/* $OpenBSD: vfs_bio.c,v 1.174 2016/03/17 03:57:51 beck 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 int nobuffers; int needbuffer; struct bio_ops bioops; /* private bufcache functions */ void bufcache_init(void); void bufcache_adjust(void); /* * Buffer pool for I/O buffers. */ struct pool bufpool; struct bufhead bufhead = LIST_HEAD_INITIALIZER(bufhead); void buf_put(struct buf *); struct buf *bio_doread(struct vnode *, daddr_t, int, int); struct buf *buf_get(struct vnode *, daddr_t, size_t); void bread_cluster_callback(struct buf *); struct bcachestats bcstats; /* counters */ long lodirtypages; /* dirty page count low water mark */ long hidirtypages; /* dirty page count high water mark */ long targetpages; /* target number of pages for cache size */ long buflowpages; /* smallest size cache allowed */ long bufhighpages; /* largest size cache allowed */ long bufbackpages; /* minimum number of pages we shrink when asked to */ vsize_t bufkvm; struct proc *cleanerproc; int bd_req; /* Sleep point for cleaner daemon. */ #define NUM_CACHES 2 #define DMA_CACHE 0 struct bufcache cleancache[NUM_CACHES]; struct bufqueue dirtyqueue; void buf_put(struct buf *bp) { splassert(IPL_BIO); #ifdef DIAGNOSTIC if (bp->b_pobj != NULL) KASSERT(bp->b_bufsize > 0); if (ISSET(bp->b_flags, B_DELWRI)) panic("buf_put: releasing dirty buffer"); if (bp->b_freelist.tqe_next != NOLIST && bp->b_freelist.tqe_next != (void *)-1) panic("buf_put: still on the free list"); if (bp->b_vnbufs.le_next != NOLIST && bp->b_vnbufs.le_next != (void *)-1) panic("buf_put: still on the vnode list"); if (!LIST_EMPTY(&bp->b_dep)) panic("buf_put: b_dep is not empty"); #endif LIST_REMOVE(bp, b_list); bcstats.numbufs--; if (buf_dealloc_mem(bp) != 0) return; pool_put(&bufpool, bp); } /* * Initialize buffers and hash links for buffers. */ void bufinit(void) { u_int64_t dmapages; dmapages = uvm_pagecount(&dma_constraint); /* take away a guess at how much of this the kernel will consume */ dmapages -= (atop(physmem) - atop(uvmexp.free)); /* * If MD code doesn't say otherwise, use up to 10% of DMA'able * memory for buffers. */ if (bufcachepercent == 0) bufcachepercent = 10; /* * XXX these values and their same use in kern_sysctl * need to move into buf.h */ KASSERT(bufcachepercent <= 90); KASSERT(bufcachepercent >= 5); if (bufpages == 0) bufpages = dmapages * bufcachepercent / 100; if (bufpages < BCACHE_MIN) bufpages = BCACHE_MIN; KASSERT(bufpages < dmapages); bufhighpages = bufpages; /* * Set the base backoff level for the buffer cache. We will * not allow uvm to steal back more than this number of pages. */ buflowpages = dmapages * 5 / 100; if (buflowpages < BCACHE_MIN) buflowpages = BCACHE_MIN; /* * set bufbackpages to 100 pages, or 10 percent of the low water mark * if we don't have that many pages. */ bufbackpages = buflowpages * 10 / 100; if (bufbackpages > 100) bufbackpages = 100; /* * If the MD code does not say otherwise, reserve 10% of kva * space for mapping buffers. */ if (bufkvm == 0) bufkvm = VM_KERNEL_SPACE_SIZE / 10; /* * Don't use more than twice the amount of bufpages for mappings. * It's twice since we map things sparsely. */ if (bufkvm > bufpages * PAGE_SIZE) bufkvm = bufpages * PAGE_SIZE; /* * Round bufkvm to MAXPHYS because we allocate chunks of va space * in MAXPHYS chunks. */ bufkvm &= ~(MAXPHYS - 1); pool_init(&bufpool, sizeof(struct buf), 0, 0, 0, "bufpl", NULL); pool_setipl(&bufpool, IPL_BIO); bufcache_init(); /* * hmm - bufkvm is an argument because it's static, while * bufpages is global because it can change while running. */ buf_mem_init(bufkvm); /* * Set