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freebsd-nq/sys/kern/vfs_bio.c
Kirk McKusick e929c00d23 The buffer queue mechanism has been reformulated. Instead of having 
QUEUE_AGE, QUEUE_LRU, and QUEUE_EMPTY we instead have QUEUE_CLEAN,
QUEUE_DIRTY, QUEUE_EMPTY, and QUEUE_EMPTYKVA.  With this patch clean
and dirty buffers have been separated.  Empty buffers with KVM
assignments have been separated from truely empty buffers.  getnewbuf()
has been rewritten and now operates in a 100% optimal fashion.  That is,
it is able to find precisely the right kind of buffer it needs to
allocate a new buffer, defragment KVM, or to free-up an existing buffer
when the buffer cache is full (which is a steady-state situation for
the buffer cache).

Buffer flushing has been reorganized.  Previously buffers were flushed
in the context of whatever process hit the conditions forcing buffer
flushing to occur.  This resulted in processes blocking on conditions
unrelated to what they were doing.  This also resulted in inappropriate
VFS stacking chains due to multiple processes getting stuck trying to
flush dirty buffers or due to a single process getting into a situation
where it might attempt to flush buffers recursively - a situation that
was only partially fixed in prior commits.  We have added a new daemon
called the buf_daemon which is responsible for flushing dirty buffers
when the number of dirty buffers exceeds the vfs.hidirtybuffers limit.
This daemon attempts to dynamically adjust the rate at which dirty buffers
are flushed such that getnewbuf() calls (almost) never block.

The number of nbufs and amount of buffer space is now scaled past the
8MB limit that was previously imposed for systems with over 64MB of
memory, and the vfs.{lo,hi}dirtybuffers limits have been relaxed
somewhat.  The number of physical buffers has been increased with the
intention that we will manage physical I/O differently in the future.

reassignbuf previously attempted to keep the dirtyblkhd list sorted which
could result in non-deterministic operation under certain conditions,
such as when a large number of dirty buffers are being managed.  This
algorithm has been changed.  reassignbuf now keeps buffers locally sorted
if it can do so cheaply, and otherwise gives up and adds buffers to
the head of the dirtyblkhd list.  The new algorithm is deterministic but
not perfect.  The new algorithm greatly reduces problems that previously
occured when write_behind was turned off in the system.

The P_FLSINPROG proc->p_flag bit has been replaced by the more descriptive
P_BUFEXHAUST bit.  This bit allows processes working with filesystem
buffers to use available emergency reserves.  Normal processes do not set
this bit and are not allowed to dig into emergency reserves.  The purpose
of this bit is to avoid low-memory deadlocks.

A small race condition was fixed in getpbuf() in vm/vm_pager.c.

Submitted by:	Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by:	Kirk McKusick <mckusick@mckusick.com>
1999-07-04 00:25:38 +00:00

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/*
* Copyright (c) 1994,1997 John S. Dyson
* All rights reserved.
*
* 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 immediately at the beginning of the file, without modification,
* this list of conditions, and the following disclaimer.
* 2. Absolutely no warranty of function or purpose is made by the author
* John S. Dyson.
*
* $Id: vfs_bio.c,v 1.219 1999/06/29 05:59:41 peter Exp $
*/
/*
* this file contains a new buffer I/O scheme implementing a coherent
* VM object and buffer cache scheme. Pains have been taken to make
* sure that the performance degradation associated with schemes such
* as this is not realized.
*
* Author: John S. Dyson
* Significant help during the development and debugging phases
* had been provided by David Greenman, also of the FreeBSD core team.
*
* see man buf(9) for more info.
*/
#define VMIO
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/proc.h>
#include <sys/kthread.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/lock.h>
#include <miscfs/specfs/specdev.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_prot.h>
#include <vm/vm_kern.h>
#include <vm/vm_pageout.h>
#include <vm/vm_page.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_map.h>
#include <sys/buf.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/resourcevar.h>
static MALLOC_DEFINE(M_BIOBUF, "BIO buffer", "BIO buffer");
struct bio_ops bioops; /* I/O operation notification */
struct buf *buf; /* buffer header pool */
struct swqueue bswlist;
static void vm_hold_free_pages(struct buf * bp, vm_offset_t from,
vm_offset_t to);
static void vm_hold_load_pages(struct buf * bp, vm_offset_t from,
vm_offset_t to);
static void vfs_page_set_valid(struct buf *bp, vm_ooffset_t off,
int pageno, vm_page_t m);
static void vfs_clean_pages(struct buf * bp);
static void vfs_setdirty(struct buf *bp);
static void vfs_vmio_release(struct buf *bp);
static int flushbufqueues(void);
static int bd_request;
static void buf_daemon __P((void));
/*
* bogus page -- for I/O to/from partially complete buffers
* this is a temporary solution to the problem, but it is not
* really that bad. it would be better to split the buffer
* for input in the case of buffers partially already in memory,
* but the code is intricate enough already.
*/
vm_page_t bogus_page;
int runningbufspace;
static vm_offset_t bogus_offset;
static int bufspace, maxbufspace, vmiospace,
bufmallocspace, maxbufmallocspace, hibufspace;
#if 0
static int maxvmiobufspace;
#endif
static int needsbuffer;
static int numdirtybuffers, lodirtybuffers, hidirtybuffers;
static int numfreebuffers, lofreebuffers, hifreebuffers;
static int getnewbufcalls;
static int getnewbufloops;
static int getnewbufloops1;
static int getnewbufloops2;
static int getnewbufloops3;
static int getnewbufrestarts;
static int kvafreespace;
SYSCTL_INT(_vfs, OID_AUTO, numdirtybuffers, CTLFLAG_RD,
&numdirtybuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, lodirtybuffers, CTLFLAG_RW,
&lodirtybuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, hidirtybuffers, CTLFLAG_RW,
&hidirtybuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, numfreebuffers, CTLFLAG_RD,
&numfreebuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, lofreebuffers, CTLFLAG_RW,
&lofreebuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, hifreebuffers, CTLFLAG_RW,
&hifreebuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, runningbufspace, CTLFLAG_RD,
&runningbufspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, maxbufspace, CTLFLAG_RW,
&maxbufspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, hibufspace, CTLFLAG_RD,
&hibufspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, bufspace, CTLFLAG_RD,
&bufspace, 0, "");
#if 0
SYSCTL_INT(_vfs, OID_AUTO, maxvmiobufspace, CTLFLAG_RW,
&maxvmiobufspace, 0, "");
#endif
SYSCTL_INT(_vfs, OID_AUTO, vmiospace, CTLFLAG_RD,
&vmiospace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, maxmallocbufspace, CTLFLAG_RW,
&maxbufmallocspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, bufmallocspace, CTLFLAG_RD,
&bufmallocspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, kvafreespace, CTLFLAG_RD,
&kvafreespace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufcalls, CTLFLAG_RW,
&getnewbufcalls, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufloops, CTLFLAG_RW,
&getnewbufloops, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufloops1, CTLFLAG_RW,
&getnewbufloops1, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufloops2, CTLFLAG_RW,
&getnewbufloops2, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufloops3, CTLFLAG_RW,
&getnewbufloops3, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufrestarts, CTLFLAG_RW,
&getnewbufrestarts, 0, "");
static LIST_HEAD(bufhashhdr, buf) bufhashtbl[BUFHSZ], invalhash;
struct bqueues bufqueues[BUFFER_QUEUES] = { { 0 } };
char *buf_wmesg = BUF_WMESG;
extern int vm_swap_size;
#define BUF_MAXUSE 24
#define VFS_BIO_NEED_ANY 0x01 /* any freeable buffer */
#define VFS_BIO_NEED_RESERVED02 0x02 /* unused */
#define VFS_BIO_NEED_FREE 0x04 /* wait for free bufs, hi hysteresis */
#define VFS_BIO_NEED_BUFSPACE 0x08 /* wait for buf space, lo hysteresis */
#define VFS_BIO_NEED_KVASPACE 0x10 /* wait for buffer_map space, emerg */
/*
* kvaspacewakeup:
*
* Called when kva space is potential available for recovery or when
* kva space is recovered in the buffer_map. This function wakes up
* anyone waiting for buffer_map kva space. Even though the buffer_map
* is larger then maxbufspace, this situation will typically occur
* when the buffer_map gets fragmented.
*/
static __inline void
kvaspacewakeup(void)
{
/*
* If someone is waiting for KVA space, wake them up. Even
* though we haven't freed the kva space yet, the waiting
* process will be able to now.
*/
if (needsbuffer & VFS_BIO_NEED_KVASPACE) {
needsbuffer &= ~VFS_BIO_NEED_KVASPACE;
wakeup(&needsbuffer);
}
}
/*
* bufspacewakeup:
*
* Called when buffer space is potentially available for recovery or when
* buffer space is recovered. getnewbuf() will block on this flag when
* it is unable to free sufficient buffer space. Buffer space becomes
* recoverable when bp's get placed back in the queues.
*/
static __inline void
bufspacewakeup(void)
{
/*
* If someone is waiting for BUF space, wake them up. Even
* though we haven't freed the kva space yet, the waiting
* process will be able to now.
*/
if (needsbuffer & VFS_BIO_NEED_BUFSPACE) {
needsbuffer &= ~VFS_BIO_NEED_BUFSPACE;
wakeup(&needsbuffer);
}
}
/*
* bufcountwakeup:
*
* Called when a buffer has been added to one of the free queues to
* account for the buffer and to wakeup anyone waiting for free buffers.
* This typically occurs when large amounts of metadata are being handled
* by the buffer cache ( else buffer space runs out first, usually ).
*/
static __inline void
bufcountwakeup(void)
{
++numfreebuffers;
if (needsbuffer) {
needsbuffer &= ~VFS_BIO_NEED_ANY;
if (numfreebuffers >= hifreebuffers)
needsbuffer &= ~VFS_BIO_NEED_FREE;
wakeup(&needsbuffer);
}
}
/*
* vfs_buf_test_cache:
*
* Called when a buffer is extended. This function clears the B_CACHE
* bit if the newly extended portion of the buffer does not contain
* valid data.
*/
static __inline__
void
vfs_buf_test_cache(struct buf *bp,
vm_ooffset_t foff, vm_offset_t off, vm_offset_t size,
vm_page_t m)
{
if (bp->b_flags & B_CACHE) {
int base = (foff + off) & PAGE_MASK;
if (vm_page_is_valid(m, base, size) == 0)
bp->b_flags &= ~B_CACHE;
}
}
static __inline__
void
bd_wakeup(int dirtybuflevel)
{
if (numdirtybuffers >= dirtybuflevel && bd_request == 0) {
bd_request = 1;
wakeup(&bd_request);
}
}
/*
* Initialize buffer headers and related structures.
*/
void
bufinit()
{
struct buf *bp;
int i;
TAILQ_INIT(&bswlist);
LIST_INIT(&invalhash);
simple_lock_init(&buftimelock);
/* first, make a null hash table */
for (i = 0; i < BUFHSZ; i++)
LIST_INIT(&bufhashtbl[i]);
/* next, make a null set of free lists */
for (i = 0; i < BUFFER_QUEUES; i++)
TAILQ_INIT(&bufqueues[i]);
/* finally, initialize each buffer header and stick on empty q */
for (i = 0; i < nbuf; i++) {
bp = &buf[i];
bzero(bp, sizeof *bp);
bp->b_flags = B_INVAL; /* we're just an empty header */
bp->b_dev = NODEV;
bp->b_rcred = NOCRED;
bp->b_wcred = NOCRED;
bp->b_qindex = QUEUE_EMPTY;
bp->b_xflags = 0;
LIST_INIT(&bp->b_dep);
BUF_LOCKINIT(bp);
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_EMPTY], bp, b_freelist);
LIST_INSERT_HEAD(&invalhash, bp, b_hash);
}
/*
* maxbufspace is currently calculated to support all filesystem
* blocks to be 8K. If you happen to use a 16K filesystem, the size
* of the buffer cache is still the same as it would be for 8K
* filesystems. This keeps the size of the buffer cache "in check"
* for big block filesystems.
