File: [local] / src / sys / kern / vfs_bio.c (download)
Revision 1.68, Mon Jun 2 23:28:07 2003 UTC (21 years ago) by millert
Branch: MAIN
CVS Tags: SMP_SYNC_B, SMP_SYNC_A, OPENBSD_3_5_BASE, OPENBSD_3_5, OPENBSD_3_4_BASE, OPENBSD_3_4 Changes since 1.67: +2 -6 lines
Remove the advertising clause in the UCB license which Berkeley
rescinded 22 July 1999. Proofed by myself and Theo.
|
/* $OpenBSD: vfs_bio.c,v 1.68 2003/06/02 23:28:07 millert Exp $ */
/* $NetBSD: vfs_bio.c,v 1.44 1996/06/11 11:15:36 pk 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. 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 <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/pool.h>
#include <sys/resourcevar.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <uvm/uvm_extern.h>
#include <miscfs/specfs/specdev.h>
/*
* Definitions for the buffer hash lists.
*/
#define BUFHASH(dvp, lbn) \
(&bufhashtbl[((long)(dvp) / sizeof(*(dvp)) + (int)(lbn)) & bufhash])
LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash;
u_long bufhash;
/*
* 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_CLEAN 1 /* LRU queue with clean buffers */
#define BQ_DIRTY 2 /* LRU queue with dirty buffers */
#define BQ_EMPTY 3 /* buffer headers with no memory */
TAILQ_HEAD(bqueues, buf) bufqueues[BQUEUES];
int needbuffer;
int nobuffers;
struct bio_ops bioops;
/*
* Buffer pool for I/O buffers.
*/
struct pool bufpool;
/*
* Insq/Remq for the buffer free lists.
*/
#define binsheadfree(bp, dp) TAILQ_INSERT_HEAD(dp, bp, b_freelist)
#define binstailfree(bp, dp) TAILQ_INSERT_TAIL(dp, bp, b_freelist)
static __inline struct buf *bio_doread(struct vnode *, daddr_t, int, int);
int getnewbuf(int slpflag, int slptimeo, struct buf **);
/*
* We keep a few counters to monitor the utilization of the buffer cache
*
* numdirtypages - number of pages on BQ_DIRTY queue.
* lodirtypages - low water mark for buffer cleaning daemon.
* hidirtypages - high water mark for buffer cleaning daemon.
* numfreepages - number of pages on BQ_CLEAN and BQ_DIRTY queues. unused.
* numcleanpages - number of pages on BQ_CLEAN queue.
* Used to track the need to speedup the cleaner and
* as a reserve for special processes like syncer.
* mincleanpages - the lowest byte count on BQ_CLEAN.
* numemptybufs - number of buffers on BQ_EMPTY. unused.
*/
long numdirtypages;
long lodirtypages;
long hidirtypages;
long numfreepages;
long numcleanpages;
long locleanpages;
int numemptybufs;
#ifdef DEBUG
long mincleanpages;
#endif
struct proc *cleanerproc;
int bd_req; /* Sleep point for cleaner daemon. */
void
bremfree(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 (bp->b_freelist.tqe_next == 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");
}
if (bp->b_bufsize <= 0) {
numemptybufs--;
} else if (!ISSET(bp->b_flags, B_LOCKED)) {
numfreepages -= btoc(bp->b_bufsize);
if (!ISSET(bp->b_flags, B_DELWRI)) {
numcleanpages -= btoc(bp->b_bufsize);
#ifdef DEBUG
if (mincleanpages > numcleanpages)
mincleanpages = numcleanpages;
#endif
} else {
numdirtypages -= btoc(bp->b_bufsize);
}
}
TAILQ_REMOVE(dp, bp, b_freelist);
}
/*
* Initialize buffers and hash links for buffers.