the dirty page high water mark to be less than the low * water mark for pages in the buffer cache. This ensures we * can always back off by throwing away clean pages, and give * ourselves a chance to write out the dirty pages eventually. */ hidirtypages = (buflowpages / 4) * 3; lodirtypages = buflowpages / 2; /* * We are allowed to use up to the reserve. */ targetpages = bufpages - RESERVE_PAGES; } /* * Change cachepct */ void bufadjust(int newbufpages) { struct buf *bp; int s; if (newbufpages < buflowpages) newbufpages = buflowpages; s = splbio(); bufpages = newbufpages; /* * We are allowed to use up to the reserve */ targetpages = bufpages - RESERVE_PAGES; /* * Shrinking the cache happens here only if someone has manually * adjusted bufcachepercent - or the pagedaemon has told us * to give back memory *now* - so we give it all back. */ while ((bp = bufcache_getanycleanbuf()) && (bcstats.numbufpages > targetpages)) { bufcache_take(bp); if (bp->b_vp) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } buf_put(bp); } bufcache_adjust(); /* * Wake up the cleaner if we have lots of dirty pages, * or if we are getting low on buffer cache kva. */ if ((UNCLEAN_PAGES >= hidirtypages) || bcstats.kvaslots_avail <= 2 * RESERVE_SLOTS) wakeup(&bd_req); splx(s); } /* * Make the buffer cache back off from cachepct. */ int bufbackoff(struct uvm_constraint_range *range, long size) { /* * Back off "size" buffer cache pages. Called by the page * daemon to consume buffer cache pages rather than scanning. * * It returns 0 to the pagedaemon to indicate that it has * succeeded in freeing enough pages. It returns -1 to * indicate that it could not and the pagedaemon should take * other measures. * */ long pdelta, oldbufpages; /* * Back off by at least bufbackpages. If the page daemon gave us * a larger size, back off by that much. */ pdelta = (size > bufbackpages) ? size : bufbackpages; if (bufpages <= buflowpages) return(-1); if (bufpages - pdelta < buflowpages) pdelta = bufpages - buflowpages; oldbufpages = bufpages; bufadjust(bufpages - pdelta); if (oldbufpages - bufpages < size) return (-1); /* we did not free what we were asked */ else return(0); } void buf_flip_high(struct buf *bp) { KASSERT(ISSET(bp->b_flags, B_BC)); KASSERT(ISSET(bp->b_flags, B_DMA)); KASSERT(bp->cache == DMA_CACHE); CLR(bp->b_flags, B_DMA); /* XXX does nothing to buffer for now */ } void buf_flip_dma(struct buf *bp) { KASSERT(ISSET(bp->b_flags, B_BC)); KASSERT(ISSET(bp->b_flags, B_BUSY)); if (!ISSET(bp->b_flags, B_DMA)) { KASSERT(bp->cache > DMA_CACHE); KASSERT(bp->cache < NUM_CACHES); /* XXX does not flip buffer for now */ /* make buffer hot, in DMA_CACHE, once it gets released. */ CLR(bp->b_flags, B_COLD); CLR(bp->b_flags, B_WARM); SET(bp->b_flags, B_DMA); bp->cache = DMA_CACHE; } } struct buf * bio_doread(struct vnode *vp, daddr_t blkno, int size, int async) { struct buf *bp; struct mount *mp; bp = getblk(vp, blkno, size, 0, 0); /* * If buffer does not have valid data, start a read. * Note that if buffer is B_INVAL, getblk() won't return it. * Therefore, it's valid if its I/O has completed or been delayed. */ if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) { SET(bp->b_flags, B_READ | async); bcstats.pendingreads++; bcstats.numreads++; VOP_STRATEGY(bp); /* Pay for the read. */ curproc->p_ru.ru_inblock++; /* XXX */ } else if (async) { brelse(bp); } mp = vp->v_type == VBLK? vp->v_specmountpoint : vp->v_mount; /* * Collect statistics on synchronous and asynchronous reads. * Reads from block devices are charged to their associated * filesystem (if any). */ if (mp != NULL) { if (async == 0) mp->mnt_stat.f_syncreads++; else mp->mnt_stat.f_asyncreads++; } return (bp); } /* * Read a disk block. * This algorithm described in Bach (p.54). */ int bread(struct vnode *vp, daddr_t blkno, int size, struct buf **bpp) { struct buf *bp; /* Get buffer for block. */ bp = *bpp = bio_doread(vp, blkno, size, 0); /* Wait for the read to complete, and return result. */ return (biowait(bp)); } /* * Read-ahead multiple disk blocks. The first is sync, the rest async. * Trivial modification to the breada algorithm presented in Bach (p.55). */ int breadn(struct vnode *vp, daddr_t blkno, int size, daddr_t rablks[], int rasizes[], int nrablks, struct buf **bpp) { struct buf *bp; int i; bp = *bpp = bio_doread(vp, blkno, size, 0); /* * For each of the read-ahead blocks, start a read, if necessary. */ for (i = 0; i < nrablks; i++) { /* If it's in the cache, just go on to next one. */ if (incore(vp, rablks[i])) continue; /* Get a buffer for the read-ahead block */ (void) bio_doread(vp, rablks[i], rasizes[i], B_ASYNC); } /* Otherwise, we had to start a read for it; wait until it's valid. */ return (biowait(bp)); } /* * Called from interrupt context. */ void bread_cluster_callback(struct buf *bp) { struct buf **xbpp = bp->b_saveaddr; int i; if (xbpp[1] != NULL) { size_t newsize = xbpp[1]->b_bufsize; /* * Shrink this buffer's mapping to only cover its part of * the total I/O. */ buf_fix_mapping(bp, newsize); bp->b_bcount = newsize; } 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, 0); if (ISSET(bp->b_flags, B_ASYNC)) { brelse(bp); } else { CLR(bp->b_flags, B_WANTED); wakeup(bp); } } int bread_cluster(struct vnode *vp, daddr_t blkno, int size, struct buf **rbpp) { struct buf *bp, **xbpp; int howmany, maxra, i, inc; daddr_t sblkno; *rbpp = bio_doread(vp, blkno, size, 0); /* * If the buffer is in the cache skip any I/O operation. */ if (ISSET((*rbpp)->b_flags, B_CACHE)) goto out; if (size != round_page(size)) goto out; if (VOP_BMAP(vp, blkno + 1, NULL, &sblkno, &maxra)) goto out; maxra++; if (sblkno == -1 || maxra < 2) goto out; howmany = MAXPHYS / size; if (howmany > maxra) howmany = maxra; xbpp = mallocarray(howmany + 1, sizeof(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, 0); goto out; } } bp = xbpp[0]; xbpp[howmany] = 0; inc = btodb(size); for (i = 1; i < howmany; i++) { bcstats.pendingreads++; bcstats.numreads++; /* * We set B_DMA here because bp above will be B_DMA, * and we are playing buffer slice-n-dice games from * the memory allocated in bp. */ SET(xbpp[i]->b_flags, B_DMA | B_READ | B_ASYNC); xbpp[i]->b_blkno = sblkno + (i * inc); xbpp[i]->b_bufsize = xbpp[i]->b_bcount = size; xbpp[i]->b_data = NULL; xbpp[i]->b_pobj = bp->b_pobj; xbpp[i]->b_poffs = bp->b_poffs + (i * size); } KASSERT(bp->b_lblkno == blkno + 1); KASSERT(bp->b_vp == vp); bp->b_blkno = sblkno; SET(bp->b_flags, B_READ | B_ASYNC | B_CALL); bp->b_saveaddr = (void *)xbpp; bp->b_iodone = bread_cluster_callback; bcstats.pendingreads++; bcstats.numreads++; VOP_STRATEGY(bp); curproc->p_ru.ru_inblock++; out: return (biowait(*rbpp)); } /* * Block write. Described in Bach (p.56) */ int bwrite(struct buf *bp) { int rv, async, wasdelayed, s; struct vnode *vp; struct mount *mp; vp = bp->b_vp; if (vp != NULL) mp = vp->v_type == VBLK? vp->v_specmountpoint : vp->v_mount; else mp = NULL; /* * Remember buffer type, to switch on it later. If the write was * synchronous, but the file system was mounted with MNT_ASYNC, * convert it to a delayed write. * XXX note that this relies on delayed tape writes being converted * to async, not sync writes (which is safe, but