OpenBSD-4.6/sys/kern/vfs_bio.c
/* $OpenBSD: vfs_bio.c,v 1.118 2009/06/25 15:49:26 thib 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 2 /* number of free buffer queues */
#define BQ_DIRTY 0 /* LRU queue with dirty buffers */
#define BQ_CLEAN 1 /* LRU queue with clean buffers */
TAILQ_HEAD(bqueues, buf) bufqueues[BQUEUES];
int needbuffer;
struct bio_ops bioops;
/*
* Buffer pool for I/O buffers.
*/
struct pool bufpool;
struct bufhead bufhead = LIST_HEAD_INITIALIZER(bufhead);
void buf_put(struct buf *);
/*
* 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)
struct buf *bio_doread(struct vnode *, daddr64_t, int, int);
struct buf *buf_get(struct vnode *, daddr64_t, size_t);
void bread_cluster_callback(struct buf *);
/*
* We keep a few counters to monitor the utilization of the buffer cache
*
* numbufpages - number of pages totally allocated.
* numdirtypages - number of pages on BQ_DIRTY queue.
* lodirtypages - low water mark for buffer cleaning daemon.
* hidirtypages - high water mark for buffer cleaning daemon.
* 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.
* maxcleanpages - the highest page count on BQ_CLEAN.
*/
struct bcachestats bcstats;
long lodirtypages;
long hidirtypages;
long locleanpages;
long hicleanpages;
long maxcleanpages;
/* XXX - should be defined here. */
extern int bufcachepercent;
vsize_t bufkvm;
struct proc *cleanerproc;
int bd_req; /* Sleep point for cleaner daemon. */
void
bremfree(struct buf *bp)
{
struct bqueues *dp = NULL;
splassert(IPL_BIO);
/*
* 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 == &TAILQ_NEXT(bp, b_freelist))
break;
if (dp == &bufqueues[BQUEUES])
panic("bremfree: lost tail");
}
if (!ISSET(bp->b_flags, B_DELWRI)) {
bcstats.numcleanpages -= atop(bp->b_bufsize);
} else {
bcstats.numdirtypages -= atop(bp->b_bufsize);
}
TAILQ_REMOVE(dp, bp, b_freelist);
bcstats.freebufs--;
}
void
buf_put(struct buf *bp)
{
splassert(IPL_BIO);
#ifdef DIAGNOSTIC
if (bp->b_pobj != NULL)
KASSERT(bp->b_bufsize > 0);
if (ISSET(bp->b_flags, B_DELWRI))
panic("buf_put: releasing dirty buffer");
if (bp->b_freelist.tqe_next != NOLIST &&
bp->b_freelist.tqe_next != (void *)-1)
panic("buf_put: still on the free list");
if (bp->b_vnbufs.le_next != NOLIST &&
bp->b_vnbufs.le_next != (void *)-1)
panic("buf_put: still on the vnode list");
if (!LIST_EMPTY(&bp->b_dep))
panic("buf_put: b_dep is not empty");
#endif
bremhash(bp);
LIST_REMOVE(bp, b_list);
bcstats.numbufs--;
if (buf_dealloc_mem(bp) != 0)
return;
pool_put(&bufpool, bp);
}
/*
* Initialize buffers and hash links for buffers.
*/
void
bufinit(void)
{
struct bqueues *dp;
/* XXX - for now */
bufpages = bufcachepercent = bufkvm = 0;
/*
* If MD code doesn't say otherwise, use 10% of kvm for mappings and
* 10% physmem for pages.
*/
if (bufcachepercent == 0)
bufcachepercent = 10;
if (bufpages == 0)
bufpages = physmem * bufcachepercent / 100;
if (bufkvm == 0)
bufkvm = (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) / 10;
/*
* Don't use more than twice the amount of bufpages for mappings.
* It's twice since we map things sparsely.
*/
if (bufkvm > bufpages * PAGE_SIZE)
bufkvm = bufpages * PAGE_SIZE;
/*
* Round bufkvm to MAXPHYS because we allocate chunks of va space
* in MAXPHYS chunks.
*/
bufkvm &= ~(MAXPHYS - 1);
pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", NULL);
pool_setipl(&bufpool, IPL_BIO);
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
TAILQ_INIT(dp);
/*
* hmm - bufkvm is an argument because it's static, while
* bufpages is global because it can change while running.
*/
buf_mem_init(bufkvm);
bufhashtbl = hashinit(bufpages / 4, M_CACHE, M_WAITOK, &bufhash);
hidirtypages = (bufpages / 4) * 3;
lodirtypages = bufpages / 2;
/*
* When we hit 95% of pages being clean, we bring them down to
* 90% to have some slack.
