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NetBSD/sys/kern/vfs_bio.c

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/* $NetBSD: vfs_bio.c,v 1.92 2003/04/09 12:55:51 yamt Exp $ */
/*-
* Copyright (c) 1994 Christopher G. Demetriou
* Copyright (c) 1982, 1986, 1989, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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.
*
* @(#)vfs_bio.c 8.6 (Berkeley) 1/11/94
*/
/*
* Some references:
* Bach: The Design of the UNIX Operating System (Prentice Hall, 1986)
* Leffler, et al.: The Design and Implementation of the 4.3BSD
* UNIX Operating System (Addison Welley, 1989)
*/
#include "opt_softdep.h"
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.92 2003/04/09 12:55:51 yamt Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/resourcevar.h>
#include <sys/conf.h>
#include <uvm/uvm.h>
#include <miscfs/specfs/specdev.h>
/* Macros to clear/set/test flags. */
#define SET(t, f) (t) |= (f)
#define CLR(t, f) (t) &= ~(f)
#define ISSET(t, f) ((t) & (f))
/*
* Definitions for the buffer hash lists.
*/
#define BUFHASH(dvp, lbn) \
(&bufhashtbl[(((long)(dvp) >> 8) + (int)(lbn)) & bufhash])
LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash;
u_long bufhash;
#ifndef SOFTDEP
struct bio_ops bioops; /* I/O operation notification */
#endif
/*
* Insq/Remq for the buffer hash lists.
*/
#define binshash(bp, dp) LIST_INSERT_HEAD(dp, bp, b_hash)
#define bremhash(bp) LIST_REMOVE(bp, b_hash)
/*
* Definitions for the buffer free lists.
*/
#define BQUEUES 4 /* number of free buffer queues */
#define BQ_LOCKED 0 /* super-blocks &c */
#define BQ_LRU 1 /* lru, useful buffers */
#define BQ_AGE 2 /* rubbish */
#define BQ_EMPTY 3 /* buffer headers with no memory */
TAILQ_HEAD(bqueues, buf) bufqueues[BQUEUES];
int needbuffer;
/*
* Buffer queue lock.
* Take this lock first if also taking some buffer's b_interlock.
*/
struct simplelock bqueue_slock = SIMPLELOCK_INITIALIZER;
/*
* Buffer pool for I/O buffers.
*/
struct pool bufpool;
/*
* bread()/breadn() helper.
*/
static __inline struct buf *bio_doread(struct vnode *, daddr_t, int,
struct ucred *, int);
int count_lock_queue(void);
/*
* Insq/Remq for the buffer free lists.
* Call with buffer queue locked.
*/
#define binsheadfree(bp, dp) TAILQ_INSERT_HEAD(dp, bp, b_freelist)
#define binstailfree(bp, dp) TAILQ_INSERT_TAIL(dp, bp, b_freelist)
void
bremfree(bp)
struct buf *bp;
{
struct bqueues *dp = NULL;
/*
* We only calculate the head of the freelist when removing
* the last element of the list as that is the only time that
* it is needed (e.g. to reset the tail pointer).
*
* NB: This makes an assumption about how tailq's are implemented.
*/
if (TAILQ_NEXT(bp, b_freelist) == NULL) {
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
if (dp->tqh_last == &bp->b_freelist.tqe_next)
break;
if (dp == &bufqueues[BQUEUES])
panic("bremfree: lost tail");
}
TAILQ_REMOVE(dp, bp, b_freelist);
}
/*
* Initialize buffers and hash links for buffers.
*/
void
bufinit()
{
struct buf *bp;
struct bqueues *dp;
u_int i, base, residual;
/*
* Initialize the buffer pool. This pool is used for buffers
* which are strictly I/O control blocks, not buffer cache
* buffers.