ugly). */ async = ISSET(bp->b_flags, B_ASYNC); if (!async && mp && ISSET(mp->mnt_flag, MNT_ASYNC)) { bdwrite(bp); return (0); } /* * Collect statistics on synchronous and asynchronous writes. * Writes to block devices are charged to their associated * filesystem (if any). */ if (mp != NULL) { if (async) mp->mnt_stat.f_asyncwrites++; else mp->mnt_stat.f_syncwrites++; } bcstats.pendingwrites++; bcstats.numwrites++; wasdelayed = ISSET(bp->b_flags, B_DELWRI); CLR(bp->b_flags, (B_READ | B_DONE | B_ERROR | B_DELWRI)); s = splbio(); /* * If not synchronous, pay for the I/O operation and make * sure the buf is on the correct vnode queue. We have * to do this now, because if we don't, the vnode may not * be properly notified that its I/O has completed. */ if (wasdelayed) { reassignbuf(bp); } else curproc->p_ru.ru_oublock++; /* Initiate disk write. Make sure the appropriate party is charged. */ bp->b_vp->v_numoutput++; splx(s); buf_flip_dma(bp); SET(bp->b_flags, B_WRITEINPROG); VOP_STRATEGY(bp); /* * If the queue is above the high water mark, wait till * the number of outstanding write bufs drops below the low * water mark. */ if (bp->b_bq) bufq_wait(bp->b_bq); if (async) return (0); /* * If I/O was synchronous, wait for it to complete. */ rv = biowait(bp); /* Release the buffer. */ brelse(bp); return (rv); } /* * Delayed write. * * The buffer is marked dirty, but is not queued for I/O. * This routine should be used when the buffer is expected * to be modified again soon, typically a small write that * partially fills a buffer. * * NB: magnetic tapes cannot be delayed; they must be * written in the order that the writes are requested. * * Described in Leffler, et al. (pp. 208-213). */ void bdwrite(struct buf *bp) { int s; /* * If the block hasn't been seen before: * (1) Mark it as having been seen, * (2) Charge for the write. * (3) Make sure it's on its vnode's correct block list, * (4) If a buffer is rewritten, move it to end of dirty list */ if (!ISSET(bp->b_flags, B_DELWRI)) { SET(bp->b_flags, B_DELWRI); s = splbio(); buf_flip_dma(bp); reassignbuf(bp); splx(s); curproc->p_ru.ru_oublock++; /* XXX */ } /* 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); buf_flip_dma(bp); reassignbuf(bp); } } /* * Must be called at splbio() */ void buf_undirty(struct buf *bp) { splassert(IPL_BIO); #ifdef DIAGNOSTIC if (!ISSET(bp->b_flags, B_BUSY)) panic("Trying to undirty buffer on freelist!"); #endif if (ISSET(bp->b_flags, B_DELWRI)) { CLR(bp->b_flags, B_DELWRI); reassignbuf(bp); } } /* * Release a buffer on to the free lists. * Described in Bach (p. 46). */ void brelse(struct buf *bp) { int s; s = splbio(); if (bp->b_data != NULL) KASSERT(bp->b_bufsize > 0); /* * Determine which queue the buffer should be on, then put it there. */ /* If it's not cacheable, or an error, mark it invalid. */ if (ISSET(bp->b_flags, (B_NOCACHE|B_ERROR))) SET(bp->b_flags, B_INVAL); if (ISSET(bp->b_flags, B_INVAL)) { /* * If the buffer is invalid, free it now rather than leaving * it in a queue and wasting memory. */ if (LIST_FIRST(&bp->b_dep) != NULL) buf_deallocate(bp); if (ISSET(bp->b_flags, B_DELWRI)) { CLR(bp->b_flags, B_DELWRI); } if (bp->b_vp) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } bp->b_vp = NULL; /* * Wake up any processes waiting for _this_ buffer to * become free. They are not allowed to grab it * since it will be freed. But the only sleeper is * getblk and it will restart the operation after * sleep. */ if (ISSET(bp->b_flags, B_WANTED)) { CLR(bp->b_flags, B_WANTED); wakeup(bp); } buf_put(bp); } else { /* * It has valid data. Put it on the end of