NULL)
*ticksp = ticks;
vrefact(*vpp);
/*
* When we lookup "." we still can be asked to lock it
* differently...
*/
ltype = cnp->cn_lkflags & LK_TYPE_MASK;
if (ltype != VOP_ISLOCKED(*vpp)) {
if (ltype == LK_EXCLUSIVE) {
vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
if (VN_IS_DOOMED((*vpp))) {
/* forced unmount */
vrele(*vpp);
*vpp = NULL;
return (ENOENT);
}
} else
vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
}
return (-1);
}
static int __noinline
cache_lookup_dotdot(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
struct timespec *tsp, int *ticksp)
{
struct namecache_ts *ncp_ts;
struct namecache *ncp;
struct mtx *dvlp;
enum vgetstate vs;
int error, ltype;
bool whiteout;
MPASS((cnp->cn_flags & ISDOTDOT) != 0);
if ((cnp->cn_flags & MAKEENTRY) == 0) {
cache_remove_cnp(dvp, cnp);
return (0);
}
counter_u64_add(dotdothits, 1);
retry:
dvlp = VP2VNODELOCK(dvp);
mtx_lock(dvlp);
ncp = dvp->v_cache_dd;
if (ncp == NULL) {
SDT_PROBE3(vfs, namecache, lookup, miss, dvp, "..", NULL);
mtx_unlock(dvlp);
return (0);
}
if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
if (ncp->nc_flag & NCF_NEGATIVE)
*vpp = NULL;
else
*vpp = ncp->nc_vp;
} else
*vpp = ncp->nc_dvp;
if (*vpp == NULL)
goto negative_success;
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, "..", *vpp);
cache_out_ts(ncp, tsp, ticksp);
if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
NCF_DTS && tsp != NULL) {
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
*tsp = ncp_ts->nc_dotdottime;
}
MPASS(dvp != *vpp);
ltype = VOP_ISLOCKED(dvp);
VOP_UNLOCK(dvp);
vs = vget_prep(*vpp);
mtx_unlock(dvlp);
error = vget_finish(*vpp, cnp->cn_lkflags, vs);
vn_lock(dvp, ltype | LK_RETRY);
if (VN_IS_DOOMED(dvp)) {
if (error == 0)
vput(*vpp);
*vpp = NULL;
return (ENOENT);
}
if (error) {
*vpp = NULL;
goto retry;
}
return (-1);
negative_success:
if (__predict_false(cnp->cn_nameiop == CREATE)) {
if (cnp->cn_flags & ISLASTCN) {
counter_u64_add(numnegzaps, 1);
cache_zap_negative_locked_vnode_kl(ncp, dvp);
mtx_unlock(dvlp);
cache_free(ncp);
return (0);
}
}
whiteout = (ncp->nc_flag & NCF_WHITE);
cache_out_ts(ncp, tsp, ticksp);
if (cache_neg_hit_prep(ncp))
cache_neg_promote(ncp);
else
cache_neg_hit_finish(ncp);
mtx_unlock(dvlp);
if (whiteout)
cnp->cn_flags |= ISWHITEOUT;
return (ENOENT);
}
/**
* Lookup a name in the name cache
*
* # Arguments
*
* - dvp: Parent directory in which to search.
* - vpp: Return argument. Will contain desired vnode on cache hit.
* - cnp: Parameters of the name search. The most interesting bits of
* the cn_flags field have the following meanings:
* - MAKEENTRY: If clear, free an entry from the cache rather than look
* it up.
* - ISDOTDOT: Must be set if and only if cn_nameptr == ".."
* - tsp: Return storage for cache timestamp. On a successful (positive
* or negative) lookup, tsp will be filled with any timespec that
* was stored when this cache entry was created. However, it will
* be clear for "." entries.
* - ticks: Return storage for alternate cache timestamp. On a successful
* (positive or negative) lookup, it will contain the ticks value
* that was current when the cache entry was created, unless cnp
* was ".".
*
* Either both tsp and ticks have to be provided or neither of them.
*
* # Returns
*
* - -1: A positive cache hit. vpp will contain the desired vnode.
* - ENOENT: A negative cache hit, or dvp was recycled out from under us due
* to a forced unmount. vpp will not be modified. If the entry
* is a whiteout, then the ISWHITEOUT flag will be set in
* cnp->cn_flags.
* - 0: A cache miss. vpp will not be modified.
*
* # Locking
*
* On a cache hit, vpp will be returned locked and ref'd. If we're looking up
* .., dvp is unlocked. If we're looking up . an extra ref is taken, but the
* lock is not recursively acquired.
*/
static int __noinline
cache_lookup_fallback(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
struct timespec *tsp, int *ticksp)
{
struct namecache *ncp;
struct mtx *blp;
uint32_t hash;
enum vgetstate vs;
int error;
bool whiteout;
MPASS((cnp->cn_flags & ISDOTDOT) == 0);
MPASS((cnp->cn_flags & (MAKEENTRY | NC_KEEPPOSENTRY)) != 0);
retry:
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
blp = HASH2BUCKETLOCK(hash);
mtx_lock(blp);
CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
break;
}
if (__predict_false(ncp == NULL)) {
mtx_unlock(blp);
SDT_PROBE3(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
NULL);
counter_u64_add(nummiss, 1);
return (0);
}
if (ncp->nc_flag & NCF_NEGATIVE)
goto negative_success;
counter_u64_add(numposhits, 1);
*vpp = ncp->nc_vp;
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, *vpp);
cache_out_ts(ncp, tsp, ticksp);
MPASS(dvp != *vpp);
vs = vget_prep(*vpp);
mtx_unlock(blp);
error = vget_finish(*vpp, cnp->cn_lkflags, vs);
if (error) {
*vpp = NULL;
goto retry;
}
return (-1);
negative_success:
if (__predict_false(cnp->cn_nameiop == CREATE)) {
if (cnp->cn_flags & ISLASTCN) {
counter_u64_add(numnegzaps, 1);
error = cache_zap_locked_bucket(ncp, cnp, hash, blp);
if (__predict_false(error != 0)) {
zap_bucket_fail2++;
goto retry;
}
cache_free(ncp);
return (0);
}
}
whiteout = (ncp->nc_flag & NCF_WHITE);
cache_out_ts(ncp, tsp, ticksp);
if (cache_neg_hit_prep(ncp))
cache_neg_promote(ncp);
else
cache_neg_hit_finish(ncp);
mtx_unlock(blp);
if (whiteout)
cnp->cn_flags |= ISWHITEOUT;
return (ENOENT);
}
int
cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
struct timespec *tsp, int *ticksp)
{
struct namecache *ncp;
uint32_t hash;
enum vgetstate vs;
int error;
bool whiteout, neg_promote;
u_short nc_flag;
MPASS((tsp == NULL && ticksp == NULL) || (tsp != NULL && ticksp != NULL));
#ifdef DEBUG_CACHE
if (__predict_false(!doingcache)) {
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
#endif
if (__predict_false(cnp->cn_nameptr[0] == '.')) {
if (cnp->cn_namelen == 1)
return (cache_lookup_dot(dvp, vpp, cnp, tsp, ticksp));
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.')
return (cache_lookup_dotdot(dvp, vpp, cnp, tsp, ticksp));
}
MPASS((cnp->cn_flags & ISDOTDOT) == 0);
if ((cnp->cn_flags & (MAKEENTRY | NC_KEEPPOSENTRY)) == 0) {
cache_remove_cnp(dvp, cnp);
return (0);
}
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
vfs_smr_enter();
CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
break;
}
if (__predict_false(ncp == NULL)) {
vfs_smr_exit();
SDT_PROBE3(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
NULL);
counter_u64_add(nummiss, 1);
return (0);
}
nc_flag = atomic_load_char(&ncp->nc_flag);
if (nc_flag & NCF_NEGATIVE)
goto negative_success;
counter_u64_add(numposhits, 1);
*vpp = ncp->nc_vp;
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, *vpp);
cache_out_ts(ncp, tsp, ticksp);
MPASS(dvp != *vpp);
if (!cache_ncp_canuse(ncp)) {
vfs_smr_exit();
*vpp = NULL;
goto out_fallback;
}
vs = vget_prep_smr(*vpp);
vfs_smr_exit();
if (__predict_false(vs == VGET_NONE)) {
*vpp = NULL;
goto out_fallback;
}
error = vget_finish(*vpp, cnp->cn_lkflags, vs);
if (error) {
*vpp = NULL;
goto out_fallback;
}
return (-1);
negative_success:
if (__predict_false(cnp->cn_nameiop == CREATE)) {
if (cnp->cn_flags & ISLASTCN) {
vfs_smr_exit();
goto out_fallback;
}
}
cache_out_ts(ncp, tsp, ticksp);
whiteout = (ncp->nc_flag & NCF_WHITE);
neg_promote = cache_neg_hit_prep(ncp);
if (!cache_ncp_canuse(ncp)) {
cache_neg_hit_abort(ncp);
vfs_smr_exit();
goto out_fallback;
}
if (neg_promote) {
vfs_smr_exit();
if (!cache_neg_promote_cond(dvp, cnp, ncp, hash))
goto out_fallback;
} else {
cache_neg_hit_finish(ncp);
vfs_smr_exit();
}
if (whiteout)
cnp->cn_flags |= ISWHITEOUT;
return (ENOENT);
out_fallback:
return (cache_lookup_fallback(dvp, vpp, cnp, tsp, ticksp));
}
struct celockstate {
struct mtx *vlp[3];
struct mtx *blp[2];
};
CTASSERT((nitems(((struct celockstate *)0)->vlp) == 3));
CTASSERT((nitems(((struct celockstate *)0)->blp) == 2));
static inline void
cache_celockstate_init(struct celockstate *cel)
{
bzero(cel, sizeof(*cel));
}
static void
cache_lock_vnodes_cel(struct celockstate *cel, struct vnode *vp,
struct vnode *dvp)
{
struct mtx *vlp1, *vlp2;
MPASS(cel->vlp[0] == NULL);
MPASS(cel->vlp[1] == NULL);
MPASS(cel->vlp[2] == NULL);
MPASS(vp != NULL || dvp != NULL);
vlp1 = VP2VNODELOCK(vp);
vlp2 = VP2VNODELOCK(dvp);
cache_sort_vnodes(&vlp1, &vlp2);
if (vlp1 != NULL) {
mtx_lock(vlp1);
cel->vlp[0] = vlp1;
}
mtx_lock(vlp2);
cel->vlp[1] = vlp2;
}
static void
cache_unlock_vnodes_cel(struct celockstate *cel)
{
MPASS(cel->vlp[0] != NULL || cel->vlp[1] != NULL);
if (cel->vlp[0] != NULL)
mtx_unlock(cel->vlp[0]);
if (cel->vlp[1] != NULL)
mtx_unlock(cel->vlp[1]);
if (cel->vlp[2] != NULL)
mtx_unlock(cel->vlp[2]);
}
static bool
cache_lock_vnodes_cel_3(struct celockstate *cel, struct vnode *vp)
{
struct mtx *vlp;
bool ret;
cache_assert_vlp_locked(cel->vlp[0]);
cache_assert_vlp_locked(cel->vlp[1]);
MPASS(cel->vlp[2] == NULL);
MPASS(vp != NULL);
vlp = VP2VNODELOCK(vp);
ret = true;
if (vlp >= cel->vlp[1]) {
mtx_lock(vlp);
} else {
if (mtx_trylock(vlp))
goto out;
cache_lock_vnodes_cel_3_failures++;
cache_unlock_vnodes_cel(cel);
if (vlp < cel->vlp[0]) {
mtx_lock(vlp);
mtx_lock(cel->vlp[0]);
mtx_lock(cel->vlp[1]);
} else {
if (cel->vlp[0] != NULL)
mtx_lock(cel->vlp[0]);
mtx_lock(vlp);
mtx_lock(cel->vlp[1]);
}
ret = false;
}
out:
cel->vlp[2] = vlp;
return (ret);
}
static void
cache_lock_buckets_cel(struct celockstate *cel, struct mtx *blp1,
struct mtx *blp2)
{
MPASS(cel->blp[0] == NULL);
MPASS(cel->blp[1] == NULL);
cache_sort_vnodes(&blp1, &blp2);
if (blp1 != NULL) {
mtx_lock(blp1);
cel->blp[0] = blp1;
}
mtx_lock(blp2);
cel->blp[1] = blp2;
}
static void
cache_unlock_buckets_cel(struct celockstate *cel)
{
if (cel->blp[0] != NULL)
mtx_unlock(cel->blp[0]);
mtx_unlock(cel->blp[1]);
}
/*
* Lock part of the cache affected by the insertion.