*/
pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", NULL);
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
TAILQ_INIT(dp);
bufhashtbl = hashinit(nbuf, HASH_LIST, M_CACHE, M_WAITOK, &bufhash);
base = bufpages / nbuf;
residual = bufpages % nbuf;
for (i = 0; i < nbuf; i++) {
bp = &buf[i];
memset((char *)bp, 0, sizeof(*bp));
BUF_INIT(bp);
bp->b_dev = NODEV;
bp->b_vnbufs.le_next = NOLIST;
bp->b_data = buffers + i * MAXBSIZE;
if (i < residual)
bp->b_bufsize = (base + 1) * PAGE_SIZE;
else
bp->b_bufsize = base * PAGE_SIZE;
bp->b_flags = B_INVAL;
dp = bp->b_bufsize ? &bufqueues[BQ_AGE] : &bufqueues[BQ_EMPTY];
binsheadfree(bp, dp);
binshash(bp, &invalhash);
}
}
static __inline struct buf *
bio_doread(vp, blkno, size, cred, async)
struct vnode *vp;
daddr_t blkno;
int size;
struct ucred *cred;
int async;
{
struct buf *bp;
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
bp = getblk(vp, blkno, size, 0, 0);
#ifdef DIAGNOSTIC
if (bp == NULL) {
panic("bio_doread: no such buf");
}
#endif
/*
* If buffer does not have data valid, start a read.
* Note that if buffer is B_INVAL, getblk() won't return it.
* Therefore, it's valid if its I/O has completed or been delayed.
*/
if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) {
/* Start I/O for the buffer. */
SET(bp->b_flags, B_READ | async);
VOP_STRATEGY(bp);
/* Pay for the read. */
p->p_stats->p_ru.ru_inblock++;
} else if (async) {
brelse(bp);
}
return (bp);
}
/*
* Read a disk block.
* This algorithm described in Bach (p.54).
*/
int
bread(vp, blkno, size, cred, bpp)
struct vnode *vp;
daddr_t blkno;
int size;
struct ucred *cred;
struct buf **bpp;
{
struct buf *bp;
/* Get buffer for block. */
bp = *bpp = bio_doread(vp, blkno, size, cred, 0);
/* Wait for the read to complete, and return result. */
return (biowait(bp));
}
/*
* Read-ahead multiple disk blocks. The first is sync, the rest async.
* Trivial modification to the breada algorithm presented in Bach (p.55).
*/
int
breadn(vp, blkno, size, rablks, rasizes, nrablks, cred, bpp)
struct vnode *vp;
daddr_t blkno; int size;
daddr_t rablks[]; int rasizes[];
int nrablks;
struct ucred *cred;
struct buf **bpp;
{
struct buf *bp;
int i;
bp = *bpp = bio_doread(vp, blkno, size, cred, 0);
/*
* For each of the read-ahead blocks, start a read, if necessary.
*/
for (i = 0; i < nrablks; i++) {
/* If it's in the cache, just go on to next one. */
if (incore(vp, rablks[i]))
continue;
/* Get a buffer for the read-ahead block */
(void) bio_doread(vp, rablks[i], rasizes[i], cred, B_ASYNC);
}
/* Otherwise, we had to start a read for it; wait until it's valid. */
return (biowait(bp));
}
/*
* Read with single-block read-ahead. Defined in Bach (p.55), but
* implemented as a call to breadn().
* XXX for compatibility with old file systems.
*/
int
breada(vp, blkno, size, rablkno, rabsize, cred, bpp)
struct vnode *vp;
daddr_t blkno; int size;
daddr_t rablkno; int rabsize;
struct ucred *cred;
struct buf **bpp;
{
return (breadn(vp, blkno, size, &rablkno, &rabsize, 1, cred, bpp));
}
/*
* Block write. Described in Bach (p.56)
*/
int
bwrite(bp)
struct buf *bp;
{
int rv, sync, wasdelayed, s;
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
struct vnode *vp;
struct mount *mp;
KASSERT(ISSET(bp->b_flags, B_BUSY));
vp = bp->b_vp;
if (vp != NULL) {
if (vp->v_type == VBLK)
mp = vp->v_specmountpoint;
else
mp = vp->v_mount;
} else {
mp = NULL;
}
/*
* Remember buffer type, to switch on it later. If the write was
* synchronous, but the file system was mounted with MNT_ASYNC,
* convert it to a delayed write.