the appropriate * queue, so that it'll stick around for as long as possible. */ bufcache_release(bp); /* Unlock the buffer. */ CLR(bp->b_flags, (B_AGE | B_ASYNC | B_NOCACHE | B_DEFERRED)); buf_release(bp); /* Wake up any processes waiting for _this_ buffer to * become free. */ if (ISSET(bp->b_flags, B_WANTED)) { CLR(bp->b_flags, B_WANTED); wakeup(bp); } } /* Wake up syncer and cleaner processes waiting for buffers. */ if (nobuffers) { nobuffers = 0; wakeup(&nobuffers); } /* Wake up any processes waiting for any buffer to become free. */ if (needbuffer && bcstats.numbufpages < targetpages && bcstats.kvaslots_avail > RESERVE_SLOTS) { needbuffer = 0; wakeup(&needbuffer); } splx(s); } /* * Determine if a block is in the cache. Just look on what would be its hash * chain. If it's there, return a pointer to it, unless it's marked invalid. */ struct buf * incore(struct vnode *vp, daddr_t blkno) { struct buf *bp; struct buf b; int s; s = splbio(); /* Search buf lookup tree */ b.b_lblkno = blkno; bp = 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, daddr_t blkno, int size, int slpflag, int slptimeo) { struct buf *bp; struct buf b; int s, error; /* * XXX * The following is an inlined version of 'incore()', but with * the 'invalid' test moved to after the 'busy' test. It's * necessary because there are some cases in which the NFS * code sets B_INVAL prior to writing data to the server, but * in which the buffers actually contain valid data. In this * case, we can't allow the system to allocate a new buffer for * the block until the write is finished. */ start: s = splbio(); b.b_lblkno = blkno; bp = 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); bufcache_take(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, daddr_t blkno, size_t size) { struct buf *bp; int poolwait = size == 0 ? PR_NOWAIT : PR_WAITOK; int npages; int s; s = splbio(); if (size) { /* * Wake up the cleaner if we have lots of dirty pages, * or if we are getting low on buffer cache kva. */ if (UNCLEAN_PAGES >= hidirtypages || bcstats.kvaslots_avail <= 2 * RESERVE_SLOTS) wakeup(&bd_req); npages = atop(round_page(size)); /* * if our cache has been previously shrunk, * allow it to grow again with use up to * bufhighpages (cachepercent) */ if (bufpages < bufhighpages) bufadjust(bufhighpages); /* * If we would go over the page target with our * new allocation, free enough buffers first * to stay at the target with our new allocation. */ while ((bcstats.numbufpages + npages > targetpages) && (bp = bufcache_getanycleanbuf())) { bufcache_take(bp); if (bp->b_vp) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } buf_put(bp); } /* * If we get here, we tried to free the world down * above, and couldn't get down - Wake the cleaner * and wait for it to push some buffers out. */ if ((bcstats.numbufpages + npages > targetpages || bcstats.kvaslots_avail <= RESERVE_SLOTS) && curproc != syncerproc && curproc != cleanerproc) { wakeup(&bd_req); needbuffer++; tsleep(&needbuffer, PRIBIO, "needbuffer", 0); splx(s); return (NULL); } if (bcstats.numbufpages + npages > bufpages) { /* cleaner or syncer */ nobuffers = 1; tsleep(&nobuffers, PRIBIO, "nobuffers", 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_dev = NODEV; LIST_INIT(&bp->b_dep); bp->b_bcount = size; buf_acquire_nomap(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 buf_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)); KASSERT(ISSET(bp->b_flags, B_DMA)); buf_map(bp); } SET(bp->b_flags, B_BC); splx(s); return (bp); } /* * Buffer cleaning daemon. */ void buf_daemon(struct proc *p) { struct buf *bp = NULL; int