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8837b0dd09
freebsd-skq/sys/kern/kern_lockf.c
Doug Rabson 06c85cef9d When blocking on an F_FLOCK style lock request which is upgrading a 
shared lock to exclusive, drop the shared lock before deadlock
detection.

MFC after: 2 days
2008-05-09 10:34:23 +00:00

2418 lines
61 KiB
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/*-
* Copyright (c) 2008 Isilon Inc http://www.isilon.com/
* Authors: Doug Rabson <dfr@rabson.org>
* Developed with Red Inc: Alfred Perlstein <alfred@freebsd.org>
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*/
/*-
* Copyright (c) 1982, 1986, 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Scooter Morris at Genentech Inc.
*
* 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.
* 4. 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.
*
* @(#)ufs_lockf.c 8.3 (Berkeley) 1/6/94
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_debug_lockf.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/hash.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sx.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <sys/lockf.h>
#include <sys/taskqueue.h>
#ifdef LOCKF_DEBUG
#include <sys/sysctl.h>
#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>
static int lockf_debug = 0; /* control debug output */
SYSCTL_INT(_debug, OID_AUTO, lockf_debug, CTLFLAG_RW, &lockf_debug, 0, "");
#endif
MALLOC_DEFINE(M_LOCKF, "lockf", "Byte-range locking structures");
struct owner_edge;
struct owner_vertex;
struct owner_vertex_list;
struct owner_graph;
#define NOLOCKF (struct lockf_entry *)0
#define SELF 0x1
#define OTHERS 0x2
static void lf_init(void *);
static int lf_hash_owner(caddr_t, struct flock *, int);
static int lf_owner_matches(struct lock_owner *, caddr_t, struct flock *,
int);
static struct lockf_entry *
lf_alloc_lock(struct lock_owner *);
static void lf_free_lock(struct lockf_entry *);
static int lf_clearlock(struct lockf *, struct lockf_entry *);
static int lf_overlaps(struct lockf_entry *, struct lockf_entry *);
static int lf_blocks(struct lockf_entry *, struct lockf_entry *);
static void lf_free_edge(struct lockf_edge *);
static struct lockf_edge *
lf_alloc_edge(void);
static void lf_alloc_vertex(struct lockf_entry *);
static int lf_add_edge(struct lockf_entry *, struct lockf_entry *);
static void lf_remove_edge(struct lockf_edge *);
static void lf_remove_outgoing(struct lockf_entry *);
static void lf_remove_incoming(struct lockf_entry *);
static int lf_add_outgoing(struct lockf *, struct lockf_entry *);
static int lf_add_incoming(struct lockf *, struct lockf_entry *);
static int lf_findoverlap(struct lockf_entry **, struct lockf_entry *,
int);
static struct lockf_entry *
lf_getblock(struct lockf *, struct lockf_entry *);
static int lf_getlock(struct lockf *, struct lockf_entry *, struct flock *);
static void lf_insert_lock(struct lockf *, struct lockf_entry *);
static void lf_wakeup_lock(struct lockf *, struct lockf_entry *);
static void lf_update_dependancies(struct lockf *, struct lockf_entry *,
int all, struct lockf_entry_list *);
static void lf_set_start(struct lockf *, struct lockf_entry *, off_t,
struct lockf_entry_list*);
static void lf_set_end(struct lockf *, struct lockf_entry *, off_t,
struct lockf_entry_list*);
static int lf_setlock(struct lockf *, struct lockf_entry *,
struct vnode *, void **cookiep);
static int lf_cancel(struct lockf *, struct lockf_entry *, void *);
static void lf_split(struct lockf *, struct lockf_entry *,
struct lockf_entry *, struct lockf_entry_list *);
#ifdef LOCKF_DEBUG
static int graph_reaches(struct owner_vertex *x, struct owner_vertex *y,
struct owner_vertex_list *path);
static void graph_check(struct owner_graph *g, int checkorder);
static void graph_print_vertices(struct owner_vertex_list *set);
#endif
static int graph_delta_forward(struct owner_graph *g,
struct owner_vertex *x, struct owner_vertex *y,
struct owner_vertex_list *delta);
static int graph_delta_backward(struct owner_graph *g,
struct owner_vertex *x, struct owner_vertex *y,
struct owner_vertex_list *delta);
static int graph_add_indices(int *indices, int n,
struct owner_vertex_list *set);
static int graph_assign_indices(struct owner_graph *g, int *indices,
int nextunused, struct owner_vertex_list *set);
static int graph_add_edge(struct owner_graph *g,
struct owner_vertex *x, struct owner_vertex *y);
static void graph_remove_edge(struct owner_graph *g,
struct owner_vertex *x, struct owner_vertex *y);
static struct owner_vertex *graph_alloc_vertex(struct owner_graph *g,
struct lock_owner *lo);
static void graph_free_vertex(struct owner_graph *g,
struct owner_vertex *v);
static struct owner_graph * graph_init(struct owner_graph *g);
#ifdef LOCKF_DEBUG
static void lf_print(char *, struct lockf_entry *);
static void lf_printlist(char *, struct lockf_entry *);
static void lf_print_owner(struct lock_owner *);
#endif
/*
* This structure is used to keep track of both local and remote lock
* owners. The lf_owner field of the struct lockf_entry points back at
* the lock owner structure. Each possible lock owner (local proc for
* POSIX fcntl locks, local file for BSD flock locks or <pid,sysid>
* pair for remote locks) is represented by a unique instance of
* struct lock_owner.
*
* If a lock owner has a lock that blocks some other lock or a lock
* that is waiting for some other lock, it also has a vertex in the
* owner_graph below.
*
* Locks:
* (s) locked by state->ls_lock
* (S) locked by lf_lock_states_lock
* (l) locked by lf_lock_owners_lock
* (g) locked by lf_owner_graph_lock
* (c) const until freeing
*/
#define LOCK_OWNER_HASH_SIZE 256
struct lock_owner {
LIST_ENTRY(lock_owner) lo_link; /* (l) hash chain */
int lo_refs; /* (l) Number of locks referring to this */
int lo_flags; /* (c) Flags passwd to lf_advlock */
caddr_t lo_id; /* (c) Id value passed to lf_advlock */
pid_t lo_pid; /* (c) Process Id of the lock owner */
int lo_sysid; /* (c) System Id of the lock owner */
struct owner_vertex *lo_vertex; /* (g) entry in deadlock graph */
};
LIST_HEAD(lock_owner_list, lock_owner);
static struct sx lf_lock_states_lock;
static struct lockf_list lf_lock_states; /* (S) */
static struct sx lf_lock_owners_lock;
static struct lock_owner_list lf_lock_owners[LOCK_OWNER_HASH_SIZE]; /* (l) */
/*
* Structures for deadlock detection.
*
* We have two types of directed graph, the first is the set of locks,
* both active and pending on a vnode. Within this graph, active locks
* are terminal nodes in the graph (i.e. have no out-going
* edges). Pending locks have out-going edges to each blocking active
* lock that prevents the lock from being granted and also to each
* older pending lock that would block them if it was active. The
* graph for each vnode is naturally acyclic; new edges are only ever
* added to or from new nodes (either new pending locks which only add
* out-going edges or new active locks which only add in-coming edges)
* therefore they cannot create loops in the lock graph.
*
* The second graph is a global graph of lock owners. Each lock owner
* is a vertex in that graph and an edge is added to the graph
* whenever an edge is added to a vnode graph, with end points
* corresponding to owner of the new pending lock and the owner of the
* lock upon which it waits. In order to prevent deadlock, we only add
* an edge to this graph if the new edge would not create a cycle.
*
* The lock owner graph is topologically sorted, i.e. if a node has
* any outgoing edges, then it has an order strictly less than any
* node to which it has an outgoing edge. We preserve this ordering
* (and detect cycles) on edge insertion using Algorithm PK from the
* paper "A Dynamic Topological Sort Algorithm for Directed Acyclic
* Graphs" (ACM Journal of Experimental Algorithms, Vol 11, Article
* No. 1.7)
*/
struct owner_vertex;
struct owner_edge {
LIST_ENTRY(owner_edge) e_outlink; /* (g) link from's out-edge list */
LIST_ENTRY(owner_edge) e_inlink; /* (g) link to's in-edge list */
int e_refs; /* (g) number of times added */
struct owner_vertex *e_from; /* (c) out-going from here */
struct owner_vertex *e_to; /* (c) in-coming to here */
};
LIST_HEAD(owner_edge_list, owner_edge);
struct owner_vertex {
TAILQ_ENTRY(owner_vertex) v_link; /* (g) workspace for edge insertion */
uint32_t v_gen; /* (g) workspace for edge insertion */
int v_order; /* (g) order of vertex in graph */
struct owner_edge_list v_outedges;/* (g) list of out-edges */
struct owner_edge_list v_inedges; /* (g) list of in-edges */
struct lock_owner *v_owner; /* (c) corresponding lock owner */
};
TAILQ_HEAD(owner_vertex_list, owner_vertex);
struct owner_graph {
struct owner_vertex** g_vertices; /* (g) pointers to vertices */
int g_size; /* (g) number of vertices */
int g_space; /* (g) space allocated for vertices */
int *g_indexbuf; /* (g) workspace for loop detection */
uint32_t g_gen; /* (g) increment when re-ordering */
};
static struct sx lf_owner_graph_lock;
static struct owner_graph lf_owner_graph;
/*
* Initialise various structures and locks.
