/* $NetBSD: vfs_bio.c,v 1.148 2005/12/24 19:12:23 perry 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_bufcache.h" #include "opt_softdep.h" #include __KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.148 2005/12/24 19:12:23 perry Exp $"); #include #include #include #include #include #include #include #include #include #include #include #include #include #ifndef BUFPAGES # define BUFPAGES 0 #endif #ifdef BUFCACHE # if (BUFCACHE < 5) || (BUFCACHE > 95) # error BUFCACHE is not between 5 and 95 # endif #else # define BUFCACHE 15 #endif u_int nbuf; /* XXX - for softdep_lockedbufs */ u_int bufpages = BUFPAGES; /* optional hardwired count */ u_int bufcache = BUFCACHE; /* max % of RAM to use for buffer cache */ /* Function prototypes */ struct bqueue; static void buf_setwm(void); static int buf_trim(void); static void *bufpool_page_alloc(struct pool *, int); static void bufpool_page_free(struct pool *, void *); static inline struct buf *bio_doread(struct vnode *, daddr_t, int, struct ucred *, int); static int buf_lotsfree(void); static int buf_canrelease(void); static inline u_long buf_mempoolidx(u_long); static inline u_long buf_roundsize(u_long); static inline caddr_t buf_malloc(size_t); static void buf_mrelease(caddr_t, size_t); static inline void binsheadfree(struct buf *, struct bqueue *); static inline void binstailfree(struct buf *, struct bqueue *); int count_lock_queue(void); /* XXX */ #ifdef DEBUG static int checkfreelist(struct buf *, struct bqueue *); #endif /* 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; #if !defined(SOFTDEP) || !defined(FFS) 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 3 /* number of free buffer queues */ #define BQ_LOCKED 0 /* super-blocks &c */ #define BQ_LRU 1 /* lru, useful buffers */ #define BQ_AGE 2 /* rubbish */ struct bqueue { TAILQ_HEAD(, buf) bq_queue; uint64_t bq_bytes; } 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; /* XXX - somewhat gross.. */ #if MAXBSIZE == 0x2000 #define NMEMPOOLS 4 #elif MAXBSIZE == 0x4000 #define NMEMPOOLS 5 #elif MAXBSIZE == 0x8000 #define NMEMPOOLS 6 #else #define NMEMPOOLS 7 #endif #define MEMPOOL_INDEX_OFFSET 10 /* smallest pool is 1k */ #if (1 << (NMEMPOOLS + MEMPOOL_INDEX_OFFSET - 1)) != MAXBSIZE #error update vfs_bio buffer memory parameters #endif /* Buffer memory pools */ static struct pool bmempools[NMEMPOOLS]; struct vm_map *buf_map; /* * Buffer memory pool allocator. */ static void * bufpool_page_alloc(struct pool *pp, int flags) { return (void *)uvm_km_alloc(buf_map, MAXBSIZE, MAXBSIZE, ((flags & PR_WAITOK) ? 0 : UVM_KMF_NOWAIT | UVM_KMF_TRYLOCK) | UVM_KMF_WIRED); } static void bufpool_page_free(struct pool *pp, void *v) { uvm_km_free(buf_map, (vaddr_t)v, MAXBSIZE, UVM_KMF_WIRED); } static struct pool_allocator bufmempool_allocator = { bufpool_page_alloc, bufpool_page_free, MAXBSIZE, }; /* Buffer memory management variables */ u_long bufmem_valimit; u_long bufmem_hiwater; u_long bufmem_lowater; u_long bufmem; /* * MD code can call this to set a hard limit on the amount * of virtual memory used by the buffer cache. */ int buf_setvalimit(vsize_t sz) { /* We need to accommodate at least NMEMPOOLS of MAXBSIZE each */ if (sz < NMEMPOOLS * MAXBSIZE) return EINVAL; bufmem_valimit = sz; return 0; } static void buf_setwm(void) { bufmem_hiwater = buf_memcalc(); /* lowater is approx. 