*
* This means vnodelocks for dvp, vp and the relevant bucketlock.
* However, insertion can result in removal of an old entry. In this
* case we have an additional vnode and bucketlock pair to lock.
*
* That is, in the worst case we have to lock 3 vnodes and 2 bucketlocks, while
* preserving the locking order (smaller address first).
*/
static void
cache_enter_lock(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
uint32_t hash)
{
struct namecache *ncp;
struct mtx *blps[2];
blps[0] = HASH2BUCKETLOCK(hash);
for (;;) {
blps[1] = NULL;
cache_lock_vnodes_cel(cel, dvp, vp);
if (vp == NULL || vp->v_type != VDIR)
break;
ncp = vp->v_cache_dd;
if (ncp == NULL)
break;
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
MPASS(ncp->nc_dvp == vp);
blps[1] = NCP2BUCKETLOCK(ncp);
if (ncp->nc_flag & NCF_NEGATIVE)
break;
if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
break;
/*
* All vnodes got re-locked. Re-validate the state and if
* nothing changed we are done. Otherwise restart.
*/
if (ncp == vp->v_cache_dd &&
(ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
blps[1] == NCP2BUCKETLOCK(ncp) &&
VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
break;
cache_unlock_vnodes_cel(cel);
cel->vlp[0] = NULL;
cel->vlp[1] = NULL;
cel->vlp[2] = NULL;
}
cache_lock_buckets_cel(cel, blps[0], blps[1]);
}
static void
cache_enter_lock_dd(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
uint32_t hash)
{
struct namecache *ncp;
struct mtx *blps[2];
blps[0] = HASH2BUCKETLOCK(hash);
for (;;) {
blps[1] = NULL;
cache_lock_vnodes_cel(cel, dvp, vp);
ncp = dvp->v_cache_dd;
if (ncp == NULL)
break;
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
MPASS(ncp->nc_dvp == dvp);
blps[1] = NCP2BUCKETLOCK(ncp);
if (ncp->nc_flag & NCF_NEGATIVE)
break;
if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
break;
if (ncp == dvp->v_cache_dd &&
(ncp->nc_flag & NCF_ISDOTDOT) != 0 &&
blps[1] == NCP2BUCKETLOCK(ncp) &&
VP2VNODELOCK(ncp->nc_vp) == cel->vlp[2])
break;
cache_unlock_vnodes_cel(cel);
cel->vlp[0] = NULL;
cel->vlp[1] = NULL;
cel->vlp[2] = NULL;
}
cache_lock_buckets_cel(cel, blps[0], blps[1]);
}
static void
cache_enter_unlock(struct celockstate *cel)
{
cache_unlock_buckets_cel(cel);
cache_unlock_vnodes_cel(cel);
}
static void __noinline
cache_enter_dotdot_prep(struct vnode *dvp, struct vnode *vp,
struct componentname *cnp)
{
struct celockstate cel;
struct namecache *ncp;
uint32_t hash;
int len;
if (dvp->v_cache_dd == NULL)
return;
len = cnp->cn_namelen;
cache_celockstate_init(&cel);
hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
cache_enter_lock_dd(&cel, dvp, vp, hash);
vn_seqc_write_begin(dvp);
ncp = dvp->v_cache_dd;
if (ncp != NULL && (ncp->nc_flag & NCF_ISDOTDOT)) {
KASSERT(ncp->nc_dvp == dvp, ("wrong isdotdot parent"));
cache_zap_locked(ncp);
} else {
ncp = NULL;
}
dvp->v_cache_dd = NULL;
vn_seqc_write_end(dvp);
cache_enter_unlock(&cel);
if (ncp != NULL)
cache_free(ncp);
}
/*
* Add an entry to the cache.
*/
void
cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
struct timespec *tsp, struct timespec *dtsp)
{
struct celockstate cel;
struct namecache *ncp, *n2, *ndd;
struct namecache_ts *ncp_ts;
struct nchashhead *ncpp;
uint32_t hash;
int flag;
int len;
VNPASS(dvp != vp, dvp);
VNPASS(!VN_IS_DOOMED(dvp), dvp);
VNPASS(dvp->v_type != VNON, dvp);
if (vp != NULL) {
VNPASS(!VN_IS_DOOMED(vp), vp);
VNPASS(vp->v_type != VNON, vp);
}
#ifdef DEBUG_CACHE
if (__predict_false(!doingcache))
return;
#endif
flag = 0;
if (__predict_false(cnp->cn_nameptr[0] == '.')) {
if (cnp->cn_namelen == 1)
return;
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
cache_enter_dotdot_prep(dvp, vp, cnp);
flag = NCF_ISDOTDOT;
}
}
ncp = cache_alloc(cnp->cn_namelen, tsp != NULL);
if (ncp == NULL)
return;
cache_celockstate_init(&cel);
ndd = NULL;
ncp_ts = NULL;
/*
* Calculate the hash key and setup as much of the new
* namecache entry as possible before acquiring the lock.
*/
ncp->nc_flag = flag | NCF_WIP;
ncp->nc_vp = vp;
if (vp == NULL)
cache_neg_init(ncp);
ncp->nc_dvp = dvp;
if (tsp != NULL) {
ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
ncp_ts->nc_time = *tsp;
ncp_ts->nc_ticks = ticks;
ncp_ts->nc_nc.nc_flag |= NCF_TS;
if (dtsp != NULL) {
ncp_ts->nc_dotdottime = *dtsp;
ncp_ts->nc_nc.nc_flag |= NCF_DTS;
}
}
len = ncp->nc_nlen = cnp->cn_namelen;
hash = cache_get_hash(cnp->cn_nameptr, len, dvp);
memcpy(ncp->nc_name, cnp->cn_nameptr, len);
ncp->nc_name[len] = '\0';
cache_enter_lock(&cel, dvp, vp, hash);
/*
* See if this vnode or negative entry is already in the cache
* with this name. This can happen with concurrent lookups of
* the same path name.
*/
ncpp = NCHHASH(hash);
CK_SLIST_FOREACH(n2, ncpp, nc_hash) {
if (n2->nc_dvp == dvp &&
n2->nc_nlen == cnp->cn_namelen &&
!bcmp(n2->nc_name, cnp->cn_nameptr, n2->nc_nlen)) {
MPASS(cache_ncp_canuse(n2));
if ((n2->nc_flag & NCF_NEGATIVE) != 0)
KASSERT(vp == NULL,
("%s: found entry pointing to a different vnode (%p != %p)",
__func__, NULL, vp));
else
KASSERT(n2->nc_vp == vp,
("%s: found entry pointing to a different vnode (%p != %p)",
__func__, n2->nc_vp, vp));
/*
* Entries are supposed to be immutable unless in the
* process of getting destroyed. Accommodating for
* changing timestamps is possible but not worth it.
* This should be harmless in terms of correctness, in
* the worst case resulting in an earlier expiration.
* Alternatively, the found entry can be replaced
* altogether.
*/
MPASS((n2->nc_flag & (NCF_TS | NCF_DTS)) == (ncp->nc_flag & (NCF_TS | NCF_DTS)));
#if 0
if (tsp != NULL) {
KASSERT((n2->nc_flag & NCF_TS) != 0,
("no NCF_TS"));
n2_ts = __containerof(n2, struct namecache_ts, nc_nc);
n2_ts->nc_time = ncp_ts->nc_time;
n2_ts->nc_ticks = ncp_ts->nc_ticks;
if (dtsp != NULL) {
n2_ts->nc_dotdottime = ncp_ts->nc_dotdottime;
n2_ts->nc_nc.nc_flag |= NCF_DTS;
}
}
#endif
SDT_PROBE3(vfs, namecache, enter, duplicate, dvp, ncp->nc_name,
vp);
goto out_unlock_free;
}
}
if (flag == NCF_ISDOTDOT) {
/*
* See if we are trying to add .. entry, but some other lookup
* has populated v_cache_dd pointer already.
*/
if (dvp->v_cache_dd != NULL)
goto out_unlock_free;
KASSERT(vp == NULL || vp->v_type == VDIR,
("wrong vnode type %p", vp));
vn_seqc_write_begin(dvp);
dvp->v_cache_dd = ncp;
vn_seqc_write_end(dvp);
}
if (vp != NULL) {
if (flag != NCF_ISDOTDOT) {
/*
* For this case, the cache entry maps both the
* directory name in it and the name ".." for the
* directory's parent.
*/
vn_seqc_write_begin(vp);
if ((ndd = vp->v_cache_dd) != NULL) {
if ((ndd->nc_flag & NCF_ISDOTDOT) != 0)
cache_zap_locked(ndd);
else
ndd = NULL;
}
vp->v_cache_dd = ncp;
vn_seqc_write_end(vp);
} else if (vp->v_type != VDIR) {
if (vp->v_cache_dd != NULL) {
vn_seqc_write_begin(vp);
vp->v_cache_dd = NULL;
vn_seqc_write_end(vp);
}
}
}
if (flag != NCF_ISDOTDOT) {
if (LIST_EMPTY(&dvp->v_cache_src)) {
cache_hold_vnode(dvp);
}
LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
}
/*
* If the entry is "negative", we place it into the
* "negative" cache queue, otherwise, we place it into the
* destination vnode's cache entries queue.
*/
if (vp != NULL) {
TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
SDT_PROBE3(vfs, namecache, enter, done, dvp, ncp->nc_name,
vp);
} else {
if (cnp->cn_flags & ISWHITEOUT)
ncp->nc_flag |= NCF_WHITE;
cache_neg_insert(ncp);
SDT_PROBE2(vfs, namecache, enter_negative, done, dvp,
ncp->nc_name);
}
/*
* Insert the new namecache entry into the appropriate chain
* within the cache entries table.
*/
CK_SLIST_INSERT_HEAD(ncpp, ncp, nc_hash);
atomic_thread_fence_rel();
/*
* Mark the entry as fully constructed.
* It is immutable past this point until its removal.