*/
static void
lf_init(void *dummy)
{
int i;
sx_init(&lf_lock_states_lock, "lock states lock");
LIST_INIT(&lf_lock_states);
sx_init(&lf_lock_owners_lock, "lock owners lock");
for (i = 0; i < LOCK_OWNER_HASH_SIZE; i++)
LIST_INIT(&lf_lock_owners[i]);
sx_init(&lf_owner_graph_lock, "owner graph lock");
graph_init(&lf_owner_graph);
}
SYSINIT(lf_init, SI_SUB_LOCK, SI_ORDER_FIRST, lf_init, NULL);
/*
* Generate a hash value for a lock owner.
*/
static int
lf_hash_owner(caddr_t id, struct flock *fl, int flags)
{
uint32_t h;
if (flags & F_REMOTE) {
h = HASHSTEP(0, fl->l_pid);
h = HASHSTEP(h, fl->l_sysid);
} else if (flags & F_FLOCK) {
h = ((uintptr_t) id) >> 7;
} else {
struct proc *p = (struct proc *) id;
h = HASHSTEP(0, p->p_pid);
h = HASHSTEP(h, 0);
}
return (h % LOCK_OWNER_HASH_SIZE);
}
/*
* Return true if a lock owner matches the details passed to
* lf_advlock.
*/
static int
lf_owner_matches(struct lock_owner *lo, caddr_t id, struct flock *fl,
int flags)
{
if (flags & F_REMOTE) {
return lo->lo_pid == fl->l_pid
&& lo->lo_sysid == fl->l_sysid;
} else {
return lo->lo_id == id;
}
}
static struct lockf_entry *
lf_alloc_lock(struct lock_owner *lo)
{
struct lockf_entry *lf;
lf = malloc(sizeof(struct lockf_entry), M_LOCKF, M_WAITOK|M_ZERO);
#ifdef LOCKF_DEBUG
if (lockf_debug & 4)
printf("Allocated lock %p\n", lf);
#endif
if (lo) {
sx_xlock(&lf_lock_owners_lock);
lo->lo_refs++;
sx_xunlock(&lf_lock_owners_lock);
lf->lf_owner = lo;
}
return (lf);
}
static void
lf_free_lock(struct lockf_entry *lock)
{
/*
* Adjust the lock_owner reference count and
* reclaim the entry if this is the last lock
* for that owner.
*/
struct lock_owner *lo = lock->lf_owner;
if (lo) {
KASSERT(LIST_EMPTY(&lock->lf_outedges),
("freeing lock with dependancies"));
KASSERT(LIST_EMPTY(&lock->lf_inedges),
("freeing lock with dependants"));
sx_xlock(&lf_lock_owners_lock);
KASSERT(lo->lo_refs > 0, ("lock owner refcount"));
lo->lo_refs--;
if (lo->lo_refs == 0) {
#ifdef LOCKF_DEBUG
if (lockf_debug & 1)
printf("lf_free_lock: freeing lock owner %p\n",
lo);
#endif
if (lo->lo_vertex) {
sx_xlock(&lf_owner_graph_lock);
graph_free_vertex(&lf_owner_graph,
lo->lo_vertex);
sx_xunlock(&lf_owner_graph_lock);
}
LIST_REMOVE(lo, lo_link);
free(lo, M_LOCKF);
#ifdef LOCKF_DEBUG
if (lockf_debug & 4)
printf("Freed lock owner %p\n", lo);
#endif
}
sx_unlock(&lf_lock_owners_lock);
}
if ((lock->lf_flags & F_REMOTE) && lock->lf_vnode) {
vrele(lock->lf_vnode);
lock->lf_vnode = NULL;
}
#ifdef LOCKF_DEBUG
if (lockf_debug & 4)
printf("Freed lock %p\n", lock);
#endif
free(lock, M_LOCKF);
}
/*
* Advisory record locking support
*/
int
lf_advlockasync(struct vop_advlockasync_args *ap, struct lockf **statep,
u_quad_t size)
{
struct lockf *state, *freestate = NULL;
struct flock *fl = ap->a_fl;
struct lockf_entry *lock;
struct vnode *vp = ap->a_vp;
caddr_t id = ap->a_id;
int flags = ap->a_flags;
int hash;
struct lock_owner *lo;
off_t start, end, oadd;
int error;
/*
* Handle the F_UNLKSYS case first - no need to mess about
* creating a lock owner for this one.
*/
if (ap->a_op == F_UNLCKSYS) {
lf_clearremotesys(fl->l_sysid);
return (0);
}
/*
* Convert the flock structure into a start and end.
*/
switch (fl->l_whence) {
case SEEK_SET:
case SEEK_CUR:
/*
* Caller is responsible for adding any necessary offset
* when SEEK_CUR is used.
*/
start = fl->l_start;
break;
case SEEK_END:
if (size > OFF_MAX ||
(fl->l_start > 0 && size > OFF_MAX - fl->l_start))
return (EOVERFLOW);
start = size + fl->l_start;
break;
default:
return (EINVAL);
}
if (start < 0)
return (EINVAL);
if (fl->l_len < 0) {
if (start == 0)
return (EINVAL);
end = start - 1;
start += fl->l_len;
if (start < 0)
return (EINVAL);
} else if (fl->l_len == 0) {
end = OFF_MAX;
} else {
oadd = fl->l_len - 1;
if (oadd > OFF_MAX - start)
return (EOVERFLOW);
end = start + oadd;
}
/*
* Avoid the common case of unlocking when inode has no locks.
*/
if ((*statep) == NULL || LIST_EMPTY(&(*statep)->ls_active)) {
if (ap->a_op != F_SETLK) {
fl->l_type = F_UNLCK;
return (0);
}
}
/*
* Map our arguments to an existing lock owner or create one
* if this is the first time we have seen this owner.
*/
hash = lf_hash_owner(id, fl, flags);
sx_xlock(&lf_lock_owners_lock);
LIST_FOREACH(lo, &lf_lock_owners[hash], lo_link)
if (lf_owner_matches(lo, id, fl, flags))
break;
if (!lo) {
/*
* We initialise the lock with a reference
* count which matches the new lockf_entry
* structure created below.
*/
lo = malloc(sizeof(struct lock_owner), M_LOCKF,
M_WAITOK|M_ZERO);
#ifdef LOCKF_DEBUG
if (lockf_debug & 4)
printf("Allocated lock owner %p\n", lo);
#endif
lo->lo_refs = 1;
lo->lo_flags = flags;
lo->lo_id = id;
if (flags & F_REMOTE) {
lo->lo_pid = fl->l_pid;
lo->lo_sysid = fl->l_sysid;
} else if (flags & F_FLOCK) {
lo->lo_pid = -1;
lo->lo_sysid = 0;
} else {
struct proc *p = (struct proc *) id;
lo->lo_pid = p->p_pid;
lo->lo_sysid = 0;
}
lo->lo_vertex = NULL;
#ifdef LOCKF_DEBUG
if (lockf_debug & 1) {
printf("lf_advlockasync: new lock owner %p ", lo);
lf_print_owner(lo);
printf("\n");
}
#endif
LIST_INSERT_HEAD(&lf_lock_owners[hash], lo, lo_link);
} else {
/*
* We have seen this lock owner before, increase its
* reference count to account for the new lockf_entry
* structure we create below.
*/
lo->lo_refs++;
}
sx_xunlock(&lf_lock_owners_lock);
/*
* Create the lockf structure. We initialise the lf_owner
* field here instead of in lf_alloc_lock() to avoid paying
* the lf_lock_owners_lock tax twice.
*/
lock = lf_alloc_lock(NULL);
lock->lf_start = start;
lock->lf_end = end;
lock->lf_owner = lo;
lock->lf_vnode = vp;
if (flags & F_REMOTE) {
/*
* For remote locks, the caller may release its ref to
* the vnode at any time - we have to ref it here to
* prevent it from being recycled unexpectedly.