2% of memory (with bufcache = 15) */ #define BUFMEM_WMSHIFT 3 #define BUFMEM_HIWMMIN (64 * 1024 << BUFMEM_WMSHIFT) if (bufmem_hiwater < BUFMEM_HIWMMIN) /* Ensure a reasonable minimum value */ bufmem_hiwater = BUFMEM_HIWMMIN; bufmem_lowater = bufmem_hiwater >> BUFMEM_WMSHIFT; } #ifdef DEBUG int debug_verify_freelist = 0; static int checkfreelist(struct buf *bp, struct bqueue *dp) { struct buf *b; TAILQ_FOREACH(b, &dp->bq_queue, b_freelist) { if (b == bp) return 1; } return 0; } #endif /* * Insq/Remq for the buffer hash lists. * Call with buffer queue locked. */ static inline void binsheadfree(struct buf *bp, struct bqueue *dp) { KASSERT(bp->b_freelistindex == -1); TAILQ_INSERT_HEAD(&dp->bq_queue, bp, b_freelist); dp->bq_bytes += bp->b_bufsize; bp->b_freelistindex = dp - bufqueues; } static inline void binstailfree(struct buf *bp, struct bqueue *dp) { KASSERT(bp->b_freelistindex == -1); TAILQ_INSERT_TAIL(&dp->bq_queue, bp, b_freelist); dp->bq_bytes += bp->b_bufsize; bp->b_freelistindex = dp - bufqueues; } void bremfree(struct buf *bp) { struct bqueue *dp; int bqidx = bp->b_freelistindex; LOCK_ASSERT(simple_lock_held(&bqueue_slock)); KASSERT(bqidx != -1); dp = &bufqueues[bqidx]; KDASSERT(!debug_verify_freelist || checkfreelist(bp, dp)); KASSERT(dp->bq_bytes >= bp->b_bufsize); TAILQ_REMOVE(&dp->bq_queue, bp, b_freelist); dp->bq_bytes -= bp->b_bufsize; #if defined(DIAGNOSTIC) bp->b_freelistindex = -1; #endif /* defined(DIAGNOSTIC) */ } u_long buf_memcalc(void) { u_long n; /* * Determine the upper bound of memory to use for buffers. * * - If bufpages is specified, use that as the number * pages. * * - Otherwise, use bufcache as the percentage of * physical memory. */ if (bufpages != 0) { n = bufpages; } else { if (bufcache < 5) { printf("forcing bufcache %d -> 5", bufcache); bufcache = 5; } if (bufcache > 95) { printf("forcing bufcache %d -> 95", bufcache); bufcache = 95; } n = physmem / 100 * bufcache; } n <<= PAGE_SHIFT; if (bufmem_valimit != 0 && n > bufmem_valimit) n = bufmem_valimit; return (n); } /* * Initialize buffers and hash links for buffers. */ void bufinit(void) { struct bqueue *dp; int use_std; u_int i; /* * Initialize buffer cache memory parameters. */ bufmem = 0; buf_setwm(); if (bufmem_valimit != 0) { vaddr_t minaddr = 0, maxaddr; buf_map = uvm_km_suballoc(kernel_map, &minaddr, &maxaddr, bufmem_valimit, VM_MAP_PAGEABLE, FALSE, 0); if (buf_map == NULL) panic("bufinit: cannot allocate submap"); } else buf_map = kernel_map; /* * Initialize the buffer pools. */ pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", NULL); /* On "small" machines use small pool page sizes where possible */ use_std = (physmem < atop(16*1024*1024)); /* * Also use them on systems that can map the pool pages using * a direct-mapped segment. */ #ifdef PMAP_MAP_POOLPAGE use_std = 1; #endif for (i = 0; i < NMEMPOOLS; i++) { struct pool_allocator *pa; struct pool *pp = &bmempools[i]; u_int size = 1 << (i + MEMPOOL_INDEX_OFFSET); char *name = malloc(8, M_TEMP, M_WAITOK); snprintf(name, 8, "buf%dk", 1 << i); pa = (size <= PAGE_SIZE && use_std) ? &pool_allocator_nointr : &bufmempool_allocator; pool_init(pp, size, 0, 0, 0, name, pa); pool_setlowat(pp, 1); pool_sethiwat(pp, 1); } /* Initialize the buffer queues */ for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++) { TAILQ_INIT(&dp->bq_queue); dp->bq_bytes = 0; } /* * Estimate hash table size based on the amount of memory we * intend to use for the buffer cache. The average buffer * size is dependent on our clients (i.e. filesystems). * * For now, use an empirical 3K per buffer. */ nbuf = (bufmem_hiwater / 1024) / 3; bufhashtbl = hashinit(nbuf, HASH_LIST, M_CACHE, M_WAITOK, &bufhash); } static int buf_lotsfree(void) { int try, thresh; struct lwp *l = curlwp; /* Always allocate if doing copy on write */ if (l->l_flag & L_COWINPROGRESS) return 1; /* Always allocate if less than the low water