*
* maxbufspace is calculated as around 50% of the KVA available in
* the buffer_map ( DFLTSIZE vs BKVASIZE ), I presume to reduce the
* effect of fragmentation.
*/
maxbufspace = (nbuf + 8) * DFLTBSIZE;
if ((hibufspace = maxbufspace - MAXBSIZE * 5) <= MAXBSIZE)
hibufspace = 3 * maxbufspace / 4;
#if 0
/*
* reserve 1/3 of the buffers for metadata (VDIR) which might not be VMIO'ed
*/
maxvmiobufspace = 2 * hibufspace / 3;
#endif
/*
* Limit the amount of malloc memory since it is wired permanently into
* the kernel space. Even though this is accounted for in the buffer
* allocation, we don't want the malloced region to grow uncontrolled.
* The malloc scheme improves memory utilization significantly on average
* (small) directories.
*/
maxbufmallocspace = hibufspace / 20;
/*
* Reduce the chance of a deadlock occuring by limiting the number
* of delayed-write dirty buffers we allow to stack up.
*/
lodirtybuffers = nbuf / 6 + 10;
hidirtybuffers = nbuf / 3 + 20;
numdirtybuffers = 0;
/*
* Try to keep the number of free buffers in the specified range,
* and give the syncer access to an emergency reserve.
*/
lofreebuffers = nbuf / 18 + 5;
hifreebuffers = 2 * lofreebuffers;
numfreebuffers = nbuf;
kvafreespace = 0;
bogus_offset = kmem_alloc_pageable(kernel_map, PAGE_SIZE);
bogus_page = vm_page_alloc(kernel_object,
((bogus_offset - VM_MIN_KERNEL_ADDRESS) >> PAGE_SHIFT),
VM_ALLOC_NORMAL);
}
/*
* Free the kva allocation for a buffer
* Must be called only at splbio or higher,
* as this is the only locking for buffer_map.
*/
static void
bfreekva(struct buf * bp)
{
if (bp->b_kvasize) {
vm_map_delete(buffer_map,
(vm_offset_t) bp->b_kvabase,
(vm_offset_t) bp->b_kvabase + bp->b_kvasize
);
bp->b_kvasize = 0;
kvaspacewakeup();
}
}
/*
* bremfree:
*
* Remove the buffer from the appropriate free list.
*/
void
bremfree(struct buf * bp)
{
int s = splbio();
int old_qindex = bp->b_qindex;
if (bp->b_qindex != QUEUE_NONE) {
if (bp->b_qindex == QUEUE_EMPTYKVA) {
kvafreespace -= bp->b_kvasize;
}
if (BUF_REFCNT(bp) == 1)
TAILQ_REMOVE(&bufqueues[bp->b_qindex], bp, b_freelist);
else if (BUF_REFCNT(bp) == 0)
panic("bremfree: not locked");
else
/* Temporary panic to verify exclusive locking */
/* This panic goes away when we allow shared refs */
panic("bremfree: multiple refs");
bp->b_qindex = QUEUE_NONE;
runningbufspace += bp->b_bufsize;
} else {
#if !defined(MAX_PERF)
panic("bremfree: removing a buffer when not on a queue");
#endif
}
/*
* Fixup numfreebuffers count. If the buffer is invalid or not
* delayed-write, and it was on the EMPTY, LRU, or AGE queues,
* the buffer was free and we must decrement numfreebuffers.
*/
if ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0) {
switch(old_qindex) {
case QUEUE_DIRTY:
case QUEUE_CLEAN:
case QUEUE_EMPTY:
case QUEUE_EMPTYKVA:
--numfreebuffers;
break;
default:
break;
}
}
splx(s);
}
/*
* Get a buffer with the specified data. Look in the cache first. We
* must clear B_ERROR and B_INVAL prior to initiating I/O. If B_CACHE
* is set, the buffer is valid and we do not have to do anything ( see
* getblk() ).
*/
int
bread(struct vnode * vp, daddr_t blkno, int size, struct ucred * cred,
struct buf ** bpp)
{
struct buf *bp;
bp = getblk(vp, blkno, size, 0, 0);
*bpp = bp;
/* if not found in cache, do some I/O */
if ((bp->b_flags & B_CACHE) == 0) {
if (curproc != NULL)
curproc->p_stats->p_ru.ru_inblock++;
KASSERT(!(bp->b_flags & B_ASYNC), ("bread: illegal async bp %p", bp));
bp->b_flags |= B_READ;
bp->b_flags &= ~(B_ERROR | B_INVAL);
if (bp->b_rcred == NOCRED) {
if (cred != NOCRED)
crhold(cred);
bp->b_rcred = cred;
}
vfs_busy_pages(bp, 0);
VOP_STRATEGY(vp, bp);
return (biowait(bp));
}
return (0);
}
/*
* Operates like bread, but also starts asynchronous I/O on
* read-ahead blocks. We must clear B_ERROR and B_INVAL prior
* to initiating I/O . If B_CACHE is set, the buffer is valid
* and we do not have to do anything.
*/
int
breadn(struct vnode * vp, daddr_t blkno, int size,
daddr_t * rablkno, int *rabsize,
int cnt, struct ucred * cred, struct buf ** bpp)
{
struct buf *bp, *rabp;
int i;
int rv = 0, readwait = 0;
*bpp = bp = getblk(vp, blkno, size, 0, 0);
/* if not found in cache, do some I/O */
if ((bp->b_flags & B_CACHE) == 0) {
if (curproc != NULL)
curproc->p_stats->p_ru.ru_inblock++;
bp->b_flags |= B_READ;
bp->b_flags &= ~(B_ERROR | B_INVAL);
if (bp->b_rcred == NOCRED) {
if (cred != NOCRED)
crhold(cred);
bp->b_rcred = cred;
}
vfs_busy_pages(bp, 0);
VOP_STRATEGY(vp, bp);
++readwait;
}
for (i = 0; i < cnt; i++, rablkno++, rabsize++) {
if (inmem(vp, *rablkno))
continue;
rabp = getblk(vp, *rablkno, *rabsize, 0, 0);
if ((rabp->b_flags & B_CACHE) == 0) {
if (curproc != NULL)
curproc->p_stats->p_ru.ru_inblock++;
rabp->b_flags |= B_READ | B_ASYNC;
rabp->b_flags &= ~(B_ERROR | B_INVAL);
if (rabp->b_rcred == NOCRED) {
if (cred != NOCRED)
crhold(cred);
rabp->b_rcred = cred;
}
vfs_busy_pages(rabp, 0);
BUF_KERNPROC(rabp);
VOP_STRATEGY(vp, rabp);
} else {
brelse(rabp);
}
}
if (readwait) {
rv = biowait(bp);
}
return (rv);
}
/*
* Write, release buffer on completion. (Done by iodone
* if async). Do not bother writing anything if the buffer
* is invalid.
*
* Note that we set B_CACHE here, indicating that buffer is
* fully valid and thus cacheable. This is true even of NFS
* now so we set it generally. This could be set either here
* or in biodone() since the I/O is synchronous. We put it
* here.
*/
int
bwrite(struct buf * bp)
{
int oldflags, s;
struct vnode *vp;
struct mount *mp;
if (bp->b_flags & B_INVAL) {
brelse(bp);
return (0);
}
oldflags = bp->b_flags;
#if !defined(MAX_PERF)
if (BUF_REFCNT(bp) == 0)
panic("bwrite: buffer is not busy???");
#endif
s = splbio();
bundirty(bp);
bp->b_flags &= ~(B_READ | B_DONE | B_ERROR);
bp->b_flags |= B_WRITEINPROG | B_CACHE;
bp->b_vp->v_numoutput++;
vfs_busy_pages(bp, 1);
if (curproc != NULL)
curproc->p_stats->p_ru.ru_oublock++;
splx(s);
if (oldflags & B_ASYNC)
BUF_KERNPROC(bp);
VOP_STRATEGY(bp->b_vp, bp);
/*
* Collect statistics on synchronous and asynchronous writes.
* Writes to block devices are charged to their associated
* filesystem (if any).
*/
if ((vp = bp->b_vp) != NULL) {
if (vp->v_type == VBLK)
mp = vp->v_specmountpoint;
else
mp = vp->v_mount;
if (mp != NULL) {
if ((oldflags & B_ASYNC) == 0)
mp->mnt_stat.f_syncwrites++;
else
mp->mnt_stat.f_asyncwrites++;
}
}
if ((oldflags & B_ASYNC) == 0) {
int rtval = biowait(bp);
brelse(bp);
return (rtval);
}
return (0);
}
/*
* Delayed write. (Buffer is marked dirty). Do not bother writing
* anything if the buffer is marked invalid.
*
* Note that since the buffer must be completely valid, we can safely
* set B_CACHE. In fact, we have to set B_CACHE here rather then in
* biodone() in order to prevent getblk from writing the buffer
* out synchronously.
*/
void
bdwrite(struct buf * bp)
{
struct vnode *vp;
#if !defined(MAX_PERF)
if (BUF_REFCNT(bp) == 0)
panic("bdwrite: buffer is not busy");
#endif
if (bp->b_flags & B_INVAL) {
brelse(bp);
return;
}
bdirty(bp);
/*
* Set B_CACHE, indicating that the buffer is fully valid. This is
* true even of NFS now.
*/
bp->b_flags |= B_CACHE;
/*
* This bmap keeps the system from needing to do the bmap later,
* perhaps when the system is attempting to do a sync. Since it
* is likely that the indirect block -- or whatever other datastructure
* that the filesystem needs is still in memory now, it is a good
* thing to do this. Note also, that if the pageout daemon is
* requesting a sync -- there might not be enough memory to do
* the bmap then... So, this is important to do.
*/
if (bp->b_lblkno == bp->b_blkno) {
VOP_BMAP(bp->b_vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL);
}
/*
* Set the *dirty* buffer range based upon the VM system dirty pages.
*/
vfs_setdirty(bp);
/*
* We need to do this here to satisfy the vnode_pager and the
* pageout daemon, so that it thinks that the pages have been
* "cleaned". Note that since the pages are in a delayed write
* buffer -- the VFS layer "will" see that the pages get written
* out on the next sync, or perhaps the cluster will be completed.
*/
vfs_clean_pages(bp);
bqrelse(bp);
/*
* Wakeup the buffer flushing daemon if we have saturated the
* buffer cache.
*/
bd_wakeup(hidirtybuffers);
/*
* XXX The soft dependency code is not prepared to
* have I/O done when a bdwrite is requested. For
* now we just let the write be delayed if it is
* requested by the soft dependency code.
*/
if ((vp = bp->b_vp) &&
((vp->v_type == VBLK && vp->v_specmountpoint &&
(vp->v_specmountpoint->mnt_flag & MNT_SOFTDEP)) ||
(vp->v_mount && (vp->v_mount->mnt_flag & MNT_SOFTDEP))))
return;
}
/*
* bdirty:
*
* Turn buffer into delayed write request. We must clear B_READ and
* B_RELBUF, and we must set B_DELWRI. We reassign the buffer to
* itself to properly update it in the dirty/clean lists. We mark it
* B_DONE to ensure that any asynchronization of the buffer properly
* clears B_DONE ( else a panic will occur later ).