* XXX note that this relies on delayed tape writes being converted
* to async, not sync writes (which is safe, but ugly).
*/
sync = !ISSET(bp->b_flags, B_ASYNC);
if (sync && mp != NULL && ISSET(mp->mnt_flag, MNT_ASYNC)) {
bdwrite(bp);
return (0);
}
/*
* Collect statistics on synchronous and asynchronous writes.
* Writes to block devices are charged to their associated
* filesystem (if any).
*/
if (mp != NULL) {
if (sync)
mp->mnt_stat.f_syncwrites++;
else
mp->mnt_stat.f_asyncwrites++;
}
wasdelayed = ISSET(bp->b_flags, B_DELWRI);
s = splbio();
simple_lock(&bp->b_interlock);
CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI));
/*
* Pay for the I/O operation and make sure the buf is on the correct
* vnode queue.
*/
if (wasdelayed)
reassignbuf(bp, bp->b_vp);
else
p->p_stats->p_ru.ru_oublock++;
/* Initiate disk write. Make sure the appropriate party is charged. */
V_INCR_NUMOUTPUT(bp->b_vp);
simple_unlock(&bp->b_interlock);
splx(s);
VOP_STRATEGY(bp);
if (sync) {
/* If I/O was synchronous, wait for it to complete. */
rv = biowait(bp);
/* Release the buffer. */
brelse(bp);
return (rv);
} else {
return (0);
}
}
int
vn_bwrite(v)
void *v;
{
struct vop_bwrite_args *ap = v;
return (bwrite(ap->a_bp));
}
/*
* Delayed write.
*
* The buffer is marked dirty, but is not queued for I/O.
* This routine should be used when the buffer is expected
* to be modified again soon, typically a small write that
* partially fills a buffer.
*
* NB: magnetic tapes cannot be delayed; they must be
* written in the order that the writes are requested.
*
* Described in Leffler, et al. (pp. 208-213).
*/
void
bdwrite(bp)
struct buf *bp;
{
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
const struct bdevsw *bdev;
int s;
KASSERT(ISSET(bp->b_flags, B_BUSY));
/* If this is a tape block, write the block now. */
bdev = bdevsw_lookup(bp->b_dev);
if (bdev != NULL && bdev->d_type == D_TAPE) {
bawrite(bp);
return;
}
/*
* If the block hasn't been seen before:
* (1) Mark it as having been seen,
* (2) Charge for the write,
* (3) Make sure it's on its vnode's correct block list.
*/
s = splbio();
simple_lock(&bp->b_interlock);
if (!ISSET(bp->b_flags, B_DELWRI)) {
SET(bp->b_flags, B_DELWRI);
p->p_stats->p_ru.ru_oublock++;
reassignbuf(bp, bp->b_vp);
}
/* Otherwise, the "write" is done, so mark and release the buffer. */
CLR(bp->b_flags, B_DONE);
simple_unlock(&bp->b_interlock);
splx(s);
brelse(bp);
}
/*
* Asynchronous block write; just an asynchronous bwrite().
*/
void
bawrite(bp)
struct buf *bp;
{
int s;
KASSERT(ISSET(bp->b_flags, B_BUSY));
s = splbio();
simple_lock(&bp->b_interlock);
SET(bp->b_flags, B_ASYNC);
simple_unlock(&bp->b_interlock);
splx(s);
VOP_BWRITE(bp);
}
/*
* Same as first half of bdwrite, mark buffer dirty, but do not release it.
* Call at splbio() and with the buffer interlock locked.