*/
hicleanpages = bufpages - (bufpages / 20);
locleanpages = bufpages - (bufpages / 10);
maxcleanpages = locleanpages;
}
struct buf *
bio_doread(struct vnode *vp, daddr64_t blkno, int size, int async)
{
struct buf *bp;
struct mount *mp;
bp = getblk(vp, blkno, size, 0, 0);
/*
* If buffer does not have valid data, 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))) {
SET(bp->b_flags, B_READ | async);
bcstats.pendingreads++;
bcstats.numreads++;
VOP_STRATEGY(bp);
/* Pay for the read. */
curproc->p_stats->p_ru.ru_inblock++; /* XXX */
} else if (async) {
brelse(bp);
}
mp = vp->v_type == VBLK? vp->v_specmountpoint : vp->v_mount;
/*
* Collect statistics on synchronous and asynchronous reads.
* Reads from block devices are charged to their associated
* filesystem (if any).
*/
if (mp != NULL) {
if (async == 0)
mp->mnt_stat.f_syncreads++;
else
mp->mnt_stat.f_asyncreads++;
}
return (bp);
}
/*
* Read a disk block.
* This algorithm described in Bach (p.54).
*/
int
bread(struct vnode *vp, daddr64_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, daddr64_t blkno, int size, daddr64_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));
}
/*
* Called from interrupt context.
*/
void
bread_cluster_callback(struct buf *bp)
{
struct buf **xbpp = bp->b_saveaddr;
int i;
if (xbpp[1] != NULL) {
size_t newsize = xbpp[1]->b_bufsize;
/*
* Shrink this buffer to only cover its part of the total I/O.
*/
buf_shrink_mem(bp, newsize);
bp->b_bcount = newsize;
}
for (i = 1; xbpp[i] != 0; i++) {
if (ISSET(bp->b_flags, B_ERROR))
SET(xbpp[i]->b_flags, B_INVAL | B_ERROR);
biodone(xbpp[i]);
}
free(xbpp, M_TEMP);
if (ISSET(bp->b_flags, B_ASYNC)) {
brelse(bp);
} else {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
}
int
bread_cluster(struct vnode *vp, daddr64_t blkno, int size, struct buf **rbpp)
{
struct buf *bp, **xbpp;
int howmany, maxra, i, inc;
daddr64_t sblkno;
*rbpp = bio_doread(vp, blkno, size, 0);
if (size != round_page(size))
goto out;
if (VOP_BMAP(vp, blkno + 1, NULL, &sblkno, &maxra))
goto out;
maxra++;
if (sblkno == -1 || maxra < 2)
goto out;
howmany = MAXPHYS / size;
if (howmany > maxra)
howmany = maxra;
xbpp = malloc((howmany + 1) * sizeof(struct buf *), M_TEMP, M_NOWAIT);
if (xbpp == NULL)
goto out;
for (i = howmany - 1; i >= 0; i--) {
size_t sz;
/*
* First buffer allocates big enough size to cover what
* all the other buffers need.
*/
sz = i == 0 ? howmany * size : 0;
xbpp[i] = buf_get(vp, blkno + i + 1, sz);
if (xbpp[i] == NULL) {
for (++i; i < howmany; i++) {
SET(xbpp[i]->b_flags, B_INVAL);
brelse(xbpp[i]);
}
free(xbpp, M_TEMP);
goto out;
}
}
bp = xbpp[0];
xbpp[howmany] = 0;
inc = btodb(size);
for (i = 1; i < howmany; i++) {
bcstats.pendingreads++;
bcstats.numreads++;
SET(xbpp[i]->b_flags, B_READ | B_ASYNC);
xbpp[i]->b_blkno = sblkno + (i * inc);
xbpp[i]->b_bufsize = xbpp[i]->b_bcount = size;
xbpp[i]->b_data = NULL;
xbpp[i]->b_pobj = bp->b_pobj;
xbpp[i]->b_poffs = bp->b_poffs + (i * size);
}
KASSERT(bp->b_lblkno == blkno + 1);
KASSERT(bp->b_vp == vp);
bp->b_blkno = sblkno;
SET(bp->b_flags, B_READ | B_ASYNC | B_CALL);
bp->b_saveaddr = (void *)xbpp;
bp->b_iodone = bread_cluster_callback;
bcstats.pendingreads++;
bcstats.numreads++;
VOP_STRATEGY(bp);
curproc->p_stats->p_ru.ru_inblock++;
out:
return (biowait(*rbpp));
}
/*
* Block write. Described in Bach (p.56)
*/
int
bwrite(struct buf *bp)
{
int rv, async, wasdelayed, s;
struct vnode *vp;
struct mount *mp;
vp = bp->b_vp;
if (vp != NULL)
mp = vp->v_type == VBLK? vp->v_specmountpoint : 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).