*/
void
bufinit(void)
{
struct buf *bp;
struct bqueues *dp;
int i;
int base, residual;
pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", NULL);
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
TAILQ_INIT(dp);
bufhashtbl = hashinit(nbuf, M_CACHE, M_WAITOK, &bufhash);
base = bufpages / nbuf;
residual = bufpages % nbuf;
for (i = 0; i < nbuf; i++) {
bp = &buf[i];
bzero((char *)bp, sizeof *bp);
bp->b_dev = NODEV;
bp->b_vnbufs.le_next = NOLIST;
bp->b_data = buffers + i * MAXBSIZE;
LIST_INIT(&bp->b_dep);
if (i < residual)
bp->b_bufsize = (base + 1) * PAGE_SIZE;
else
bp->b_bufsize = base * PAGE_SIZE;
bp->b_flags = B_INVAL;
if (bp->b_bufsize) {
dp = &bufqueues[BQ_CLEAN];
numfreepages += btoc(bp->b_bufsize);
numcleanpages += btoc(bp->b_bufsize);
} else {
dp = &bufqueues[BQ_EMPTY];
numemptybufs++;
}
binsheadfree(bp, dp);
binshash(bp, &invalhash);
}
hidirtypages = bufpages / 4;
lodirtypages = hidirtypages / 2;
/*
* Reserve 5% of bufpages for syncer's needs,
* but not more than 25% and if possible
* not less then 2 * MAXBSIZE. locleanpages
* value must be not too small, but probably
* there are no reason to set it more than 1-2 MB.
*/
locleanpages = bufpages / 20;
if (locleanpages < btoc(2 * MAXBSIZE))
locleanpages = btoc(2 * MAXBSIZE);
if (locleanpages > bufpages / 4)
locleanpages = bufpages / 4;
if (locleanpages > btoc(2 * 1024 * 1024))
locleanpages = btoc(2 * 1024 * 1024);
#ifdef DEBUG
mincleanpages = locleanpages;
#endif
}
static __inline struct buf *
bio_doread(struct vnode *vp, daddr_t blkno, int size, int async)
{
struct buf *bp;
bp = getblk(vp, blkno, size, 0, 0);
/*
* 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 it's I/O has completed or been delayed.
*/
if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) {
SET(bp->b_flags, B_READ | async);
VOP_STRATEGY(bp);
/* Pay for the read. */
curproc->p_stats->p_ru.ru_inblock++; /* XXX */
} else if (async) {
brelse(bp);
}
return (bp);
}
/*
* Read a disk block.
* This algorithm described in Bach (p.54).
*/
int
bread(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, 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(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, 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], 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(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(struct buf *bp)
{
int rv, async, wasdelayed, s;
struct vnode *vp;
struct mount *mp;
/*
* 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).
*/
async = ISSET(bp->b_flags, B_ASYNC);
if (!async && bp->b_vp && bp->b_vp->v_mount &&
ISSET(bp->b_vp->v_mount->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 ((vp = bp->b_vp) != NULL) {
if (vp->v_type == VBLK)
mp = vp->v_specmountpoint;
else
mp = vp->v_mount;
if (mp != NULL) {
if (async)
mp->mnt_stat.f_asyncwrites++;
else
mp->mnt_stat.f_syncwrites++;
}
}
wasdelayed = ISSET(bp->b_flags, B_DELWRI);
CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI));
s = splbio();
/*
* If not synchronous, pay for the I/O operation and make
* sure the buf is on the correct vnode queue. We have
* to do this now, because if we don't, the vnode may not
* be properly notified that its I/O has completed.
*/
if (wasdelayed) {
reassignbuf(bp);
} else
curproc->p_stats->p_ru.ru_oublock++;
/* Initiate disk write. Make sure the appropriate party is charged. */
bp->b_vp->v_numoutput++;
splx(s);
SET(bp->b_flags, B_WRITEINPROG);
VOP_STRATEGY(bp);
if (async)
return (0);
/*
* If I/O was synchronous, wait for it to complete.
*/
rv = biowait(bp);
/* Release the buffer. */
brelse(bp);
return (rv);
}
/*
* 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(struct buf *bp)
{
int s;
/*
* 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,
* (4) If a buffer is rewritten, move it to end of dirty list
*/
if (!ISSET(bp->b_flags, B_DELWRI)) {
SET(bp->b_flags, B_DELWRI);
s = splbio();
reassignbuf(bp);
splx(s);
curproc->p_stats->p_ru.ru_oublock++; /* XXX */
}
/* If this is a tape block, write the block now. */
if (major(bp->b_dev) < nblkdev &&
bdevsw[major(bp->b_dev)].d_type == D_TAPE) {
bawrite(bp);
return;
}
/* Otherwise, the "write" is done, so mark and release the buffer. */
CLR(bp->b_flags, B_NEEDCOMMIT);
SET(bp->b_flags, B_DONE);
brelse(bp);
}
/*
* Asynchronous block write; just an asynchronous bwrite().