*/
atomic_store_char(&ncp->nc_flag, ncp->nc_flag & ~NCF_WIP);
cache_enter_unlock(&cel);
if (ndd != NULL)
cache_free(ndd);
return;
out_unlock_free:
cache_enter_unlock(&cel);
cache_free(ncp);
return;
}
static u_int
cache_roundup_2(u_int val)
{
u_int res;
for (res = 1; res <= val; res <<= 1)
continue;
return (res);
}
static struct nchashhead *
nchinittbl(u_long elements, u_long *hashmask)
{
struct nchashhead *hashtbl;
u_long hashsize, i;
hashsize = cache_roundup_2(elements) / 2;
hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl), M_VFSCACHE, M_WAITOK);
for (i = 0; i < hashsize; i++)
CK_SLIST_INIT(&hashtbl[i]);
*hashmask = hashsize - 1;
return (hashtbl);
}
static void
ncfreetbl(struct nchashhead *hashtbl)
{
free(hashtbl, M_VFSCACHE);
}
/*
* Name cache initialization, from vfs_init() when we are booting
*/
static void
nchinit(void *dummy __unused)
{
u_int i;
cache_zone_small = uma_zcreate("S VFS Cache", CACHE_ZONE_SMALL_SIZE,
NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
cache_zone_small_ts = uma_zcreate("STS VFS Cache", CACHE_ZONE_SMALL_TS_SIZE,
NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
cache_zone_large = uma_zcreate("L VFS Cache", CACHE_ZONE_LARGE_SIZE,
NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
cache_zone_large_ts = uma_zcreate("LTS VFS Cache", CACHE_ZONE_LARGE_TS_SIZE,
NULL, NULL, NULL, NULL, CACHE_ZONE_ALIGNMENT, UMA_ZONE_ZINIT);
VFS_SMR_ZONE_SET(cache_zone_small);
VFS_SMR_ZONE_SET(cache_zone_small_ts);
VFS_SMR_ZONE_SET(cache_zone_large);
VFS_SMR_ZONE_SET(cache_zone_large_ts);
ncsize = desiredvnodes * ncsizefactor;
cache_recalc_neg_min(ncnegminpct);
nchashtbl = nchinittbl(desiredvnodes * 2, &nchash);
ncbuckethash = cache_roundup_2(mp_ncpus * mp_ncpus) - 1;
if (ncbuckethash < 7) /* arbitrarily chosen to avoid having one lock */
ncbuckethash = 7;
if (ncbuckethash > nchash)
ncbuckethash = nchash;
bucketlocks = malloc(sizeof(*bucketlocks) * numbucketlocks, M_VFSCACHE,
M_WAITOK | M_ZERO);
for (i = 0; i < numbucketlocks; i++)
mtx_init(&bucketlocks[i], "ncbuc", NULL, MTX_DUPOK | MTX_RECURSE);
ncvnodehash = ncbuckethash;
vnodelocks = malloc(sizeof(*vnodelocks) * numvnodelocks, M_VFSCACHE,
M_WAITOK | M_ZERO);
for (i = 0; i < numvnodelocks; i++)
mtx_init(&vnodelocks[i], "ncvn", NULL, MTX_DUPOK | MTX_RECURSE);
for (i = 0; i < numneglists; i++) {
mtx_init(&neglists[i].nl_evict_lock, "ncnege", NULL, MTX_DEF);
mtx_init(&neglists[i].nl_lock, "ncnegl", NULL, MTX_DEF);
TAILQ_INIT(&neglists[i].nl_list);
TAILQ_INIT(&neglists[i].nl_hotlist);
}
}
SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL);
void
cache_vnode_init(struct vnode *vp)
{
LIST_INIT(&vp->v_cache_src);
TAILQ_INIT(&vp->v_cache_dst);
vp->v_cache_dd = NULL;
cache_prehash(vp);
}
void
cache_changesize(u_long newmaxvnodes)
{
struct nchashhead *new_nchashtbl, *old_nchashtbl;
u_long new_nchash, old_nchash;
struct namecache *ncp;
uint32_t hash;
u_long newncsize;
int i;
newncsize = newmaxvnodes * ncsizefactor;
newmaxvnodes = cache_roundup_2(newmaxvnodes * 2);
if (newmaxvnodes < numbucketlocks)
newmaxvnodes = numbucketlocks;
new_nchashtbl = nchinittbl(newmaxvnodes, &new_nchash);
/* If same hash table size, nothing to do */
if (nchash == new_nchash) {
ncfreetbl(new_nchashtbl);
return;
}
/*
* Move everything from the old hash table to the new table.
* None of the namecache entries in the table can be removed
* because to do so, they have to be removed from the hash table.
*/
cache_lock_all_vnodes();
cache_lock_all_buckets();
old_nchashtbl = nchashtbl;
old_nchash = nchash;
nchashtbl = new_nchashtbl;
nchash = new_nchash;
for (i = 0; i <= old_nchash; i++) {
while ((ncp = CK_SLIST_FIRST(&old_nchashtbl[i])) != NULL) {
hash = cache_get_hash(ncp->nc_name, ncp->nc_nlen,
ncp->nc_dvp);
CK_SLIST_REMOVE(&old_nchashtbl[i], ncp, namecache, nc_hash);
CK_SLIST_INSERT_HEAD(NCHHASH(hash), ncp, nc_hash);
}
}
ncsize = newncsize;
cache_recalc_neg_min(ncnegminpct);
cache_unlock_all_buckets();
cache_unlock_all_vnodes();
ncfreetbl(old_nchashtbl);
}
/*
* Invalidate all entries from and to a particular vnode.
*/
static void
cache_purge_impl(struct vnode *vp)
{
struct cache_freebatch batch;
struct namecache *ncp;
struct mtx *vlp, *vlp2;
TAILQ_INIT(&batch);
vlp = VP2VNODELOCK(vp);
vlp2 = NULL;
mtx_lock(vlp);
retry:
while (!LIST_EMPTY(&vp->v_cache_src)) {
ncp = LIST_FIRST(&vp->v_cache_src);
if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
goto retry;
TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
}
while (!TAILQ_EMPTY(&vp->v_cache_dst)) {
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
goto retry;
TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
}
ncp = vp->v_cache_dd;
if (ncp != NULL) {
KASSERT(ncp->nc_flag & NCF_ISDOTDOT,
("lost dotdot link"));
if (!cache_zap_locked_vnode_kl2(ncp, vp, &vlp2))
goto retry;
TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
}
KASSERT(vp->v_cache_dd == NULL, ("incomplete purge"));
mtx_unlock(vlp);
if (vlp2 != NULL)
mtx_unlock(vlp2);
cache_free_batch(&batch);
}
/*
* Opportunistic check to see if there is anything to do.
*/
static bool
cache_has_entries(struct vnode *vp)
{
if (LIST_EMPTY(&vp->v_cache_src) && TAILQ_EMPTY(&vp->v_cache_dst) &&
vp->v_cache_dd == NULL)
return (false);
return (true);
}
void
cache_purge(struct vnode *vp)
{
SDT_PROBE1(vfs, namecache, purge, done, vp);
if (!cache_has_entries(vp))
return;
cache_purge_impl(vp);
}
/*
* Only to be used by vgone.
*/
void
cache_purge_vgone(struct vnode *vp)
{
struct mtx *vlp;
VNPASS(VN_IS_DOOMED(vp), vp);
if (cache_has_entries(vp)) {
cache_purge_impl(vp);
return;
}
/*
* Serialize against a potential thread doing cache_purge.
*/
vlp = VP2VNODELOCK(vp);
mtx_wait_unlocked(vlp);
if (cache_has_entries(vp)) {
cache_purge_impl(vp);
return;
}
return;
}
/*
* Invalidate all negative entries for a particular directory vnode.
*/
void
cache_purge_negative(struct vnode *vp)
{
struct cache_freebatch batch;
struct namecache *ncp, *nnp;
struct mtx *vlp;
SDT_PROBE1(vfs, namecache, purge_negative, done, vp);
if (LIST_EMPTY(&vp->v_cache_src))
return;
TAILQ_INIT(&batch);
vlp = VP2VNODELOCK(vp);
mtx_lock(vlp);
LIST_FOREACH_SAFE(ncp, &vp->v_cache_src, nc_src, nnp) {
if (!(ncp->nc_flag & NCF_NEGATIVE))
continue;
cache_zap_negative_locked_vnode_kl(ncp, vp);
TAILQ_INSERT_TAIL(&batch, ncp, nc_dst);
}
mtx_unlock(vlp);
cache_free_batch(&batch);
}
/*
* Entry points for modifying VOP operations.
*/
void
cache_vop_rename(struct vnode *fdvp, struct vnode *fvp, struct vnode *tdvp,
struct vnode *tvp, struct componentname *fcnp, struct componentname *tcnp)
{
ASSERT_VOP_IN_SEQC(fdvp);
ASSERT_VOP_IN_SEQC(fvp);
ASSERT_VOP_IN_SEQC(tdvp);
if (tvp != NULL)
ASSERT_VOP_IN_SEQC(tvp);
cache_purge(fvp);
if (tvp != NULL) {
cache_purge(tvp);
KASSERT(!cache_remove_cnp(tdvp, tcnp),
("%s: lingering negative entry", __func__));
} else {
cache_remove_cnp(tdvp, tcnp);
}
}
void
cache_vop_rmdir(struct vnode *dvp, struct vnode *vp)
{
ASSERT_VOP_IN_SEQC(dvp);
ASSERT_VOP_IN_SEQC(vp);
cache_purge(vp);
}
#ifdef INVARIANTS
/*
* Validate that if an entry exists it matches.
*/
void
cache_validate(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
{
struct namecache *ncp;
struct mtx *blp;
uint32_t hash;
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
if (CK_SLIST_EMPTY(NCHHASH(hash)))
return;
blp = HASH2BUCKETLOCK(hash);
mtx_lock(blp);
CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen)) {
if (ncp->nc_vp != vp)
panic("%s: mismatch (%p != %p); ncp %p [%s] dvp %p vp %p\n",
__func__, vp, ncp->nc_vp, ncp, ncp->nc_name, ncp->nc_dvp,
ncp->nc_vp);
}
}
mtx_unlock(blp);
}
#endif
/*
* Flush all entries referencing a particular filesystem.
*/
void
cache_purgevfs(struct mount *mp)
{
struct vnode *vp, *mvp;
SDT_PROBE1(vfs, namecache, purgevfs, done, mp);
/*
* Somewhat wasteful iteration over all vnodes. Would be better to
* support filtering and avoid the interlock to begin with.
*/
MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
if (!cache_has_entries(vp)) {
VI_UNLOCK(vp);
continue;
}
vholdl(vp);
VI_UNLOCK(vp);
cache_purge(vp);
vdrop(vp);
}
}
/*
* Perform canonical checks and cache lookup and pass on to filesystem
* through the vop_cachedlookup only if needed.
