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vfs_bio.c
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vfs_bio.c
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/* $OpenBSD: vfs_bio.c,v 1.187 2018/11/21 16:14:43 mpi 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 <sys/specdev.h>
#include <uvm/uvm_extern.h>
/* XXX Should really be in buf.h, but for uvm_constraint_range.. */
int buf_realloc_pages(struct buf *, struct uvm_constraint_range *, int);
struct uvm_constraint_range high_constraint;
int fliphigh;
int nobuffers;
int needbuffer;
struct bio_ops bioops;
/* private bufcache functions */
void bufcache_init(void);
void bufcache_adjust(void);
struct buf *bufcache_gethighcleanbuf(void);
struct buf *bufcache_getdmacleanbuf(void);
/*
* Buffer pool for I/O buffers.
*/
struct pool bufpool;
struct bufhead bufhead = LIST_HEAD_INITIALIZER(bufhead);
void buf_put(struct buf *);
struct buf *bio_doread(struct vnode *, daddr_t, int, int);
struct buf *buf_get(struct vnode *, daddr_t, size_t);
void bread_cluster_callback(struct buf *);
struct bcachestats bcstats; /* counters */
long lodirtypages; /* dirty page count low water mark */
long hidirtypages; /* dirty page count high water mark */
long targetpages; /* target number of pages for cache size */
long buflowpages; /* smallest size cache allowed */
long bufhighpages; /* largest size cache allowed */
long bufbackpages; /* minimum number of pages we shrink when asked to */
vsize_t bufkvm;
struct proc *cleanerproc;
int bd_req; /* Sleep point for cleaner daemon. */
#define NUM_CACHES 2
#define DMA_CACHE 0
struct bufcache cleancache[NUM_CACHES];
struct bufqueue dirtyqueue;
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
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)
{
u_int64_t dmapages;
u_int64_t highpages;
dmapages = uvm_pagecount(&dma_constraint);
/* take away a guess at how much of this the kernel will consume */
dmapages -= (atop(physmem) - atop(uvmexp.free));
/* See if we have memory above the dma accessible region. */
high_constraint.ucr_low = dma_constraint.ucr_high;
high_constraint.ucr_high = no_constraint.ucr_high;
if (high_constraint.ucr_low != high_constraint.ucr_high)
high_constraint.ucr_low++;
highpages = uvm_pagecount(&high_constraint);
/*
* Do we have any significant amount of high memory above
* the DMA region? if so enable moving buffers there, if not,
* don't bother.
*/
if (highpages > dmapages / 4)
fliphigh = 1;
else
fliphigh = 0;
/*
* If MD code doesn't say otherwise, use up to 10% of DMA'able
* memory for buffers.
*/
if (bufcachepercent == 0)
bufcachepercent = 10;
/*
* XXX these values and their same use in kern_sysctl
* need to move into buf.h
*/
KASSERT(bufcachepercent <= 90);
KASSERT(bufcachepercent >= 5);
if (bufpages == 0)
bufpages = dmapages * bufcachepercent / 100;
if (bufpages < BCACHE_MIN)
bufpages = BCACHE_MIN;
KASSERT(bufpages < dmapages);
bufhighpages = bufpages;
/*
* Set the base backoff level for the buffer cache. We will
* not allow uvm to steal back more than this number of pages.
*/
buflowpages = dmapages * 5 / 100;
if (buflowpages < BCACHE_MIN)
buflowpages = BCACHE_MIN;
/*
* set bufbackpages to 100 pages, or 10 percent of the low water mark
* if we don't have that many pages.
*/
bufbackpages = buflowpages * 10 / 100;
if (bufbackpages > 100)
bufbackpages = 100;
/*
* If the MD code does not say otherwise, reserve 10% of kva
* space for mapping buffers.
*/
if (bufkvm == 0)
bufkvm = VM_KERNEL_SPACE_SIZE / 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, IPL_BIO, 0, "bufpl", NULL);
bufcache_init();
/*
* hmm - bufkvm is an argument because it's static, while
* bufpages is global because it can change while running.
*/
buf_mem_init(bufkvm);
/*
* Set the dirty page high water mark to be less than the low
* water mark for pages in the buffer cache. This ensures we
* can always back off by throwing away clean pages, and give
* ourselves a chance to write out the dirty pages eventually.
*/
hidirtypages = (buflowpages / 4) * 3;
lodirtypages = buflowpages / 2;
/*
* We are allowed to use up to the reserve.