*/
vref(vp);
}
/*
* XXX The problem is that VTOI is ufs specific, so it will
* break LOCKF_DEBUG for all other FS's other than UFS because
* it casts the vnode->data ptr to struct inode *.
*/
/* lock->lf_inode = VTOI(ap->a_vp); */
lock->lf_inode = (struct inode *)0;
lock->lf_type = fl->l_type;
LIST_INIT(&lock->lf_outedges);
LIST_INIT(&lock->lf_inedges);
lock->lf_async_task = ap->a_task;
lock->lf_flags = ap->a_flags;
/*
* Do the requested operation. First find our state structure
* and create a new one if necessary - the caller's *statep
* variable and the state's ls_threads count is protected by
* the vnode interlock.
*/
VI_LOCK(vp);
if (vp->v_iflag & VI_DOOMED) {
VI_UNLOCK(vp);
lf_free_lock(lock);
return (ENOENT);
}
/*
* Allocate a state structure if necessary.
*/
state = *statep;
if (state == NULL) {
struct lockf *ls;
VI_UNLOCK(vp);
ls = malloc(sizeof(struct lockf), M_LOCKF, M_WAITOK|M_ZERO);
sx_init(&ls->ls_lock, "ls_lock");
LIST_INIT(&ls->ls_active);
LIST_INIT(&ls->ls_pending);
ls->ls_threads = 1;
sx_xlock(&lf_lock_states_lock);
LIST_INSERT_HEAD(&lf_lock_states, ls, ls_link);
sx_xunlock(&lf_lock_states_lock);
/*
* Cope if we lost a race with some other thread while
* trying to allocate memory.
*/
VI_LOCK(vp);
if (vp->v_iflag & VI_DOOMED) {
VI_UNLOCK(vp);
sx_xlock(&lf_lock_states_lock);
LIST_REMOVE(ls, ls_link);
sx_xunlock(&lf_lock_states_lock);
sx_destroy(&ls->ls_lock);
free(ls, M_LOCKF);
lf_free_lock(lock);
return (ENOENT);
}
if ((*statep) == NULL) {
state = *statep = ls;
VI_UNLOCK(vp);
} else {
state = *statep;
state->ls_threads++;
VI_UNLOCK(vp);
sx_xlock(&lf_lock_states_lock);
LIST_REMOVE(ls, ls_link);
sx_xunlock(&lf_lock_states_lock);
sx_destroy(&ls->ls_lock);
free(ls, M_LOCKF);
}
} else {
state->ls_threads++;
VI_UNLOCK(vp);
}
sx_xlock(&state->ls_lock);
switch(ap->a_op) {
case F_SETLK:
error = lf_setlock(state, lock, vp, ap->a_cookiep);
break;
case F_UNLCK:
error = lf_clearlock(state, lock);
lf_free_lock(lock);
break;
case F_GETLK:
error = lf_getlock(state, lock, fl);
lf_free_lock(lock);
break;
case F_CANCEL:
if (ap->a_cookiep)
error = lf_cancel(state, lock, *ap->a_cookiep);
else
error = EINVAL;
lf_free_lock(lock);
break;
default:
lf_free_lock(lock);
error = EINVAL;
break;
}
#ifdef INVARIANTS
/*
* Check for some can't happen stuff. In this case, the active
* lock list becoming disordered or containing mutually
* blocking locks. We also check the pending list for locks
* which should be active (i.e. have no out-going edges).
*/
LIST_FOREACH(lock, &state->ls_active, lf_link) {
struct lockf_entry *lf;
if (LIST_NEXT(lock, lf_link))
KASSERT((lock->lf_start
<= LIST_NEXT(lock, lf_link)->lf_start),
("locks disordered"));
LIST_FOREACH(lf, &state->ls_active, lf_link) {
if (lock == lf)
break;
KASSERT(!lf_blocks(lock, lf),
("two conflicting active locks"));
if (lock->lf_owner == lf->lf_owner)
KASSERT(!lf_overlaps(lock, lf),
("two overlapping locks from same owner"));
}
}
LIST_FOREACH(lock, &state->ls_pending, lf_link) {
KASSERT(!LIST_EMPTY(&lock->lf_outedges),
("pending lock which should be active"));
}
#endif
sx_xunlock(&state->ls_lock);
/*
* If we have removed the last active lock on the vnode and
* this is the last thread that was in-progress, we can free
* the state structure. We update the caller's pointer inside
* the vnode interlock but call free outside.
*
* XXX alternatively, keep the state structure around until
* the filesystem recycles - requires a callback from the
* filesystem.
*/
VI_LOCK(vp);
state->ls_threads--;
wakeup(state);
if (LIST_EMPTY(&state->ls_active) && state->ls_threads == 0) {
KASSERT(LIST_EMPTY(&state->ls_pending),
("freeing state with pending locks"));
freestate = state;
*statep = NULL;
}
VI_UNLOCK(vp);
if (freestate) {
sx_xlock(&lf_lock_states_lock);
LIST_REMOVE(freestate, ls_link);
sx_xunlock(&lf_lock_states_lock);
sx_destroy(&freestate->ls_lock);
free(freestate, M_LOCKF);
}
return (error);
}
int
lf_advlock(struct vop_advlock_args *ap, struct lockf **statep, u_quad_t size)
{
struct vop_advlockasync_args a;
a.a_vp = ap->a_vp;
a.a_id = ap->a_id;
a.a_op = ap->a_op;
a.a_fl = ap->a_fl;
a.a_flags = ap->a_flags;
a.a_task = NULL;
a.a_cookiep = NULL;
return (lf_advlockasync(&a, statep, size));
}
void
lf_purgelocks(struct vnode *vp, struct lockf **statep)
{
struct lockf *state;
struct lockf_entry *lock, *nlock;
/*
* For this to work correctly, the caller must ensure that no
* other threads enter the locking system for this vnode,
* e.g. by checking VI_DOOMED. We wake up any threads that are
* sleeping waiting for locks on this vnode and then free all
* the remaining locks.
*/
VI_LOCK(vp);
state = *statep;
if (state) {
state->ls_threads++;
VI_UNLOCK(vp);
sx_xlock(&state->ls_lock);
sx_xlock(&lf_owner_graph_lock);
LIST_FOREACH_SAFE(lock, &state->ls_pending, lf_link, nlock) {
LIST_REMOVE(lock, lf_link);
lf_remove_outgoing(lock);
lf_remove_incoming(lock);
/*
* If its an async lock, we can just free it
* here, otherwise we let the sleeping thread
* free it.
*/
if (lock->lf_async_task) {
lf_free_lock(lock);
} else {
lock->lf_flags |= F_INTR;
wakeup(lock);
}
}
sx_xunlock(&lf_owner_graph_lock);
sx_xunlock(&state->ls_lock);
/*
* Wait for all other threads, sleeping and otherwise
* to leave.
*/
VI_LOCK(vp);
while (state->ls_threads > 1)
msleep(state, VI_MTX(vp), 0, "purgelocks", 0);
*statep = 0;
VI_UNLOCK(vp);
/*
* We can just free all the active locks since they
* will have no dependancies (we removed them all
* above). We don't need to bother locking since we
* are the last thread using this state structure.
*/
LIST_FOREACH_SAFE(lock, &state->ls_pending, lf_link, nlock) {
LIST_REMOVE(lock, lf_link);
lf_free_lock(lock);
}
sx_xlock(&lf_lock_states_lock);
LIST_REMOVE(state, ls_link);
sx_xunlock(&lf_lock_states_lock);
sx_destroy(&state->ls_lock);
free(state, M_LOCKF);
} else {
VI_UNLOCK(vp);
}
}
/*
* Return non-zero if locks 'x' and 'y' overlap.
*/
static int
lf_overlaps(struct lockf_entry *x, struct lockf_entry *y)
{
return (x->lf_start <= y->lf_end && x->lf_end >= y->lf_start);
}
/*
* Return non-zero if lock 'x' is blocked by lock 'y' (or vice versa).
*/
static int
lf_blocks(struct lockf_entry *x, struct lockf_entry *y)
{
return x->lf_owner != y->lf_owner
&& (x->lf_type == F_WRLCK || y->lf_type == F_WRLCK)
&& lf_overlaps(x, y);
}
/*
* Allocate a lock edge from the free list
*/
static struct lockf_edge *
lf_alloc_edge(void)
{
return (malloc(sizeof(struct lockf_edge), M_LOCKF, M_WAITOK|M_ZERO));
}
/*
* Free a lock edge.
*/
static void
lf_free_edge(struct lockf_edge *e)
{
free(e, M_LOCKF);
}
/*
* Ensure that the lock's owner has a corresponding vertex in the
* owner graph.