*
* bdirty() is kinda like bdwrite() - we have to clear B_INVAL which
* might have been set pre-getblk(). Unlike bwrite/bdwrite, bdirty()
* should only be called if the buffer is known-good.
*
* Since the buffer is not on a queue, we do not update the numfreebuffers
* count.
*
* Must be called at splbio().
* The buffer must be on QUEUE_NONE.
*/
void
bdirty(bp)
struct buf *bp;
{
KASSERT(bp->b_qindex == QUEUE_NONE, ("bdirty: buffer %p still on queue %d", bp, bp->b_qindex));
bp->b_flags &= ~(B_READ|B_RELBUF);
if ((bp->b_flags & B_DELWRI) == 0) {
bp->b_flags |= B_DONE | B_DELWRI;
reassignbuf(bp, bp->b_vp);
++numdirtybuffers;
bd_wakeup(hidirtybuffers);
}
}
/*
* bundirty:
*
* Clear B_DELWRI for buffer.
*
* Since the buffer is not on a queue, we do not update the numfreebuffers
* count.
*
* Must be called at splbio().
* The buffer must be on QUEUE_NONE.
*/
void
bundirty(bp)
struct buf *bp;
{
KASSERT(bp->b_qindex == QUEUE_NONE, ("bundirty: buffer %p still on queue %d", bp, bp->b_qindex));
if (bp->b_flags & B_DELWRI) {
bp->b_flags &= ~B_DELWRI;
reassignbuf(bp, bp->b_vp);
--numdirtybuffers;
}
}
/*
* bawrite:
*
* Asynchronous write. Start output on a buffer, but do not wait for
* it to complete. The buffer is released when the output completes.
*
* bwrite() ( or the VOP routine anyway ) is responsible for handling
* B_INVAL buffers. Not us.
*/
void
bawrite(struct buf * bp)
{
bp->b_flags |= B_ASYNC;
(void) VOP_BWRITE(bp->b_vp, bp);
}
/*
* bowrite:
*
* Ordered write. Start output on a buffer, and flag it so that the
* device will write it in the order it was queued. The buffer is
* released when the output completes. bwrite() ( or the VOP routine
* anyway ) is responsible for handling B_INVAL buffers.
*/
int
bowrite(struct buf * bp)
{
bp->b_flags |= B_ORDERED | B_ASYNC;
return (VOP_BWRITE(bp->b_vp, bp));
}
/*
* brelse:
*
* Release a busy buffer and, if requested, free its resources. The
* buffer will be stashed in the appropriate bufqueue[] allowing it
* to be accessed later as a cache entity or reused for other purposes.
*/
void
brelse(struct buf * bp)
{
int s;
KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), ("brelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp));
#if 0
if (bp->b_flags & B_CLUSTER) {
relpbuf(bp, NULL);
return;
}
#endif
s = splbio();
if (bp->b_flags & B_LOCKED)
bp->b_flags &= ~B_ERROR;
if ((bp->b_flags & (B_READ | B_ERROR)) == B_ERROR) {
/*
* Failed write, redirty. Must clear B_ERROR to prevent
* pages from being scrapped. Note: B_INVAL is ignored
* here but will presumably be dealt with later.
*/
bp->b_flags &= ~B_ERROR;
bdirty(bp);
} else if ((bp->b_flags & (B_NOCACHE | B_INVAL | B_ERROR | B_FREEBUF)) ||
(bp->b_bufsize <= 0)) {
/*
* Either a failed I/O or we were asked to free or not
* cache the buffer.
*/
bp->b_flags |= B_INVAL;
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
if (bp->b_flags & B_DELWRI)
--numdirtybuffers;
bp->b_flags &= ~(B_DELWRI | B_CACHE | B_FREEBUF);
if ((bp->b_flags & B_VMIO) == 0) {
if (bp->b_bufsize)
allocbuf(bp, 0);
if (bp->b_vp)
brelvp(bp);
}
}
/*
* We must clear B_RELBUF if B_DELWRI is set. If vfs_vmio_release()
* is called with B_DELWRI set, the underlying pages may wind up
* getting freed causing a previous write (bdwrite()) to get 'lost'
* because pages associated with a B_DELWRI bp are marked clean.
*
* We still allow the B_INVAL case to call vfs_vmio_release(), even
* if B_DELWRI is set.
*/
if (bp->b_flags & B_DELWRI)
bp->b_flags &= ~B_RELBUF;
/*
* VMIO buffer rundown. It is not very necessary to keep a VMIO buffer
* constituted, not even NFS buffers now. Two flags effect this. If
* B_INVAL, the struct buf is invalidated but the VM object is kept
* around ( i.e. so it is trivial to reconstitute the buffer later ).
*
* If B_ERROR or B_NOCACHE is set, pages in the VM object will be
* invalidated. B_ERROR cannot be set for a failed write unless the
* buffer is also B_INVAL because it hits the re-dirtying code above.
*
* Normally we can do this whether a buffer is B_DELWRI or not. If
* the buffer is an NFS buffer, it is tracking piecemeal writes or
* the commit state and we cannot afford to lose the buffer.
*/
if ((bp->b_flags & B_VMIO)
&& !(bp->b_vp->v_tag == VT_NFS &&
bp->b_vp->v_type != VBLK &&
(bp->b_flags & B_DELWRI))
) {
int i, j, resid;
vm_page_t m;
off_t foff;
vm_pindex_t poff;
vm_object_t obj;
struct vnode *vp;
vp = bp->b_vp;
/*
* Get the base offset and length of the buffer. Note that
* for block sizes that are less then PAGE_SIZE, the b_data
* base of the buffer does not represent exactly b_offset and
* neither b_offset nor b_size are necessarily page aligned.
* Instead, the starting position of b_offset is:
*
* b_data + (b_offset & PAGE_MASK)
*
* block sizes less then DEV_BSIZE (usually 512) are not
* supported due to the page granularity bits (m->valid,
* m->dirty, etc...).
*
* See man buf(9) for more information
*/
resid = bp->b_bufsize;
foff = bp->b_offset;
for (i = 0; i < bp->b_npages; i++) {
m = bp->b_pages[i];
vm_page_flag_clear(m, PG_ZERO);
if (m == bogus_page) {
obj = (vm_object_t) vp->v_object;
poff = OFF_TO_IDX(bp->b_offset);
for (j = i; j < bp->b_npages; j++) {
m = bp->b_pages[j];
if (m == bogus_page) {
m = vm_page_lookup(obj, poff + j);
#if !defined(MAX_PERF)
if (!m) {
panic("brelse: page missing\n");
}
#endif
bp->b_pages[j] = m;
}
}
if ((bp->b_flags & B_INVAL) == 0) {
pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages);
}
}
if (bp->b_flags & (B_NOCACHE|B_ERROR)) {
int poffset = foff & PAGE_MASK;
int presid = resid > (PAGE_SIZE - poffset) ?
(PAGE_SIZE - poffset) : resid;
KASSERT(presid >= 0, ("brelse: extra page"));
vm_page_set_invalid(m, poffset, presid);
}
resid -= PAGE_SIZE - (foff & PAGE_MASK);
foff = (foff + PAGE_SIZE) & ~PAGE_MASK;
}
if (bp->b_flags & (B_INVAL | B_RELBUF))
vfs_vmio_release(bp);
} else if (bp->b_flags & B_VMIO) {
if (bp->b_flags & (B_INVAL | B_RELBUF))
vfs_vmio_release(bp);
}
#if !defined(MAX_PERF)
if (bp->b_qindex != QUEUE_NONE)
panic("brelse: free buffer onto another queue???");
#endif
if (BUF_REFCNT(bp) > 1) {
/* Temporary panic to verify exclusive locking */
/* This panic goes away when we allow shared refs */
panic("brelse: multiple refs");
/* do not release to free list */
BUF_UNLOCK(bp);
splx(s);
return;
}
/* enqueue */
/* buffers with no memory */
if (bp->b_bufsize == 0) {
bp->b_flags |= B_INVAL;
if (bp->b_kvasize)
bp->b_qindex = QUEUE_EMPTYKVA;
else
bp->b_qindex = QUEUE_EMPTY;
TAILQ_INSERT_HEAD(&bufqueues[bp->b_qindex], bp, b_freelist);
LIST_REMOVE(bp, b_hash);
LIST_INSERT_HEAD(&invalhash, bp, b_hash);
bp->b_dev = NODEV;
kvafreespace += bp->b_kvasize;
if (bp->b_kvasize)
kvaspacewakeup();
/* buffers with junk contents */
} else if (bp->b_flags & (B_ERROR | B_INVAL | B_NOCACHE | B_RELBUF)) {
bp->b_flags |= B_INVAL;
bp->b_qindex = QUEUE_CLEAN;
TAILQ_INSERT_HEAD(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
LIST_REMOVE(bp, b_hash);
LIST_INSERT_HEAD(&invalhash, bp, b_hash);
bp->b_dev = NODEV;
/* buffers that are locked */
} else if (bp->b_flags & B_LOCKED) {
bp->b_qindex = QUEUE_LOCKED;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LOCKED], bp, b_freelist);
/* remaining buffers */
} else {
switch(bp->b_flags & (B_DELWRI|B_AGE)) {
case B_DELWRI | B_AGE:
bp->b_qindex = QUEUE_DIRTY;
TAILQ_INSERT_HEAD(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
break;
case B_DELWRI:
bp->b_qindex = QUEUE_DIRTY;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
break;
case B_AGE:
bp->b_qindex = QUEUE_CLEAN;
TAILQ_INSERT_HEAD(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
break;
default:
bp->b_qindex = QUEUE_CLEAN;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
break;
}
}
/*
* If B_INVAL, clear B_DELWRI. We've already placed the buffer
* on the correct queue.
*/
if ((bp->b_flags & (B_INVAL|B_DELWRI)) == (B_INVAL|B_DELWRI)) {
bp->b_flags &= ~B_DELWRI;
--numdirtybuffers;
}
runningbufspace -= bp->b_bufsize;
/*
* Fixup numfreebuffers count. The bp is on an appropriate queue
* unless locked. We then bump numfreebuffers if it is not B_DELWRI.
* We've already handled the B_INVAL case ( B_DELWRI will be clear
* if B_INVAL is set ).
*/
if ((bp->b_flags & B_LOCKED) == 0 && !(bp->b_flags & B_DELWRI))
bufcountwakeup();
/*
* Something we can maybe free.
*/
if (bp->b_bufsize)
bufspacewakeup();
/* unlock */
BUF_UNLOCK(bp);
bp->b_flags &= ~(B_ORDERED | B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF);
splx(s);
}
/*
* Release a buffer back to the appropriate queue but do not try to free
* it.
*
* bqrelse() is used by bdwrite() to requeue a delayed write, and used by
* biodone() to requeue an async I/O on completion. It is also used when
* known good buffers need to be requeued but we think we may need the data
* again soon.