*/
int
vfs_cache_lookup(struct vop_lookup_args *ap)
{
struct vnode *dvp;
int error;
struct vnode **vpp = ap->a_vpp;
struct componentname *cnp = ap->a_cnp;
int flags = cnp->cn_flags;
*vpp = NULL;
dvp = ap->a_dvp;
if (dvp->v_type != VDIR)
return (ENOTDIR);
if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
return (EROFS);
error = vn_dir_check_exec(dvp, cnp);
if (error != 0)
return (error);
error = cache_lookup(dvp, vpp, cnp, NULL, NULL);
if (error == 0)
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
if (error == -1)
return (0);
return (error);
}
/* Implementation of the getcwd syscall. */
int
sys___getcwd(struct thread *td, struct __getcwd_args *uap)
{
char *buf, *retbuf;
size_t buflen;
int error;
buflen = uap->buflen;
if (__predict_false(buflen < 2))
return (EINVAL);
if (buflen > MAXPATHLEN)
buflen = MAXPATHLEN;
buf = uma_zalloc(namei_zone, M_WAITOK);
error = vn_getcwd(buf, &retbuf, &buflen);
if (error == 0)
error = copyout(retbuf, uap->buf, buflen);
uma_zfree(namei_zone, buf);
return (error);
}
int
vn_getcwd(char *buf, char **retbuf, size_t *buflen)
{
struct pwd *pwd;
int error;
vfs_smr_enter();
pwd = pwd_get_smr();
error = vn_fullpath_any_smr(pwd->pwd_cdir, pwd->pwd_rdir, buf, retbuf,
buflen, 0);
VFS_SMR_ASSERT_NOT_ENTERED();
if (error < 0) {
pwd = pwd_hold(curthread);
error = vn_fullpath_any(pwd->pwd_cdir, pwd->pwd_rdir, buf,
retbuf, buflen);
pwd_drop(pwd);
}
#ifdef KTRACE
if (KTRPOINT(curthread, KTR_NAMEI) && error == 0)
ktrnamei(*retbuf);
#endif
return (error);
}
static int
kern___realpathat(struct thread *td, int fd, const char *path, char *buf,
size_t size, int flags, enum uio_seg pathseg)
{
struct nameidata nd;
char *retbuf, *freebuf;
int error;
if (flags != 0)
return (EINVAL);
NDINIT_ATRIGHTS(&nd, LOOKUP, FOLLOW | SAVENAME | WANTPARENT | AUDITVNODE1,
pathseg, path, fd, &cap_fstat_rights, td);
if ((error = namei(&nd)) != 0)
return (error);
error = vn_fullpath_hardlink(&nd, &retbuf, &freebuf, &size);
if (error == 0) {
error = copyout(retbuf, buf, size);
free(freebuf, M_TEMP);
}
NDFREE(&nd, 0);
return (error);
}
int
sys___realpathat(struct thread *td, struct __realpathat_args *uap)
{
return (kern___realpathat(td, uap->fd, uap->path, uap->buf, uap->size,
uap->flags, UIO_USERSPACE));
}
/*
* Retrieve the full filesystem path that correspond to a vnode from the name
* cache (if available)
*/
int
vn_fullpath(struct vnode *vp, char **retbuf, char **freebuf)
{
struct pwd *pwd;
char *buf;
size_t buflen;
int error;
if (__predict_false(vp == NULL))
return (EINVAL);
buflen = MAXPATHLEN;
buf = malloc(buflen, M_TEMP, M_WAITOK);
vfs_smr_enter();
pwd = pwd_get_smr();
error = vn_fullpath_any_smr(vp, pwd->pwd_rdir, buf, retbuf, &buflen, 0);
VFS_SMR_ASSERT_NOT_ENTERED();
if (error < 0) {
pwd = pwd_hold(curthread);
error = vn_fullpath_any(vp, pwd->pwd_rdir, buf, retbuf, &buflen);
pwd_drop(pwd);
}
if (error == 0)
*freebuf = buf;
else
free(buf, M_TEMP);
return (error);
}
/*
* This function is similar to vn_fullpath, but it attempts to lookup the
* pathname relative to the global root mount point. This is required for the
* auditing sub-system, as audited pathnames must be absolute, relative to the
* global root mount point.
*/
int
vn_fullpath_global(struct vnode *vp, char **retbuf, char **freebuf)
{
char *buf;
size_t buflen;
int error;
if (__predict_false(vp == NULL))
return (EINVAL);
buflen = MAXPATHLEN;
buf = malloc(buflen, M_TEMP, M_WAITOK);
vfs_smr_enter();
error = vn_fullpath_any_smr(vp, rootvnode, buf, retbuf, &buflen, 0);
VFS_SMR_ASSERT_NOT_ENTERED();
if (error < 0) {
error = vn_fullpath_any(vp, rootvnode, buf, retbuf, &buflen);
}
if (error == 0)
*freebuf = buf;
else
free(buf, M_TEMP);
return (error);
}
static struct namecache *
vn_dd_from_dst(struct vnode *vp)
{
struct namecache *ncp;
cache_assert_vnode_locked(vp);
TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst) {
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
return (ncp);
}
return (NULL);
}
int
vn_vptocnp(struct vnode **vp, char *buf, size_t *buflen)
{
struct vnode *dvp;
struct namecache *ncp;
struct mtx *vlp;
int error;
vlp = VP2VNODELOCK(*vp);
mtx_lock(vlp);
ncp = (*vp)->v_cache_dd;
if (ncp != NULL && (ncp->nc_flag & NCF_ISDOTDOT) == 0) {
KASSERT(ncp == vn_dd_from_dst(*vp),
("%s: mismatch for dd entry (%p != %p)", __func__,
ncp, vn_dd_from_dst(*vp)));
} else {
ncp = vn_dd_from_dst(*vp);
}
if (ncp != NULL) {
if (*buflen < ncp->nc_nlen) {
mtx_unlock(vlp);
vrele(*vp);
counter_u64_add(numfullpathfail4, 1);
error = ENOMEM;
SDT_PROBE3(vfs, namecache, fullpath, return, error,
vp, NULL);
return (error);
}
*buflen -= ncp->nc_nlen;
memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen);
SDT_PROBE3(vfs, namecache, fullpath, hit, ncp->nc_dvp,
ncp->nc_name, vp);
dvp = *vp;
*vp = ncp->nc_dvp;
vref(*vp);
mtx_unlock(vlp);
vrele(dvp);
return (0);
}
SDT_PROBE1(vfs, namecache, fullpath, miss, vp);
mtx_unlock(vlp);
vn_lock(*vp, LK_SHARED | LK_RETRY);
error = VOP_VPTOCNP(*vp, &dvp, buf, buflen);
vput(*vp);
if (error) {
counter_u64_add(numfullpathfail2, 1);
SDT_PROBE3(vfs, namecache, fullpath, return, error, vp, NULL);
return (error);
}
*vp = dvp;
if (VN_IS_DOOMED(dvp)) {
/* forced unmount */
vrele(dvp);
error = ENOENT;
SDT_PROBE3(vfs, namecache, fullpath, return, error, vp, NULL);
return (error);
}
/*
* *vp has its use count incremented still.
*/
return (0);
}
/*
* Resolve a directory to a pathname.
*
* The name of the directory can always be found in the namecache or fetched
* from the filesystem. There is also guaranteed to be only one parent, meaning
* we can just follow vnodes up until we find the root.
*
* The vnode must be referenced.
*/
static int
vn_fullpath_dir(struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf,
size_t *len, size_t addend)
{
#ifdef KDTRACE_HOOKS
struct vnode *startvp = vp;
#endif
struct vnode *vp1;
size_t buflen;
int error;
bool slash_prefixed;
VNPASS(vp->v_type == VDIR || VN_IS_DOOMED(vp), vp);
VNPASS(vp->v_usecount > 0, vp);
buflen = *len;
slash_prefixed = true;
if (addend == 0) {
MPASS(*len >= 2);
buflen--;
buf[buflen] = '\0';
slash_prefixed = false;
}
error = 0;
SDT_PROBE1(vfs, namecache, fullpath, entry, vp);
counter_u64_add(numfullpathcalls, 1);
while (vp != rdir && vp != rootvnode) {
/*
* The vp vnode must be already fully constructed,
* since it is either found in namecache or obtained
* from VOP_VPTOCNP(). We may test for VV_ROOT safely
* without obtaining the vnode lock.
*/
if ((vp->v_vflag & VV_ROOT) != 0) {
vn_lock(vp, LK_RETRY | LK_SHARED);
/*
* With the vnode locked, check for races with
* unmount, forced or not. Note that we
* already verified that vp is not equal to
* the root vnode, which means that
* mnt_vnodecovered can be NULL only for the
* case of unmount.
*/
if (VN_IS_DOOMED(vp) ||
(vp1 = vp->v_mount->mnt_vnodecovered) == NULL ||
vp1->v_mountedhere != vp->v_mount) {
vput(vp);
error = ENOENT;
SDT_PROBE3(vfs, namecache, fullpath, return,
error, vp, NULL);
break;
}
vref(vp1);
vput(vp);
vp = vp1;
continue;
}
if (vp->v_type != VDIR) {
vrele(vp);
counter_u64_add(numfullpathfail1, 1);
error = ENOTDIR;
SDT_PROBE3(vfs, namecache, fullpath, return,
error, vp, NULL);
break;
}
error = vn_vptocnp(&vp, buf, &buflen);
if (error)
break;
if (buflen == 0) {
vrele(vp);
error = ENOMEM;
SDT_PROBE3(vfs, namecache, fullpath, return, error,
startvp, NULL);
break;
}
buf[--buflen] = '/';
slash_prefixed = true;
}
if (error)
return (error);
if (!slash_prefixed) {
if (buflen == 0) {
vrele(vp);
counter_u64_add(numfullpathfail4, 1);
SDT_PROBE3(vfs, namecache, fullpath, return, ENOMEM,
startvp, NULL);
return (ENOMEM);
}
buf[--buflen] = '/';
}
counter_u64_add(numfullpathfound, 1);
vrele(vp);
*retbuf = buf + buflen;
SDT_PROBE3(vfs, namecache, fullpath, return, 0, startvp, *retbuf);
*len -= buflen;
*len += addend;
return (0);
}
/*
* Resolve an arbitrary vnode to a pathname.