* Note: called only from biodone() through ffs softdep's bioops.io_complete()
*/
void
bdirty(bp)
struct buf *bp;
{
struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */
struct proc *p = l->l_proc;
KASSERT(ISSET(bp->b_flags, B_BUSY));
LOCK_ASSERT(simple_lock_held(&bp->b_interlock));
CLR(bp->b_flags, B_AGE);
if (!ISSET(bp->b_flags, B_DELWRI)) {
SET(bp->b_flags, B_DELWRI);
p->p_stats->p_ru.ru_oublock++;
reassignbuf(bp, bp->b_vp);
}
}
/*
* Release a buffer on to the free lists.
* Described in Bach (p. 46).
*/
void
brelse(bp)
struct buf *bp;
{
struct bqueues *bufq;
int s;
KASSERT(ISSET(bp->b_flags, B_BUSY));
/* Block disk interrupts. */
s = splbio();
simple_lock(&bqueue_slock);
simple_lock(&bp->b_interlock);
/* Wake up any processes waiting for any buffer to become free. */
if (needbuffer) {
needbuffer = 0;
wakeup(&needbuffer);
}
/* Wake up any proceeses waiting for _this_ buffer to become free. */
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED|B_AGE);
wakeup(bp);
}
/*
* Determine which queue the buffer should be on, then put it there.
*/
/* If it's locked, don't report an error; try again later. */
if (ISSET(bp->b_flags, (B_LOCKED|B_ERROR)) == (B_LOCKED|B_ERROR))
CLR(bp->b_flags, B_ERROR);
/* If it's not cacheable, or an error, mark it invalid. */
if (ISSET(bp->b_flags, (B_NOCACHE|B_ERROR)))
SET(bp->b_flags, B_INVAL);
if (ISSET(bp->b_flags, B_VFLUSH)) {
/*
* This is a delayed write buffer that was just flushed to
* disk. It is still on the LRU queue. If it's become
* invalid, then we need to move it to a different queue;
* otherwise leave it in its current position.
*/
CLR(bp->b_flags, B_VFLUSH);
if (!ISSET(bp->b_flags, B_ERROR|B_INVAL|B_LOCKED|B_AGE))
goto already_queued;
else
bremfree(bp);
}
if ((bp->b_bufsize <= 0) || ISSET(bp->b_flags, B_INVAL)) {
/*
* If it's invalid or empty, dissociate it from its vnode
* and put on the head of the appropriate queue.
*/
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
CLR(bp->b_flags, B_DONE|B_DELWRI);
if (bp->b_vp) {
reassignbuf(bp, bp->b_vp);
brelvp(bp);
}
if (bp->b_bufsize <= 0)
/* no data */
bufq = &bufqueues[BQ_EMPTY];
else
/* invalid data */
bufq = &bufqueues[BQ_AGE];
binsheadfree(bp, bufq);
} else {
/*
* It has valid data. Put it on the end of the appropriate
* queue, so that it'll stick around for as long as possible.
* If buf is AGE, but has dependencies, must put it on last
* bufqueue to be scanned, ie LRU. This protects against the
* livelock where BQ_AGE only has buffers with dependencies,
* and we thus never get to the dependent buffers in BQ_LRU.
*/
if (ISSET(bp->b_flags, B_LOCKED))
/* locked in core */
bufq = &bufqueues[BQ_LOCKED];
else if (!ISSET(bp->b_flags, B_AGE))
/* valid data */
bufq = &bufqueues[BQ_LRU];
else {
/* stale but valid data */
int has_deps;
if (LIST_FIRST(&bp->b_dep) != NULL &&
bioops.io_countdeps)
has_deps = (*bioops.io_countdeps)(bp, 0);
else
has_deps = 0;
bufq = has_deps ? &bufqueues[BQ_LRU] :
&bufqueues[BQ_AGE];
}
binstailfree(bp, bufq);
}
already_queued:
/* Unlock the buffer. */
CLR(bp->b_flags, B_AGE|B_ASYNC|B_BUSY|B_NOCACHE);
SET(bp->b_flags, B_CACHE);
/* Allow disk interrupts. */
simple_unlock(&bp->b_interlock);
simple_unlock(&bqueue_slock);
splx(s);
}
/*
* Determine if a block is in the cache.