*/
void
bqrelse(struct buf * bp)
{
int s;
s = splbio();
KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), ("bqrelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp));
#if !defined(MAX_PERF)
if (bp->b_qindex != QUEUE_NONE)
panic("bqrelse: free buffer onto another queue???");
#endif
if (BUF_REFCNT(bp) > 1) {
/* do not release to free list */
panic("bqrelse: multiple refs");
BUF_UNLOCK(bp);
splx(s);
return;
}
if (bp->b_flags & B_LOCKED) {
bp->b_flags &= ~B_ERROR;
bp->b_qindex = QUEUE_LOCKED;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LOCKED], bp, b_freelist);
/* buffers with stale but valid contents */
} else if (bp->b_flags & B_DELWRI) {
bp->b_qindex = QUEUE_DIRTY;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
} else {
bp->b_qindex = QUEUE_CLEAN;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
}
runningbufspace -= bp->b_bufsize;
if ((bp->b_flags & B_LOCKED) == 0 &&
((bp->b_flags & B_INVAL) || !(bp->b_flags & B_DELWRI))) {
bufcountwakeup();
}
/*
* Something we can maybe wakeup
*/
if (bp->b_bufsize)
bufspacewakeup();
/* unlock */
BUF_UNLOCK(bp);
bp->b_flags &= ~(B_ORDERED | B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF);
splx(s);
}
static void
vfs_vmio_release(bp)
struct buf *bp;
{
int i, s;
vm_page_t m;
s = splvm();
for (i = 0; i < bp->b_npages; i++) {
m = bp->b_pages[i];
bp->b_pages[i] = NULL;
/*
* In order to keep page LRU ordering consistent, put
* everything on the inactive queue.
*/
vm_page_unwire(m, 0);
/*
* We don't mess with busy pages, it is
* the responsibility of the process that
* busied the pages to deal with them.
*/
if ((m->flags & PG_BUSY) || (m->busy != 0))
continue;
if (m->wire_count == 0) {
vm_page_flag_clear(m, PG_ZERO);
/*
* Might as well free the page if we can and it has
* no valid data.
*/
if ((bp->b_flags & B_ASYNC) == 0 && !m->valid && m->hold_count == 0) {
vm_page_busy(m);
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
}
}
}
bufspace -= bp->b_bufsize;
vmiospace -= bp->b_bufsize;
runningbufspace -= bp->b_bufsize;
splx(s);
pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
if (bp->b_bufsize)
bufspacewakeup();
bp->b_npages = 0;
bp->b_bufsize = 0;
bp->b_flags &= ~B_VMIO;
if (bp->b_vp)
brelvp(bp);
}
/*
* Check to see if a block is currently memory resident.
*/
struct buf *
gbincore(struct vnode * vp, daddr_t blkno)
{
struct buf *bp;
struct bufhashhdr *bh;
bh = BUFHASH(vp, blkno);
bp = bh->lh_first;
/* Search hash chain */
while (bp != NULL) {
/* hit */
if (bp->b_vp == vp && bp->b_lblkno == blkno &&
(bp->b_flags & B_INVAL) == 0) {
break;
}
bp = bp->b_hash.le_next;
}
return (bp);
}
/*
* this routine implements clustered async writes for
* clearing out B_DELWRI buffers... This is much better
* than the old way of writing only one buffer at a time.
*/
int
vfs_bio_awrite(struct buf * bp)
{
int i;
daddr_t lblkno = bp->b_lblkno;
struct vnode *vp = bp->b_vp;
int s;
int ncl;
struct buf *bpa;
int nwritten;
int size;
int maxcl;
s = splbio();
/*
* right now we support clustered writing only to regular files, and
* then only if our I/O system is not saturated.
*/
if ((vp->v_type == VREG) &&
(vp->v_mount != 0) && /* Only on nodes that have the size info */
(bp->b_flags & (B_CLUSTEROK | B_INVAL)) == B_CLUSTEROK) {
size = vp->v_mount->mnt_stat.f_iosize;
maxcl = MAXPHYS / size;
for (i = 1; i < maxcl; i++) {
if ((bpa = gbincore(vp, lblkno + i)) &&
BUF_REFCNT(bpa) == 0 &&
((bpa->b_flags & (B_DELWRI | B_CLUSTEROK | B_INVAL)) ==
(B_DELWRI | B_CLUSTEROK)) &&
(bpa->b_bufsize == size)) {
if ((bpa->b_blkno == bpa->b_lblkno) ||
(bpa->b_blkno != bp->b_blkno + ((i * size) >> DEV_BSHIFT)))
break;
} else {
break;
}
}
ncl = i;
/*
* this is a possible cluster write
*/
if (ncl != 1) {
nwritten = cluster_wbuild(vp, size, lblkno, ncl);
splx(s);
return nwritten;
}
}
BUF_LOCK(bp, LK_EXCLUSIVE);
bremfree(bp);
bp->b_flags |= B_ASYNC;
splx(s);
/*
* default (old) behavior, writing out only one block
*
* XXX returns b_bufsize instead of b_bcount for nwritten?
*/
nwritten = bp->b_bufsize;
(void) VOP_BWRITE(bp->b_vp, bp);
return nwritten;
}
/*
* getnewbuf:
*
* Find and initialize a new buffer header, freeing up existing buffers
* in the bufqueues as necessary. The new buffer is returned locked.
*
* Important: B_INVAL is not set. If the caller wishes to throw the
* buffer away, the caller must set B_INVAL prior to calling brelse().
*
* We block if:
* We have insufficient buffer headers
* We have insufficient buffer space
* buffer_map is too fragmented ( space reservation fails )
* If we have to flush dirty buffers ( but we try to avoid this )
*
* To avoid VFS layer recursion we do not flush dirty buffers ourselves.
* Instead we ask the pageout daemon to do it for us. We attempt to
* avoid piecemeal wakeups of the pageout daemon.
*/
/*
* We fully expect to be able to handle any fragmentation and buffer
* space issues by freeing QUEUE_CLEAN buffers. If this fails, we
* have to wakeup the pageout daemon and ask it to flush some of our
* QUEUE_DIRTY buffers. We have to be careful to prevent a deadlock.
* XXX
*/
static struct buf *
getnewbuf(struct vnode *vp, daddr_t blkno,
int slpflag, int slptimeo, int size, int maxsize)
{
struct buf *bp;
struct buf *nbp;
struct buf *dbp;
int outofspace;
int nqindex;
int defrag = 0;
static int newbufcnt = 0;
int lastnewbuf = newbufcnt;
++getnewbufcalls;
--getnewbufrestarts;
restart:
++getnewbufrestarts;
/*
* Calculate whether we are out of buffer space. This state is
* recalculated on every restart. If we are out of space, we
* have to turn off defragmentation. Setting defrag to -1 when
* outofspace is positive means "defrag while freeing buffers".
* The looping conditional will be muffed up if defrag is left
* positive when outofspace is positive.
*/
dbp = NULL;
outofspace = 0;
if (bufspace >= hibufspace) {
if ((curproc->p_flag & P_BUFEXHAUST) == 0 ||
bufspace >= maxbufspace) {
outofspace = 1;
if (defrag > 0)
defrag = -1;
}
}
/*
* defrag state is semi-persistant. 1 means we are flagged for
* defragging. -1 means we actually defragged something.
*/
/* nop */
/*
* Setup for scan. If we do not have enough free buffers,
* we setup a degenerate case that immediately fails. Note
* that if we are specially marked process, we are allowed to
* dip into our reserves.
*
* Normally we want to find an EMPTYKVA buffer. That is, a
* buffer with kva already allocated. If there are no EMPTYKVA
* buffers we back up to the truely EMPTY buffers. When defragging
* we do not bother backing up since we have to locate buffers with
* kva to defrag. If we are out of space we skip both EMPTY and
* EMPTYKVA and dig right into the CLEAN queue.
*
* In this manner we avoid scanning unnecessary buffers. It is very
* important for us to do this because the buffer cache is almost
* constantly out of space or in need of defragmentation.
*/
if ((curproc->p_flag & P_BUFEXHAUST) == 0 &&
numfreebuffers < lofreebuffers) {
nqindex = QUEUE_CLEAN;
nbp = NULL;
} else {
nqindex = QUEUE_EMPTYKVA;
nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTYKVA]);
if (nbp == NULL) {
if (defrag <= 0) {
nqindex = QUEUE_EMPTY;
nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTY]);
}
}
if (outofspace || nbp == NULL) {
nqindex = QUEUE_CLEAN;
nbp = TAILQ_FIRST(&bufqueues[QUEUE_CLEAN]);
}
}
/*
* Run scan, possibly freeing data and/or kva mappings on the fly
* depending.
*/
if (nbp)
--getnewbufloops;
while ((bp = nbp) != NULL) {
int qindex = nqindex;
++getnewbufloops;
/*
* Calculate next bp ( we can only use it if we do not block
* or do other fancy things ).
*/
if ((nbp = TAILQ_NEXT(bp, b_freelist)) == NULL) {
switch(qindex) {
case QUEUE_EMPTY:
nqindex = QUEUE_EMPTYKVA;
if ((nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTYKVA])))
break;
/* fall through */
case QUEUE_EMPTYKVA:
nqindex = QUEUE_CLEAN;
if ((nbp = TAILQ_FIRST(&bufqueues[QUEUE_CLEAN])))
break;
/* fall through */
case QUEUE_CLEAN:
/*
* nbp is NULL.
*/
break;
}
}
/*
* Sanity Checks
*/
KASSERT(BUF_REFCNT(bp) == 0, ("getnewbuf: busy buffer %p on free list", bp));
KASSERT(bp->b_qindex == qindex, ("getnewbuf: inconsistant queue %d bp %p", qindex, bp));
/*
* Note: we no longer distinguish between VMIO and non-VMIO
* buffers.
*/
KASSERT((bp->b_flags & B_DELWRI) == 0, ("delwri buffer %p found in queue %d", bp, qindex));
/*
* If we are defragging and the buffer isn't useful for fixing
* that problem we continue. If we are out of space and the
* buffer isn't useful for fixing that problem we continue.
*/
if (defrag > 0 && bp->b_kvasize == 0) {
++getnewbufloops1;
continue;
}
if (outofspace > 0 && bp->b_bufsize == 0) {
++getnewbufloops2;
continue;
}
/*
* Start freeing the bp. This is somewhat involved. nbp
* remains valid only for QUEUE_EMPTY[KVA] bp's.
*/
if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0)
panic("getnewbuf: locked buf");
bremfree(bp);
if (qindex == QUEUE_CLEAN) {
if (bp->b_flags & B_VMIO) {
bp->b_flags &= ~B_ASYNC;
vfs_vmio_release(bp);
}
if (bp->b_vp)
brelvp(bp);
}
/*
* NOTE: nbp is now entirely invalid. We can only restart
* the scan from this point on.
*
* Get the rest of the buffer freed up. b_kva* is still
* valid after this operation.
*/
if (bp->b_rcred != NOCRED) {
crfree(bp->b_rcred);
bp->b_rcred = NOCRED;
}
if (bp->b_wcred != NOCRED) {
crfree(bp->b_wcred);
bp->b_wcred = NOCRED;
}
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
LIST_REMOVE(bp, b_hash);
LIST_INSERT_HEAD(&invalhash, bp, b_hash);
if (bp->b_bufsize)
allocbuf(bp, 0);
bp->b_flags = 0;
bp->b_dev = NODEV;
bp->b_vp = NULL;
bp->b_blkno = bp->b_lblkno = 0;
bp->b_offset = NOOFFSET;
bp->b_iodone = 0;
bp->b_error = 0;
bp->b_resid = 0;
bp->b_bcount = 0;
bp->b_npages = 0;
bp->b_dirtyoff = bp->b_dirtyend = 0;
bp->b_usecount = 5;
LIST_INIT(&bp->b_dep);
/*
* Ok, now that we have a free buffer, if we are defragging
* we have to recover the kvaspace. If we are out of space
* we have to free the buffer (which we just did), but we
* do not have to recover kva space unless we hit a defrag
* hicup. Being able to avoid freeing the kva space leads
* to a significant reduction in overhead.
