/* $NetBSD: vfs_bio.c,v 1.99 2003/12/02 04:18:19 dbj Exp $ */ /*- * 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 */ /*- * Copyright (c) 1994 Christopher G. Demetriou * * 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. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. 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 "opt_softdep.h" #include __KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.99 2003/12/02 04:18:19 dbj Exp $"); #include #include #include #include #include #include #include #include #include #include #include /* Macros to clear/set/test flags. */ #define SET(t, f) (t) |= (f) #define CLR(t, f) (t) &= ~(f) #define ISSET(t, f) ((t) & (f)) /* * Definitions for the buffer hash lists. */ #define BUFHASH(dvp, lbn) \ (&bufhashtbl[(((long)(dvp) >> 8) + (int)(lbn)) & bufhash]) LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash; u_long bufhash; #ifndef SOFTDEP struct bio_ops bioops; /* I/O operation notification */ #endif /* * 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_LRU 1 /* lru, useful buffers */ #define BQ_AGE 2 /* rubbish */ #define BQ_EMPTY 3 /* buffer headers with no memory */ TAILQ_HEAD(bqueues, buf) bufqueues[BQUEUES]; int needbuffer; /* * Buffer queue lock. * Take this lock first if also taking some buffer's b_interlock. */ struct simplelock bqueue_slock = SIMPLELOCK_INITIALIZER; /* * Buffer pool for I/O buffers. */ struct pool bufpool; /* * bread()/breadn() helper. */ static __inline struct buf *bio_doread(struct vnode *, daddr_t, int, struct ucred *, int); int count_lock_queue(void); /* * Insq/Remq for the buffer free lists. * Call with buffer queue locked. */ #define binsheadfree(bp, dp) TAILQ_INSERT_HEAD(dp, bp, b_freelist) #define binstailfree(bp, dp) TAILQ_INSERT_TAIL(dp, bp, b_freelist) #ifdef DEBUG int debug_verify_freelist = 0; int checkfreelist(struct buf *, struct bqueues *); int checkfreelist(struct buf *bp, struct bqueues *dp) { struct buf *b; TAILQ_FOREACH(b, dp, b_freelist) { if (b == bp) return 1; } return 0; } #endif void bremfree(bp) struct buf *bp; { struct bqueues *dp = NULL; LOCK_ASSERT(simple_lock_held(&bqueue_slock)); KDASSERT(!debug_verify_freelist || checkfreelist(bp, &bufqueues[BQ_AGE]) || checkfreelist(bp, &bufqueues[BQ_LRU]) || checkfreelist(bp, &bufqueues[BQ_LOCKED]) || checkfreelist(bp, &bufqueues[BQ_EMPTY])); /* * 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. * * We break the TAILQ abstraction in order to efficiently remove a * buffer from its freelist without having to know exactly which * freelist it is on. */ if (TAILQ_NEXT(bp, b_freelist) == NULL) { for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) if (dp->tqh_last == &bp->b_freelist.tqe_next) break; if (dp == &bufqueues[BQUEUES]) panic("bremfree: lost tail"); } TAILQ_REMOVE(dp, bp, b_freelist); } /* * Initialize buffers and hash links for buffers. */ void bufinit() { struct buf *bp; struct bqueues *dp; u_int i, base, residual; /* * Initialize the buffer pool. This pool is used for buffers * which are strictly I/O control blocks, not buffer cache * buffers. */ pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", NULL); for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) TAILQ_INIT(dp); bufhashtbl = hashinit(nbuf, HASH_LIST, M_CACHE, M_WAITOK, &bufhash); base = bufpages / nbuf; residual = bufpages % nbuf; for (i = 0; i < nbuf; i++) { bp = &buf[i]; memset((char *)bp, 0, sizeof(*bp)); BUF_INIT(bp); bp->b_dev = NODEV; bp->b_vnbufs.le_next = NOLIST; bp->b_data = buffers + i * MAXBSIZE; if (i < residual) bp->b_bufsize = (base + 1) * PAGE_SIZE; else bp->b_bufsize = base * PAGE_SIZE; bp->b_flags = B_INVAL; dp = bp->b_bufsize ? &bufqueues[BQ_AGE] : &bufqueues[BQ_EMPTY]; binsheadfree(bp, dp); binshash(bp, &invalhash); } } static __inline struct buf * bio_doread(vp, blkno, size, cred, async) struct vnode *vp; daddr_t blkno; int size; struct ucred *cred; int async; { struct buf *bp; struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */ struct proc *p = l->l_proc; bp = getblk(vp, blkno, size, 0, 0); #ifdef DIAGNOSTIC if (bp == NULL) { panic("bio_doread: no such buf"); } #endif /* * If buffer does not have data valid, start a read. * Note that if buffer is B_INVAL, getblk() won't return it. * Therefore, it's valid if its I/O has completed or been delayed. */ if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) { /* Start I/O for the buffer. */ SET(bp->b_flags, B_READ | async); VOP_STRATEGY(bp); /* Pay for the read. */ p->p_stats->p_ru.ru_inblock++; } else if (async) { brelse(bp); } return (bp); } /* * Read a disk block. * This algorithm described in Bach (p.54). */ int bread(vp, blkno, size, cred, bpp) 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, cred, 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(vp, blkno, size, rablks, rasizes, nrablks, cred, bpp) 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, cred, 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], cred, B_ASYNC); } /* Otherwise, we had to start a read for it; wait until it's valid. */ return (biowait(bp)); } /* * Read with single-block read-ahead. Defined in Bach (p.55), but * implemented as a call to breadn(). * XXX for compatibility with old file systems. */ int breada(vp, blkno, size, rablkno, rabsize, cred, bpp) struct vnode *vp; daddr_t blkno; int size; daddr_t rablkno; int rabsize; struct ucred *cred; struct buf **bpp; { return (breadn(vp, blkno, size, &rablkno, &rabsize, 1, cred, bpp)); } /* * Block write. Described in Bach (p.56) */ int bwrite(bp) struct buf *bp; { int rv, sync, wasdelayed, s; struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */ struct proc *p = l->l_proc; struct vnode *vp; struct mount *mp; KASSERT(ISSET(bp->b_flags, B_BUSY)); vp = bp->b_vp; if (vp != NULL) { if (vp->v_type == VBLK) mp = vp->v_specmountpoint; else mp = 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). */ sync = !ISSET(bp->b_flags, B_ASYNC); if (sync && mp != NULL && 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 (sync) mp->mnt_stat.f_syncwrites++; else mp->mnt_stat.f_asyncwrites++; } s = splbio(); simple_lock(&bp->b_interlock); wasdelayed = ISSET(bp->b_flags, B_DELWRI); CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI)); /* * Pay for the I/O operation and make sure the buf is on the correct * vnode queue. */ if (wasdelayed) reassignbuf(bp, bp->b_vp); else p->p_stats->p_ru.ru_oublock++; /* Initiate disk write. Make sure the appropriate party is charged. */ V_INCR_NUMOUTPUT(bp->b_vp); simple_unlock(&bp->b_interlock); splx(s); VOP_STRATEGY(bp); if (sync) { /* If I/O was synchronous, wait for it to complete. */ rv = biowait(bp); /* Release the buffer. */ brelse(bp); return (rv); } else { return (0); } } int vn_bwrite(v) void *v; { struct vop_bwrite_args *ap = v; return (bwrite(ap->a_bp)); } /* * 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(bp) struct buf *bp; { struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */ struct proc *p = l->l_proc; const struct bdevsw *bdev; int s; /* If this is a tape block, write the block now. */ bdev = bdevsw_lookup(bp->b_dev); if (bdev != NULL && bdev->d_type == D_TAPE) { bawrite(bp); return; } /* * 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. */ s = splbio(); simple_lock(&bp->b_interlock); KASSERT(ISSET(bp->b_flags, B_BUSY)); if (!ISSET(bp->b_flags, B_DELWRI)) { SET(bp->b_flags, B_DELWRI); p->p_stats->p_ru.ru_oublock++; reassignbuf(bp, bp->b_vp); } /* Otherwise, the "write" is done, so mark and release the buffer. */ CLR(bp->b_flags, B_DONE); simple_unlock(&bp->b_interlock); splx(s); brelse(bp); } /* * Asynchronous block write; just an asynchronous bwrite(). */ void bawrite(bp) struct buf *bp; { int s; s = splbio(); simple_lock(&bp->b_interlock); KASSERT(ISSET(bp->b_flags, B_BUSY)); SET(bp->b_flags, B_ASYNC); simple_unlock(&bp->b_interlock); splx(s); VOP_BWRITE(bp); } /* * Same as first half of bdwrite, mark buffer dirty, but do not release it. * Call at splbio() and with the buffer interlock locked. * Note: called only from biodone() through ffs softdep's bioops.io_complete() */ void bdirty(bp) struct buf *bp; { struct lwp *l = (curlwp != NULL ? curlwp : &lwp0); /* XXX */ struct proc *p = l->l_proc; LOCK_ASSERT(simple_lock_held(&bp->b_interlock)); KASSERT(ISSET(bp->b_flags, B_BUSY)); CLR(bp->b_flags, B_AGE); if (!ISSET(bp->b_flags, B_DELWRI)) { SET(bp->b_flags, B_DELWRI); p->p_stats->p_ru.ru_oublock++; reassignbuf(bp, bp->b_vp); } } /* * Release a buffer on to the free lists. * Described in Bach (p. 46). */ void brelse(bp) struct buf *bp; { struct bqueues *bufq; int s; /* Block disk interrupts. */ s = splbio(); simple_lock(&bqueue_slock); simple_lock(&bp->b_interlock); KASSERT(ISSET(bp->b_flags, B_BUSY)); KASSERT(!ISSET(bp->b_flags, B_CALL)); /* Wake up any processes waiting for any buffer to become free. */ if (needbuffer) { needbuffer = 0; wakeup(&needbuffer); } /* Wake up any proceeses waiting for _this_ buffer to become free. */ if (ISSET(bp->b_flags, B_WANTED)) { CLR(bp->b_flags, B_WANTED|B_AGE); wakeup(bp); } /* * 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 (ISSET(bp->b_flags, B_VFLUSH)) { /* * This is a delayed write buffer that was just flushed to * disk. It is still on the LRU queue. If it's become * invalid, then we need to move it to a different queue; * otherwise leave it in its current position. */ CLR(bp->b_flags, B_VFLUSH); if (!ISSET(bp->b_flags, B_ERROR|B_INVAL|B_LOCKED|B_AGE)) { KDASSERT(!debug_verify_freelist || checkfreelist(bp, &bufqueues[BQ_LRU])); goto already_queued; } else { bremfree(bp); } } KDASSERT(!debug_verify_freelist || !checkfreelist(bp, &bufqueues[BQ_AGE])); KDASSERT(!debug_verify_freelist || !checkfreelist(bp, &bufqueues[BQ_LRU])); KDASSERT(!debug_verify_freelist || !checkfreelist(bp, &bufqueues[BQ_EMPTY])); KDASSERT(!debug_verify_freelist || !checkfreelist(bp, &bufqueues[BQ_LOCKED])); 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 && bioops.io_deallocate) (*bioops.io_deallocate)(bp); CLR(bp->b_flags, B_DONE|B_DELWRI); if (bp->b_vp) { reassignbuf(bp, bp->b_vp); brelvp(bp); } if (bp->b_bufsize <= 0) /* no data */ bufq = &bufqueues[BQ_EMPTY]; else /* invalid data */ bufq = &bufqueues[BQ_AGE]; 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 buf is AGE, but has dependencies, must put it on last * bufqueue to be scanned, ie LRU. This protects against the * livelock where BQ_AGE only has buffers with dependencies, * and we thus never get to the dependent buffers in BQ_LRU. */ if (ISSET(bp->b_flags, B_LOCKED)) /* locked in core */ bufq = &bufqueues[BQ_LOCKED]; else if (!ISSET(bp->b_flags, B_AGE)) /* valid data */ bufq = &bufqueues[BQ_LRU]; else { /* stale but valid data */ int has_deps; if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_countdeps) has_deps = (*bioops.io_countdeps)(bp, 0); else has_deps = 0; bufq = has_deps ? &bufqueues[BQ_LRU] : &bufqueues[BQ_AGE]; } binstailfree(bp, bufq); } already_queued: /* Unlock the buffer. */ CLR(bp->b_flags, B_AGE|B_ASYNC|B_BUSY|B_NOCACHE); SET(bp->b_flags, B_CACHE); /* Allow disk interrupts. */ simple_unlock(&bp->b_interlock); simple_unlock(&bqueue_slock); 