* Just look on what would be its hash chain. If it's there, return
* a pointer to it, unless it's marked invalid. If it's marked invalid,
* we normally don't return the buffer, unless the caller explicitly
* wants us to.
*/
struct buf *
incore(vp, blkno)
struct vnode *vp;
daddr_t blkno;
{
struct buf *bp;
/* Search hash chain */
LIST_FOREACH(bp, BUFHASH(vp, blkno), b_hash) {
if (bp->b_lblkno == blkno && bp->b_vp == vp &&
!ISSET(bp->b_flags, B_INVAL))
return (bp);
}
return (NULL);
}
/*
* Get a block of requested size that is associated with
* a given vnode and block offset. If it is found in the
* block cache, mark it as having been found, make it busy
* and return it. Otherwise, return an empty block of the
* correct size. It is up to the caller to insure that the
* cached blocks be of the correct size.
*/
struct buf *
getblk(vp, blkno, size, slpflag, slptimeo)
struct vnode *vp;
daddr_t blkno;
int size, slpflag, slptimeo;
{
struct buf *bp;
int s, err;
start:
s = splbio();
simple_lock(&bqueue_slock);
bp = incore(vp, blkno);
if (bp != NULL) {
simple_lock(&bp->b_interlock);
if (ISSET(bp->b_flags, B_BUSY)) {
simple_unlock(&bqueue_slock);
if (curproc == uvm.pagedaemon_proc) {
simple_unlock(&bp->b_interlock);
splx(s);
return NULL;
}
SET(bp->b_flags, B_WANTED);
err = ltsleep(bp, slpflag | (PRIBIO + 1) | PNORELOCK,
"getblk", slptimeo, &bp->b_interlock);
splx(s);
if (err)
return (NULL);
goto start;
}
#ifdef DIAGNOSTIC
if (ISSET(bp->b_flags, B_DONE|B_DELWRI) &&
bp->b_bcount < size && vp->v_type != VBLK)
panic("getblk: block size invariant failed");
#endif
SET(bp->b_flags, B_BUSY);
bremfree(bp);
} else {
if ((bp = getnewbuf(slpflag, slptimeo)) == NULL) {
simple_unlock(&bqueue_slock);
splx(s);
goto start;
}
binshash(bp, BUFHASH(vp, blkno));
bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = blkno;
bgetvp(vp, bp);
}
simple_unlock(&bp->b_interlock);
simple_unlock(&bqueue_slock);
splx(s);
allocbuf(bp, size);
return (bp);
}
/*
* Get an empty, disassociated buffer of given size.
*/
struct buf *
geteblk(size)
int size;
{
struct buf *bp;
int s;
s = splbio();
simple_lock(&bqueue_slock);
while ((bp = getnewbuf(0, 0)) == 0)
;
SET(bp->b_flags, B_INVAL);
binshash(bp, &invalhash);
simple_unlock(&bqueue_slock);
simple_unlock(&bp->b_interlock);
splx(s);
allocbuf(bp, size);
return (bp);
}
/*
* Expand or contract the actual memory allocated to a buffer.
*
* If the buffer shrinks, data is lost, so it's up to the
* caller to have written it out *first*; this routine will not
* start a write. If the buffer grows, it's the callers
* responsibility to fill out the buffer's additional contents.
*/
void
allocbuf(bp, size)
struct buf *bp;
int size;
{
struct buf *nbp;
vsize_t desired_size;
int s;
desired_size = round_page((vsize_t)size);
if (desired_size > MAXBSIZE)
panic("allocbuf: buffer larger than MAXBSIZE requested");
if (bp->b_bufsize == desired_size)
goto out;
/*
* If the buffer is smaller than the desired size, we need to snarf
* it from other buffers. Get buffers (via getnewbuf()), and
* steal their pages.