*/
targetpages = bufpages - RESERVE_PAGES;
}
/*
* Change cachepct
*/
void
bufadjust(int newbufpages)
{
struct buf *bp;
int s;
if (newbufpages < buflowpages)
newbufpages = buflowpages;
s = splbio();
bufpages = newbufpages;
/*
* We are allowed to use up to the reserve
*/
targetpages = bufpages - RESERVE_PAGES;
/*
* Shrinking the cache happens here only if someone has manually
* adjusted bufcachepercent - or the pagedaemon has told us
* to give back memory *now* - so we give it all back.
*/
while ((bp = bufcache_getdmacleanbuf()) &&
(bcstats.dmapages > targetpages)) {
bufcache_take(bp);
if (bp->b_vp) {
RBT_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp);
brelvp(bp);
}
buf_put(bp);
}
bufcache_adjust();
/*
* Wake up the cleaner if we have lots of dirty pages,
* or if we are getting low on buffer cache kva.
*/
if ((UNCLEAN_PAGES >= hidirtypages) ||
bcstats.kvaslots_avail <= 2 * RESERVE_SLOTS)
wakeup(&bd_req);
splx(s);
}
/*
* Make the buffer cache back off from cachepct.
*/
int
bufbackoff(struct uvm_constraint_range *range, long size)
{
/*
* Back off "size" buffer cache pages. Called by the page
* daemon to consume buffer cache pages rather than scanning.
*
* It returns 0 to the pagedaemon to indicate that it has
* succeeded in freeing enough pages. It returns -1 to
* indicate that it could not and the pagedaemon should take
* other measures.
*
*/
long pdelta, oldbufpages;
/*
* If we will accept high memory for this backoff
* try to steal it from the high memory buffer cache.
*/
if (range->ucr_high > dma_constraint.ucr_high) {
struct buf *bp;
int64_t start = bcstats.numbufpages, recovered = 0;
int s = splbio();
while ((recovered < size) &&
(bp = bufcache_gethighcleanbuf())) {
bufcache_take(bp);
if (bp->b_vp) {
RBT_REMOVE(buf_rb_bufs,
&bp->b_vp->v_bufs_tree, bp);
brelvp(bp);
}
buf_put(bp);
recovered = start - bcstats.numbufpages;
}
bufcache_adjust();
splx(s);
/* If we got enough, return success */
if (recovered >= size)
return 0;
/*
* If we needed only memory above DMA,
* return failure
*/
if (range->ucr_low > dma_constraint.ucr_high)
return -1;
/* Otherwise get the rest from DMA */
size -= recovered;
}
/*
* XXX Otherwise do the dma memory cache dance. this needs
* refactoring later to get rid of 'bufpages'
*/
/*
* Back off by at least bufbackpages. If the page daemon gave us
* a larger size, back off by that much.
*/
pdelta = (size > bufbackpages) ? size : bufbackpages;
if (bufpages <= buflowpages)
return(-1);
if (bufpages - pdelta < buflowpages)
pdelta = bufpages - buflowpages;
oldbufpages = bufpages;
bufadjust(bufpages - pdelta);
if (oldbufpages - bufpages < size)
return (-1); /* we did not free what we were asked */
else
return(0);
}
/*
* Opportunistically flip a buffer into high memory. Will move the buffer
* if memory is available without sleeping, and return 0, otherwise will
* fail and return -1 with the buffer unchanged.
*/
int
buf_flip_high(struct buf *bp)
{
int s;
int ret = -1;
KASSERT(ISSET(bp->b_flags, B_BC));
KASSERT(ISSET(bp->b_flags, B_DMA));
KASSERT(bp->cache == DMA_CACHE);
KASSERT(fliphigh);
/* Attempt to move the buffer to high memory if we can */
s = splbio();
if (buf_realloc_pages(bp, &high_constraint, UVM_PLA_NOWAIT) == 0) {
KASSERT(!ISSET(bp->b_flags, B_DMA));
bcstats.highflips++;
ret = 0;
} else
bcstats.highflops++;
splx(s);
return ret;
}
/*
* Flip a buffer to dma reachable memory, when we need it there for
* I/O. This can sleep since it will wait for memory alloacation in the
* DMA reachable area since we have to have the buffer there to proceed.
*/
void
buf_flip_dma(struct buf *bp)
{
KASSERT(ISSET(bp->b_flags, B_BC));
KASSERT(ISSET(bp->b_flags, B_BUSY));
KASSERT(bp->cache < NUM_CACHES);
if (!ISSET(bp->b_flags, B_DMA)) {
int s = splbio();
/* move buf to dma reachable memory */
(void) buf_realloc_pages(bp, &dma_constraint, UVM_PLA_WAITOK);
KASSERT(ISSET(bp->b_flags, B_DMA));
bcstats.dmaflips++;
splx(s);
}
if (bp->cache > DMA_CACHE) {
CLR(bp->b_flags, B_COLD);
CLR(bp->b_flags, B_WARM);
bp->cache = DMA_CACHE;
}
}
struct buf *
bio_doread(struct vnode *vp, daddr_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_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, daddr_t blkno, int size, 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 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's mapping to only cover its part of
* the total I/O.