*/
async = ISSET(bp->b_flags, B_ASYNC);
if (!async && mp && 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 (async)
mp->mnt_stat.f_asyncwrites++;
else
mp->mnt_stat.f_syncwrites++;
}
bcstats.pendingwrites++;
bcstats.numwrites++;
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);
bp->b_synctime = time_uptime + 35;
s = splbio();
reassignbuf(bp);
splx(s);
curproc->p_stats->p_ru.ru_oublock++; /* XXX */
} else {
/*
* see if this buffer has slacked through the syncer
* and enforce an async write upon it.
*/
if (bp->b_synctime < time_uptime) {
bawrite(bp);
return;
}
}
/* 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);
#ifdef DIAGNOSTIC
if (!ISSET(bp->b_flags, B_BUSY))
panic("Trying to dirty buffer on freelist!");
#endif
if (ISSET(bp->b_flags, B_DELWRI) == 0) {
SET(bp->b_flags, B_DELWRI);
bp->b_synctime = time_uptime + 35;
reassignbuf(bp);
}
}
/*
* Must be called at splbio()
*/
void
buf_undirty(struct buf *bp)
{
splassert(IPL_BIO);
#ifdef DIAGNOSTIC
if (!ISSET(bp->b_flags, B_BUSY))
panic("Trying to undirty buffer on freelist!");
#endif
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;
s = splbio();
if (bp->b_data != NULL)
KASSERT(bp->b_bufsize > 0);
/*
* Determine which queue the buffer should be on, then put it there.
*/
/* 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_INVAL)) {
/*
* If the buffer is invalid, place it in the clean queue, so it
* can be reused.
*/
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)
brelvp(bp);
bremhash(bp);
binshash(bp, &invalhash);
/*
* If the buffer has no associated data, place it back in the
* pool.
*/
if (bp->b_data == NULL && bp->b_pobj == NULL) {
/*
* Wake up any processes waiting for _this_ buffer to
* become free. They are not allowed to grab it
* since it will be freed. But the only sleeper is
* getblk and it's restarting the operation after
* sleep.
*/
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
buf_put(bp);
splx(s);
return;
}
bcstats.numcleanpages += atop(bp->b_bufsize);
if (maxcleanpages < bcstats.numcleanpages)
maxcleanpages = bcstats.numcleanpages;
binsheadfree(bp, &bufqueues[BQ_CLEAN]);
} 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_DELWRI)) {
bcstats.numcleanpages += atop(bp->b_bufsize);
if (maxcleanpages < bcstats.numcleanpages)
maxcleanpages = bcstats.numcleanpages;
bufq = &bufqueues[BQ_CLEAN];
} else {
bcstats.numdirtypages += atop(bp->b_bufsize);
bufq = &bufqueues[BQ_DIRTY];
}
if (ISSET(bp->b_flags, B_AGE)) {
binsheadfree(bp, bufq);
bp->b_synctime = time_uptime + 30;
} else {
binstailfree(bp, bufq);
bp->b_synctime = time_uptime + 300;
}
}
/* Unlock the buffer. */
bcstats.freebufs++;
CLR(bp->b_flags, (B_AGE | B_ASYNC | B_NOCACHE | B_DEFERRED));
buf_release(bp);
/* Wake up any processes waiting for any buffer to become free. */
if (needbuffer) {
needbuffer--;
wakeup(&needbuffer);
}
/* 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);
}
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.
*/
struct buf *
incore(struct vnode *vp, daddr64_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 ensure that the
* cached blocks be of the correct size.
*/
struct buf *
getblk(struct vnode *vp, daddr64_t blkno, int size, int slpflag, int slptimeo)
{
struct buf *bp;
int s, error;
/*
* 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.
*/
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);
error = tsleep(bp, slpflag | (PRIBIO + 1), "getblk",
slptimeo);
splx(s);
if (error)
return (NULL);
goto start;
}
if (!ISSET(bp->b_flags, B_INVAL)) {
bcstats.cachehits++;
SET(bp->b_flags, B_CACHE);
bremfree(bp);
buf_acquire(bp);
splx(s);
return (bp);
}
splx(s);
}
if ((bp = buf_get(vp, blkno, size)) == NULL)
goto start;
return (bp);
}
/*
* Get an empty, disassociated buffer of given size.