*/
while (bp->b_bufsize < desired_size) {
int amt;
/* find a buffer */
s = splbio();
simple_lock(&bqueue_slock);
while ((nbp = getnewbuf(0, 0)) == NULL)
;
SET(nbp->b_flags, B_INVAL);
binshash(nbp, &invalhash);
simple_unlock(&nbp->b_interlock);
simple_unlock(&bqueue_slock);
splx(s);
/* and steal its pages, up to the amount we need */
amt = min(nbp->b_bufsize, (desired_size - bp->b_bufsize));
pagemove((nbp->b_data + nbp->b_bufsize - amt),
bp->b_data + bp->b_bufsize, amt);
bp->b_bufsize += amt;
nbp->b_bufsize -= amt;
/* reduce transfer count if we stole some data */
if (nbp->b_bcount > nbp->b_bufsize)
nbp->b_bcount = nbp->b_bufsize;
#ifdef DIAGNOSTIC
if (nbp->b_bufsize < 0)
panic("allocbuf: negative bufsize");
#endif
brelse(nbp);
}
/*
* If we want a buffer smaller than the current size,
* shrink this buffer. Grab a buf head from the EMPTY queue,
* move a page onto it, and put it on front of the AGE queue.
* If there are no free buffer headers, leave the buffer alone.
*/
if (bp->b_bufsize > desired_size) {
s = splbio();
simple_lock(&bqueue_slock);
if ((nbp = TAILQ_FIRST(&bufqueues[BQ_EMPTY])) == NULL) {
/* No free buffer head */
simple_unlock(&bqueue_slock);
splx(s);
goto out;
}
/* No need to lock nbp since it came from the empty queue */
bremfree(nbp);
SET(nbp->b_flags, B_BUSY | B_INVAL);
simple_unlock(&bqueue_slock);
splx(s);
/* move the page to it and note this change */
pagemove(bp->b_data + desired_size,
nbp->b_data, bp->b_bufsize - desired_size);
nbp->b_bufsize = bp->b_bufsize - desired_size;
bp->b_bufsize = desired_size;
nbp->b_bcount = 0;
/* release the newly-filled buffer and leave */
brelse(nbp);
}
out:
bp->b_bcount = size;
}
/*
* Find a buffer which is available for use.
* Select something from a free list.
* Preference is to AGE list, then LRU list.
*
* Called with buffer queues locked.
* Return buffer locked.
*/
struct buf *
getnewbuf(slpflag, slptimeo)
int slpflag, slptimeo;
{
struct buf *bp;
start:
LOCK_ASSERT(simple_lock_held(&bqueue_slock));
if ((bp = TAILQ_FIRST(&bufqueues[BQ_AGE])) != NULL ||
(bp = TAILQ_FIRST(&bufqueues[BQ_LRU])) != NULL) {
simple_lock(&bp->b_interlock);
bremfree(bp);
} else {
/* wait for a free buffer of any kind */
needbuffer = 1;
ltsleep(&needbuffer, slpflag|(PRIBIO+1),
"getnewbuf", slptimeo, &bqueue_slock);
return (NULL);
}
if (ISSET(bp->b_flags, B_VFLUSH)) {
/*
* This is a delayed write buffer being flushed to disk. Make
* sure it gets aged out of the queue when it's finished, and
* leave it off the LRU queue.
*/
CLR(bp->b_flags, B_VFLUSH);
SET(bp->b_flags, B_AGE);
simple_unlock(&bp->b_interlock);
goto start;
}
/* Buffer is no longer on free lists. */
SET(bp->b_flags, B_BUSY);
/*
* If buffer was a delayed write, start it and return NULL
* (since we might sleep while starting the write).
*/
if (ISSET(bp->b_flags, B_DELWRI)) {
/*
* This buffer has gone through the LRU, so make sure it gets
* reused ASAP.
*/
SET(bp->b_flags, B_AGE);
simple_unlock(&bp->b_interlock);
simple_unlock(&bqueue_slock);
bawrite(bp);
simple_lock(&bqueue_slock);
return (NULL);
}
/* disassociate us from our vnode, if we had one... */
if (bp->b_vp)
brelvp(bp);
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
/* clear out various other fields */
bp->b_flags = B_BUSY;
bp->b_dev = NODEV;
bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = 0;
bp->b_iodone = 0;
bp->b_error = 0;
bp->b_resid = 0;
bp->b_bcount = 0;
bremhash(bp);
return (bp);
}
/*
* Wait for operations on the buffer to complete.