*/
void
bawrite(struct buf *bp)
{
SET(bp->b_flags, B_ASYNC);
VOP_BWRITE(bp);
}
/*
* Must be called at splbio()
*/
void
buf_dirty(struct buf *bp)
{
splassert(IPL_BIO);
if (ISSET(bp->b_flags, B_DELWRI) == 0) {
SET(bp->b_flags, B_DELWRI);
reassignbuf(bp);
}
}
/*
* Must be called at splbio()
*/
void
buf_undirty(struct buf *bp)
{
splassert(IPL_BIO);
if (ISSET(bp->b_flags, B_DELWRI)) {
CLR(bp->b_flags, B_DELWRI);
reassignbuf(bp);
}
}
/*
* Release a buffer on to the free lists.
* Described in Bach (p. 46).
*/
void
brelse(struct buf *bp)
{
struct bqueues *bufq;
int s;
/* Block disk interrupts. */
s = splbio();
/*
* 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 ((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)
buf_deallocate(bp);
if (ISSET(bp->b_flags, B_DELWRI)) {
CLR(bp->b_flags, B_DELWRI);
}
if (bp->b_vp) {
reassignbuf(bp);
brelvp(bp);
}
if (bp->b_bufsize <= 0) {
/* no data */
bufq = &bufqueues[BQ_EMPTY];
numemptybufs++;
} else {
/* invalid data */
bufq = &bufqueues[BQ_CLEAN];
numfreepages += btoc(bp->b_bufsize);
numcleanpages += btoc(bp->b_bufsize);
}
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 (ISSET(bp->b_flags, B_LOCKED))
/* locked in core */
bufq = &bufqueues[BQ_LOCKED];
else {
numfreepages += btoc(bp->b_bufsize);
if (!ISSET(bp->b_flags, B_DELWRI)) {
numcleanpages += btoc(bp->b_bufsize);
bufq = &bufqueues[BQ_CLEAN];
} else {
numdirtypages += btoc(bp->b_bufsize);
bufq = &bufqueues[BQ_DIRTY];
}
}
if (ISSET(bp->b_flags, B_AGE))
binsheadfree(bp, bufq);
else
binstailfree(bp, bufq);
}
/* Unlock the buffer. */
CLR(bp->b_flags, (B_AGE | B_ASYNC | B_BUSY | B_NOCACHE | B_DEFERRED));
/* Wake up syncer and cleaner processes waiting for buffers */
if (nobuffers) {
wakeup(&nobuffers);
nobuffers = 0;
}
/* Wake up any processes waiting for any buffer to become free. */
if (needbuffer && (numcleanpages > locleanpages)) {
needbuffer--;
wakeup_one(&needbuffer);
}
splx(s);
/* Wake up any processes waiting for _this_ buffer to become free. */
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
}
/*
* 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(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 (0);
}
/*
* 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(struct vnode *vp, daddr_t blkno, int size, int slpflag, int slptimeo)
{
struct bufhashhdr *bh;
struct buf *bp, *nbp = NULL;
int s, err;
/*
* XXX
* The following is an inlined version of 'incore()', but with
* the 'invalid' test moved to after the 'busy' test. It's
* necessary because there are some cases in which the NFS
* code sets B_INVAL prior to writing data to the server, but
* in which the buffers actually contain valid data. In this
* case, we can't allow the system to allocate a new buffer for
* the block until the write is finished.
*/
bh = BUFHASH(vp, blkno);
start:
LIST_FOREACH(bp, BUFHASH(vp, blkno), b_hash) {
if (bp->b_lblkno != blkno || bp->b_vp != vp)
continue;
s = splbio();
if (ISSET(bp->b_flags, B_BUSY)) {
SET(bp->b_flags, B_WANTED);
err = tsleep(bp, slpflag | (PRIBIO + 1), "getblk",
slptimeo);
splx(s);
if (err)
return (NULL);
goto start;
}
if (!ISSET(bp->b_flags, B_INVAL)) {
SET(bp->b_flags, (B_BUSY | B_CACHE));
bremfree(bp);
splx(s);
break;
}
splx(s);
}
if (bp == NULL) {
if (nbp == NULL && getnewbuf(slpflag, slptimeo, &nbp) != 0) {
goto start;
}
bp = nbp;
binshash(bp, bh);
bp->b_blkno = bp->b_lblkno = blkno;
s = splbio();
bgetvp(vp, bp);
splx(s);
} else if (nbp != NULL) {
/*
* Set B_AGE so that buffer appear at BQ_CLEAN head
* and gets reused ASAP.