*/
static void
lf_alloc_vertex(struct lockf_entry *lock)
{
struct owner_graph *g = &lf_owner_graph;
if (!lock->lf_owner->lo_vertex)
lock->lf_owner->lo_vertex =
graph_alloc_vertex(g, lock->lf_owner);
}
/*
* Attempt to record an edge from lock x to lock y. Return EDEADLK if
* the new edge would cause a cycle in the owner graph.
*/
static int
lf_add_edge(struct lockf_entry *x, struct lockf_entry *y)
{
struct owner_graph *g = &lf_owner_graph;
struct lockf_edge *e;
int error;
#ifdef INVARIANTS
LIST_FOREACH(e, &x->lf_outedges, le_outlink)
KASSERT(e->le_to != y, ("adding lock edge twice"));
#endif
/*
* Make sure the two owners have entries in the owner graph.
*/
lf_alloc_vertex(x);
lf_alloc_vertex(y);
error = graph_add_edge(g, x->lf_owner->lo_vertex,
y->lf_owner->lo_vertex);
if (error)
return (error);
e = lf_alloc_edge();
LIST_INSERT_HEAD(&x->lf_outedges, e, le_outlink);
LIST_INSERT_HEAD(&y->lf_inedges, e, le_inlink);
e->le_from = x;
e->le_to = y;
return (0);
}
/*
* Remove an edge from the lock graph.
*/
static void
lf_remove_edge(struct lockf_edge *e)
{
struct owner_graph *g = &lf_owner_graph;
struct lockf_entry *x = e->le_from;
struct lockf_entry *y = e->le_to;
graph_remove_edge(g, x->lf_owner->lo_vertex, y->lf_owner->lo_vertex);
LIST_REMOVE(e, le_outlink);
LIST_REMOVE(e, le_inlink);
e->le_from = NULL;
e->le_to = NULL;
lf_free_edge(e);
}
/*
* Remove all out-going edges from lock x.
*/
static void
lf_remove_outgoing(struct lockf_entry *x)
{
struct lockf_edge *e;
while ((e = LIST_FIRST(&x->lf_outedges)) != NULL) {
lf_remove_edge(e);
}
}
/*
* Remove all in-coming edges from lock x.
*/
static void
lf_remove_incoming(struct lockf_entry *x)
{
struct lockf_edge *e;
while ((e = LIST_FIRST(&x->lf_inedges)) != NULL) {
lf_remove_edge(e);
}
}
/*
* Walk the list of locks for the file and create an out-going edge
* from lock to each blocking lock.
*/
static int
lf_add_outgoing(struct lockf *state, struct lockf_entry *lock)
{
struct lockf_entry *overlap;
int error;
LIST_FOREACH(overlap, &state->ls_active, lf_link) {
/*
* We may assume that the active list is sorted by
* lf_start.
*/
if (overlap->lf_start > lock->lf_end)
break;
if (!lf_blocks(lock, overlap))
continue;
/*
* We've found a blocking lock. Add the corresponding
* edge to the graphs and see if it would cause a
* deadlock.
*/
error = lf_add_edge(lock, overlap);
/*
* The only error that lf_add_edge returns is EDEADLK.
* Remove any edges we added and return the error.
*/
if (error) {
lf_remove_outgoing(lock);
return (error);
}
}
/*
* We also need to add edges to sleeping locks that block
* us. This ensures that lf_wakeup_lock cannot grant two
* mutually blocking locks simultaneously and also enforces a
* 'first come, first served' fairness model. Note that this
* only happens if we are blocked by at least one active lock
* due to the call to lf_getblock in lf_setlock below.
*/
LIST_FOREACH(overlap, &state->ls_pending, lf_link) {
if (!lf_blocks(lock, overlap))
continue;
/*
* We've found a blocking lock. Add the corresponding
* edge to the graphs and see if it would cause a
* deadlock.
*/
error = lf_add_edge(lock, overlap);
/*
* The only error that lf_add_edge returns is EDEADLK.
* Remove any edges we added and return the error.
*/
if (error) {
lf_remove_outgoing(lock);
return (error);
}
}
return (0);
}
/*
* Walk the list of pending locks for the file and create an in-coming
* edge from lock to each blocking lock.
*/
static int
lf_add_incoming(struct lockf *state, struct lockf_entry *lock)
{
struct lockf_entry *overlap;
int error;
LIST_FOREACH(overlap, &state->ls_pending, lf_link) {
if (!lf_blocks(lock, overlap))
continue;
/*
* We've found a blocking lock. Add the corresponding
* edge to the graphs and see if it would cause a
* deadlock.
*/
error = lf_add_edge(overlap, lock);
/*
* The only error that lf_add_edge returns is EDEADLK.
* Remove any edges we added and return the error.
*/
if (error) {
lf_remove_incoming(lock);
return (error);
}
}
return (0);
}
/*
* Insert lock into the active list, keeping list entries ordered by
* increasing values of lf_start.
*/
static void
lf_insert_lock(struct lockf *state, struct lockf_entry *lock)
{
struct lockf_entry *lf, *lfprev;
if (LIST_EMPTY(&state->ls_active)) {
LIST_INSERT_HEAD(&state->ls_active, lock, lf_link);
return;
}
lfprev = NULL;
LIST_FOREACH(lf, &state->ls_active, lf_link) {
if (lf->lf_start > lock->lf_start) {
LIST_INSERT_BEFORE(lf, lock, lf_link);
return;
}
lfprev = lf;
}
LIST_INSERT_AFTER(lfprev, lock, lf_link);
}
/*
* Wake up a sleeping lock and remove it from the pending list now
* that all its dependancies have been resolved. The caller should
* arrange for the lock to be added to the active list, adjusting any
* existing locks for the same owner as needed.
*/
static void
lf_wakeup_lock(struct lockf *state, struct lockf_entry *wakelock)
{
/*
* Remove from ls_pending list and wake up the caller
* or start the async notification, as appropriate.
*/
LIST_REMOVE(wakelock, lf_link);
#ifdef LOCKF_DEBUG
if (lockf_debug & 1)
lf_print("lf_wakeup_lock: awakening", wakelock);
#endif /* LOCKF_DEBUG */
if (wakelock->lf_async_task) {
taskqueue_enqueue(taskqueue_thread, wakelock->lf_async_task);
} else {
wakeup(wakelock);
}
}
/*
* Re-check all dependant locks and remove edges to locks that we no
* longer block. If 'all' is non-zero, the lock has been removed and
* we must remove all the dependancies, otherwise it has simply been
* reduced but remains active. Any pending locks which have been been
* unblocked are added to 'granted'
*/
static void
lf_update_dependancies(struct lockf *state, struct lockf_entry *lock, int all,
struct lockf_entry_list *granted)
{
struct lockf_edge *e, *ne;
struct lockf_entry *deplock;
LIST_FOREACH_SAFE(e, &lock->lf_inedges, le_inlink, ne) {
deplock = e->le_from;
if (all || !lf_blocks(lock, deplock)) {
sx_xlock(&lf_owner_graph_lock);
lf_remove_edge(e);
sx_xunlock(&lf_owner_graph_lock);
if (LIST_EMPTY(&deplock->lf_outedges)) {
lf_wakeup_lock(state, deplock);
LIST_INSERT_HEAD(granted, deplock, lf_link);
}
}
}
}
/*
* Set the start of an existing active lock, updating dependancies and
* adding any newly woken locks to 'granted'.
*/
static void
lf_set_start(struct lockf *state, struct lockf_entry *lock, off_t new_start,
struct lockf_entry_list *granted)
{
KASSERT(new_start >= lock->lf_start, ("can't increase lock"));
lock->lf_start = new_start;
LIST_REMOVE(lock, lf_link);
lf_insert_lock(state, lock);
lf_update_dependancies(state, lock, FALSE, granted);
}
/*
* Set the end of an existing active lock, updating dependancies and
* adding any newly woken locks to 'granted'.
*/
static void
lf_set_end(struct lockf *state, struct lockf_entry *lock, off_t new_end,
struct lockf_entry_list *granted)
{
KASSERT(new_end <= lock->lf_end, ("can't increase lock"));
lock->lf_end = new_end;
lf_update_dependancies(state, lock, FALSE, granted);
}
/*
* Add a lock to the active list, updating or removing any current
* locks owned by the same owner and processing any pending locks that
* become unblocked as a result. This code is also used for unlock
* since the logic for updating existing locks is identical.
*
* As a result of processing the new lock, we may unblock existing
* pending locks as a result of downgrading/unlocking. We simply
* activate the newly granted locks by looping.