*/
if (defrag > 0) {
defrag = -1;
bp->b_flags |= B_INVAL;
bfreekva(bp);
brelse(bp);
goto restart;
}
if (outofspace > 0) {
outofspace = -1;
bp->b_flags |= B_INVAL;
if (defrag < 0)
bfreekva(bp);
brelse(bp);
goto restart;
}
/*
* We are done
*/
break;
}
/*
* If we exhausted our list, sleep as appropriate. We may have to
* wakeup the pageout daemon to write out some dirty buffers.
*/
if (bp == NULL) {
int flags;
dosleep:
if (defrag > 0)
flags = VFS_BIO_NEED_KVASPACE;
else if (outofspace > 0)
flags = VFS_BIO_NEED_BUFSPACE;
else
flags = VFS_BIO_NEED_ANY;
/* XXX */
(void) speedup_syncer();
needsbuffer |= flags;
while (needsbuffer & flags) {
if (tsleep(&needsbuffer, (PRIBIO + 4) | slpflag,
"newbuf", slptimeo))
return (NULL);
}
} else {
/*
* We finally have a valid bp. We aren't quite out of the
* woods, we still have to reserve kva space.
*/
vm_offset_t addr = 0;
maxsize = (maxsize + PAGE_MASK) & ~PAGE_MASK;
if (maxsize != bp->b_kvasize) {
bfreekva(bp);
if (vm_map_findspace(buffer_map,
vm_map_min(buffer_map), maxsize, &addr)) {
/*
* Uh oh. Buffer map is to fragmented. Try
* to defragment.
*/
if (defrag <= 0) {
defrag = 1;
bp->b_flags |= B_INVAL;
brelse(bp);
goto restart;
}
/*
* Uh oh. We couldn't seem to defragment
*/
bp = NULL;
goto dosleep;
}
}
if (addr) {
vm_map_insert(buffer_map, NULL, 0,
addr, addr + maxsize,
VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
bp->b_kvabase = (caddr_t) addr;
bp->b_kvasize = maxsize;
}
bp->b_data = bp->b_kvabase;
}
/*
* If we have slept at some point in this process and another
* process has managed to allocate a new buffer while we slept,
* we have to return NULL so that our caller can recheck to
* ensure that the other process did not create an identically
* identified buffer to the one we were requesting. We make this
* check by incrementing the static int newbufcnt each time we
* successfully allocate a new buffer. By saving the value of
* newbufcnt in our local lastnewbuf, we can compare newbufcnt
* with lastnewbuf to see if any other process managed to
* allocate a buffer while we were doing so ourselves.
*
* Note that bp, if valid, is locked.
*/
if (lastnewbuf == newbufcnt) {
/*
* No buffers allocated, so we can return one if we were
* successful, or continue trying if we were not successful.
*/
if (bp != NULL) {
newbufcnt += 1;
return (bp);
}
goto restart;
}
/*
* Another process allocated a buffer since we were called, so
* we have to free the one we allocated and return NULL to let
* our caller recheck to see if a new buffer is still needed.
*/
if (bp != NULL) {
bp->b_flags |= B_INVAL;
brelse(bp);
}
return (NULL);
}
/*
* waitfreebuffers:
*
* Wait for sufficient free buffers. Only called from normal processes.
*/
static void
waitfreebuffers(int slpflag, int slptimeo)
{
while (numfreebuffers < hifreebuffers) {
bd_wakeup(0);
if (numfreebuffers >= hifreebuffers)
break;
needsbuffer |= VFS_BIO_NEED_FREE;
if (tsleep(&needsbuffer, (PRIBIO + 4)|slpflag, "biofre", slptimeo))
break;
}
}
/*
* buf_daemon:
*
* buffer flushing daemon. Buffers are normally flushed by the
* update daemon but if it cannot keep up this process starts to
* take the load in an attempt to prevent getnewbuf() from blocking.
*/
static struct proc *bufdaemonproc;
static int bd_interval;
static int bd_flushto;
static struct kproc_desc buf_kp = {
"bufdaemon",
buf_daemon,
&bufdaemonproc
};
SYSINIT(bufdaemon, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST, kproc_start, &buf_kp)
static void
buf_daemon()
{
int s;
/*
* This process is allowed to take the buffer cache to the limit
*/
curproc->p_flag |= P_BUFEXHAUST;
s = splbio();
bd_interval = 5 * hz; /* dynamically adjusted */
bd_flushto = hidirtybuffers; /* dynamically adjusted */
while (TRUE) {
bd_request = 0;
/*
* Do the flush.
*/
{
while (numdirtybuffers > bd_flushto) {
if (flushbufqueues() == 0)
break;
}
}
/*
* Whew. If nobody is requesting anything we sleep until the
* next event. If we sleep and the sleep times out and
* nobody is waiting for interesting things we back-off.
* Otherwise we get more aggressive.
*/
if (bd_request == 0 &&
tsleep(&bd_request, PVM, "psleep", bd_interval) &&
needsbuffer == 0) {
/*
* timed out and nothing serious going on,
* increase the flushto high water mark to reduce
* the flush rate.
*/
bd_flushto += 10;
} else {
/*
* We were woken up or hit a serious wall that needs
* to be addressed.
*/
bd_flushto -= 10;
if (needsbuffer) {
int middb = (lodirtybuffers+hidirtybuffers)/2;
bd_interval >>= 1;
if (bd_flushto > middb)
bd_flushto = middb;
}
}
if (bd_flushto < lodirtybuffers) {
bd_flushto = lodirtybuffers;
bd_interval -= hz / 10;
}
if (bd_flushto > hidirtybuffers) {
bd_flushto = hidirtybuffers;
bd_interval += hz / 10;
}
if (bd_interval < hz / 10)
bd_interval = hz / 10;
if (bd_interval > 5 * hz)
bd_interval = 5 * hz;
}
}
static int
flushbufqueues(void)
{
struct buf *bp;
int r = 0;
bp = TAILQ_FIRST(&bufqueues[QUEUE_DIRTY]);
while (bp) {
/*
* Try to free up B_INVAL delayed-write buffers rather then
* writing them out. Note also that NFS is somewhat sensitive
* to B_INVAL buffers so it is doubly important that we do
* this.
*
* We do not try to sync buffers whos vnodes are locked, we
* cannot afford to block in this process.
*/
KASSERT((bp->b_flags & B_DELWRI), ("unexpected clean buffer %p", bp));
if ((bp->b_flags & B_DELWRI) != 0) {
if (bp->b_flags & B_INVAL) {
if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0)
panic("flushbufqueues: locked buf");
bremfree(bp);
brelse(bp);
++r;
break;
}
if (!VOP_ISLOCKED(bp->b_vp)) {
vfs_bio_awrite(bp);
++r;
break;
}
}
bp = TAILQ_NEXT(bp, b_freelist);
}
return(r);
}
/*
* Check to see if a block is currently memory resident.
*/
struct buf *
incore(struct vnode * vp, daddr_t blkno)
{
struct buf *bp;
int s = splbio();
bp = gbincore(vp, blkno);
splx(s);
return (bp);
}
/*
* Returns true if no I/O is needed to access the
* associated VM object. This is like incore except
* it also hunts around in the VM system for the data.
*/
int
inmem(struct vnode * vp, daddr_t blkno)
{
vm_object_t obj;
vm_offset_t toff, tinc, size;
vm_page_t m;
vm_ooffset_t off;
if (incore(vp, blkno))
return 1;
if (vp->v_mount == NULL)
return 0;
if ((vp->v_object == NULL) || (vp->v_flag & VOBJBUF) == 0)
return 0;
obj = vp->v_object;
size = PAGE_SIZE;
if (size > vp->v_mount->mnt_stat.f_iosize)
size = vp->v_mount->mnt_stat.f_iosize;
off = (vm_ooffset_t)blkno * (vm_ooffset_t)vp->v_mount->mnt_stat.f_iosize;
for (toff = 0; toff < vp->v_mount->mnt_stat.f_iosize; toff += tinc) {
m = vm_page_lookup(obj, OFF_TO_IDX(off + toff));
if (!m)
return 0;
tinc = size;
if (tinc > PAGE_SIZE - ((toff + off) & PAGE_MASK))
tinc = PAGE_SIZE - ((toff + off) & PAGE_MASK);
if (vm_page_is_valid(m,
(vm_offset_t) ((toff + off) & PAGE_MASK), tinc) == 0)
return 0;
}
return 1;
}
/*
* vfs_setdirty:
*
* Sets the dirty range for a buffer based on the status of the dirty
* bits in the pages comprising the buffer.
*
* The range is limited to the size of the buffer.
*
* This routine is primarily used by NFS, but is generalized for the
* B_VMIO case.
*/
static void
vfs_setdirty(struct buf *bp)
{
int i;
vm_object_t object;
/*
* Degenerate case - empty buffer
*/
if (bp->b_bufsize == 0)
return;
/*
* We qualify the scan for modified pages on whether the
* object has been flushed yet. The OBJ_WRITEABLE flag
* is not cleared simply by protecting pages off.
*/
if ((bp->b_flags & B_VMIO) == 0)
return;
object = bp->b_pages[0]->object;
if ((object->flags & OBJ_WRITEABLE) && !(object->flags & OBJ_MIGHTBEDIRTY))
printf("Warning: object %p writeable but not mightbedirty\n", object);
if (!(object->flags & OBJ_WRITEABLE) && (object->flags & OBJ_MIGHTBEDIRTY))
printf("Warning: object %p mightbedirty but not writeable\n", object);
if (object->flags & (OBJ_MIGHTBEDIRTY|OBJ_CLEANING)) {
vm_offset_t boffset;
vm_offset_t eoffset;
/*
* test the pages to see if they have been modified directly
* by users through the VM system.
*/
for (i = 0; i < bp->b_npages; i++) {
vm_page_flag_clear(bp->b_pages[i], PG_ZERO);
vm_page_test_dirty(bp->b_pages[i]);
}
/*
* Calculate the encompassing dirty range, boffset and eoffset,
* (eoffset - boffset) bytes.
*/
for (i = 0; i < bp->b_npages; i++) {
if (bp->b_pages[i]->dirty)
break;
}
boffset = (i << PAGE_SHIFT) - (bp->b_offset & PAGE_MASK);
for (i = bp->b_npages - 1; i >= 0; --i) {
if (bp->b_pages[i]->dirty) {
break;
}
}
eoffset = ((i + 1) << PAGE_SHIFT) - (bp->b_offset & PAGE_MASK);
/*
* Fit it to the buffer.
*/
if (eoffset > bp->b_bcount)
eoffset = bp->b_bcount;
/*
* If we have a good dirty range, merge with the existing
* dirty range.
*/
if (boffset < eoffset) {
if (bp->b_dirtyoff > boffset)
bp->b_dirtyoff = boffset;
if (bp->b_dirtyend < eoffset)
bp->b_dirtyend = eoffset;
}
}
}
/*
* getblk:
*
* Get a block given a specified block and offset into a file/device.
* The buffers B_DONE bit will be cleared on return, making it almost
* ready for an I/O initiation. B_INVAL may or may not be set on
* return. The caller should clear B_INVAL prior to initiating a
* READ.
*
* For a non-VMIO buffer, B_CACHE is set to the opposite of B_INVAL for
* an existing buffer.
*
* For a VMIO buffer, B_CACHE is modified according to the backing VM.
* If getblk()ing a previously 0-sized invalid buffer, B_CACHE is set
* and then cleared based on the backing VM. If the previous buffer is
* non-0-sized but invalid, B_CACHE will be cleared.
*
* If getblk() must create a new buffer, the new buffer is returned with
* both B_INVAL and B_CACHE clear unless it is a VMIO buffer, in which
* case it is returned with B_INVAL clear and B_CACHE set based on the
* backing VM.