*/
SET(nbp->b_flags, B_AGE);
brelse(nbp);
}
allocbuf(bp, size);
return (bp);
}
/*
* Get an empty, disassociated buffer of given size.
*/
struct buf *
geteblk(int size)
{
struct buf *bp;
getnewbuf(0, 0, &bp);
SET(bp->b_flags, B_INVAL);
binshash(bp, &invalhash);
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(struct buf *bp, int size)
{
struct buf *nbp;
vsize_t desired_size;
int s;
desired_size = round_page(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 */
getnewbuf(0, 0, &nbp);
SET(nbp->b_flags, B_INVAL);
binshash(nbp, &invalhash);
/* 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();
if ((nbp = bufqueues[BQ_EMPTY].tqh_first) == NULL) {
/* No free buffer head */
splx(s);
goto out;
}
bremfree(nbp);
SET(nbp->b_flags, B_BUSY);
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;
SET(nbp->b_flags, B_INVAL);
/* release the newly-filled buffer and leave */
brelse(nbp);
}
out:
bp->b_bcount = size;
}
/*
* Find a buffer which is available for use.
*
* We must notify getblk if we slept during the buffer allocation. When
* that happens, we allocate a buffer anyway (unless tsleep is interrupted
* or times out) and return !0.
*/
int
getnewbuf(int slpflag, int slptimeo, struct buf **bpp)
{
struct buf *bp;
int s, ret, error;
*bpp = NULL;
ret = 0;
start:
s = splbio();
/*
* Wake up cleaner if we're getting low on buffers.
*/
if (numdirtypages >= hidirtypages)
wakeup(&bd_req);
if ((numcleanpages <= locleanpages) &&
curproc != syncerproc && curproc != cleanerproc) {
needbuffer++;
error = tsleep(&needbuffer, slpflag|(PRIBIO+1), "getnewbuf",
slptimeo);
splx(s);
if (error)
return (1);
ret = 1;
goto start;
}
if ((bp = TAILQ_FIRST(&bufqueues[BQ_CLEAN])) == NULL) {
/* wait for a free buffer of any kind */
nobuffers = 1;
error = tsleep(&nobuffers, slpflag|(PRIBIO-3),
"getnewbuf", slptimeo);
splx(s);
if (error)
return (1);
ret = 1;
goto start;
}
bremfree(bp);
/* Buffer is no longer on free lists. */
SET(bp->b_flags, B_BUSY);
#ifdef DIAGNOSTIC
if (ISSET(bp->b_flags, B_DELWRI))
panic("Dirty buffer on BQ_CLEAN");
#endif
/* disassociate us from our vnode, if we had one... */
if (bp->b_vp)
brelvp(bp);
splx(s);
#ifdef DIAGNOSTIC
/* CLEAN buffers must have no dependencies */
if (LIST_FIRST(&bp->b_dep) != NULL)
panic("BQ_CLEAN has buffer with dependencies");
#endif
/* clear out various other fields */
bp->b_flags = B_BUSY;
bp->b_dev = NODEV;
bp->b_blkno = bp->b_lblkno = 0;
bp->b_iodone = 0;
bp->b_error = 0;
bp->b_resid = 0;
bp->b_bcount = 0;
bp->b_dirtyoff = bp->b_dirtyend = 0;
bp->b_validoff = bp->b_validend = 0;
bremhash(bp);
*bpp = bp;
return (ret);
}
/*
* Buffer cleaning daemon.