*
* Note 2 caveats:
* - hardlinks are not tracked, thus if the vnode is not a directory this can
* resolve to a different path than the one used to find it
* - namecache is not mandatory, meaning names are not guaranteed to be added
* (in which case resolving fails)
*/
static void __inline
cache_rev_failed_impl(int *reason, int line)
{
*reason = line;
}
#define cache_rev_failed(var) cache_rev_failed_impl((var), __LINE__)
static int
vn_fullpath_any_smr(struct vnode *vp, struct vnode *rdir, char *buf,
char **retbuf, size_t *buflen, size_t addend)
{
#ifdef KDTRACE_HOOKS
struct vnode *startvp = vp;
#endif
struct vnode *tvp;
struct mount *mp;
struct namecache *ncp;
size_t orig_buflen;
int reason;
int error;
#ifdef KDTRACE_HOOKS
int i;
#endif
seqc_t vp_seqc, tvp_seqc;
u_char nc_flag;
VFS_SMR_ASSERT_ENTERED();
if (!cache_fast_revlookup) {
vfs_smr_exit();
return (-1);
}
orig_buflen = *buflen;
if (addend == 0) {
MPASS(*buflen >= 2);
*buflen -= 1;
buf[*buflen] = '\0';
}
if (vp == rdir || vp == rootvnode) {
if (addend == 0) {
*buflen -= 1;
buf[*buflen] = '/';
}
goto out_ok;
}
#ifdef KDTRACE_HOOKS
i = 0;
#endif
error = -1;
ncp = NULL; /* for sdt probe down below */
vp_seqc = vn_seqc_read_any(vp);
if (seqc_in_modify(vp_seqc)) {
cache_rev_failed(&reason);
goto out_abort;
}
for (;;) {
#ifdef KDTRACE_HOOKS
i++;
#endif
if ((vp->v_vflag & VV_ROOT) != 0) {
mp = atomic_load_ptr(&vp->v_mount);
if (mp == NULL) {
cache_rev_failed(&reason);
goto out_abort;
}
tvp = atomic_load_ptr(&mp->mnt_vnodecovered);
tvp_seqc = vn_seqc_read_any(tvp);
if (seqc_in_modify(tvp_seqc)) {
cache_rev_failed(&reason);
goto out_abort;
}
if (!vn_seqc_consistent(vp, vp_seqc)) {
cache_rev_failed(&reason);
goto out_abort;
}
vp = tvp;
vp_seqc = tvp_seqc;
continue;
}
ncp = atomic_load_ptr(&vp->v_cache_dd);
if (ncp == NULL) {
cache_rev_failed(&reason);
goto out_abort;
}
nc_flag = atomic_load_char(&ncp->nc_flag);
if ((nc_flag & NCF_ISDOTDOT) != 0) {
cache_rev_failed(&reason);
goto out_abort;
}
if (!cache_ncp_canuse(ncp)) {
cache_rev_failed(&reason);
goto out_abort;
}
if (ncp->nc_nlen >= *buflen) {
cache_rev_failed(&reason);
error = ENOMEM;
goto out_abort;
}
*buflen -= ncp->nc_nlen;
memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen);
*buflen -= 1;
buf[*buflen] = '/';
tvp = ncp->nc_dvp;
tvp_seqc = vn_seqc_read_any(tvp);
if (seqc_in_modify(tvp_seqc)) {
cache_rev_failed(&reason);
goto out_abort;
}
if (!vn_seqc_consistent(vp, vp_seqc)) {
cache_rev_failed(&reason);
goto out_abort;
}
vp = tvp;
vp_seqc = tvp_seqc;
if (vp == rdir || vp == rootvnode)
break;
}
out_ok:
vfs_smr_exit();
*retbuf = buf + *buflen;
*buflen = orig_buflen - *buflen + addend;
SDT_PROBE2(vfs, namecache, fullpath_smr, hit, startvp, *retbuf);
return (0);
out_abort:
*buflen = orig_buflen;
SDT_PROBE4(vfs, namecache, fullpath_smr, miss, startvp, ncp, reason, i);
vfs_smr_exit();
return (error);
}
static int
vn_fullpath_any(struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf,
size_t *buflen)
{
size_t orig_buflen, addend;
int error;
if (*buflen < 2)
return (EINVAL);
orig_buflen = *buflen;
vref(vp);
addend = 0;
if (vp->v_type != VDIR) {
*buflen -= 1;
buf[*buflen] = '\0';
error = vn_vptocnp(&vp, buf, buflen);
if (error)
return (error);
if (*buflen == 0) {
vrele(vp);
return (ENOMEM);
}
*buflen -= 1;
buf[*buflen] = '/';
addend = orig_buflen - *buflen;
}
return (vn_fullpath_dir(vp, rdir, buf, retbuf, buflen, addend));
}
/*
* Resolve an arbitrary vnode to a pathname (taking care of hardlinks).
*
* Since the namecache does not track hardlinks, the caller is expected to first
* look up the target vnode with SAVENAME | WANTPARENT flags passed to namei.
*
* Then we have 2 cases:
* - if the found vnode is a directory, the path can be constructed just by
* following names up the chain
* - otherwise we populate the buffer with the saved name and start resolving
* from the parent
*/
static int
vn_fullpath_hardlink(struct nameidata *ndp, char **retbuf, char **freebuf,
size_t *buflen)
{
char *buf, *tmpbuf;
struct pwd *pwd;
struct componentname *cnp;
struct vnode *vp;
size_t addend;
int error;
enum vtype type;
if (*buflen < 2)
return (EINVAL);
if (*buflen > MAXPATHLEN)
*buflen = MAXPATHLEN;
buf = malloc(*buflen, M_TEMP, M_WAITOK);
addend = 0;
vp = ndp->ni_vp;
/*
* Check for VBAD to work around the vp_crossmp bug in lookup().
*
* For example consider tmpfs on /tmp and realpath /tmp. ni_vp will be
* set to mount point's root vnode while ni_dvp will be vp_crossmp.
* If the type is VDIR (like in this very case) we can skip looking
* at ni_dvp in the first place. However, since vnodes get passed here
* unlocked the target may transition to doomed state (type == VBAD)
* before we get to evaluate the condition. If this happens, we will
* populate part of the buffer and descend to vn_fullpath_dir with
* vp == vp_crossmp. Prevent the problem by checking for VBAD.
*
* This should be atomic_load(&vp->v_type) but it is illegal to take
* an address of a bit field, even if said field is sized to char.
* Work around the problem by reading the value into a full-sized enum
* and then re-reading it with atomic_load which will still prevent
* the compiler from re-reading down the road.
*/
type = vp->v_type;
type = atomic_load_int(&type);
if (type == VBAD) {
error = ENOENT;
goto out_bad;
}
if (type != VDIR) {
cnp = &ndp->ni_cnd;
addend = cnp->cn_namelen + 2;
if (*buflen < addend) {
error = ENOMEM;
goto out_bad;
}
*buflen -= addend;
tmpbuf = buf + *buflen;
tmpbuf[0] = '/';
memcpy(&tmpbuf[1], cnp->cn_nameptr, cnp->cn_namelen);
tmpbuf[addend - 1] = '\0';
vp = ndp->ni_dvp;
}
vfs_smr_enter();
pwd = pwd_get_smr();
error = vn_fullpath_any_smr(vp, pwd->pwd_rdir, buf, retbuf, buflen,
addend);
VFS_SMR_ASSERT_NOT_ENTERED();
if (error < 0) {
pwd = pwd_hold(curthread);
vref(vp);
error = vn_fullpath_dir(vp, pwd->pwd_rdir, buf, retbuf, buflen,
addend);
pwd_drop(pwd);
if (error != 0)
goto out_bad;
}
*freebuf = buf;
return (0);
out_bad:
free(buf, M_TEMP);
return (error);
}
struct vnode *
vn_dir_dd_ino(struct vnode *vp)
{
struct namecache *ncp;
struct vnode *ddvp;
struct mtx *vlp;
enum vgetstate vs;
ASSERT_VOP_LOCKED(vp, "vn_dir_dd_ino");
vlp = VP2VNODELOCK(vp);
mtx_lock(vlp);
TAILQ_FOREACH(ncp, &(vp->v_cache_dst), nc_dst) {
if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
continue;
ddvp = ncp->nc_dvp;
vs = vget_prep(ddvp);
mtx_unlock(vlp);
if (vget_finish(ddvp, LK_SHARED | LK_NOWAIT, vs))
return (NULL);
return (ddvp);
}
mtx_unlock(vlp);
return (NULL);
}
int
vn_commname(struct vnode *vp, char *buf, u_int buflen)
{
struct namecache *ncp;
struct mtx *vlp;
int l;
vlp = VP2VNODELOCK(vp);
mtx_lock(vlp);
TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
break;
if (ncp == NULL) {
mtx_unlock(vlp);
return (ENOENT);
}
l = min(ncp->nc_nlen, buflen - 1);
memcpy(buf, ncp->nc_name, l);
mtx_unlock(vlp);
buf[l] = '\0';
return (0);
}
/*
* This function updates path string to vnode's full global path
* and checks the size of the new path string against the pathlen argument.
*
* Requires a locked, referenced vnode.
* Vnode is re-locked on success or ENODEV, otherwise unlocked.
*
* If vp is a directory, the call to vn_fullpath_global() always succeeds
* because it falls back to the ".." lookup if the namecache lookup fails.
*/
int
vn_path_to_global_path(struct thread *td, struct vnode *vp, char *path,
u_int pathlen)
{
struct nameidata nd;
struct vnode *vp1;
char *rpath, *fbuf;
int error;
ASSERT_VOP_ELOCKED(vp, __func__);
/* Construct global filesystem path from vp. */
VOP_UNLOCK(vp);
error = vn_fullpath_global(vp, &rpath, &fbuf);
if (error != 0) {
vrele(vp);
return (error);
}
if (strlen(rpath) >= pathlen) {
vrele(vp);
error = ENAMETOOLONG;
goto out;
}
/*
* Re-lookup the vnode by path to detect a possible rename.
* As a side effect, the vnode is relocked.
* If vnode was renamed, return ENOENT.
*/
NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1,
UIO_SYSSPACE, path, td);
error = namei(&nd);
if (error != 0) {
vrele(vp);
goto out;
}
NDFREE(&nd, NDF_ONLY_PNBUF);
vp1 = nd.ni_vp;
vrele(vp);
if (vp1 == vp)
strcpy(path, rpath);
else {
vput(vp1);
error = ENOENT;
}
out:
free(fbuf, M_TEMP);
return (error);
}
#ifdef DDB
static void
db_print_vpath(struct vnode *vp)
{
while (vp != NULL) {
db_printf("%p: ", vp);
if (vp == rootvnode) {
db_printf("/");
vp = NULL;
} else {
if (vp->v_vflag & VV_ROOT) {
db_printf("<mount point>");
vp = vp->v_mount->mnt_vnodecovered;
} else {
struct namecache *ncp;
char *ncn;
int i;
ncp = TAILQ_FIRST(&vp->v_cache_dst);
if (ncp != NULL) {
ncn = ncp->nc_name;
for (i = 0; i < ncp->nc_nlen; i++)
db_printf("%c", *ncn++);
vp = ncp->nc_dvp;
} else {
vp = NULL;
}
}
}
db_printf("\n");
}
return;
}
DB_SHOW_COMMAND(vpath, db_show_vpath)
{
struct vnode *vp;
if (!have_addr) {
db_printf("usage: show vpath <struct vnode *>\n");
return;
}
vp = (struct vnode *)addr;
db_print_vpath(vp);
}
#endif
static bool __read_frequently cache_fast_lookup = true;
SYSCTL_BOOL(_vfs, OID_AUTO, cache_fast_lookup, CTLFLAG_RW,
&cache_fast_lookup, 0, "");
#define CACHE_FPL_FAILED -2020
static void
cache_fpl_cleanup_cnp(struct componentname *cnp)
{
uma_zfree(namei_zone, cnp->cn_pnbuf);
#ifdef DIAGNOSTIC
cnp->cn_pnbuf = NULL;
cnp->cn_nameptr = NULL;
#endif
}
static void
cache_fpl_handle_root(struct nameidata *ndp, struct vnode **dpp)
{
struct componentname *cnp;
cnp = &ndp->ni_cnd;
while (*(cnp->cn_nameptr) == '/') {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
}
*dpp = ndp->ni_rootdir;
}
/*
* Components of nameidata (or objects it can point to) which may
* need restoring in case fast path lookup fails.
