/* $OpenBSD: vfs_bio.c,v 1.84 2006/08/28 16:15:29 tom 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 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); struct buf *getnewbuf(int, int, int *); /* * 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 (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 (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 than 2 * MAXBSIZE. locleanpages * value must be not too small, but probably * there is no reason to set it to 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 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); 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)); } /* * 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++; } 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) 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); } /* 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, daddr_t blkno) { struct buf *bp; /* Search hash chain */ LIST_FOREACH(bp, BUFHASH(vp, blkno), b_hash) { if (bp->b_lblkno == blkno && bp->b_vp == vp && !ISSET(bp->b_flags, B_INVAL)) return (bp); } return (NULL); } /* * Get a block of requested size that is associated with * a given vnode and block offset. If it is found in the * block cache, mark it as having been found, make it busy * and return it. Otherwise, return an empty block of the * correct size. It is up to the caller to 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 bufhashhdr *bh; 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. */ 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); error = tsleep(bp, slpflag | (PRIBIO + 1), "getblk", slptimeo); splx(s); if (error) 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) { bp = getnewbuf(slpflag, slptimeo, &error); if (bp == NULL) { if (error == ERESTART || error == EINTR) return (NULL); goto start; } binshash(bp, bh); bp->b_blkno = bp->b_lblkno = blkno; s = splbio(); bgetvp(vp, bp); splx(s); } allocbuf(bp, size); return (bp); } /* * Get an empty, disassociated buffer of given size. */ struct buf * geteblk(int size) { struct buf *bp; while ((bp = getnewbuf(0, 0, NULL)) == NULL) ; 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 caller's * 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 */ while ((nbp = getnewbuf(0, 0, NULL)) == NULL) ; 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 = TAILQ_FIRST(&bufqueues[BQ_EMPTY])) == 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. */ struct buf * getnewbuf(int slpflag, int slptimeo, int *ep) { struct buf *bp; int s, error; 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 (ep != NULL) *ep = error; return (NULL); } bp = TAILQ_FIRST(&bufqueues[BQ_CLEAN]); if (bp == NULL) { /* wait for a free buffer of any kind */ nobuffers = 1; error = tsleep(&nobuffers, slpflag | (PRIBIO - 3), "getnewbuf", slptimeo); splx(s); if (ep != NULL) *ep = error; return (NULL); } 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 = NULL; 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); return (bp); } /* * 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); } getmicrouptime(&starttime); s = splbio(); while ((bp = TAILQ_FIRST(&bufqueues[BQ_DIRTY]))) { struct timeval tv; 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, 0)) { 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 */ getmicrouptime(&tv); timersub(&tv, &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(void) { 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; TAILQ_FOREACH(bp, dp, b_freelist) { 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 */