*/
void
buf_daemon(struct proc *p)
{
int s;
struct buf *bp;
struct timeval starttime, timediff;
cleanerproc = curproc;
for (;;) {
if (numdirtypages < hidirtypages) {
tsleep(&bd_req, PRIBIO - 7, "cleaner", 0);
}
starttime = time;
s = splbio();
while ((bp = TAILQ_FIRST(&bufqueues[BQ_DIRTY]))) {
bremfree(bp);
SET(bp->b_flags, B_BUSY);
splx(s);
if (ISSET(bp->b_flags, B_INVAL)) {
brelse(bp);
s = splbio();
continue;
}
#ifdef DIAGNOSTIC
if (!ISSET(bp->b_flags, B_DELWRI))
panic("Clean buffer on BQ_DIRTY");
#endif
if (LIST_FIRST(&bp->b_dep) != NULL &&
!ISSET(bp->b_flags, B_DEFERRED) &&
buf_countdeps(bp, 0, 1)) {
SET(bp->b_flags, B_DEFERRED);
s = splbio();
numfreepages += btoc(bp->b_bufsize);
numdirtypages += btoc(bp->b_bufsize);
binstailfree(bp, &bufqueues[BQ_DIRTY]);
CLR(bp->b_flags, B_BUSY);
continue;
}
bawrite(bp);
if (numdirtypages < lodirtypages)
break;
/* Never allow processing to run for more than 1 sec */
timersub(&time, &starttime, &timediff);
if (timediff.tv_sec)
break;
s = splbio();
}
}
}
/*
* Wait for operations on the buffer to complete.
* When they do, extract and return the I/O's error value.
*/
int
biowait(struct buf *bp)
{
int s;
s = splbio();
while (!ISSET(bp->b_flags, B_DONE))
tsleep(bp, PRIBIO + 1, "biowait", 0);
splx(s);
/* 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);
return (EINTR);
}
if (ISSET(bp->b_flags, B_ERROR))
return (bp->b_error ? bp->b_error : EIO);
else
return (0);
}
/*
* 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!)
*
* Must be called at splbio().
*/
void
biodone(struct buf *bp)
{
splassert(IPL_BIO);
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)
buf_complete(bp);
if (!ISSET(bp->b_flags, B_READ)) {
CLR(bp->b_flags, B_WRITEINPROG);
vwakeup(bp->b_vp);
}
if (ISSET(bp->b_flags, B_CALL)) { /* if necessary, call out */
CLR(bp->b_flags, B_CALL); /* but note callout done */
(*bp->b_iodone)(bp);
} else {
if (ISSET(bp->b_flags, B_ASYNC)) {/* if async, release it */
brelse(bp);
} else { /* or just wakeup the buffer */
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
}
}
#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;
register struct buf *bp;
register struct bqueues *dp;
int counts[MAXBSIZE/PAGE_SIZE+1];
int totals[BQUEUES];
long ptotals[BQUEUES];
long pages;
static char *bname[BQUEUES] = { "LOCKED", "CLEAN", "DIRTY", "EMPTY" };
s = splbio();
for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) {
count = 0;
pages = 0;
for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
counts[j] = 0;
for (bp = dp->tqh_first; bp; bp = bp->b_freelist.tqe_next) {
counts[bp->b_bufsize/PAGE_SIZE]++;
count++;
pages += btoc(bp->b_bufsize);
}
totals[i] = count;
ptotals[i] = pages;
printf("%s: total-%d(%d pages)", bname[i], count, pages);
for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
if (counts[j] != 0)
printf(", %d-%d", j * PAGE_SIZE, counts[j]);
printf("\n");
}
if (totals[BQ_EMPTY] != numemptybufs)
printf("numemptybufs counter wrong: %d != %d\n",
numemptybufs, totals[BQ_EMPTY]);
if ((ptotals[BQ_CLEAN] + ptotals[BQ_DIRTY]) != numfreepages)
printf("numfreepages counter wrong: %ld != %ld\n",
numfreepages, ptotals[BQ_CLEAN] + ptotals[BQ_DIRTY]);
if (ptotals[BQ_CLEAN] != numcleanpages)
printf("numcleanpages counter wrong: %ld != %ld\n",
numcleanpages, ptotals[BQ_CLEAN]);
else
printf("numcleanpages: %ld\n", numcleanpages);
if (numdirtypages != ptotals[BQ_DIRTY])
printf("numdirtypages counter wrong: %ld != %ld\n",
numdirtypages, ptotals[BQ_DIRTY]);
else
printf("numdirtypages: %ld\n", numdirtypages);
printf("syncer eating up to %ld pages from %ld reserved\n",
locleanpages - mincleanpages, locleanpages);
splx(s);
}
#endif /* DEBUG */