*/
struct nameidata_saved {
long cn_namelen;
char *cn_nameptr;
size_t ni_pathlen;
int cn_flags;
};
struct cache_fpl {
struct nameidata *ndp;
struct componentname *cnp;
struct pwd *pwd;
struct vnode *dvp;
struct vnode *tvp;
seqc_t dvp_seqc;
seqc_t tvp_seqc;
struct nameidata_saved snd;
int line;
enum cache_fpl_status status:8;
bool in_smr;
bool fsearch;
};
static void
cache_fpl_checkpoint(struct cache_fpl *fpl, struct nameidata_saved *snd)
{
snd->cn_flags = fpl->ndp->ni_cnd.cn_flags;
snd->cn_namelen = fpl->ndp->ni_cnd.cn_namelen;
snd->cn_nameptr = fpl->ndp->ni_cnd.cn_nameptr;
snd->ni_pathlen = fpl->ndp->ni_pathlen;
}
static void
cache_fpl_restore_partial(struct cache_fpl *fpl, struct nameidata_saved *snd)
{
fpl->ndp->ni_cnd.cn_flags = snd->cn_flags;
fpl->ndp->ni_cnd.cn_namelen = snd->cn_namelen;
fpl->ndp->ni_cnd.cn_nameptr = snd->cn_nameptr;
fpl->ndp->ni_pathlen = snd->ni_pathlen;
}
static void
cache_fpl_restore_abort(struct cache_fpl *fpl, struct nameidata_saved *snd)
{
cache_fpl_restore_partial(fpl, snd);
/*
* It is 0 on entry by API contract.
*/
fpl->ndp->ni_resflags = 0;
}
#ifdef INVARIANTS
#define cache_fpl_smr_assert_entered(fpl) ({ \
struct cache_fpl *_fpl = (fpl); \
MPASS(_fpl->in_smr == true); \
VFS_SMR_ASSERT_ENTERED(); \
})
#define cache_fpl_smr_assert_not_entered(fpl) ({ \
struct cache_fpl *_fpl = (fpl); \
MPASS(_fpl->in_smr == false); \
VFS_SMR_ASSERT_NOT_ENTERED(); \
})
#else
#define cache_fpl_smr_assert_entered(fpl) do { } while (0)
#define cache_fpl_smr_assert_not_entered(fpl) do { } while (0)
#endif
#define cache_fpl_smr_enter_initial(fpl) ({ \
struct cache_fpl *_fpl = (fpl); \
vfs_smr_enter(); \
_fpl->in_smr = true; \
})
#define cache_fpl_smr_enter(fpl) ({ \
struct cache_fpl *_fpl = (fpl); \
MPASS(_fpl->in_smr == false); \
vfs_smr_enter(); \
_fpl->in_smr = true; \
})
#define cache_fpl_smr_exit(fpl) ({ \
struct cache_fpl *_fpl = (fpl); \
MPASS(_fpl->in_smr == true); \
vfs_smr_exit(); \
_fpl->in_smr = false; \
})
static int
cache_fpl_aborted_impl(struct cache_fpl *fpl, int line)
{
if (fpl->status != CACHE_FPL_STATUS_UNSET) {
KASSERT(fpl->status == CACHE_FPL_STATUS_PARTIAL,
("%s: converting to abort from %d at %d, set at %d\n",
__func__, fpl->status, line, fpl->line));
}
fpl->status = CACHE_FPL_STATUS_ABORTED;
fpl->line = line;
return (CACHE_FPL_FAILED);
}
#define cache_fpl_aborted(x) cache_fpl_aborted_impl((x), __LINE__)
static int
cache_fpl_partial_impl(struct cache_fpl *fpl, int line)
{
KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
("%s: setting to partial at %d, but already set to %d at %d\n",
__func__, line, fpl->status, fpl->line));
cache_fpl_smr_assert_entered(fpl);
fpl->status = CACHE_FPL_STATUS_PARTIAL;
fpl->line = line;
return (CACHE_FPL_FAILED);
}
#define cache_fpl_partial(x) cache_fpl_partial_impl((x), __LINE__)
static int
cache_fpl_handled_impl(struct cache_fpl *fpl, int error, int line)
{
KASSERT(fpl->status == CACHE_FPL_STATUS_UNSET,
("%s: setting to handled at %d, but already set to %d at %d\n",
__func__, line, fpl->status, fpl->line));
cache_fpl_smr_assert_not_entered(fpl);
MPASS(error != CACHE_FPL_FAILED);
fpl->status = CACHE_FPL_STATUS_HANDLED;
fpl->line = line;
return (error);
}
#define cache_fpl_handled(x, e) cache_fpl_handled_impl((x), (e), __LINE__)
#define CACHE_FPL_SUPPORTED_CN_FLAGS \
(NC_NOMAKEENTRY | NC_KEEPPOSENTRY | LOCKLEAF | LOCKPARENT | WANTPARENT | \
FOLLOW | LOCKSHARED | SAVENAME | SAVESTART | WILLBEDIR | ISOPEN | \
NOMACCHECK | AUDITVNODE1 | AUDITVNODE2 | NOCAPCHECK)
#define CACHE_FPL_INTERNAL_CN_FLAGS \
(ISDOTDOT | MAKEENTRY | ISLASTCN)
_Static_assert((CACHE_FPL_SUPPORTED_CN_FLAGS & CACHE_FPL_INTERNAL_CN_FLAGS) == 0,
"supported and internal flags overlap");
static bool
cache_fpl_islastcn(struct nameidata *ndp)
{
return (*ndp->ni_next == 0);
}
static bool
cache_fpl_isdotdot(struct componentname *cnp)
{
if (cnp->cn_namelen == 2 &&
cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
return (true);
return (false);
}
static bool
cache_can_fplookup(struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
struct thread *td;
ndp = fpl->ndp;
cnp = fpl->cnp;
td = cnp->cn_thread;
if (!cache_fast_lookup) {
cache_fpl_aborted(fpl);
return (false);
}
#ifdef MAC
if (mac_vnode_check_lookup_enabled()) {
cache_fpl_aborted(fpl);
return (false);
}
#endif
if ((cnp->cn_flags & ~CACHE_FPL_SUPPORTED_CN_FLAGS) != 0) {
cache_fpl_aborted(fpl);
return (false);
}
if (IN_CAPABILITY_MODE(td)) {
cache_fpl_aborted(fpl);
return (false);
}
if (AUDITING_TD(td)) {
cache_fpl_aborted(fpl);
return (false);
}
if (ndp->ni_startdir != NULL) {
cache_fpl_aborted(fpl);
return (false);
}
return (true);
}
static int
cache_fplookup_dirfd(struct cache_fpl *fpl, struct vnode **vpp)
{
struct nameidata *ndp;
int error;
bool fsearch;
ndp = fpl->ndp;
error = fgetvp_lookup_smr(ndp->ni_dirfd, ndp, vpp, &fsearch);
if (__predict_false(error != 0)) {
cache_fpl_smr_exit(fpl);
return (cache_fpl_aborted(fpl));
}
fpl->fsearch = fsearch;
return (0);
}
static bool
cache_fplookup_vnode_supported(struct vnode *vp)
{
return (vp->v_type != VLNK);
}
static int __noinline
cache_fplookup_negative_promote(struct cache_fpl *fpl, struct namecache *oncp,
uint32_t hash)
{
struct componentname *cnp;
struct vnode *dvp;
cnp = fpl->cnp;
dvp = fpl->dvp;
cache_fpl_smr_exit(fpl);
if (cache_neg_promote_cond(dvp, cnp, oncp, hash))
return (cache_fpl_handled(fpl, ENOENT));
else
return (cache_fpl_aborted(fpl));
}
/*
* The target vnode is not supported, prepare for the slow path to take over.
*/
static int __noinline
cache_fplookup_partial_setup(struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
enum vgetstate dvs;
struct vnode *dvp;
struct pwd *pwd;
seqc_t dvp_seqc;
ndp = fpl->ndp;
cnp = fpl->cnp;
pwd = fpl->pwd;
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
if (!pwd_hold_smr(pwd)) {
cache_fpl_smr_exit(fpl);
return (cache_fpl_aborted(fpl));
}
dvs = vget_prep_smr(dvp);
cache_fpl_smr_exit(fpl);
if (__predict_false(dvs == VGET_NONE)) {
pwd_drop(pwd);
return (cache_fpl_aborted(fpl));
}
vget_finish_ref(dvp, dvs);
if (!vn_seqc_consistent(dvp, dvp_seqc)) {
vrele(dvp);
pwd_drop(pwd);
return (cache_fpl_aborted(fpl));
}
cache_fpl_restore_partial(fpl, &fpl->snd);
ndp->ni_startdir = dvp;
cnp->cn_flags |= MAKEENTRY;
if (cache_fpl_islastcn(ndp))
cnp->cn_flags |= ISLASTCN;
if (cache_fpl_isdotdot(cnp))
cnp->cn_flags |= ISDOTDOT;
return (0);
}
static int
cache_fplookup_final_child(struct cache_fpl *fpl, enum vgetstate tvs)
{
struct componentname *cnp;
struct vnode *tvp;
seqc_t tvp_seqc;
int error, lkflags;
cnp = fpl->cnp;
tvp = fpl->tvp;
tvp_seqc = fpl->tvp_seqc;
if ((cnp->cn_flags & LOCKLEAF) != 0) {
lkflags = LK_SHARED;
if ((cnp->cn_flags & LOCKSHARED) == 0)
lkflags = LK_EXCLUSIVE;
error = vget_finish(tvp, lkflags, tvs);
if (__predict_false(error != 0)) {
return (cache_fpl_aborted(fpl));
}
} else {
vget_finish_ref(tvp, tvs);
}
if (!vn_seqc_consistent(tvp, tvp_seqc)) {
if ((cnp->cn_flags & LOCKLEAF) != 0)
vput(tvp);
else
vrele(tvp);
return (cache_fpl_aborted(fpl));
}
return (cache_fpl_handled(fpl, 0));
}
/*
* They want to possibly modify the state of the namecache.
*
* Don't try to match the API contract, just leave.
* TODO: this leaves scalability on the table
*/
static int
cache_fplookup_final_modifying(struct cache_fpl *fpl)
{
struct componentname *cnp;
cnp = fpl->cnp;
MPASS(cnp->cn_nameiop != LOOKUP);
return (cache_fpl_partial(fpl));
}
static int __noinline
cache_fplookup_final_withparent(struct cache_fpl *fpl)
{
struct componentname *cnp;
enum vgetstate dvs, tvs;
struct vnode *dvp, *tvp;
seqc_t dvp_seqc;
int error;
cnp = fpl->cnp;
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
tvp = fpl->tvp;
MPASS((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0);
/*
* This is less efficient than it can be for simplicity.