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. If it's marked invalid, * we normally don't return the buffer, unless the caller explicitly * wants us to. */ struct buf * incore(vp, blkno) 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 insure that the * cached blocks be of the correct size. */ struct buf * getblk(vp, blkno, size, slpflag, slptimeo) struct vnode *vp; daddr_t blkno; int size, slpflag, slptimeo; { struct buf *bp; int s, err; start: s = splbio(); simple_lock(&bqueue_slock); bp = incore(vp, blkno); if (bp != NULL) { simple_lock(&bp->b_interlock); if (ISSET(bp->b_flags, B_BUSY)) { simple_unlock(&bqueue_slock); if (curproc == uvm.pagedaemon_proc) { simple_unlock(&bp->b_interlock); splx(s); return NULL; } SET(bp->b_flags, B_WANTED); err = ltsleep(bp, slpflag | (PRIBIO + 1) | PNORELOCK, "getblk", slptimeo, &bp->b_interlock); splx(s); if (err) return (NULL); goto start; } #ifdef DIAGNOSTIC if (ISSET(bp->b_flags, B_DONE|B_DELWRI) && bp->b_bcount < size && vp->v_type != VBLK) panic("getblk: block size invariant failed"); #endif SET(bp->b_flags, B_BUSY); bremfree(bp); } else { if ((bp = getnewbuf(slpflag, slptimeo)) == NULL) { simple_unlock(&bqueue_slock); splx(s); goto start; } binshash(bp, BUFHASH(vp, blkno)); bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = blkno; bgetvp(vp, bp); } simple_unlock(&bp->b_interlock); simple_unlock(&bqueue_slock); splx(s); /* * LFS can't track total size of B_LOCKED buffer (locked_queue_bytes) * if we re-size buffers here. */ if (ISSET(bp->b_flags, B_LOCKED)) { KASSERT(bp->b_bufsize >= size); } else { allocbuf(bp, size); } return (bp); } /* * Get an empty, disassociated buffer of given size. */ struct buf * geteblk(size) int size; { struct buf *bp; int s; s = splbio(); simple_lock(&bqueue_slock); while ((bp = getnewbuf(0, 0)) == 0) ; SET(bp->b_flags, B_INVAL); binshash(bp, &invalhash); simple_unlock(&bqueue_slock); simple_unlock(&bp->b_interlock); splx(s); allocbuf(bp, size); return (bp); } /* * Expand or contract the actual memory allocated to a buffer. * * If the buffer shrinks, data is lost, so it's up to the * caller to have written it out *first*; this routine will not * start a write. If the buffer grows, it's the callers * responsibility to fill out the buffer's additional contents. */ void allocbuf(bp, size) struct buf *bp; int size; { struct buf *nbp; vsize_t desired_size; int s; desired_size = round_page((vsize_t)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 */ s = splbio(); simple_lock(&bqueue_slock); while ((nbp = getnewbuf(0, 0)) == NULL) ; SET(nbp->b_flags, B_INVAL); binshash(nbp, &invalhash); simple_unlock(&nbp->b_interlock); simple_unlock(&bqueue_slock); splx(s); /* 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(); simple_lock(&bqueue_slock); if ((nbp = TAILQ_FIRST(&bufqueues[BQ_EMPTY])) == NULL) { /* No free buffer head */ simple_unlock(&bqueue_slock); splx(s); goto out; } /* No need to lock nbp since it came from the empty queue */ bremfree(nbp); SET(nbp->b_flags, B_BUSY | B_INVAL); simple_unlock(&bqueue_slock); 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; /* release the newly-filled buffer and leave */ brelse(nbp); } out: bp->b_bcount = size; } /* * Find a buffer which is available for use. * Select something from a free list. * Preference is to AGE list, then LRU list. * * Called with buffer queues locked. * Return buffer locked. */ struct buf * getnewbuf(slpflag, slptimeo) int slpflag, slptimeo; { struct buf *bp; start: LOCK_ASSERT(simple_lock_held(&bqueue_slock)); if ((bp = TAILQ_FIRST(&bufqueues[BQ_AGE])) != NULL || (bp = TAILQ_FIRST(&bufqueues[BQ_LRU])) != NULL) { simple_lock(&bp->b_interlock); bremfree(bp); } else { /* wait for a free buffer of any kind */ needbuffer = 1; ltsleep(&needbuffer, slpflag|(PRIBIO+1), "getnewbuf", slptimeo, &bqueue_slock); return (NULL); } if (ISSET(bp->b_flags, B_VFLUSH)) { /* * This is a delayed write buffer being flushed to disk. Make * sure it gets aged out of the queue when it's finished, and * leave it off the LRU queue. */ CLR(bp->b_flags, B_VFLUSH); SET(bp->b_flags, B_AGE); simple_unlock(&bp->b_interlock); goto start; } /* Buffer is no longer on free lists. */ SET(bp->b_flags, B_BUSY); /* * If buffer was a delayed write, start it and return NULL * (since we might sleep while starting the write). */ if (ISSET(bp->b_flags, B_DELWRI)) { /* * This buffer has gone through the LRU, so make sure it gets * reused ASAP. */ SET(bp->b_flags, B_AGE); simple_unlock(&bp->b_interlock); simple_unlock(&bqueue_slock); bawrite(bp); simple_lock(&bqueue_slock); return (NULL); } /* disassociate us from our vnode, if we had one... */ if (bp->b_vp) brelvp(bp); if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_deallocate) (*bioops.io_deallocate)(bp); /* clear out various other fields */ bp->b_flags = B_BUSY; bp->b_dev = NODEV; bp->b_blkno = bp->b_lblkno = bp->b_rawblkno = 0; bp->b_iodone = 0; bp->b_error = 0; bp->b_resid = 0; bp->b_bcount = 0; bremhash(bp); return (bp); } /* * Wait for operations on the buffer to complete. * When they do, extract and return the I/O's error value. */ int biowait(bp) struct buf *bp; { int s, error; s = splbio(); simple_lock(&bp->b_interlock); while (!ISSET(bp->b_flags, B_DONE | B_DELWRI)) ltsleep(bp, PRIBIO + 1, "biowait", 0, &bp->b_interlock); /* 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); error = EINTR; } else if (ISSET(bp->b_flags, B_ERROR)) error = bp->b_error ? bp->b_error : EIO; else error = 0; simple_unlock(&bp->b_interlock); splx(s); return (error); } /* * 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!) */ void biodone(bp) struct buf *bp; { int s = splbio(); simple_lock(&bp->b_interlock); 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 && bioops.io_complete) (*bioops.io_complete)(bp); if (!ISSET(bp->b_flags, B_READ)) /* wake up reader */ vwakeup(bp); /* * If necessary, call out. Unlock the buffer before calling * iodone() as the buffer isn't valid any more when it return. */ if (ISSET(bp->b_flags, B_CALL)) { CLR(bp->b_flags, B_CALL); /* but note callout done */ simple_unlock(&bp->b_interlock); (*bp->b_iodone)(bp); } else { if (ISSET(bp->b_flags, B_ASYNC)) { /* if async, release */ simple_unlock(&bp->b_interlock); brelse(bp); } else { /* or just wakeup the buffer */ CLR(bp->b_flags, B_WANTED); wakeup(bp); simple_unlock(&bp->b_interlock); } } splx(s); } /* * Return a count of buffers on the "locked" queue. */ int count_lock_queue() { struct buf *bp; int n = 0; simple_lock(&bqueue_slock); TAILQ_FOREACH(bp, &bufqueues[BQ_LOCKED], b_freelist) n++; simple_unlock(&bqueue_slock); return (n); } #ifdef DEBUG /* * Print out statistics on the current allocation of the buffer pool. * Can be enabled to print out on every ``sync'' by setting "syncprt" * in vfs_syscalls.c using sysctl. */ void vfs_bufstats() { int s, i, j, count; struct buf *bp; struct bqueues *dp; int counts[(MAXBSIZE / PAGE_SIZE) + 1]; static char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE", "EMPTY" }; for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) { count = 0; for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++) counts[j] = 0; s = splbio(); TAILQ_FOREACH(bp, dp, b_freelist) { counts[bp->b_bufsize/PAGE_SIZE]++; count++; } splx(s); printf("%s: total-%d", bname[i], count); for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++) if (counts[j] != 0) printf(", %d-%d", j * PAGE_SIZE, counts[j]); printf("\n"); } } #endif /* DEBUG */