*/
buf_fix_mapping(bp, newsize);
bp->b_bcount = newsize;
}
/* Invalidate read-ahead buffers if read short */
if (bp->b_resid > 0) {
for (i = 1; xbpp[i] != NULL; i++)
continue;
for (i = i - 1; i != 0; i--) {
if (xbpp[i]->b_bufsize <= bp->b_resid) {
bp->b_resid -= xbpp[i]->b_bufsize;
SET(xbpp[i]->b_flags, B_INVAL);
} else if (bp->b_resid > 0) {
bp->b_resid = 0;
SET(xbpp[i]->b_flags, B_INVAL);
} else
break;
}
}
for (i = 1; xbpp[i] != NULL; i++) {
if (ISSET(bp->b_flags, B_ERROR))
SET(xbpp[i]->b_flags, B_INVAL | B_ERROR);
biodone(xbpp[i]);
}
free(xbpp, M_TEMP, (i + 1) * sizeof(*xbpp));
if (ISSET(bp->b_flags, B_ASYNC)) {
brelse(bp);
} else {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
}
/*
* Read-ahead multiple disk blocks, but make sure only one (big) I/O
* request is sent to the disk.
* XXX This should probably be dropped and breadn should instead be optimized
* XXX to do fewer I/O requests.
*/
int
bread_cluster(struct vnode *vp, daddr_t blkno, int size, struct buf **rbpp)
{
struct buf *bp, **xbpp;
int howmany, maxra, i, inc;
daddr_t sblkno;
*rbpp = bio_doread(vp, blkno, size, 0);
/*
* If the buffer is in the cache skip any I/O operation.
*/
if (ISSET((*rbpp)->b_flags, B_CACHE))
goto out;
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 = mallocarray(howmany + 1, sizeof(*xbpp), 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, (howmany + 1) * sizeof(*xbpp));
goto out;
}
}
bp = xbpp[0];
xbpp[howmany] = NULL;
inc = btodb(size);
for (i = 1; i < howmany; i++) {
bcstats.pendingreads++;
bcstats.numreads++;
/*
* We set B_DMA here because bp above will be B_DMA,
* and we are playing buffer slice-n-dice games from
* the memory allocated in bp.
*/
SET(xbpp[i]->b_flags, B_DMA | 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_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_ru.ru_oublock++;
/* Initiate disk write. Make sure the appropriate party is charged. */
bp->b_vp->v_numoutput++;
splx(s);
buf_flip_dma(bp);
SET(bp->b_flags, B_WRITEINPROG);
VOP_STRATEGY(bp);
/*
* If the queue is above the high water mark, wait till
* the number of outstanding write bufs drops below the low
* water mark.
*/
if (bp->b_bq)
bufq_wait(bp->b_bq);
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();
buf_flip_dma(bp);
reassignbuf(bp);
splx(s);
curproc->p_ru.ru_oublock++; /* XXX */
}
/* 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);
buf_flip_dma(bp);
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)
{
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, free it now rather than leaving
* it in a queue and wasting memory.
*/
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) {
RBT_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp);
brelvp(bp);
}
bp->b_vp = 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 will restart the operation after
* sleep.
*/
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
buf_put(bp);
} 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.
*/
bufcache_release(bp);
/* Unlock the buffer. */
CLR(bp->b_flags, (B_AGE | B_ASYNC | B_NOCACHE | B_DEFERRED));
buf_release(bp);
/* 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);
}
}
/* Wake up syncer and cleaner processes waiting for buffers. */
if (nobuffers) {
nobuffers = 0;
wakeup(&nobuffers);
}
/* Wake up any processes waiting for any buffer to become free. */
if (needbuffer && bcstats.dmapages < targetpages &&
bcstats.kvaslots_avail > RESERVE_SLOTS) {
needbuffer = 0;
wakeup(&needbuffer);
}
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, daddr_t blkno)
{
struct buf *bp;
struct buf b;
int s;
s = splbio();
/* Search buf lookup tree */
b.b_lblkno = blkno;
bp = RBT_FIND(buf_rb_bufs, &vp->v_bufs_tree, &b);
if (bp != NULL && ISSET(bp->b_flags, B_INVAL))
bp = NULL;
splx(s);
return (bp);
}
/*
* 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, daddr_t blkno, int size, int slpflag, int slptimeo)
{
struct buf *bp;
struct buf b;
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:
s = splbio();
b.b_lblkno = blkno;
bp = RBT_FIND(buf_rb_bufs, &vp->v_bufs_tree, &b);
if (bp != NULL) {
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++;