*
* Since the new lock already has its dependancies set up, we always
* add it to the list (unless its an unlock request). This may
* fragment the lock list in some pathological cases but its probably
* not a real problem.
*/
static void
lf_activate_lock(struct lockf *state, struct lockf_entry *lock)
{
struct lockf_entry *overlap, *lf;
struct lockf_entry_list granted;
int ovcase;
LIST_INIT(&granted);
LIST_INSERT_HEAD(&granted, lock, lf_link);
while (!LIST_EMPTY(&granted)) {
lock = LIST_FIRST(&granted);
LIST_REMOVE(lock, lf_link);
/*
* Skip over locks owned by other processes. Handle
* any locks that overlap and are owned by ourselves.
*/
overlap = LIST_FIRST(&state->ls_active);
for (;;) {
ovcase = lf_findoverlap(&overlap, lock, SELF);
#ifdef LOCKF_DEBUG
if (ovcase && (lockf_debug & 2)) {
printf("lf_setlock: overlap %d", ovcase);
lf_print("", overlap);
}
#endif
/*
* Six cases:
* 0) no overlap
* 1) overlap == lock
* 2) overlap contains lock
* 3) lock contains overlap
* 4) overlap starts before lock
* 5) overlap ends after lock
*/
switch (ovcase) {
case 0: /* no overlap */
break;
case 1: /* overlap == lock */
/*
* We have already setup the
* dependants for the new lock, taking
* into account a possible downgrade
* or unlock. Remove the old lock.
*/
LIST_REMOVE(overlap, lf_link);
lf_update_dependancies(state, overlap, TRUE,
&granted);
lf_free_lock(overlap);
break;
case 2: /* overlap contains lock */
/*
* Just split the existing lock.
*/
lf_split(state, overlap, lock, &granted);
break;
case 3: /* lock contains overlap */
/*
* Delete the overlap and advance to
* the next entry in the list.
*/
lf = LIST_NEXT(overlap, lf_link);
LIST_REMOVE(overlap, lf_link);
lf_update_dependancies(state, overlap, TRUE,
&granted);
lf_free_lock(overlap);
overlap = lf;
continue;
case 4: /* overlap starts before lock */
/*
* Just update the overlap end and
* move on.
*/
lf_set_end(state, overlap, lock->lf_start - 1,
&granted);
overlap = LIST_NEXT(overlap, lf_link);
continue;
case 5: /* overlap ends after lock */
/*
* Change the start of overlap and
* re-insert.
*/
lf_set_start(state, overlap, lock->lf_end + 1,
&granted);
break;
}
break;
}
#ifdef LOCKF_DEBUG
if (lockf_debug & 1) {
if (lock->lf_type != F_UNLCK)
lf_print("lf_activate_lock: activated", lock);
else
lf_print("lf_activate_lock: unlocked", lock);
lf_printlist("lf_activate_lock", lock);
}
#endif /* LOCKF_DEBUG */
if (lock->lf_type != F_UNLCK)
lf_insert_lock(state, lock);
}
}
/*
* Cancel a pending lock request, either as a result of a signal or a
* cancel request for an async lock.
*/
static void
lf_cancel_lock(struct lockf *state, struct lockf_entry *lock)
{
struct lockf_entry_list granted;
/*
* Note it is theoretically possible that cancelling this lock
* may allow some other pending lock to become
* active. Consider this case:
*
* Owner Action Result Dependancies
*
* A: lock [0..0] succeeds
* B: lock [2..2] succeeds
* C: lock [1..2] blocked C->B
* D: lock [0..1] blocked C->B,D->A,D->C
* A: unlock [0..0] C->B,D->C
* C: cancel [1..2]
*/
LIST_REMOVE(lock, lf_link);
/*
* Removing out-going edges is simple.
*/
sx_xlock(&lf_owner_graph_lock);
lf_remove_outgoing(lock);
sx_xunlock(&lf_owner_graph_lock);
/*
* Removing in-coming edges may allow some other lock to
* become active - we use lf_update_dependancies to figure
* this out.
*/
LIST_INIT(&granted);
lf_update_dependancies(state, lock, TRUE, &granted);
lf_free_lock(lock);
/*
* Feed any newly active locks to lf_activate_lock.
*/
while (!LIST_EMPTY(&granted)) {
lock = LIST_FIRST(&granted);
LIST_REMOVE(lock, lf_link);
lf_activate_lock(state, lock);
}
}
/*
* Set a byte-range lock.
*/
static int
lf_setlock(struct lockf *state, struct lockf_entry *lock, struct vnode *vp,
void **cookiep)
{
struct lockf_entry *block;
static char lockstr[] = "lockf";
int priority, error;
#ifdef LOCKF_DEBUG
if (lockf_debug & 1)
lf_print("lf_setlock", lock);
#endif /* LOCKF_DEBUG */
/*
* Set the priority
*/
priority = PLOCK;
if (lock->lf_type == F_WRLCK)
priority += 4;
priority |= PCATCH;
/*
* Scan lock list for this file looking for locks that would block us.
*/
while ((block = lf_getblock(state, lock))) {
/*
* Free the structure and return if nonblocking.
*/
if ((lock->lf_flags & F_WAIT) == 0
&& lock->lf_async_task == NULL) {
lf_free_lock(lock);
error = EAGAIN;
goto out;
}
/*
* For flock type locks, we must first remove
* any shared locks that we hold before we sleep
* waiting for an exclusive lock.
*/
if ((lock->lf_flags & F_FLOCK) &&
lock->lf_type == F_WRLCK) {
lock->lf_type = F_UNLCK;
lf_activate_lock(state, lock);
lock->lf_type = F_WRLCK;
}
/*
* We are blocked. Create edges to each blocking lock,
* checking for deadlock using the owner graph. For
* simplicity, we run deadlock detection for all
* locks, posix and otherwise.
*/
sx_xlock(&lf_owner_graph_lock);
error = lf_add_outgoing(state, lock);
sx_xunlock(&lf_owner_graph_lock);
if (error) {
#ifdef LOCKF_DEBUG
if (lockf_debug & 1)
lf_print("lf_setlock: deadlock", lock);
#endif
lf_free_lock(lock);
goto out;
}
/*
* We have added edges to everything that blocks
* us. Sleep until they all go away.
*/
LIST_INSERT_HEAD(&state->ls_pending, lock, lf_link);
#ifdef LOCKF_DEBUG
if (lockf_debug & 1) {
struct lockf_edge *e;
LIST_FOREACH(e, &lock->lf_outedges, le_outlink) {
lf_print("lf_setlock: blocking on", e->le_to);
lf_printlist("lf_setlock", e->le_to);
}
}
#endif /* LOCKF_DEBUG */
if ((lock->lf_flags & F_WAIT) == 0) {
/*
* The caller requested async notification -
* this callback happens when the blocking
* lock is released, allowing the caller to
* make another attempt to take the lock.
*/
*cookiep = (void *) lock;
error = EINPROGRESS;
goto out;
}
error = sx_sleep(lock, &state->ls_lock, priority, lockstr, 0);
/*
* We may have been awakened by a signal and/or by a
* debugger continuing us (in which cases we must
* remove our lock graph edges) and/or by another
* process releasing a lock (in which case our edges
* have already been removed and we have been moved to
* the active list). We may also have been woken by
* lf_purgelocks which we report to the caller as
* EINTR. In that case, lf_purgelocks will have
* removed our lock graph edges.
*
* Note that it is possible to receive a signal after
* we were successfully woken (and moved to the active
* list) but before we resumed execution. In this
* case, our lf_outedges list will be clear. We
* pretend there was no error.
*
* Note also, if we have been sleeping long enough, we
* may now have incoming edges from some newer lock
* which is waiting behind us in the queue.
*/
if (lock->lf_flags & F_INTR) {
error = EINTR;
lf_free_lock(lock);
goto out;
}
if (LIST_EMPTY(&lock->lf_outedges)) {
error = 0;
} else {
lf_cancel_lock(state, lock);
goto out;
}
#ifdef LOCKF_DEBUG
if (lockf_debug & 1) {
lf_print("lf_setlock: granted", lock);
}
#endif
goto out;
}
/*
* It looks like we are going to grant the lock. First add
* edges from any currently pending lock that the new lock
* would block.
*/
sx_xlock(&lf_owner_graph_lock);
error = lf_add_incoming(state, lock);
sx_xunlock(&lf_owner_graph_lock);
if (error) {
#ifdef LOCKF_DEBUG
if (lockf_debug & 1)
lf_print("lf_setlock: deadlock", lock);
#endif
lf_free_lock(lock);
goto out;
}
/*
* No blocks!! Add the lock. Note that we will
* downgrade or upgrade any overlapping locks this
* process already owns.