*
* getblk() also forces a VOP_BWRITE() for any B_DELWRI buffer whos
* B_CACHE bit is clear.
*
* What this means, basically, is that the caller should use B_CACHE to
* determine whether the buffer is fully valid or not and should clear
* B_INVAL prior to issuing a read. If the caller intends to validate
* the buffer by loading its data area with something, the caller needs
* to clear B_INVAL. If the caller does this without issuing an I/O,
* the caller should set B_CACHE ( as an optimization ), else the caller
* should issue the I/O and biodone() will set B_CACHE if the I/O was
* a write attempt or if it was a successfull read. If the caller
* intends to issue a READ, the caller must clear B_INVAL and B_ERROR
* prior to issuing the READ. biodone() will *not* clear B_INVAL.
*/
struct buf *
getblk(struct vnode * vp, daddr_t blkno, int size, int slpflag, int slptimeo)
{
struct buf *bp;
int s;
struct bufhashhdr *bh;
#if !defined(MAX_PERF)
if (size > MAXBSIZE)
panic("getblk: size(%d) > MAXBSIZE(%d)\n", size, MAXBSIZE);
#endif
s = splbio();
loop:
/*
* Block if we are low on buffers. Certain processes are allowed
* to completely exhaust the buffer cache.
*/
if (curproc->p_flag & P_BUFEXHAUST) {
if (numfreebuffers == 0) {
needsbuffer |= VFS_BIO_NEED_ANY;
tsleep(&needsbuffer, (PRIBIO + 4) | slpflag, "newbuf",
slptimeo);
}
} else if (numfreebuffers < lofreebuffers) {
waitfreebuffers(slpflag, slptimeo);
}
if ((bp = gbincore(vp, blkno))) {
/*
* Buffer is in-core. If the buffer is not busy, it must
* be on a queue.
*/
if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
if (bp->b_usecount < BUF_MAXUSE)
++bp->b_usecount;
if (BUF_TIMELOCK(bp, LK_EXCLUSIVE | LK_SLEEPFAIL,
"getblk", slpflag, slptimeo) == ENOLCK)
goto loop;
splx(s);
return (struct buf *) NULL;
}
/*
* The buffer is locked. B_CACHE is cleared if the buffer is
* invalid. Ohterwise, for a non-VMIO buffer, B_CACHE is set
* and for a VMIO buffer B_CACHE is adjusted according to the
* backing VM cache.
*/
if (bp->b_flags & B_INVAL)
bp->b_flags &= ~B_CACHE;
else if ((bp->b_flags & (B_VMIO | B_INVAL)) == 0)
bp->b_flags |= B_CACHE;
bremfree(bp);
/*
* check for size inconsistancies for non-VMIO case.
*/
if (bp->b_bcount != size) {
if ((bp->b_flags & B_VMIO) == 0 ||
(size > bp->b_kvasize)) {
if (bp->b_flags & B_DELWRI) {
bp->b_flags |= B_NOCACHE;
VOP_BWRITE(bp->b_vp, bp);
} else {
if ((bp->b_flags & B_VMIO) &&
(LIST_FIRST(&bp->b_dep) == NULL)) {
bp->b_flags |= B_RELBUF;
brelse(bp);
} else {
bp->b_flags |= B_NOCACHE;
VOP_BWRITE(bp->b_vp, bp);
}
}
goto loop;
}
}
/*
* If the size is inconsistant in the VMIO case, we can resize
* the buffer. This might lead to B_CACHE getting set or
* cleared. If the size has not changed, B_CACHE remains
* unchanged from its previous state.
*/
if (bp->b_bcount != size)
allocbuf(bp, size);
KASSERT(bp->b_offset != NOOFFSET,
("getblk: no buffer offset"));
/*
* A buffer with B_DELWRI set and B_CACHE clear must
* be committed before we can return the buffer in
* order to prevent the caller from issuing a read
* ( due to B_CACHE not being set ) and overwriting
* it.
*
* Most callers, including NFS and FFS, need this to
* operate properly either because they assume they
* can issue a read if B_CACHE is not set, or because
* ( for example ) an uncached B_DELWRI might loop due
* to softupdates re-dirtying the buffer. In the latter
* case, B_CACHE is set after the first write completes,
* preventing further loops.
*/
if ((bp->b_flags & (B_CACHE|B_DELWRI)) == B_DELWRI) {
VOP_BWRITE(bp->b_vp, bp);
goto loop;
}
if (bp->b_usecount < BUF_MAXUSE)
++bp->b_usecount;
splx(s);
bp->b_flags &= ~B_DONE;
} else {
/*
* Buffer is not in-core, create new buffer. The buffer
* returned by getnewbuf() is locked. Note that the returned
* buffer is also considered valid (not marked B_INVAL).
*/
int bsize, maxsize, vmio;
off_t offset;
if (vp->v_type == VBLK)
bsize = DEV_BSIZE;
else if (vp->v_mountedhere)
bsize = vp->v_mountedhere->mnt_stat.f_iosize;
else if (vp->v_mount)
bsize = vp->v_mount->mnt_stat.f_iosize;
else
bsize = size;
offset = (off_t)blkno * bsize;
vmio = (vp->v_object != 0) && (vp->v_flag & VOBJBUF);
maxsize = vmio ? size + (offset & PAGE_MASK) : size;
maxsize = imax(maxsize, bsize);
if ((bp = getnewbuf(vp, blkno,
slpflag, slptimeo, size, maxsize)) == NULL) {
if (slpflag || slptimeo) {
splx(s);
return NULL;
}
goto loop;
}
/*
* This code is used to make sure that a buffer is not
* created while the getnewbuf routine is blocked.
* This can be a problem whether the vnode is locked or not.
* If the buffer is created out from under us, we have to
* throw away the one we just created. There is now window
* race because we are safely running at splbio() from the
* point of the duplicate buffer creation through to here.
*/
if (gbincore(vp, blkno)) {
bp->b_flags |= B_INVAL;
brelse(bp);
goto loop;
}
/*
* Insert the buffer into the hash, so that it can
* be found by incore.
*/
bp->b_blkno = bp->b_lblkno = blkno;
bp->b_offset = offset;
bgetvp(vp, bp);
LIST_REMOVE(bp, b_hash);
bh = BUFHASH(vp, blkno);
LIST_INSERT_HEAD(bh, bp, b_hash);
/*
* set B_VMIO bit. allocbuf() the buffer bigger. Since the
* buffer size starts out as 0, B_CACHE will be set by
* allocbuf() for the VMIO case prior to it testing the
* backing store for validity.
*/
if (vmio) {
bp->b_flags |= B_VMIO;
#if defined(VFS_BIO_DEBUG)
if (vp->v_type != VREG && vp->v_type != VBLK)
printf("getblk: vmioing file type %d???\n", vp->v_type);
#endif
} else {
bp->b_flags &= ~B_VMIO;
}
allocbuf(bp, size);
splx(s);
bp->b_flags &= ~B_DONE;
}
return (bp);
}
/*
* Get an empty, disassociated buffer of given size. The buffer is initially
* set to B_INVAL.
*/
struct buf *
geteblk(int size)
{
struct buf *bp;
int s;
s = splbio();
while ((bp = getnewbuf(0, (daddr_t) 0, 0, 0, size, MAXBSIZE)) == 0);
splx(s);
allocbuf(bp, size);
bp->b_flags |= B_INVAL; /* b_dep cleared by getnewbuf() */
return (bp);
}
/*
* This code constitutes the buffer memory from either anonymous system
* memory (in the case of non-VMIO operations) or from an associated
* VM object (in the case of VMIO operations). This code is able to
* resize a buffer up or down.
*
* Note that this code is tricky, and has many complications to resolve
* deadlock or inconsistant data situations. Tread lightly!!!
* There are B_CACHE and B_DELWRI interactions that must be dealt with by
* the caller. Calling this code willy nilly can result in the loss of data.
*
* allocbuf() only adjusts B_CACHE for VMIO buffers. getblk() deals with
* B_CACHE for the non-VMIO case.
*/
int
allocbuf(struct buf *bp, int size)
{
int newbsize, mbsize;
int i;
#if !defined(MAX_PERF)
if (BUF_REFCNT(bp) == 0)
panic("allocbuf: buffer not busy");
if (bp->b_kvasize < size)
panic("allocbuf: buffer too small");
#endif
if ((bp->b_flags & B_VMIO) == 0) {
caddr_t origbuf;
int origbufsize;
/*
* Just get anonymous memory from the kernel. Don't
* mess with B_CACHE.
*/
mbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
#if !defined(NO_B_MALLOC)
if (bp->b_flags & B_MALLOC)
newbsize = mbsize;
else
#endif
newbsize = round_page(size);
if (newbsize < bp->b_bufsize) {
#if !defined(NO_B_MALLOC)
/*
* malloced buffers are not shrunk
*/
if (bp->b_flags & B_MALLOC) {
if (newbsize) {
bp->b_bcount = size;
} else {
free(bp->b_data, M_BIOBUF);
bufspace -= bp->b_bufsize;
bufmallocspace -= bp->b_bufsize;
runningbufspace -= bp->b_bufsize;
if (bp->b_bufsize)
bufspacewakeup();
bp->b_data = bp->b_kvabase;
bp->b_bufsize = 0;
bp->b_bcount = 0;
bp->b_flags &= ~B_MALLOC;
}
return 1;
}
#endif
vm_hold_free_pages(
bp,
(vm_offset_t) bp->b_data + newbsize,
(vm_offset_t) bp->b_data + bp->b_bufsize);
} else if (newbsize > bp->b_bufsize) {
#if !defined(NO_B_MALLOC)
/*
* We only use malloced memory on the first allocation.
* and revert to page-allocated memory when the buffer grows.
*/
if ( (bufmallocspace < maxbufmallocspace) &&
(bp->b_bufsize == 0) &&
(mbsize <= PAGE_SIZE/2)) {
bp->b_data = malloc(mbsize, M_BIOBUF, M_WAITOK);
bp->b_bufsize = mbsize;
bp->b_bcount = size;
bp->b_flags |= B_MALLOC;
bufspace += mbsize;
bufmallocspace += mbsize;
runningbufspace += bp->b_bufsize;
return 1;
}
#endif
origbuf = NULL;
origbufsize = 0;
#if !defined(NO_B_MALLOC)
/*
* If the buffer is growing on its other-than-first allocation,
* then we revert to the page-allocation scheme.
*/
if (bp->b_flags & B_MALLOC) {
origbuf = bp->b_data;
origbufsize = bp->b_bufsize;
bp->b_data = bp->b_kvabase;
bufspace -= bp->b_bufsize;
bufmallocspace -= bp->b_bufsize;
runningbufspace -= bp->b_bufsize;
if (bp->b_bufsize)
bufspacewakeup();
bp->b_bufsize = 0;
bp->b_flags &= ~B_MALLOC;
newbsize = round_page(newbsize);
}
#endif
vm_hold_load_pages(
bp,
(vm_offset_t) bp->b_data + bp->b_bufsize,
(vm_offset_t) bp->b_data + newbsize);
#if !defined(NO_B_MALLOC)
if (origbuf) {
bcopy(origbuf, bp->b_data, origbufsize);
free(origbuf, M_BIOBUF);
}
#endif
}
} else {
vm_page_t m;
int desiredpages;
newbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
desiredpages = (size == 0) ? 0 :
num_pages((bp->b_offset & PAGE_MASK) + newbsize);
#if !defined(NO_B_MALLOC)
if (bp->b_flags & B_MALLOC)
panic("allocbuf: VMIO buffer can't be malloced");
#endif
/*
* Set B_CACHE initially if buffer is 0 length or will become
* 0-length.