*/
dvs = vget_prep_smr(dvp);
if (__predict_false(dvs == VGET_NONE)) {
return (cache_fpl_aborted(fpl));
}
tvs = vget_prep_smr(tvp);
if (__predict_false(tvs == VGET_NONE)) {
cache_fpl_smr_exit(fpl);
vget_abort(dvp, dvs);
return (cache_fpl_aborted(fpl));
}
cache_fpl_smr_exit(fpl);
if ((cnp->cn_flags & LOCKPARENT) != 0) {
error = vget_finish(dvp, LK_EXCLUSIVE, dvs);
if (__predict_false(error != 0)) {
vget_abort(tvp, tvs);
return (cache_fpl_aborted(fpl));
}
} else {
vget_finish_ref(dvp, dvs);
}
if (!vn_seqc_consistent(dvp, dvp_seqc)) {
vget_abort(tvp, tvs);
if ((cnp->cn_flags & LOCKPARENT) != 0)
vput(dvp);
else
vrele(dvp);
return (cache_fpl_aborted(fpl));
}
error = cache_fplookup_final_child(fpl, tvs);
if (__predict_false(error != 0)) {
MPASS(fpl->status == CACHE_FPL_STATUS_ABORTED);
if ((cnp->cn_flags & LOCKPARENT) != 0)
vput(dvp);
else
vrele(dvp);
return (error);
}
MPASS(fpl->status == CACHE_FPL_STATUS_HANDLED);
return (0);
}
static int
cache_fplookup_final(struct cache_fpl *fpl)
{
struct componentname *cnp;
enum vgetstate tvs;
struct vnode *dvp, *tvp;
seqc_t dvp_seqc;
cnp = fpl->cnp;
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
tvp = fpl->tvp;
VNPASS(cache_fplookup_vnode_supported(dvp), dvp);
if (cnp->cn_nameiop != LOOKUP) {
return (cache_fplookup_final_modifying(fpl));
}
if ((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0)
return (cache_fplookup_final_withparent(fpl));
tvs = vget_prep_smr(tvp);
if (__predict_false(tvs == VGET_NONE)) {
return (cache_fpl_partial(fpl));
}
if (!vn_seqc_consistent(dvp, dvp_seqc)) {
cache_fpl_smr_exit(fpl);
vget_abort(tvp, tvs);
return (cache_fpl_aborted(fpl));
}
cache_fpl_smr_exit(fpl);
return (cache_fplookup_final_child(fpl, tvs));
}
static int __noinline
cache_fplookup_dot(struct cache_fpl *fpl)
{
struct vnode *dvp;
dvp = fpl->dvp;
fpl->tvp = dvp;
fpl->tvp_seqc = vn_seqc_read_any(dvp);
if (seqc_in_modify(fpl->tvp_seqc)) {
return (cache_fpl_aborted(fpl));
}
counter_u64_add(dothits, 1);
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ".", dvp);
return (0);
}
static int __noinline
cache_fplookup_dotdot(struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
struct namecache *ncp;
struct vnode *dvp;
struct prison *pr;
u_char nc_flag;
ndp = fpl->ndp;
cnp = fpl->cnp;
dvp = fpl->dvp;
/*
* XXX this is racy the same way regular lookup is
*/
for (pr = cnp->cn_cred->cr_prison; pr != NULL;
pr = pr->pr_parent)
if (dvp == pr->pr_root)
break;
if (dvp == ndp->ni_rootdir ||
dvp == ndp->ni_topdir ||
dvp == rootvnode ||
pr != NULL) {
fpl->tvp = dvp;
fpl->tvp_seqc = vn_seqc_read_any(dvp);
if (seqc_in_modify(fpl->tvp_seqc)) {
return (cache_fpl_aborted(fpl));
}
return (0);
}
if ((dvp->v_vflag & VV_ROOT) != 0) {
/*
* TODO
* The opposite of climb mount is needed here.
*/
return (cache_fpl_aborted(fpl));
}
ncp = atomic_load_ptr(&dvp->v_cache_dd);
if (ncp == NULL) {
return (cache_fpl_aborted(fpl));
}
nc_flag = atomic_load_char(&ncp->nc_flag);
if ((nc_flag & NCF_ISDOTDOT) != 0) {
if ((nc_flag & NCF_NEGATIVE) != 0)
return (cache_fpl_aborted(fpl));
fpl->tvp = ncp->nc_vp;
} else {
fpl->tvp = ncp->nc_dvp;
}
if (!cache_ncp_canuse(ncp)) {
return (cache_fpl_aborted(fpl));
}
fpl->tvp_seqc = vn_seqc_read_any(fpl->tvp);
if (seqc_in_modify(fpl->tvp_seqc)) {
return (cache_fpl_partial(fpl));
}
counter_u64_add(dotdothits, 1);
return (0);
}
static int __noinline
cache_fplookup_neg(struct cache_fpl *fpl, struct namecache *ncp, uint32_t hash)
{
u_char nc_flag;
bool neg_promote;
nc_flag = atomic_load_char(&ncp->nc_flag);
MPASS((nc_flag & NCF_NEGATIVE) != 0);
/*
* If they want to create an entry we need to replace this one.
*/
if (__predict_false(fpl->cnp->cn_nameiop != LOOKUP)) {
/*
* TODO
* This should call something similar to
* cache_fplookup_final_modifying.
*/
return (cache_fpl_partial(fpl));
}
neg_promote = cache_neg_hit_prep(ncp);
if (!cache_ncp_canuse(ncp)) {
cache_neg_hit_abort(ncp);
return (cache_fpl_partial(fpl));
}
if (__predict_false((nc_flag & NCF_WHITE) != 0)) {
cache_neg_hit_abort(ncp);
return (cache_fpl_partial(fpl));
}
if (neg_promote) {
return (cache_fplookup_negative_promote(fpl, ncp, hash));
}
cache_neg_hit_finish(ncp);
cache_fpl_smr_exit(fpl);
return (cache_fpl_handled(fpl, ENOENT));
}
static int
cache_fplookup_next(struct cache_fpl *fpl)
{
struct componentname *cnp;
struct namecache *ncp;
struct vnode *dvp, *tvp;
u_char nc_flag;
uint32_t hash;
cnp = fpl->cnp;
dvp = fpl->dvp;
if (__predict_false(cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.')) {
return (cache_fplookup_dot(fpl));
}
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
CK_SLIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
!bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
break;
}
/*
* If there is no entry we have to punt to the slow path to perform
* actual lookup. Should there be nothing with this name a negative
* entry will be created.
*/
if (__predict_false(ncp == NULL)) {
return (cache_fpl_partial(fpl));
}
tvp = atomic_load_ptr(&ncp->nc_vp);
nc_flag = atomic_load_char(&ncp->nc_flag);
if ((nc_flag & NCF_NEGATIVE) != 0) {
return (cache_fplookup_neg(fpl, ncp, hash));
}
if (!cache_ncp_canuse(ncp)) {
return (cache_fpl_partial(fpl));
}
fpl->tvp = tvp;
fpl->tvp_seqc = vn_seqc_read_any(tvp);
if (seqc_in_modify(fpl->tvp_seqc)) {
return (cache_fpl_partial(fpl));
}
if (!cache_fplookup_vnode_supported(tvp)) {
return (cache_fpl_partial(fpl));
}
counter_u64_add(numposhits, 1);
SDT_PROBE3(vfs, namecache, lookup, hit, dvp, ncp->nc_name, tvp);
return (0);
}
static bool
cache_fplookup_mp_supported(struct mount *mp)
{
if (mp == NULL)
return (false);
if ((mp->mnt_kern_flag & MNTK_FPLOOKUP) == 0)
return (false);
return (true);
}
/*
* Walk up the mount stack (if any).
*
* Correctness is provided in the following ways:
* - all vnodes are protected from freeing with SMR
* - struct mount objects are type stable making them always safe to access
* - stability of the particular mount is provided by busying it
* - relationship between the vnode which is mounted on and the mount is
* verified with the vnode sequence counter after busying
* - association between root vnode of the mount and the mount is protected
* by busy
*
* From that point on we can read the sequence counter of the root vnode
* and get the next mount on the stack (if any) using the same protection.
*
* By the end of successful walk we are guaranteed the reached state was
* indeed present at least at some point which matches the regular lookup.
*/
static int __noinline
cache_fplookup_climb_mount(struct cache_fpl *fpl)
{
struct mount *mp, *prev_mp;
struct vnode *vp;
seqc_t vp_seqc;
vp = fpl->tvp;
vp_seqc = fpl->tvp_seqc;
VNPASS(vp->v_type == VDIR || vp->v_type == VBAD, vp);
mp = atomic_load_ptr(&vp->v_mountedhere);
if (mp == NULL)
return (0);
prev_mp = NULL;
for (;;) {
if (!vfs_op_thread_enter_crit(mp)) {
if (prev_mp != NULL)
vfs_op_thread_exit_crit(prev_mp);
return (cache_fpl_partial(fpl));
}
if (prev_mp != NULL)
vfs_op_thread_exit_crit(prev_mp);
if (!vn_seqc_consistent(vp, vp_seqc)) {
vfs_op_thread_exit_crit(mp);
return (cache_fpl_partial(fpl));
}
if (!cache_fplookup_mp_supported(mp)) {
vfs_op_thread_exit_crit(mp);
return (cache_fpl_partial(fpl));
}
vp = atomic_load_ptr(&mp->mnt_rootvnode);
if (vp == NULL || VN_IS_DOOMED(vp)) {
vfs_op_thread_exit_crit(mp);
return (cache_fpl_partial(fpl));
}
vp_seqc = vn_seqc_read_any(vp);
if (seqc_in_modify(vp_seqc)) {
vfs_op_thread_exit_crit(mp);
return (cache_fpl_partial(fpl));
}
prev_mp = mp;
mp = atomic_load_ptr(&vp->v_mountedhere);
if (mp == NULL)
break;
}
vfs_op_thread_exit_crit(prev_mp);
fpl->tvp = vp;
fpl->tvp_seqc = vp_seqc;
return (0);
}
static bool
cache_fplookup_need_climb_mount(struct cache_fpl *fpl)
{
struct mount *mp;
struct vnode *vp;
vp = fpl->tvp;
/*
* Hack: while this is a union, the pointer tends to be NULL so save on
* a branch.
*/
mp = atomic_load_ptr(&vp->v_mountedhere);
if (mp == NULL)
return (false);
if (vp->v_type == VDIR)
return (true);
return (false);
}
/*
* Parse the path.
*
* The code was originally copy-pasted from regular lookup and despite
* clean ups leaves performance on the table. Any modifications here
* must take into account that in case off fallback the resulting
* nameidata state has to be compatible with the original.
*/
static int
cache_fplookup_parse(struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
char *cp;
ndp = fpl->ndp;
cnp = fpl->cnp;
/*
* Search a new directory.
*
* The last component of the filename is left accessible via
* cnp->cn_nameptr for callers that need the name. Callers needing
* the name set the SAVENAME flag. When done, they assume
* responsibility for freeing the pathname buffer.
*/
for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
continue;
cnp->cn_namelen = cp - cnp->cn_nameptr;
if (__predict_false(cnp->cn_namelen > NAME_MAX)) {
cache_fpl_smr_exit(fpl);
return (cache_fpl_handled(fpl, ENAMETOOLONG));
}
ndp->ni_pathlen -= cnp->cn_namelen;
KASSERT(ndp->ni_pathlen <= PATH_MAX,
("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen));
ndp->ni_next = cp;
/*
* Replace multiple slashes by a single slash and trailing slashes
* by a null. This must be done before VOP_LOOKUP() because some
* fs's don't know about trailing slashes. Remember if there were
* trailing slashes to handle symlinks, existing non-directories
* and non-existing files that won't be directories specially later.
*/
while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
cp++;
ndp->ni_pathlen--;
if (*cp == '\0') {
/*
* TODO
* Regular lookup performs the following:
* *ndp->ni_next = '\0';
* cnp->cn_flags |= TRAILINGSLASH;
*
* Which is problematic since it modifies data read
* from userspace. Then if fast path lookup was to
* abort we would have to either restore it or convey
* the flag. Since this is a corner case just ignore
* it for simplicity.
*/
return (cache_fpl_partial(fpl));
}
}
ndp->ni_next = cp;
/*
* Check for degenerate name (e.g. / or "")
* which is a way of talking about a directory,
* e.g. like "/." or ".".