*/
lf_activate_lock(state, lock);
error = 0;
out:
return (error);
}
/*
* Remove a byte-range lock on an inode.
*
* Generally, find the lock (or an overlap to that lock)
* and remove it (or shrink it), then wakeup anyone we can.
*/
static int
lf_clearlock(struct lockf *state, struct lockf_entry *unlock)
{
struct lockf_entry *overlap;
overlap = LIST_FIRST(&state->ls_active);
if (overlap == NOLOCKF)
return (0);
#ifdef LOCKF_DEBUG
if (unlock->lf_type != F_UNLCK)
panic("lf_clearlock: bad type");
if (lockf_debug & 1)
lf_print("lf_clearlock", unlock);
#endif /* LOCKF_DEBUG */
lf_activate_lock(state, unlock);
return (0);
}
/*
* Check whether there is a blocking lock, and if so return its
* details in '*fl'.
*/
static int
lf_getlock(struct lockf *state, struct lockf_entry *lock, struct flock *fl)
{
struct lockf_entry *block;
#ifdef LOCKF_DEBUG
if (lockf_debug & 1)
lf_print("lf_getlock", lock);
#endif /* LOCKF_DEBUG */
if ((block = lf_getblock(state, lock))) {
fl->l_type = block->lf_type;
fl->l_whence = SEEK_SET;
fl->l_start = block->lf_start;
if (block->lf_end == OFF_MAX)
fl->l_len = 0;
else
fl->l_len = block->lf_end - block->lf_start + 1;
fl->l_pid = block->lf_owner->lo_pid;
fl->l_sysid = block->lf_owner->lo_sysid;
} else {
fl->l_type = F_UNLCK;
}
return (0);
}
/*
* Cancel an async lock request.
*/
static int
lf_cancel(struct lockf *state, struct lockf_entry *lock, void *cookie)
{
struct lockf_entry *reallock;
/*
* We need to match this request with an existing lock
* request.
*/
LIST_FOREACH(reallock, &state->ls_pending, lf_link) {
if ((void *) reallock == cookie) {
/*
* Double-check that this lock looks right
* (maybe use a rolling ID for the cancel
* cookie instead?)
*/
if (!(reallock->lf_vnode == lock->lf_vnode
&& reallock->lf_start == lock->lf_start
&& reallock->lf_end == lock->lf_end)) {
return (ENOENT);
}
/*
* Make sure this lock was async and then just
* remove it from its wait lists.
*/
if (!reallock->lf_async_task) {
return (ENOENT);
}
/*
* Note that since any other thread must take
* state->ls_lock before it can possibly
* trigger the async callback, we are safe
* from a race with lf_wakeup_lock, i.e. we
* can free the lock (actually our caller does
* this).
*/
lf_cancel_lock(state, reallock);
return (0);
}
}
/*
* We didn't find a matching lock - not much we can do here.
*/
return (ENOENT);
}
/*
* Walk the list of locks for an inode and
* return the first blocking lock.
*/
static struct lockf_entry *
lf_getblock(struct lockf *state, struct lockf_entry *lock)
{
struct lockf_entry *overlap;
LIST_FOREACH(overlap, &state->ls_active, lf_link) {
/*
* We may assume that the active list is sorted by
* lf_start.
*/
if (overlap->lf_start > lock->lf_end)
break;
if (!lf_blocks(lock, overlap))
continue;
return (overlap);
}
return (NOLOCKF);
}
/*
* Walk the list of locks for an inode to find an overlapping lock (if
* any) and return a classification of that overlap.
*
* Arguments:
* *overlap The place in the lock list to start looking
* lock The lock which is being tested
* type Pass 'SELF' to test only locks with the same
* owner as lock, or 'OTHER' to test only locks
* with a different owner
*
* Returns one of six values:
* 0) no overlap
* 1) overlap == lock
* 2) overlap contains lock
* 3) lock contains overlap
* 4) overlap starts before lock
* 5) overlap ends after lock
*
* If there is an overlapping lock, '*overlap' is set to point at the
* overlapping lock.
*
* NOTE: this returns only the FIRST overlapping lock. There
* may be more than one.
*/
static int
lf_findoverlap(struct lockf_entry **overlap, struct lockf_entry *lock, int type)
{
struct lockf_entry *lf;
off_t start, end;
int res;
if ((*overlap) == NOLOCKF) {
return (0);
}
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
lf_print("lf_findoverlap: looking for overlap in", lock);
#endif /* LOCKF_DEBUG */
start = lock->lf_start;
end = lock->lf_end;
res = 0;
while (*overlap) {
lf = *overlap;
if (lf->lf_start > end)
break;
if (((type & SELF) && lf->lf_owner != lock->lf_owner) ||
((type & OTHERS) && lf->lf_owner == lock->lf_owner)) {
*overlap = LIST_NEXT(lf, lf_link);
continue;
}
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
lf_print("\tchecking", lf);
#endif /* LOCKF_DEBUG */
/*
* OK, check for overlap
*
* Six cases:
* 0) no overlap
* 1) overlap == lock
* 2) overlap contains lock
* 3) lock contains overlap
* 4) overlap starts before lock
* 5) overlap ends after lock
*/
if (start > lf->lf_end) {
/* Case 0 */
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
printf("no overlap\n");
#endif /* LOCKF_DEBUG */
*overlap = LIST_NEXT(lf, lf_link);
continue;
}
if (lf->lf_start == start && lf->lf_end == end) {
/* Case 1 */
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
printf("overlap == lock\n");
#endif /* LOCKF_DEBUG */
res = 1;
break;
}
if (lf->lf_start <= start && lf->lf_end >= end) {
/* Case 2 */
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
printf("overlap contains lock\n");
#endif /* LOCKF_DEBUG */
res = 2;
break;
}
if (start <= lf->lf_start && end >= lf->lf_end) {
/* Case 3 */
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
printf("lock contains overlap\n");
#endif /* LOCKF_DEBUG */
res = 3;
break;
}
if (lf->lf_start < start && lf->lf_end >= start) {
/* Case 4 */
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
printf("overlap starts before lock\n");
#endif /* LOCKF_DEBUG */
res = 4;
break;
}
if (lf->lf_start > start && lf->lf_end > end) {
/* Case 5 */
#ifdef LOCKF_DEBUG
if (lockf_debug & 2)
printf("overlap ends after lock\n");
#endif /* LOCKF_DEBUG */
res = 5;
break;
}
panic("lf_findoverlap: default");
}
return (res);
}
/*
* Split an the existing 'lock1', based on the extent of the lock
* described by 'lock2'. The existing lock should cover 'lock2'
* entirely.
*
* Any pending locks which have been been unblocked are added to
* 'granted'
*/
static void
lf_split(struct lockf *state, struct lockf_entry *lock1,
struct lockf_entry *lock2, struct lockf_entry_list *granted)
{
struct lockf_entry *splitlock;
#ifdef LOCKF_DEBUG
if (lockf_debug & 2) {
lf_print("lf_split", lock1);
lf_print("splitting from", lock2);
}
#endif /* LOCKF_DEBUG */
/*
* Check to see if we don't need to split at all.
*/
if (lock1->lf_start == lock2->lf_start) {
lf_set_start(state, lock1, lock2->lf_end + 1, granted);
return;
}
if (lock1->lf_end == lock2->lf_end) {
lf_set_end(state, lock1, lock2->lf_start - 1, granted);
return;
}
/*
* Make a new lock consisting of the last part of
* the encompassing lock.
*/
splitlock = lf_alloc_lock(lock1->lf_owner);
memcpy(splitlock, lock1, sizeof *splitlock);
if (splitlock->lf_flags & F_REMOTE)
vref(splitlock->lf_vnode);
/*
* This cannot cause a deadlock since any edges we would add
* to splitlock already exist in lock1. We must be sure to add
* necessary dependancies to splitlock before we reduce lock1
* otherwise we may accidentally grant a pending lock that
* was blocked by the tail end of lock1.
*/
splitlock->lf_start = lock2->lf_end + 1;
LIST_INIT(&splitlock->lf_outedges);
LIST_INIT(&splitlock->lf_inedges);
sx_xlock(&lf_owner_graph_lock);
lf_add_incoming(state, splitlock);
sx_xunlock(&lf_owner_graph_lock);
lf_set_end(state, lock1, lock2->lf_start - 1, granted);
/*
* OK, now link it in
*/
lf_insert_lock(state, splitlock);
}
struct clearlock {
STAILQ_ENTRY(clearlock) link;
struct vnode *vp;
struct flock fl;
};
STAILQ_HEAD(clearlocklist, clearlock);
void
lf_clearremotesys(int sysid)
{
struct lockf *ls;
struct lockf_entry *lf;
struct clearlock *cl;
struct clearlocklist locks;
KASSERT(sysid != 0, ("Can't clear local locks with F_UNLCKSYS"));
/*
* In order to keep the locking simple, we iterate over the
* active lock lists to build a list of locks that need
* releasing. We then call VOP_ADVLOCK for each one in turn.
