/* $OpenBSD: vfs_bio.c,v 1.135 2012/03/23 15:51:26 guenther 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 #include #include #include #include #include #include #include #include #include #include #include #include /* * 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; long backoffpages; /* backoff counter for page allocations */ long buflowpages; /* bufpages low water mark */ long bufhighpages; /* bufpages high water mark */ long bufbackpages; /* number of pages we back off when asked to shrink */ 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); bcstats.delwribufs--; } TAILQ_REMOVE(dp, bp, b_freelist); } 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 (backoffpages) { backoffpages -= atop(bp->b_bufsize); if (backoffpages < 0) backoffpages = 0; } 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; struct bqueues *dp; dmapages = uvm_pagecount(&dma_constraint); /* * If MD code doesn't say otherwise, use 10% of kvm for mappings and * 10% of dmaable pages for cache pages. */ if (bufcachepercent == 0) bufcachepercent = 10; if (bufpages == 0) bufpages = dmapages * bufcachepercent / 100; bufhighpages = bufpages; /* * set the base backoff level for the buffer cache to bufpages. * we will not allow uvm to steal back more than this number of * pages */ buflowpages = dmapages * 10 / 100; /* * 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 (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); 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; } /* * Change cachepct */ void bufadjust(int newbufpages) { /* * XXX - note, bufkvm was allocated once, based on 10% of physmem * see above. */ struct buf *bp; int s; s = splbio(); bufpages = newbufpages; 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; /* * If we we have more buffers allocated than bufpages, * free them up to get back down. this may possibly consume * all our clean pages... */ while ((bp = TAILQ_FIRST(&bufqueues[BQ_CLEAN])) && (bcstats.numbufpages > bufpages)) { bremfree(bp); if (bp->b_vp) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } buf_put(bp); } /* * Wake up cleaner if we're getting low on pages. We might * now have too much dirty, or have fallen below our low * water mark on clean pages so we need to free more stuff * up. */ if (bcstats.numdirtypages >= hidirtypages || bcstats.numcleanpages <= locleanpages) wakeup(&bd_req); /* * if immediate action has not freed up enough goo for us * to proceed - we tsleep and wait for the cleaner above * to do it's work and get us reduced down to sanity. */ while (bcstats.numbufpages > bufpages) { tsleep(&needbuffer, PRIBIO, "needbuffer", 0); } splx(s); } /* * Make the buffer cache back off from cachepct. */ int bufbackoff(struct uvm_constraint_range *range, long size) { /* * Back off the amount of buffer cache pages. Called by the page * daemon to consume buffer cache pages rather than swapping. * * On success, it frees N pages from the buffer cache, and sets * a flag so that the next N allocations from buf_get will recycle * a buffer rather than allocate a new one. It then returns 0 to the * caller. * * on failure, it could free no pages from the buffer cache, does * nothing and returns -1 to the caller. */ long d; if (bufpages <= buflowpages) return(-1); if (bufpages - bufbackpages >= buflowpages) d = bufbackpages; else d = bufpages - buflowpages; backoffpages = bufbackpages; bufadjust(bufpages - d); backoffpages = bufbackpages; return(0); } 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_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 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 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; } 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_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); 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_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); #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); 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) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } bp->b_vp = NULL; /* * 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); } if (bp->b_vp != NULL) RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, 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); bcstats.delwribufs++; 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. */ 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; struct buf b; int s; s = splbio(); /* Search buf lookup tree */ b.b_lblkno = blkno; bp = RB_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, daddr64_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 = RB_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++; 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) { static int gcount = 0; struct buf *bp; int poolwait = size == 0 ? PR_NOWAIT : PR_WAITOK; int npages; int s; /* * if we were previously backed off, slowly climb back up * to the high water mark again. */ if ((backoffpages == 0) && (bufpages < bufhighpages)) { if ( gcount == 0 ) { bufadjust(bufpages + bufbackpages); gcount += bufbackpages; } else gcount--; } 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) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } buf_put(bp); } } npages = atop(round_page(size)); /* * Free some buffers until we have enough space. */ while ((bcstats.numbufpages + npages > bufpages) || backoffpages) { int freemax = 5; int i = freemax; while ((bp = TAILQ_FIRST(&bufqueues[BQ_CLEAN])) && i--) { bremfree(bp); if (bp->b_vp) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } buf_put(bp); } if (freemax == i && (bcstats.numbufpages + npages > bufpages)) { 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); if (RB_INSERT(buf_rb_bufs, &vp->v_bufs_tree, bp)) panic("buf_get: dup lblk vp %p bp %p", vp, bp); } else { bp->b_vnbufs.le_next = NOLIST; SET(bp->b_flags, B_INVAL); bp->b_vp = NULL; } 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); bcstats.delwribufs++; binstailfree(bp, &bufqueues[BQ_DIRTY]); 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 (bp->b_bq) bufq_done(bp->b_bq, bp); 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); } } } #ifdef DDB void bcstats_print(int (*)(const char *, ...)); /* * bcstats_print: ddb hook to print interesting buffer cache counters */ void bcstats_print(int (*pr)(const char *, ...)) { (*pr)("Current Buffer Cache status:\n"); (*pr)("numbufs %lld busymapped %lld, delwri %lld\n", bcstats.numbufs, bcstats.busymapped, bcstats.delwribufs); (*pr)("kvaslots %lld avail kva slots %lld\n", bcstats.kvaslots, bcstats.kvaslots_avail); (*pr)("bufpages %lld, dirtypages %lld\n", bcstats.numbufpages, bcstats.numdirtypages); (*pr)("pendingreads %lld, pendingwrites %lld\n", bcstats.pendingreads, bcstats.pendingwrites); } #endif