*
* TODO
* Another corner case handled by the regular lookup
*/
if (__predict_false(cnp->cn_nameptr[0] == '\0')) {
return (cache_fpl_partial(fpl));
}
return (0);
}
static void
cache_fplookup_parse_advance(struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
ndp = fpl->ndp;
cnp = fpl->cnp;
cnp->cn_nameptr = ndp->ni_next;
while (*cnp->cn_nameptr == '/') {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
}
}
/*
* See the API contract for VOP_FPLOOKUP_VEXEC.
*/
static int __noinline
cache_fplookup_failed_vexec(struct cache_fpl *fpl, int error)
{
struct vnode *dvp;
seqc_t dvp_seqc;
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
/*
* Hack: they may be looking up foo/bar, where foo is a
* regular file. In such a case we need to turn ENOTDIR,
* but we may happen to get here with a different error.
*/
if (dvp->v_type != VDIR) {
/*
* The check here is predominantly to catch
* EOPNOTSUPP from dead_vnodeops. If the vnode
* gets doomed past this point it is going to
* fail seqc verification.
*/
if (VN_IS_DOOMED(dvp)) {
return (cache_fpl_aborted(fpl));
}
error = ENOTDIR;
}
/*
* Hack: handle O_SEARCH.
*
* Open Group Base Specifications Issue 7, 2018 edition states:
* If the access mode of the open file description associated with the
* file descriptor is not O_SEARCH, the function shall check whether
* directory searches are permitted using the current permissions of
* the directory underlying the file descriptor. If the access mode is
* O_SEARCH, the function shall not perform the check.
*
* Regular lookup tests for the NOEXECCHECK flag for every path
* component to decide whether to do the permission check. However,
* since most lookups never have the flag (and when they do it is only
* present for the first path component), lockless lookup only acts on
* it if there is a permission problem. Here the flag is represented
* with a boolean so that we don't have to clear it on the way out.
*
* For simplicity this always aborts.
* TODO: check if this is the first lookup and ignore the permission
* problem. Note the flag has to survive fallback (if it happens to be
* performed).
*/
if (fpl->fsearch) {
return (cache_fpl_aborted(fpl));
}
switch (error) {
case EAGAIN:
if (!vn_seqc_consistent(dvp, dvp_seqc)) {
error = cache_fpl_aborted(fpl);
} else {
cache_fpl_partial(fpl);
}
break;
default:
if (!vn_seqc_consistent(dvp, dvp_seqc)) {
error = cache_fpl_aborted(fpl);
} else {
cache_fpl_smr_exit(fpl);
cache_fpl_handled(fpl, error);
}
break;
}
return (error);
}
static int
cache_fplookup_impl(struct vnode *dvp, struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
struct mount *mp;
int error;
error = CACHE_FPL_FAILED;
ndp = fpl->ndp;
cnp = fpl->cnp;
cache_fpl_checkpoint(fpl, &fpl->snd);
fpl->dvp = dvp;
fpl->dvp_seqc = vn_seqc_read_any(fpl->dvp);
if (seqc_in_modify(fpl->dvp_seqc)) {
cache_fpl_aborted(fpl);
goto out;
}
mp = atomic_load_ptr(&fpl->dvp->v_mount);
if (!cache_fplookup_mp_supported(mp)) {
cache_fpl_aborted(fpl);
goto out;
}
VNPASS(cache_fplookup_vnode_supported(fpl->dvp), fpl->dvp);
for (;;) {
error = cache_fplookup_parse(fpl);
if (__predict_false(error != 0)) {
break;
}
VNPASS(cache_fplookup_vnode_supported(fpl->dvp), fpl->dvp);
error = VOP_FPLOOKUP_VEXEC(fpl->dvp, cnp->cn_cred);
if (__predict_false(error != 0)) {
error = cache_fplookup_failed_vexec(fpl, error);
break;
}
if (__predict_false(cache_fpl_isdotdot(cnp))) {
error = cache_fplookup_dotdot(fpl);
if (__predict_false(error != 0)) {
break;
}
} else {
error = cache_fplookup_next(fpl);
if (__predict_false(error != 0)) {
break;
}
VNPASS(!seqc_in_modify(fpl->tvp_seqc), fpl->tvp);
if (cache_fplookup_need_climb_mount(fpl)) {
error = cache_fplookup_climb_mount(fpl);
if (__predict_false(error != 0)) {
break;
}
}
}
VNPASS(!seqc_in_modify(fpl->tvp_seqc), fpl->tvp);
if (cache_fpl_islastcn(ndp)) {
error = cache_fplookup_final(fpl);
break;
}
if (!vn_seqc_consistent(fpl->dvp, fpl->dvp_seqc)) {
error = cache_fpl_aborted(fpl);
break;
}
fpl->dvp = fpl->tvp;
fpl->dvp_seqc = fpl->tvp_seqc;
cache_fplookup_parse_advance(fpl);
cache_fpl_checkpoint(fpl, &fpl->snd);
}
out:
switch (fpl->status) {
case CACHE_FPL_STATUS_UNSET:
__assert_unreachable();
break;
case CACHE_FPL_STATUS_PARTIAL:
cache_fpl_smr_assert_entered(fpl);
return (cache_fplookup_partial_setup(fpl));
case CACHE_FPL_STATUS_ABORTED:
if (fpl->in_smr)
cache_fpl_smr_exit(fpl);
return (CACHE_FPL_FAILED);
case CACHE_FPL_STATUS_HANDLED:
MPASS(error != CACHE_FPL_FAILED);
cache_fpl_smr_assert_not_entered(fpl);
if (__predict_false(error != 0)) {
ndp->ni_dvp = NULL;
ndp->ni_vp = NULL;
cache_fpl_cleanup_cnp(cnp);
return (error);
}
ndp->ni_dvp = fpl->dvp;
ndp->ni_vp = fpl->tvp;
if (cnp->cn_flags & SAVENAME)
cnp->cn_flags |= HASBUF;
else
cache_fpl_cleanup_cnp(cnp);
return (error);
}
}
/*
* Fast path lookup protected with SMR and sequence counters.
*
* Note: all VOP_FPLOOKUP_VEXEC routines have a comment referencing this one.
*
* Filesystems can opt in by setting the MNTK_FPLOOKUP flag and meeting criteria
* outlined below.
*
* Traditional vnode lookup conceptually looks like this:
*
* vn_lock(current);
* for (;;) {
* next = find();
* vn_lock(next);
* vn_unlock(current);
* current = next;
* if (last)
* break;
* }
* return (current);
*
* Each jump to the next vnode is safe memory-wise and atomic with respect to
* any modifications thanks to holding respective locks.
*
* The same guarantee can be provided with a combination of safe memory
* reclamation and sequence counters instead. If all operations which affect
* the relationship between the current vnode and the one we are looking for
* also modify the counter, we can verify whether all the conditions held as
* we made the jump. This includes things like permissions, mount points etc.
* Counter modification is provided by enclosing relevant places in
* vn_seqc_write_begin()/end() calls.
*
* Thus this translates to:
*
* vfs_smr_enter();
* dvp_seqc = seqc_read_any(dvp);
* if (seqc_in_modify(dvp_seqc)) // someone is altering the vnode
* abort();
* for (;;) {
* tvp = find();
* tvp_seqc = seqc_read_any(tvp);
* if (seqc_in_modify(tvp_seqc)) // someone is altering the target vnode
* abort();
* if (!seqc_consistent(dvp, dvp_seqc) // someone is altering the vnode
* abort();
* dvp = tvp; // we know nothing of importance has changed
* dvp_seqc = tvp_seqc; // store the counter for the tvp iteration
* if (last)
* break;
* }
* vget(); // secure the vnode
* if (!seqc_consistent(tvp, tvp_seqc) // final check
* abort();
* // at this point we know nothing has changed for any parent<->child pair
* // as they were crossed during the lookup, meaning we matched the guarantee
* // of the locked variant
* return (tvp);
*
* The API contract for VOP_FPLOOKUP_VEXEC routines is as follows:
* - they are called while within vfs_smr protection which they must never exit
* - EAGAIN can be returned to denote checking could not be performed, it is
* always valid to return it
* - if the sequence counter has not changed the result must be valid
* - if the sequence counter has changed both false positives and false negatives
* are permitted (since the result will be rejected later)
* - for simple cases of unix permission checks vaccess_vexec_smr can be used
*
* Caveats to watch out for:
* - vnodes are passed unlocked and unreferenced with nothing stopping
* VOP_RECLAIM, in turn meaning that ->v_data can become NULL. It is advised
* to use atomic_load_ptr to fetch it.
* - the aforementioned object can also get freed, meaning absent other means it
* should be protected with vfs_smr
* - either safely checking permissions as they are modified or guaranteeing
* their stability is left to the routine
*/
int
cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status,
struct pwd **pwdp)
{
struct cache_fpl fpl;
struct pwd *pwd;
struct vnode *dvp;
struct componentname *cnp;
struct nameidata_saved orig;
int error;
MPASS(ndp->ni_lcf == 0);
fpl.status = CACHE_FPL_STATUS_UNSET;
fpl.ndp = ndp;
fpl.cnp = &ndp->ni_cnd;
MPASS(curthread == fpl.cnp->cn_thread);
if ((fpl.cnp->cn_flags & SAVESTART) != 0)
MPASS(fpl.cnp->cn_nameiop != LOOKUP);
if (!cache_can_fplookup(&fpl)) {
SDT_PROBE3(vfs, fplookup, lookup, done, ndp, fpl.line, fpl.status);
*status = fpl.status;
return (EOPNOTSUPP);
}
cache_fpl_checkpoint(&fpl, &orig);
cache_fpl_smr_enter_initial(&fpl);
fpl.fsearch = false;
pwd = pwd_get_smr();
fpl.pwd = pwd;
ndp->ni_rootdir = pwd->pwd_rdir;
ndp->ni_topdir = pwd->pwd_jdir;
cnp = fpl.cnp;
cnp->cn_nameptr = cnp->cn_pnbuf;
if (cnp->cn_pnbuf[0] == '/') {
cache_fpl_handle_root(ndp, &dvp);
ndp->ni_resflags |= NIRES_ABS;
} else {
if (ndp->ni_dirfd == AT_FDCWD) {
dvp = pwd->pwd_cdir;
} else {
error = cache_fplookup_dirfd(&fpl, &dvp);
if (__predict_false(error != 0)) {
goto out;
}
}
}
SDT_PROBE4(vfs, namei, lookup, entry, dvp, cnp->cn_pnbuf, cnp->cn_flags, true);
error = cache_fplookup_impl(dvp, &fpl);
out:
cache_fpl_smr_assert_not_entered(&fpl);
SDT_PROBE3(vfs, fplookup, lookup, done, ndp, fpl.line, fpl.status);
*status = fpl.status;
switch (fpl.status) {
case CACHE_FPL_STATUS_UNSET:
__assert_unreachable();
break;
case CACHE_FPL_STATUS_HANDLED:
SDT_PROBE3(vfs, namei, lookup, return, error,
(error == 0 ? ndp->ni_vp : NULL), true);
break;
case CACHE_FPL_STATUS_PARTIAL:
*pwdp = fpl.pwd;
/*
* Status restored by cache_fplookup_partial_setup.
*/
break;
case CACHE_FPL_STATUS_ABORTED:
cache_fpl_restore_abort(&fpl, &orig);
break;
}
return (error);
}
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