*
* We take an extra reference to the vnode for the duration to
* make sure it doesn't go away before we are finished.
*/
STAILQ_INIT(&locks);
sx_xlock(&lf_lock_states_lock);
LIST_FOREACH(ls, &lf_lock_states, ls_link) {
sx_xlock(&ls->ls_lock);
LIST_FOREACH(lf, &ls->ls_active, lf_link) {
if (lf->lf_owner->lo_sysid != sysid)
continue;
cl = malloc(sizeof(struct clearlock), M_LOCKF,
M_WAITOK);
cl->vp = lf->lf_vnode;
vref(cl->vp);
cl->fl.l_start = lf->lf_start;
if (lf->lf_end == OFF_MAX)
cl->fl.l_len = 0;
else
cl->fl.l_len =
lf->lf_end - lf->lf_start + 1;
cl->fl.l_whence = SEEK_SET;
cl->fl.l_type = F_UNLCK;
cl->fl.l_pid = lf->lf_owner->lo_pid;
cl->fl.l_sysid = sysid;
STAILQ_INSERT_TAIL(&locks, cl, link);
}
sx_xunlock(&ls->ls_lock);
}
sx_xunlock(&lf_lock_states_lock);
while ((cl = STAILQ_FIRST(&locks)) != NULL) {
STAILQ_REMOVE_HEAD(&locks, link);
VOP_ADVLOCK(cl->vp, 0, F_UNLCK, &cl->fl, F_REMOTE);
vrele(cl->vp);
free(cl, M_LOCKF);
}
}
int
lf_countlocks(int sysid)
{
int i;
struct lock_owner *lo;
int count;
count = 0;
sx_xlock(&lf_lock_owners_lock);
for (i = 0; i < LOCK_OWNER_HASH_SIZE; i++)
LIST_FOREACH(lo, &lf_lock_owners[i], lo_link)
if (lo->lo_sysid == sysid)
count += lo->lo_refs;
sx_xunlock(&lf_lock_owners_lock);
return (count);
}
#ifdef LOCKF_DEBUG
/*
* Return non-zero if y is reachable from x using a brute force
* search. If reachable and path is non-null, return the route taken
* in path.
*/
static int
graph_reaches(struct owner_vertex *x, struct owner_vertex *y,
struct owner_vertex_list *path)
{
struct owner_edge *e;
if (x == y) {
if (path)
TAILQ_INSERT_HEAD(path, x, v_link);
return 1;
}
LIST_FOREACH(e, &x->v_outedges, e_outlink) {
if (graph_reaches(e->e_to, y, path)) {
if (path)
TAILQ_INSERT_HEAD(path, x, v_link);
return 1;
}
}
return 0;
}
/*
* Perform consistency checks on the graph. Make sure the values of
* v_order are correct. If checkorder is non-zero, check no vertex can
* reach any other vertex with a smaller order.
*/
static void
graph_check(struct owner_graph *g, int checkorder)
{
int i, j;
for (i = 0; i < g->g_size; i++) {
if (!g->g_vertices[i]->v_owner)
continue;
KASSERT(g->g_vertices[i]->v_order == i,
("lock graph vertices disordered"));
if (checkorder) {
for (j = 0; j < i; j++) {
if (!g->g_vertices[j]->v_owner)
continue;
KASSERT(!graph_reaches(g->g_vertices[i],
g->g_vertices[j], NULL),
("lock graph vertices disordered"));
}
}
}
}
static void
graph_print_vertices(struct owner_vertex_list *set)
{
struct owner_vertex *v;
printf("{ ");
TAILQ_FOREACH(v, set, v_link) {
printf("%d:", v->v_order);
lf_print_owner(v->v_owner);
if (TAILQ_NEXT(v, v_link))
printf(", ");
}
printf(" }\n");
}
#endif
/*
* Calculate the sub-set of vertices v from the affected region [y..x]
* where v is reachable from y. Return -1 if a loop was detected
* (i.e. x is reachable from y, otherwise the number of vertices in
* this subset.
*/
static int
graph_delta_forward(struct owner_graph *g, struct owner_vertex *x,
struct owner_vertex *y, struct owner_vertex_list *delta)
{
uint32_t gen;
struct owner_vertex *v;
struct owner_edge *e;
int n;
/*
* We start with a set containing just y. Then for each vertex
* v in the set so far unprocessed, we add each vertex that v
* has an out-edge to and that is within the affected region
* [y..x]. If we see the vertex x on our travels, stop
* immediately.
*/
TAILQ_INIT(delta);
TAILQ_INSERT_TAIL(delta, y, v_link);
v = y;
n = 1;
gen = g->g_gen;
while (v) {
LIST_FOREACH(e, &v->v_outedges, e_outlink) {
if (e->e_to == x)
return -1;
if (e->e_to->v_order < x->v_order
&& e->e_to->v_gen != gen) {
e->e_to->v_gen = gen;
TAILQ_INSERT_TAIL(delta, e->e_to, v_link);
n++;
}
}
v = TAILQ_NEXT(v, v_link);
}
return (n);
}
/*
* Calculate the sub-set of vertices v from the affected region [y..x]
* where v reaches x. Return the number of vertices in this subset.
*/
static int
graph_delta_backward(struct owner_graph *g, struct owner_vertex *x,
struct owner_vertex *y, struct owner_vertex_list *delta)
{
uint32_t gen;
struct owner_vertex *v;
struct owner_edge *e;
int n;
/*
* We start with a set containing just x. Then for each vertex
* v in the set so far unprocessed, we add each vertex that v
* has an in-edge from and that is within the affected region
* [y..x].
*/
TAILQ_INIT(delta);
TAILQ_INSERT_TAIL(delta, x, v_link);
v = x;
n = 1;
gen = g->g_gen;
while (v) {
LIST_FOREACH(e, &v->v_inedges, e_inlink) {
if (e->e_from->v_order > y->v_order
&& e->e_from->v_gen != gen) {
e->e_from->v_gen = gen;
TAILQ_INSERT_HEAD(delta, e->e_from, v_link);
n++;
}
}
v = TAILQ_PREV(v, owner_vertex_list, v_link);
}
return (n);
}
static int
graph_add_indices(int *indices, int n, struct owner_vertex_list *set)
{
struct owner_vertex *v;
int i, j;
TAILQ_FOREACH(v, set, v_link) {
for (i = n;
i > 0 && indices[i - 1] > v->v_order; i--)
;
for (j = n - 1; j >= i; j--)
indices[j + 1] = indices[j];
indices[i] = v->v_order;
n++;
}
return (n);
}
static int
graph_assign_indices(struct owner_graph *g, int *indices, int nextunused,
struct owner_vertex_list *set)
{
struct owner_vertex *v, *vlowest;
while (!TAILQ_EMPTY(set)) {
vlowest = NULL;
TAILQ_FOREACH(v, set, v_link) {
if (!vlowest || v->v_order < vlowest->v_order)
vlowest = v;
}
TAILQ_REMOVE(set, vlowest, v_link);
vlowest->v_order = indices[nextunused];
g->g_vertices[vlowest->v_order] = vlowest;
nextunused++;
}
return (nextunused);
}
static int
graph_add_edge(struct owner_graph *g, struct owner_vertex *x,
struct owner_vertex *y)
{
struct owner_edge *e;
struct owner_vertex_list deltaF, deltaB;
int nF, nB, n, vi, i;
int *indices;
sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
LIST_FOREACH(e, &x->v_outedges, e_outlink) {
if (e->e_to == y) {
e->e_refs++;
return (0);
}
}
#ifdef LOCKF_DEBUG
if (lockf_debug & 8) {
printf("adding edge %d:", x->v_order);
lf_print_owner(x->v_owner);
printf(" -> %d:", y->v_order);
lf_print_owner(y->v_owner);
printf("\n");
}
#endif
if (y->v_order < x->v_order) {
/*
* The new edge violates the order. First find the set
* of affected vertices reachable from y (deltaF) and
* the set of affect vertices affected that reach x
* (deltaB), using the graph generation number to
* detect whether we have visited a given vertex
* already. We re-order the graph so that each vertex
* in deltaB appears before each vertex in deltaF.
*
* If x is a member of deltaF, then the new edge would
* create a cycle. Otherwise, we may assume that
* deltaF and deltaB are disjoint.