* When they do, extract and return the I/O's error value.
*/
int
biowait(bp)
struct buf *bp;
{
int s, error;
s = splbio();
simple_lock(&bp->b_interlock);
while (!ISSET(bp->b_flags, B_DONE | B_DELWRI))
ltsleep(bp, PRIBIO + 1, "biowait", 0, &bp->b_interlock);
/* check for interruption of I/O (e.g. via NFS), then errors. */
if (ISSET(bp->b_flags, B_EINTR)) {
CLR(bp->b_flags, B_EINTR);
error = EINTR;
} else if (ISSET(bp->b_flags, B_ERROR))
error = bp->b_error ? bp->b_error : EIO;
else
error = 0;
simple_unlock(&bp->b_interlock);
splx(s);
return (error);
}
/*
* Mark I/O complete on a buffer.
*
* If a callback has been requested, e.g. the pageout
* daemon, do so. Otherwise, awaken waiting processes.
*
* [ Leffler, et al., says on p.247:
* "This routine wakes up the blocked process, frees the buffer
* for an asynchronous write, or, for a request by the pagedaemon
* process, invokes a procedure specified in the buffer structure" ]
*
* In real life, the pagedaemon (or other system processes) wants
* to do async stuff to, and doesn't want the buffer brelse()'d.
* (for swap pager, that puts swap buffers on the free lists (!!!),
* for the vn device, that puts malloc'd buffers on the free lists!)
*/
void
biodone(bp)
struct buf *bp;
{
int s = splbio();
simple_lock(&bp->b_interlock);
if (ISSET(bp->b_flags, B_DONE))
panic("biodone already");
SET(bp->b_flags, B_DONE); /* note that it's done */
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_complete)
(*bioops.io_complete)(bp);
if (!ISSET(bp->b_flags, B_READ)) /* wake up reader */
vwakeup(bp);
/*
* If necessary, call out. Unlock the buffer before calling
* iodone() as the buffer isn't valid any more when it return.
*/
if (ISSET(bp->b_flags, B_CALL)) {
CLR(bp->b_flags, B_CALL); /* but note callout done */
simple_unlock(&bp->b_interlock);
(*bp->b_iodone)(bp);
} else {
if (ISSET(bp->b_flags, B_ASYNC)) { /* if async, release */
simple_unlock(&bp->b_interlock);
brelse(bp);
} else { /* or just wakeup the buffer */
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
simple_unlock(&bp->b_interlock);
}
}
splx(s);
}
/*
* Return a count of buffers on the "locked" queue.
*/
int
count_lock_queue()
{
struct buf *bp;
int n = 0;
simple_lock(&bqueue_slock);
TAILQ_FOREACH(bp, &bufqueues[BQ_LOCKED], b_freelist)
n++;
simple_unlock(&bqueue_slock);
return (n);
}
#ifdef DEBUG
/*
* Print out statistics on the current allocation of the buffer pool.
* Can be enabled to print out on every ``sync'' by setting "syncprt"
* in vfs_syscalls.c using sysctl.
*/
void
vfs_bufstats()
{
int s, i, j, count;
struct buf *bp;
struct bqueues *dp;
int counts[(MAXBSIZE / PAGE_SIZE) + 1];
static char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE", "EMPTY" };
for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) {
count = 0;
for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
counts[j] = 0;
s = splbio();
TAILQ_FOREACH(bp, dp, b_freelist) {
counts[bp->b_bufsize/PAGE_SIZE]++;
count++;
}
splx(s);
printf("%s: total-%d", bname[i], count);
for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
if (counts[j] != 0)
printf(", %d-%d", j * PAGE_SIZE, counts[j]);
printf("\n");
}
}
#endif /* DEBUG */
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