*/
struct buf *
geteblk(int size)
{
struct buf *bp;
while ((bp = buf_get(NULL, 0, size)) == NULL)
;
return (bp);
}
/*
* Allocate a buffer.
*/
struct buf *
buf_get(struct vnode *vp, daddr64_t blkno, size_t size)
{
struct buf *bp;
int poolwait = size == 0 ? PR_NOWAIT : PR_WAITOK;
int npages;
int s;
s = splbio();
if (size) {
/*
* Wake up cleaner if we're getting low on pages.
*/
if (bcstats.numdirtypages >= hidirtypages ||
bcstats.numcleanpages <= locleanpages)
wakeup(&bd_req);
/*
* If we're above the high water mark for clean pages,
* free down to the low water mark.
*/
if (bcstats.numcleanpages > hicleanpages) {
while (bcstats.numcleanpages > locleanpages) {
bp = TAILQ_FIRST(&bufqueues[BQ_CLEAN]);
bremfree(bp);
if (bp->b_vp)
brelvp(bp);
buf_put(bp);
}
}
npages = atop(round_page(size));
/*
* Free some buffers until we have enough space.
*/
while (bcstats.numbufpages + npages > bufpages) {
int freemax = 5;
int i = freemax;
while ((bp = TAILQ_FIRST(&bufqueues[BQ_CLEAN])) && i--) {
bremfree(bp);
if (bp->b_vp)
brelvp(bp);
buf_put(bp);
}
if (freemax == i) {
needbuffer++;
tsleep(&needbuffer, PRIBIO, "needbuffer", 0);
splx(s);
return (NULL);
}
}
}
bp = pool_get(&bufpool, poolwait|PR_ZERO);
if (bp == NULL) {
splx(s);
return (NULL);
}
bp->b_freelist.tqe_next = NOLIST;
bp->b_synctime = time_uptime + 300;
bp->b_dev = NODEV;
LIST_INIT(&bp->b_dep);
bp->b_bcount = size;
buf_acquire_unmapped(bp);
if (vp != NULL) {
/*
* We insert the buffer into the hash with B_BUSY set
* while we allocate pages for it. This way any getblk
* that happens while we allocate pages will wait for
* this buffer instead of starting its own guf_get.
*
* But first, we check if someone beat us to it.
*/
if (incore(vp, blkno)) {
pool_put(&bufpool, bp);
splx(s);
return (NULL);
}
bp->b_blkno = bp->b_lblkno = blkno;
bgetvp(vp, bp);
binshash(bp, BUFHASH(vp, blkno));
} else {
bp->b_vnbufs.le_next = NOLIST;
SET(bp->b_flags, B_INVAL);
binshash(bp, &invalhash);
}
LIST_INSERT_HEAD(&bufhead, bp, b_list);
bcstats.numbufs++;
if (size) {
buf_alloc_pages(bp, round_page(size));
buf_map(bp);
}
splx(s);
return (bp);
}
/*
* Buffer cleaning daemon.
*/
void
buf_daemon(struct proc *p)
{
struct timeval starttime, timediff;
struct buf *bp;
int s;
cleanerproc = curproc;
s = splbio();
for (;;) {
if (bcstats.numdirtypages < hidirtypages)
tsleep(&bd_req, PRIBIO - 7, "cleaner", 0);
getmicrouptime(&starttime);
while ((bp = TAILQ_FIRST(&bufqueues[BQ_DIRTY]))) {
struct timeval tv;
if (bcstats.numdirtypages < lodirtypages)
break;
bremfree(bp);
buf_acquire(bp);
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, 0)) {
SET(bp->b_flags, B_DEFERRED);
s = splbio();
bcstats.numdirtypages += atop(bp->b_bufsize);
binstailfree(bp, &bufqueues[BQ_DIRTY]);
bcstats.freebufs++;
buf_release(bp);
continue;
}
bawrite(bp);
/* Never allow processing to run for more than 1 sec */
getmicrouptime(&tv);
timersub(&tv, &starttime, &timediff);
s = splbio();
if (timediff.tv_sec)
break;
}
}
}
/*
* 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;
KASSERT(!(bp->b_flags & B_ASYNC));
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 (bcstats.numbufs &&
(!(ISSET(bp->b_flags, B_RAW) || ISSET(bp->b_flags, B_PHYS)))) {
if (!ISSET(bp->b_flags, B_READ))
bcstats.pendingwrites--;
else
bcstats.pendingreads--;
}
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);
}
}
}