*/
g->g_gen++;
if (g->g_gen == 0) {
/*
* Generation wrap.
*/
for (vi = 0; vi < g->g_size; vi++) {
g->g_vertices[vi]->v_gen = 0;
}
g->g_gen++;
}
nF = graph_delta_forward(g, x, y, &deltaF);
if (nF < 0) {
#ifdef LOCKF_DEBUG
if (lockf_debug & 8) {
struct owner_vertex_list path;
printf("deadlock: ");
TAILQ_INIT(&path);
graph_reaches(y, x, &path);
graph_print_vertices(&path);
}
#endif
return (EDEADLK);
}
#ifdef LOCKF_DEBUG
if (lockf_debug & 8) {
printf("re-ordering graph vertices\n");
printf("deltaF = ");
graph_print_vertices(&deltaF);
}
#endif
nB = graph_delta_backward(g, x, y, &deltaB);
#ifdef LOCKF_DEBUG
if (lockf_debug & 8) {
printf("deltaB = ");
graph_print_vertices(&deltaB);
}
#endif
/*
* We first build a set of vertex indices (vertex
* order values) that we may use, then we re-assign
* orders first to those vertices in deltaB, then to
* deltaF. Note that the contents of deltaF and deltaB
* may be partially disordered - we perform an
* insertion sort while building our index set.
*/
indices = g->g_indexbuf;
n = graph_add_indices(indices, 0, &deltaF);
graph_add_indices(indices, n, &deltaB);
/*
* We must also be sure to maintain the relative
* ordering of deltaF and deltaB when re-assigning
* vertices. We do this by iteratively removing the
* lowest ordered element from the set and assigning
* it the next value from our new ordering.
*/
i = graph_assign_indices(g, indices, 0, &deltaB);
graph_assign_indices(g, indices, i, &deltaF);
#ifdef LOCKF_DEBUG
if (lockf_debug & 8) {
struct owner_vertex_list set;
TAILQ_INIT(&set);
for (i = 0; i < nB + nF; i++)
TAILQ_INSERT_TAIL(&set,
g->g_vertices[indices[i]], v_link);
printf("new ordering = ");
graph_print_vertices(&set);
}
#endif
}
KASSERT(x->v_order < y->v_order, ("Failed to re-order graph"));
#ifdef LOCKF_DEBUG
if (lockf_debug & 8) {
graph_check(g, TRUE);
}
#endif
e = malloc(sizeof(struct owner_edge), M_LOCKF, M_WAITOK);
LIST_INSERT_HEAD(&x->v_outedges, e, e_outlink);
LIST_INSERT_HEAD(&y->v_inedges, e, e_inlink);
e->e_refs = 1;
e->e_from = x;
e->e_to = y;
return (0);
}
/*
* Remove an edge x->y from the graph.
*/
static void
graph_remove_edge(struct owner_graph *g, struct owner_vertex *x,
struct owner_vertex *y)
{
struct owner_edge *e;
sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
LIST_FOREACH(e, &x->v_outedges, e_outlink) {
if (e->e_to == y)
break;
}
KASSERT(e, ("Removing non-existent edge from deadlock graph"));
e->e_refs--;
if (e->e_refs == 0) {
#ifdef LOCKF_DEBUG
if (lockf_debug & 8) {
printf("removing edge %d:", x->v_order);
lf_print_owner(x->v_owner);
printf(" -> %d:", y->v_order);
lf_print_owner(y->v_owner);
printf("\n");
}
#endif
LIST_REMOVE(e, e_outlink);
LIST_REMOVE(e, e_inlink);
free(e, M_LOCKF);
}
}
/*
* Allocate a vertex from the free list. Return ENOMEM if there are
* none.
*/
static struct owner_vertex *
graph_alloc_vertex(struct owner_graph *g, struct lock_owner *lo)
{
struct owner_vertex *v;
sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
v = malloc(sizeof(struct owner_vertex), M_LOCKF, M_WAITOK);
if (g->g_size == g->g_space) {
g->g_vertices = realloc(g->g_vertices,
2 * g->g_space * sizeof(struct owner_vertex *),
M_LOCKF, M_WAITOK);
free(g->g_indexbuf, M_LOCKF);
g->g_indexbuf = malloc(2 * g->g_space * sizeof(int),
M_LOCKF, M_WAITOK);
g->g_space = 2 * g->g_space;
}
v->v_order = g->g_size;
v->v_gen = g->g_gen;
g->g_vertices[g->g_size] = v;
g->g_size++;
LIST_INIT(&v->v_outedges);
LIST_INIT(&v->v_inedges);
v->v_owner = lo;
return (v);
}
static void
graph_free_vertex(struct owner_graph *g, struct owner_vertex *v)
{
struct owner_vertex *w;
int i;
sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
KASSERT(LIST_EMPTY(&v->v_outedges), ("Freeing vertex with edges"));
KASSERT(LIST_EMPTY(&v->v_inedges), ("Freeing vertex with edges"));
/*
* Remove from the graph's array and close up the gap,
* renumbering the other vertices.
*/
for (i = v->v_order + 1; i < g->g_size; i++) {
w = g->g_vertices[i];
w->v_order--;
g->g_vertices[i - 1] = w;
}
g->g_size--;
free(v, M_LOCKF);
}
static struct owner_graph *
graph_init(struct owner_graph *g)
{
g->g_vertices = malloc(10 * sizeof(struct owner_vertex *),
M_LOCKF, M_WAITOK);
g->g_size = 0;
g->g_space = 10;
g->g_indexbuf = malloc(g->g_space * sizeof(int), M_LOCKF, M_WAITOK);
g->g_gen = 0;
return (g);
}
#ifdef LOCKF_DEBUG
/*
* Print description of a lock owner
*/
static void
lf_print_owner(struct lock_owner *lo)
{
if (lo->lo_flags & F_REMOTE) {
printf("remote pid %d, system %d",
lo->lo_pid, lo->lo_sysid);
} else if (lo->lo_flags & F_FLOCK) {
printf("file %p", lo->lo_id);
} else {
printf("local pid %d", lo->lo_pid);
}
}
/*
* Print out a lock.
*/
static void
lf_print(char *tag, struct lockf_entry *lock)
{
printf("%s: lock %p for ", tag, (void *)lock);
lf_print_owner(lock->lf_owner);
if (lock->lf_inode != (struct inode *)0)
printf(" in ino %ju on dev <%s>,",
(uintmax_t)lock->lf_inode->i_number,
devtoname(lock->lf_inode->i_dev));
printf(" %s, start %jd, end ",
lock->lf_type == F_RDLCK ? "shared" :
lock->lf_type == F_WRLCK ? "exclusive" :
lock->lf_type == F_UNLCK ? "unlock" : "unknown",
(intmax_t)lock->lf_start);
if (lock->lf_end == OFF_MAX)
printf("EOF");
else
printf("%jd", (intmax_t)lock->lf_end);
if (!LIST_EMPTY(&lock->lf_outedges))
printf(" block %p\n",
(void *)LIST_FIRST(&lock->lf_outedges)->le_to);
else
printf("\n");
}
static void
lf_printlist(char *tag, struct lockf_entry *lock)
{
struct lockf_entry *lf, *blk;
struct lockf_edge *e;
if (lock->lf_inode == (struct inode *)0)
return;
printf("%s: Lock list for ino %ju on dev <%s>:\n",
tag, (uintmax_t)lock->lf_inode->i_number,
devtoname(lock->lf_inode->i_dev));
LIST_FOREACH(lf, &lock->lf_vnode->v_lockf->ls_active, lf_link) {
printf("\tlock %p for ",(void *)lf);
lf_print_owner(lock->lf_owner);
printf(", %s, start %jd, end %jd",
lf->lf_type == F_RDLCK ? "shared" :
lf->lf_type == F_WRLCK ? "exclusive" :
lf->lf_type == F_UNLCK ? "unlock" :
"unknown", (intmax_t)lf->lf_start, (intmax_t)lf->lf_end);
LIST_FOREACH(e, &lf->lf_outedges, le_outlink) {
blk = e->le_to;
printf("\n\t\tlock request %p for ", (void *)blk);
lf_print_owner(blk->lf_owner);
printf(", %s, start %jd, end %jd",
blk->lf_type == F_RDLCK ? "shared" :
blk->lf_type == F_WRLCK ? "exclusive" :
blk->lf_type == F_UNLCK ? "unlock" :
"unknown", (intmax_t)blk->lf_start,
(intmax_t)blk->lf_end);
if (!LIST_EMPTY(&blk->lf_inedges))
panic("lf_printlist: bad list");
}
printf("\n");
}
}
#endif /* LOCKF_DEBUG */
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