*/
if (size == 0 || bp->b_bufsize == 0)
bp->b_flags |= B_CACHE;
if (newbsize < bp->b_bufsize) {
/*
* DEV_BSIZE aligned new buffer size is less then the
* DEV_BSIZE aligned existing buffer size. Figure out
* if we have to remove any pages.
*/
if (desiredpages < bp->b_npages) {
for (i = desiredpages; i < bp->b_npages; i++) {
/*
* the page is not freed here -- it
* is the responsibility of
* vnode_pager_setsize
*/
m = bp->b_pages[i];
KASSERT(m != bogus_page,
("allocbuf: bogus page found"));
while (vm_page_sleep_busy(m, TRUE, "biodep"))
;
bp->b_pages[i] = NULL;
vm_page_unwire(m, 0);
}
pmap_qremove((vm_offset_t) trunc_page((vm_offset_t)bp->b_data) +
(desiredpages << PAGE_SHIFT), (bp->b_npages - desiredpages));
bp->b_npages = desiredpages;
}
} else if (size > bp->b_bcount) {
/*
* We are growing the buffer, possibly in a
* byte-granular fashion.
*/
struct vnode *vp;
vm_object_t obj;
vm_offset_t toff;
vm_offset_t tinc;
/*
* Step 1, bring in the VM pages from the object,
* allocating them if necessary. We must clear
* B_CACHE if these pages are not valid for the
* range covered by the buffer.
*/
vp = bp->b_vp;
obj = vp->v_object;
while (bp->b_npages < desiredpages) {
vm_page_t m;
vm_pindex_t pi;
pi = OFF_TO_IDX(bp->b_offset) + bp->b_npages;
if ((m = vm_page_lookup(obj, pi)) == NULL) {
m = vm_page_alloc(obj, pi, VM_ALLOC_NORMAL);
if (m == NULL) {
VM_WAIT;
vm_pageout_deficit += desiredpages - bp->b_npages;
} else {
vm_page_wire(m);
vm_page_wakeup(m);
bp->b_flags &= ~B_CACHE;
bp->b_pages[bp->b_npages] = m;
++bp->b_npages;
}
continue;
}
/*
* We found a page. If we have to sleep on it,
* retry because it might have gotten freed out
* from under us.
*
* We can only test PG_BUSY here. Blocking on
* m->busy might lead to a deadlock:
*
* vm_fault->getpages->cluster_read->allocbuf
*
*/
if (vm_page_sleep_busy(m, FALSE, "pgtblk"))
continue;
/*
* We have a good page. Should we wakeup the
* page daemon?
*/
if ((curproc != pageproc) &&
((m->queue - m->pc) == PQ_CACHE) &&
((cnt.v_free_count + cnt.v_cache_count) <
(cnt.v_free_min + cnt.v_cache_min))) {
pagedaemon_wakeup();
}
vm_page_flag_clear(m, PG_ZERO);
vm_page_wire(m);
bp->b_pages[bp->b_npages] = m;
++bp->b_npages;
}
/*
* Step 2. We've loaded the pages into the buffer,
* we have to figure out if we can still have B_CACHE
* set. Note that B_CACHE is set according to the
* byte-granular range ( bcount and size ), new the
* aligned range ( newbsize ).
*
* The VM test is against m->valid, which is DEV_BSIZE
* aligned. Needless to say, the validity of the data
* needs to also be DEV_BSIZE aligned. Note that this
* fails with NFS if the server or some other client
* extends the file's EOF. If our buffer is resized,
* B_CACHE may remain set! XXX
*/
toff = bp->b_bcount;
tinc = PAGE_SIZE - ((bp->b_offset + toff) & PAGE_MASK);
while ((bp->b_flags & B_CACHE) && toff < size) {
vm_pindex_t pi;
if (tinc > (size - toff))
tinc = size - toff;
pi = ((bp->b_offset & PAGE_MASK) + toff) >>
PAGE_SHIFT;
vfs_buf_test_cache(
bp,
bp->b_offset,
toff,
tinc,
bp->b_pages[pi]
);
toff += tinc;
tinc = PAGE_SIZE;
}
/*
* Step 3, fixup the KVM pmap. Remember that
* bp->b_data is relative to bp->b_offset, but
* bp->b_offset may be offset into the first page.
*/
bp->b_data = (caddr_t)
trunc_page((vm_offset_t)bp->b_data);
pmap_qenter(
(vm_offset_t)bp->b_data,
bp->b_pages,
bp->b_npages
);
bp->b_data = (caddr_t)((vm_offset_t)bp->b_data |
(vm_offset_t)(bp->b_offset & PAGE_MASK));
}
}
if (bp->b_flags & B_VMIO)
vmiospace += (newbsize - bp->b_bufsize);
bufspace += (newbsize - bp->b_bufsize);
runningbufspace += (newbsize - bp->b_bufsize);
if (newbsize < bp->b_bufsize)
bufspacewakeup();
bp->b_bufsize = newbsize; /* actual buffer allocation */
bp->b_bcount = size; /* requested buffer size */
return 1;
}
/*
* biowait:
*
* Wait for buffer I/O completion, returning error status. The buffer
* is left locked and B_DONE on return. B_EINTR is converted into a EINTR
* error and cleared.
*/
int
biowait(register struct buf * bp)
{
int s;
s = splbio();
while ((bp->b_flags & B_DONE) == 0) {
#if defined(NO_SCHEDULE_MODS)
tsleep(bp, PRIBIO, "biowait", 0);
#else
if (bp->b_flags & B_READ)
tsleep(bp, PRIBIO, "biord", 0);
else
tsleep(bp, PRIBIO, "biowr", 0);
#endif
}
splx(s);
if (bp->b_flags & B_EINTR) {
bp->b_flags &= ~B_EINTR;
return (EINTR);
}
if (bp->b_flags & B_ERROR) {
return (bp->b_error ? bp->b_error : EIO);
} else {
return (0);
}
}
/*
* biodone:
*
* Finish I/O on a buffer, optionally calling a completion function.
* This is usually called from an interrupt so process blocking is
* not allowed.
*
* biodone is also responsible for setting B_CACHE in a B_VMIO bp.
* In a non-VMIO bp, B_CACHE will be set on the next getblk()
* assuming B_INVAL is clear.
*
* For the VMIO case, we set B_CACHE if the op was a read and no
* read error occured, or if the op was a write. B_CACHE is never
* set if the buffer is invalid or otherwise uncacheable.
*
* biodone does not mess with B_INVAL, allowing the I/O routine or the
* initiator to leave B_INVAL set to brelse the buffer out of existance
* in the biodone routine.
*/
void
biodone(register struct buf * bp)
{
int s;
s = splbio();
KASSERT(BUF_REFCNT(bp) > 0, ("biodone: bp %p not busy %d", bp, BUF_REFCNT(bp)));
KASSERT(!(bp->b_flags & B_DONE), ("biodone: bp %p already done", bp));
bp->b_flags |= B_DONE;
if (bp->b_flags & B_FREEBUF) {
brelse(bp);
splx(s);
return;
}
if ((bp->b_flags & B_READ) == 0) {
vwakeup(bp);
}
/* call optional completion function if requested */
if (bp->b_flags & B_CALL) {
bp->b_flags &= ~B_CALL;
(*bp->b_iodone) (bp);
splx(s);
return;
}
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_complete)
(*bioops.io_complete)(bp);
if (bp->b_flags & B_VMIO) {
int i, resid;
vm_ooffset_t foff;
vm_page_t m;
vm_object_t obj;
int iosize;
struct vnode *vp = bp->b_vp;
obj = vp->v_object;
#if defined(VFS_BIO_DEBUG)
if (vp->v_usecount == 0) {
panic("biodone: zero vnode ref count");
}
if (vp->v_object == NULL) {
panic("biodone: missing VM object");
}
if ((vp->v_flag & VOBJBUF) == 0) {
panic("biodone: vnode is not setup for merged cache");
}
#endif
foff = bp->b_offset;
KASSERT(bp->b_offset != NOOFFSET,
("biodone: no buffer offset"));
#if !defined(MAX_PERF)
if (!obj) {
panic("biodone: no object");
}
#endif
#if defined(VFS_BIO_DEBUG)
if (obj->paging_in_progress < bp->b_npages) {
printf("biodone: paging in progress(%d) < bp->b_npages(%d)\n",
obj->paging_in_progress, bp->b_npages);
}
#endif
/*
* Set B_CACHE if the op was a normal read and no error
* occured. B_CACHE is set for writes in the b*write()
* routines.
*/
iosize = bp->b_bcount;
if ((bp->b_flags & (B_READ|B_FREEBUF|B_INVAL|B_NOCACHE|B_ERROR)) == B_READ) {
bp->b_flags |= B_CACHE;
}
for (i = 0; i < bp->b_npages; i++) {
int bogusflag = 0;
m = bp->b_pages[i];
if (m == bogus_page) {
bogusflag = 1;
m = vm_page_lookup(obj, OFF_TO_IDX(foff));
if (!m) {
#if defined(VFS_BIO_DEBUG)
printf("biodone: page disappeared\n");
#endif
vm_object_pip_subtract(obj, 1);
bp->b_flags &= ~B_CACHE;
continue;
}
bp->b_pages[i] = m;
pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages);
}
#if defined(VFS_BIO_DEBUG)
if (OFF_TO_IDX(foff) != m->pindex) {
printf(
"biodone: foff(%lu)/m->pindex(%d) mismatch\n",
(unsigned long)foff, m->pindex);
}
#endif
resid = IDX_TO_OFF(m->pindex + 1) - foff;
if (resid > iosize)
resid = iosize;
/*
* In the write case, the valid and clean bits are
* already changed correctly ( see bdwrite() ), so we
* only need to do this here in the read case.
*/
if ((bp->b_flags & B_READ) && !bogusflag && resid > 0) {
vfs_page_set_valid(bp, foff, i, m);
}
vm_page_flag_clear(m, PG_ZERO);
/*
* when debugging new filesystems or buffer I/O methods, this
* is the most common error that pops up. if you see this, you
* have not set the page busy flag correctly!!!
*/
if (m->busy == 0) {
#if !defined(MAX_PERF)
printf("biodone: page busy < 0, "
"pindex: %d, foff: 0x(%x,%x), "
"resid: %d, index: %d\n",
(int) m->pindex, (int)(foff >> 32),
(int) foff & 0xffffffff, resid, i);
#endif
if (vp->v_type != VBLK)
#if !defined(MAX_PERF)
printf(" iosize: %ld, lblkno: %d, flags: 0x%lx, npages: %d\n",
bp->b_vp->v_mount->mnt_stat.f_iosize,
(int) bp->b_lblkno,
bp->b_flags, bp->b_npages);
else
printf(" VDEV, lblkno: %d, flags: 0x%lx, npages: %d\n",
(int) bp->b_lblkno,
bp->b_flags, bp->b_npages);
printf(" valid: 0x%x, dirty: 0x%x, wired: %d\n",
m->valid, m->dirty, m->wire_count);
#endif
panic("biodone: page busy < 0\n");
}
vm_page_io_finish(m);
vm_object_pip_subtract(obj, 1);
foff += resid;
iosize -= resid;
}
if (obj)
vm_object_pip_wakeupn(obj, 0);
}
/*
* For asynchronous completions, release the buffer now. The brelse
* will do a wakeup there if necessary - so no need to do a wakeup
* here in the async case. The sync case always needs to do a wakeup.