mark. */ if (bufmem < bufmem_lowater) return 1; /* Never allocate if greater than the high water mark. */ if (bufmem > bufmem_hiwater) return 0; /* If there's anything on the AGE list, it should be eaten. */ if (TAILQ_FIRST(&bufqueues[BQ_AGE].bq_queue) != NULL) return 0; /* * The probabily of getting a new allocation is inversely * proportional to the current size of the cache, using * a granularity of 16 steps. */ try = random() & 0x0000000fL; /* Don't use "16 * bufmem" here to avoid a 32-bit overflow. */ thresh = (bufmem - bufmem_lowater) / ((bufmem_hiwater - bufmem_lowater) / 16); if (try >= thresh) return 1; /* Otherwise don't allocate. */ return 0; } /* * Return estimate of bytes we think need to be * released to help resolve low memory conditions. * * => called at splbio. * => called with bqueue_slock held. */ static int buf_canrelease(void) { int pagedemand, ninvalid = 0; LOCK_ASSERT(simple_lock_held(&bqueue_slock)); if (bufmem < bufmem_lowater) return 0; if (bufmem > bufmem_hiwater) return bufmem - bufmem_hiwater; ninvalid += bufqueues[BQ_AGE].bq_bytes; pagedemand = uvmexp.freetarg - uvmexp.free; if (pagedemand < 0) return ninvalid; return MAX(ninvalid, MIN(2 * MAXBSIZE, MIN((bufmem - bufmem_lowater) / 16, pagedemand * PAGE_SIZE))); } /* * Buffer memory allocation helper functions */ static inline u_long buf_mempoolidx(u_long size) { u_int n = 0; size -= 1; size >>= MEMPOOL_INDEX_OFFSET; while (size) { size >>= 1; n += 1; } if (n >= NMEMPOOLS) panic("buf mem pool index %d", n); return n; } static inline u_long buf_roundsize(u_long size) { /* Round up to nearest power of 2 */ return (1 << (buf_mempoolidx(size) + MEMPOOL_INDEX_OFFSET)); } static inline caddr_t buf_malloc(size_t size) { u_int n = buf_mempoolidx(size); caddr_t addr; int s; while (1) { addr = pool_get(&bmempools[n], PR_NOWAIT); if (addr != NULL) break; /* No memory, see if we can free some. If so, try again */ if (buf_drain(1) > 0) continue; /* Wait for buffers to arrive on the LRU queue */ s = splbio(); simple_lock(&bqueue_slock); needbuffer = 1; ltsleep(&needbuffer, PNORELOCK | (PRIBIO + 1), "buf_malloc", 0, &bqueue_slock); splx(s); } return addr; } static void buf_mrelease(caddr_t addr, size_t size) { pool_put(&bmempools[buf_mempoolidx(size)], addr); } /* * bread()/breadn() helper. */ static inline struct buf * bio_doread(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; struct mount *mp; 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); if (async) BIO_SETPRIO(bp, BPRIO_TIMELIMITED); else BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); VOP_STRATEGY(vp, bp); /* Pay for the read. */ p->p_stats->p_ru.ru_inblock++; } else if (async) { brelse(bp); } if (vp->v_type == VBLK) mp = vp->v_specmountpoint; else mp = 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 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(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(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(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); if (sync) BIO_SETPRIO(bp, BPRIO_TIMECRITICAL); else BIO_SETPRIO(bp, BPRIO_TIMELIMITED); VOP_STRATEGY(vp, 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(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(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(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(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(struct buf *bp) { struct bqueue *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_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 */ goto already_queued; 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); if (bp->b_bufsize <= 0) { #ifdef DEBUG memset((char *)bp, 0, sizeof(*bp)); #endif pool_put(&bufpool, 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. If it's marked invalid, * we normally don't return the buffer, unless the caller explicitly * wants us to. */ 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 insure 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; int s, err; int preserve; 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); preserve = 1; } else { if ((bp = getnewbuf(slpflag, slptimeo, 0)) == 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); preserve = 0; } 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, preserve); } BIO_SETPRIO(bp, BPRIO_DEFAULT); return (bp); } /* * Get an empty, disassociated buffer of given size. */ struct buf * geteblk(int size) { struct buf *bp; int s; s = splbio(); simple_lock(&bqueue_slock); while ((bp = getnewbuf(0, 0, 0)) == 0) ; SET(bp->b_flags, B_INVAL); binshash(bp, &invalhash); simple_unlock(&bqueue_slock); simple_unlock(&bp->b_interlock); splx(s); BIO_SETPRIO(bp, BPRIO_DEFAULT); allocbuf(bp, size, 0); 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(struct buf *bp, int size, int preserve) { vsize_t oldsize, desired_size; caddr_t addr; int s, delta; desired_size = buf_roundsize(size); if (desired_size > MAXBSIZE) printf("allocbuf: buffer larger than MAXBSIZE requested"); bp->b_bcount = size; oldsize = bp->b_bufsize; if (oldsize == desired_size) return; /* * If we want a buffer of a different size, re-allocate the * buffer's memory; copy old content only if needed. */ addr = buf_malloc(desired_size); if (preserve) memcpy(addr, bp->b_data, MIN(oldsize,desired_size)); if (bp->b_data != NULL) buf_mrelease(bp->b_data, oldsize); bp->b_data = addr; bp->b_bufsize = desired_size; /* * Update overall buffer memory counter (protected by bqueue_slock) */ delta = (long)desired_size - (long)oldsize; s = splbio(); simple_lock(&bqueue_slock); if ((bufmem += delta) > bufmem_hiwater) { /* * Need to trim overall memory usage. */ while (buf_canrelease()) { if (buf_trim() == 0) break; } } simple_unlock(&bqueue_slock); splx(s); } /* * Find a buffer which is available for use. * Select something from a free list. * Preference is to AGE list, then LRU list. * * Called at splbio and with buffer queues locked. * Return buffer locked. */ struct buf * getnewbuf(int slpflag, int slptimeo, int from_bufq) { struct buf *bp; start: LOCK_ASSERT(simple_lock_held(&bqueue_slock)); /* * Get a new buffer from the pool; but use NOWAIT because * we have the buffer queues locked. */ if (!from_bufq && buf_lotsfree() && (bp = pool_get(&bufpool, PR_NOWAIT)) != NULL) { memset((char *)bp, 0, sizeof(*bp)); BUF_INIT(bp); bp->b_dev = NODEV; bp->b_vnbufs.le_next = NOLIST; bp->b_flags = B_BUSY; simple_lock(&bp->b_interlock); #if defined(DIAGNOSTIC) bp->b_freelistindex = -1; #endif /* defined(DIAGNOSTIC) */ return (bp); } if ((bp = TAILQ_FIRST(&bufqueues[BQ_AGE].bq_queue)) != NULL || (bp = TAILQ_FIRST(&bufqueues[BQ_LRU].bq_queue)) != NULL) { simple_lock(&bp->b_interlock); bremfree(bp); } else { /* * XXX: !from_bufq should be removed. */ if (!from_bufq || curproc != uvm.pagedaemon_proc) { /* wait for a free buffer of any kind */ needbuffer = 1; ltsleep(&needbuffer, slpflag|(PRIBIO + 1), "getnewbuf", slptimeo, &bqueue_slock); } return (NULL); } #ifdef DIAGNOSTIC if (bp->b_bufsize <= 0) panic("buffer %p: on queue but empty", bp); #endif 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); } /* * Attempt to free an aged buffer off the queues. * Called at splbio and with queue lock held. * Returns the amount of buffer memory freed. */ static int buf_trim(void) { struct buf *bp; long size = 0; /* Instruct getnewbuf() to get buffers off the queues */ if ((bp = getnewbuf(PCATCH, 1, 1)) == NULL) return 0; KASSERT(!ISSET(bp->b_flags, B_WANTED)); simple_unlock(&bp->b_interlock); size = bp->b_bufsize; bufmem -= size; simple_unlock(&bqueue_slock); if (size > 0) { buf_mrelease(bp->b_data, size); bp->b_bcount = bp->b_bufsize = 0; } /* brelse() will return the buffer to the global buffer pool */ brelse(bp); simple_lock(&bqueue_slock); return size; } int buf_drain(int n) { int s, size = 0, sz; s = splbio(); simple_lock(&bqueue_slock); while (size < n && bufmem > bufmem_lowater) { sz = buf_trim(); if (sz <= 0) break; size += sz; } simple_unlock(&bqueue_slock); splx(s); return size; } /* * 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, 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(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 */ BIO_SETPRIO(bp, BPRIO_DEFAULT); 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(void) { struct buf *bp; int n = 0; simple_lock(&bqueue_slock); TAILQ_FOREACH(bp, &bufqueues[BQ_LOCKED].bq_queue, b_freelist) n++; simple_unlock(&bqueue_slock); return (n); } /* * Wait for all buffers to complete I/O * Return the number of "stuck" buffers. */ int buf_syncwait(void) { struct buf *bp; int iter, nbusy, nbusy_prev = 0, dcount, s, ihash; dcount = 10000; for (iter = 0; iter < 20;) { s = splbio(); simple_lock(&bqueue_slock); nbusy = 0; for (ihash = 0; ihash < bufhash+1; ihash++) { LIST_FOREACH(bp, &bufhashtbl[ihash], b_hash) { if ((bp->b_flags & (B_BUSY|B_INVAL|B_READ)) == B_BUSY) nbusy++; /* * With soft updates, some buffers that are * written will be remarked as dirty until other * buffers are written. */ if (bp->b_vp && bp->b_vp->v_mount && (bp->b_vp->v_mount->mnt_flag & MNT_SOFTDEP) && (bp->b_flags & B_DELWRI)) { simple_lock(&bp->b_interlock); bremfree(bp); bp->b_flags |= B_BUSY; nbusy++; simple_unlock(&bp->b_interlock); simple_unlock(&bqueue_slock); bawrite(bp); if (dcount-- <= 0) { printf("softdep "); splx(s); goto fail; } simple_lock(&bqueue_slock); } } } simple_unlock(&bqueue_slock); splx(s); if (nbusy == 0) break; if (nbusy_prev == 0) nbusy_prev = nbusy; printf("%d ", nbusy); tsleep(&nbusy, PRIBIO, "bflush", (iter == 0) ? 1 : hz / 25 * iter); if (nbusy >= nbusy_prev) /* we didn't flush anything */ iter++; else nbusy_prev = nbusy; } if (nbusy) { fail:; #if defined(DEBUG) || defined(DEBUG_HALT_BUSY) printf("giving up\nPrinting vnodes for busy buffers\n"); s = splbio(); for (ihash = 0; ihash < bufhash+1; ihash++) { LIST_FOREACH(bp, &bufhashtbl[ihash], b_hash) { if ((bp->b_flags & (B_BUSY|B_INVAL|B_READ)) == B_BUSY) vprint(NULL, bp->b_vp); } } splx(s); #endif } return nbusy; } static void sysctl_fillbuf(struct buf *i, struct buf_sysctl *o) { o->b_flags = i->b_flags; o->b_error = i->b_error; o->b_prio = i->b_prio; o->b_dev = i->b_dev; o->b_bufsize = i->b_bufsize; o->b_bcount = i->b_bcount; o->b_resid = i->b_resid; o->b_addr = PTRTOUINT64(i->b_un.b_addr); o->b_blkno = i->b_blkno; o->b_rawblkno = i->b_rawblkno; o->b_iodone = PTRTOUINT64(i->b_iodone); o->b_proc = PTRTOUINT64(i->b_proc); o->b_vp = PTRTOUINT64(i->b_vp); o->b_saveaddr = PTRTOUINT64(i->b_saveaddr); o->b_lblkno = i->b_lblkno; } #define KERN_BUFSLOP 20 static int sysctl_dobuf(SYSCTLFN_ARGS) { struct buf *bp; struct buf_sysctl bs; char *dp; u_int i, op, arg; size_t len, needed, elem_size, out_size; int error, s, elem_count; if (namelen == 1 && name[0] == CTL_QUERY) return (sysctl_query(SYSCTLFN_CALL(rnode))); if (namelen != 4) return (EINVAL); dp = oldp; len = (oldp != NULL) ? *oldlenp : 0; op = name[0]; arg = name[1]; elem_size = name[2]; elem_count = name[3]; out_size = MIN(sizeof(bs), elem_size); /* * at the moment, these are just "placeholders" to make the * API for retrieving kern.buf data more extensible in the * future. * * XXX kern.buf currently has "netbsd32" issues. hopefully * these will be resolved at a later point. */ if (op != KERN_BUF_ALL || arg != KERN_BUF_ALL || elem_size < 1 || elem_count < 0) return (EINVAL); error = 0; needed = 0; s = splbio(); simple_lock(&bqueue_slock); for (i = 0; i < BQUEUES; i++) { TAILQ_FOREACH(bp, &bufqueues[i].bq_queue, b_freelist) { if (len >= elem_size && elem_count > 0) { sysctl_fillbuf(bp, &bs); error = copyout(&bs, dp, out_size); if (error) goto cleanup; dp += elem_size; len -= elem_size; } if (elem_count > 0) { needed += elem_size; if (elem_count != INT_MAX) elem_count--; } } } cleanup: simple_unlock(&bqueue_slock); splx(s); *oldlenp = needed; if (oldp == NULL) *oldlenp += KERN_BUFSLOP * sizeof(struct buf); return (error); } static int sysctl_bufvm_update(SYSCTLFN_ARGS) { int t, error; struct sysctlnode node; node = *rnode; node.sysctl_data = &t; t = *(int *)rnode->sysctl_data; error = sysctl_lookup(SYSCTLFN_CALL(&node)); if (error || newp == NULL) return (error); if (t < 0) return EINVAL; if (rnode->sysctl_data == &bufcache) { if (t > 100) return (EINVAL); bufcache = t; buf_setwm(); } else if (rnode->sysctl_data == &bufmem_lowater) { if (bufmem_hiwater - t < 16) return (EINVAL); bufmem_lowater = t; } else if (rnode->sysctl_data == &bufmem_hiwater) { if (t - bufmem_lowater < 16) return (EINVAL); bufmem_hiwater = t; } else return (EINVAL); /* Drain until below new high water mark */ while ((t = bufmem - bufmem_hiwater) >= 0) { if (buf_drain(t / (2 * 1024)) <= 0) break; } return 0; } SYSCTL_SETUP(sysctl_kern_buf_setup, "sysctl kern.buf subtree setup") { sysctl_createv(clog, 0, NULL, NULL, CTLFLAG_PERMANENT, CTLTYPE_NODE, "kern", NULL, NULL, 0, NULL, 0, CTL_KERN, CTL_EOL); sysctl_createv(clog, 0, NULL, NULL, CTLFLAG_PERMANENT, CTLTYPE_NODE, "buf", SYSCTL_DESCR("Kernel buffer cache information"), sysctl_dobuf, 0, NULL, 0, CTL_KERN, KERN_BUF, CTL_EOL); } SYSCTL_SETUP(sysctl_vm_buf_setup, "sysctl vm.buf* subtree setup") { sysctl_createv(clog, 0, NULL, NULL, CTLFLAG_PERMANENT, CTLTYPE_NODE, "vm", NULL, NULL, 0, NULL, 0, CTL_VM, CTL_EOL); sysctl_createv(clog, 0, NULL, NULL, CTLFLAG_PERMANENT|CTLFLAG_READWRITE, CTLTYPE_INT, "bufcache", SYSCTL_DESCR("Percentage of physical memory to use for " "buffer cache"), sysctl_bufvm_update, 0, &bufcache, 0, CTL_VM, CTL_CREATE, CTL_EOL); sysctl_createv(clog, 0, NULL, NULL, CTLFLAG_PERMANENT|CTLFLAG_READONLY, CTLTYPE_INT, "bufmem", SYSCTL_DESCR("Amount of kernel memory used by buffer " "cache"), NULL, 0, &bufmem, 0, CTL_VM, CTL_CREATE, CTL_EOL); sysctl_createv(clog, 0, NULL, NULL, CTLFLAG_PERMANENT|CTLFLAG_READWRITE, CTLTYPE_INT, "bufmem_lowater", SYSCTL_DESCR("Minimum amount of kernel memory to " "reserve for buffer cache"), sysctl_bufvm_update, 0, &bufmem_lowater, 0, CTL_VM, CTL_CREATE, CTL_EOL); sysctl_createv(clog, 0, NULL, NULL, CTLFLAG_PERMANENT|CTLFLAG_READWRITE, CTLTYPE_INT, "bufmem_hiwater", SYSCTL_DESCR("Maximum amount of kernel memory to use " "for buffer cache"), sysctl_bufvm_update, 0, &bufmem_hiwater, 0, CTL_VM, CTL_CREATE, CTL_EOL); } #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; struct buf *bp; struct bqueue *dp; int counts[(MAXBSIZE / PAGE_SIZE) + 1]; static const char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE" }; 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->bq_queue, 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 */