*/
if (bp->b_flags & B_ASYNC) {
if ((bp->b_flags & (B_NOCACHE | B_INVAL | B_ERROR | B_RELBUF)) != 0)
brelse(bp);
else
bqrelse(bp);
} else {
wakeup(bp);
}
splx(s);
}
/*
* This routine is called in lieu of iodone in the case of
* incomplete I/O. This keeps the busy status for pages
* consistant.
*/
void
vfs_unbusy_pages(struct buf * bp)
{
int i;
if (bp->b_flags & B_VMIO) {
struct vnode *vp = bp->b_vp;
vm_object_t obj = vp->v_object;
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
if (m == bogus_page) {
m = vm_page_lookup(obj, OFF_TO_IDX(bp->b_offset) + i);
#if !defined(MAX_PERF)
if (!m) {
panic("vfs_unbusy_pages: page missing\n");
}
#endif
bp->b_pages[i] = m;
pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages);
}
vm_object_pip_subtract(obj, 1);
vm_page_flag_clear(m, PG_ZERO);
vm_page_io_finish(m);
}
vm_object_pip_wakeupn(obj, 0);
}
}
/*
* vfs_page_set_valid:
*
* Set the valid bits in a page based on the supplied offset. The
* range is restricted to the buffer's size.
*
* This routine is typically called after a read completes.
*/
static void
vfs_page_set_valid(struct buf *bp, vm_ooffset_t off, int pageno, vm_page_t m)
{
vm_ooffset_t soff, eoff;
/*
* Start and end offsets in buffer. eoff - soff may not cross a
* page boundry or cross the end of the buffer. The end of the
* buffer, in this case, is our file EOF, not the allocation size
* of the buffer.
*/
soff = off;
eoff = (off + PAGE_SIZE) & ~PAGE_MASK;
if (eoff > bp->b_offset + bp->b_bcount)
eoff = bp->b_offset + bp->b_bcount;
/*
* Set valid range. This is typically the entire buffer and thus the
* entire page.
*/
if (eoff > soff) {
vm_page_set_validclean(
m,
(vm_offset_t) (soff & PAGE_MASK),
(vm_offset_t) (eoff - soff)
);
}
}
/*
* This routine is called before a device strategy routine.
* It is used to tell the VM system that paging I/O is in
* progress, and treat the pages associated with the buffer
* almost as being PG_BUSY. Also the object paging_in_progress
* flag is handled to make sure that the object doesn't become
* inconsistant.
*
* Since I/O has not been initiated yet, certain buffer flags
* such as B_ERROR or B_INVAL may be in an inconsistant state
* and should be ignored.
*/
void
vfs_busy_pages(struct buf * bp, int clear_modify)
{
int i, bogus;
if (bp->b_flags & B_VMIO) {
struct vnode *vp = bp->b_vp;
vm_object_t obj = vp->v_object;
vm_ooffset_t foff;
foff = bp->b_offset;
KASSERT(bp->b_offset != NOOFFSET,
("vfs_busy_pages: no buffer offset"));
vfs_setdirty(bp);
retry:
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
if (vm_page_sleep_busy(m, FALSE, "vbpage"))
goto retry;
}
bogus = 0;
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
vm_page_flag_clear(m, PG_ZERO);
if ((bp->b_flags & B_CLUSTER) == 0) {
vm_object_pip_add(obj, 1);
vm_page_io_start(m);
}
/*
* When readying a buffer for a read ( i.e
* clear_modify == 0 ), it is important to do
* bogus_page replacement for valid pages in
* partially instantiated buffers. Partially
* instantiated buffers can, in turn, occur when
* reconstituting a buffer from its VM backing store
* base. We only have to do this if B_CACHE is
* clear ( which causes the I/O to occur in the
* first place ). The replacement prevents the read
* I/O from overwriting potentially dirty VM-backed
* pages. XXX bogus page replacement is, uh, bogus.
* It may not work properly with small-block devices.
* We need to find a better way.
*/
vm_page_protect(m, VM_PROT_NONE);
if (clear_modify)
vfs_page_set_valid(bp, foff, i, m);
else if (m->valid == VM_PAGE_BITS_ALL &&
(bp->b_flags & B_CACHE) == 0) {
bp->b_pages[i] = bogus_page;
bogus++;
}
foff = (foff + PAGE_SIZE) & ~PAGE_MASK;
}
if (bogus)
pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages);
}
}
/*
* Tell the VM system that the pages associated with this buffer
* are clean. This is used for delayed writes where the data is
* going to go to disk eventually without additional VM intevention.
*
* Note that while we only really need to clean through to b_bcount, we
* just go ahead and clean through to b_bufsize.
*/
static void
vfs_clean_pages(struct buf * bp)
{
int i;
if (bp->b_flags & B_VMIO) {
vm_ooffset_t foff;
foff = bp->b_offset;
KASSERT(bp->b_offset != NOOFFSET,
("vfs_clean_pages: no buffer offset"));
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
vm_ooffset_t noff = (foff + PAGE_SIZE) & ~PAGE_MASK;
vm_ooffset_t eoff = noff;
if (eoff > bp->b_offset + bp->b_bufsize)
eoff = bp->b_offset + bp->b_bufsize;
vfs_page_set_valid(bp, foff, i, m);
/* vm_page_clear_dirty(m, foff & PAGE_MASK, eoff - foff); */
foff = noff;
}
}
}
/*
* vfs_bio_set_validclean:
*
* Set the range within the buffer to valid and clean. The range is
* relative to the beginning of the buffer, b_offset. Note that b_offset
* itself may be offset from the beginning of the first page.
*/
void
vfs_bio_set_validclean(struct buf *bp, int base, int size)
{
if (bp->b_flags & B_VMIO) {
int i;
int n;
/*
* Fixup base to be relative to beginning of first page.
* Set initial n to be the maximum number of bytes in the
* first page that can be validated.
*/
base += (bp->b_offset & PAGE_MASK);
n = PAGE_SIZE - (base & PAGE_MASK);
for (i = base / PAGE_SIZE; size > 0 && i < bp->b_npages; ++i) {
vm_page_t m = bp->b_pages[i];
if (n > size)
n = size;
vm_page_set_validclean(m, base & PAGE_MASK, n);
base += n;
size -= n;
n = PAGE_SIZE;
}
}
}
/*
* vfs_bio_clrbuf:
*
* clear a buffer. This routine essentially fakes an I/O, so we need
* to clear B_ERROR and B_INVAL.
*
* Note that while we only theoretically need to clear through b_bcount,
* we go ahead and clear through b_bufsize.
*/
void
vfs_bio_clrbuf(struct buf *bp) {
int i, mask = 0;
caddr_t sa, ea;
if ((bp->b_flags & (B_VMIO | B_MALLOC)) == B_VMIO) {
bp->b_flags &= ~(B_INVAL|B_ERROR);
if( (bp->b_npages == 1) && (bp->b_bufsize < PAGE_SIZE) &&
(bp->b_offset & PAGE_MASK) == 0) {
mask = (1 << (bp->b_bufsize / DEV_BSIZE)) - 1;
if (((bp->b_pages[0]->flags & PG_ZERO) == 0) &&
((bp->b_pages[0]->valid & mask) != mask)) {
bzero(bp->b_data, bp->b_bufsize);
}
bp->b_pages[0]->valid |= mask;
bp->b_resid = 0;
return;
}
ea = sa = bp->b_data;
for(i=0;i<bp->b_npages;i++,sa=ea) {
int j = ((u_long)sa & PAGE_MASK) / DEV_BSIZE;
ea = (caddr_t)trunc_page((vm_offset_t)sa + PAGE_SIZE);
ea = (caddr_t)ulmin((u_long)ea,
(u_long)bp->b_data + bp->b_bufsize);
mask = ((1 << ((ea - sa) / DEV_BSIZE)) - 1) << j;
if ((bp->b_pages[i]->valid & mask) == mask)
continue;
if ((bp->b_pages[i]->valid & mask) == 0) {
if ((bp->b_pages[i]->flags & PG_ZERO) == 0) {
bzero(sa, ea - sa);
}
} else {
for (; sa < ea; sa += DEV_BSIZE, j++) {
if (((bp->b_pages[i]->flags & PG_ZERO) == 0) &&
(bp->b_pages[i]->valid & (1<<j)) == 0)
bzero(sa, DEV_BSIZE);
}
}
bp->b_pages[i]->valid |= mask;
vm_page_flag_clear(bp->b_pages[i], PG_ZERO);
}
bp->b_resid = 0;
} else {
clrbuf(bp);
}
}
/*
* vm_hold_load_pages and vm_hold_unload pages get pages into
* a buffers address space. The pages are anonymous and are
* not associated with a file object.
*/
void
vm_hold_load_pages(struct buf * bp, vm_offset_t from, vm_offset_t to)
{
vm_offset_t pg;
vm_page_t p;
int index;
to = round_page(to);
from = round_page(from);
index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT;
for (pg = from; pg < to; pg += PAGE_SIZE, index++) {
tryagain:
p = vm_page_alloc(kernel_object,
((pg - VM_MIN_KERNEL_ADDRESS) >> PAGE_SHIFT),
VM_ALLOC_NORMAL);
if (!p) {
vm_pageout_deficit += (to - from) >> PAGE_SHIFT;
VM_WAIT;
goto tryagain;
}
vm_page_wire(p);
p->valid = VM_PAGE_BITS_ALL;
vm_page_flag_clear(p, PG_ZERO);
pmap_kenter(pg, VM_PAGE_TO_PHYS(p));
bp->b_pages[index] = p;
vm_page_wakeup(p);
}
bp->b_npages = index;
}
void
vm_hold_free_pages(struct buf * bp, vm_offset_t from, vm_offset_t to)
{
vm_offset_t pg;
vm_page_t p;
int index, newnpages;
from = round_page(from);
to = round_page(to);
newnpages = index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT;
for (pg = from; pg < to; pg += PAGE_SIZE, index++) {
p = bp->b_pages[index];
if (p && (index < bp->b_npages)) {
#if !defined(MAX_PERF)
if (p->busy) {
printf("vm_hold_free_pages: blkno: %d, lblkno: %d\n",
bp->b_blkno, bp->b_lblkno);
}
#endif
bp->b_pages[index] = NULL;
pmap_kremove(pg);
vm_page_busy(p);
vm_page_unwire(p, 0);
vm_page_free(p);
}
}
bp->b_npages = newnpages;
}
#include "opt_ddb.h"
#ifdef DDB
#include <ddb/ddb.h>
DB_SHOW_COMMAND(buffer, db_show_buffer)
{
/* get args */
struct buf *bp = (struct buf *)addr;
if (!have_addr) {
db_printf("usage: show buffer <addr>\n");
return;
}
db_printf("b_flags = 0x%b\n", (u_int)bp->b_flags, PRINT_BUF_FLAGS);
db_printf("b_error = %d, b_bufsize = %ld, b_bcount = %ld, "
"b_resid = %ld\nb_dev = (%d,%d), b_data = %p, "
"b_blkno = %d, b_pblkno = %d\n",
bp->b_error, bp->b_bufsize, bp->b_bcount, bp->b_resid,
major(bp->b_dev), minor(bp->b_dev),
bp->b_data, bp->b_blkno, bp->b_pblkno);
if (bp->b_npages) {
int i;
db_printf("b_npages = %d, pages(OBJ, IDX, PA): ", bp->b_npages);
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m;
m = bp->b_pages[i];
db_printf("(%p, 0x%lx, 0x%lx)", (void *)m->object,
(u_long)m->pindex, (u_long)VM_PAGE_TO_PHYS(m));
if ((i + 1) < bp->b_npages)
db_printf(",");
}
db_printf("\n");
}
}
#endif /* DDB */
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