s, pushed = 0; cleanerproc = curproc; s = splbio(); for (;;) { if (bp == NULL || (pushed >= 16 && UNCLEAN_PAGES < hidirtypages && bcstats.kvaslots_avail > 2 * RESERVE_SLOTS)){ pushed = 0; /* * Wake up anyone who was waiting for buffers * to be released. */ if (needbuffer) { needbuffer = 0; wakeup(&needbuffer); } tsleep(&bd_req, PRIBIO - 7, "cleaner", 0); } while ((bp = bufcache_getdirtybuf())) { if (UNCLEAN_PAGES < lodirtypages && bcstats.kvaslots_avail > 2 * RESERVE_SLOTS && pushed >= 16) break; bufcache_take(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 dirty queue"); #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(); bufcache_release(bp); buf_release(bp); continue; } bawrite(bp); pushed++; sched_pause(); 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; 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 *, ...) __attribute__((__format__(__kprintf__,1,2)))); /* * bcstats_print: ddb hook to print interesting buffer cache counters */ void bcstats_print( int (*pr)(const char *, ...) __attribute__((__format__(__kprintf__,1,2)))) { (*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 void buf_adjcnt(struct buf *bp, long ncount) { KASSERT(ncount <= bp->b_bufsize); bp->b_bcount = ncount; } /* bufcache freelist code below */ /* * Copyright (c) 2014 Ted Unangst * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ /* * The code below implements a variant of the 2Q buffer cache algorithm by * Johnson and Shasha. * * General Outline * We divide the buffer cache into three working sets: current, previous, * and long term. Each list is itself LRU and buffers get promoted and moved * around between them. A buffer starts its life in the current working set. * As time passes and newer buffers push it out, it will turn into the previous * working set and is subject to recycling. But if it's accessed again from * the previous working set, that's an indication that it's actually in the * long term working set, so we promote it there. The separation of current * and previous working sets prevents us from promoting a buffer that's only * temporarily hot to the long term cache. * * The objective is to provide scan resistance by making the long term * working set ineligible for immediate recycling, even as the current * working set is rapidly turned over. * * Implementation * The code below identifies the current, previous, and long term sets as * hotqueue, coldqueue, and warmqueue. The hot and warm queues are capped at * 1/3 of the total clean pages, after which point they start pushing their * oldest buffers into coldqueue. * A buf always starts out with neither WARM or COLD flags set (implying HOT). * When released, it will be returned to the tail of the hotqueue list. * When the hotqueue gets too large, the oldest hot buf will be moved to the * coldqueue, with the B_COLD flag set. When a cold buf is released, we set * the B_WARM flag and put it onto the warmqueue. Warm bufs are also * directly returned to the end of the warmqueue. As with the hotqueue, when * the warmqueue grows too large, B_WARM bufs are moved onto the coldqueue. * * Note that this design does still support large working sets, greater * than the cap of hotqueue or warmqueue would imply. The coldqueue is still * cached and has no maximum length. The hot and warm queues form a Y feeding * into the coldqueue. Moving bufs between queues is constant time, so this * design decays to one long warm->cold queue. * * In the 2Q paper, hotqueue and coldqueue are A1in and A1out. The warmqueue * is Am. We always cache pages, as opposed to pointers to pages for A1. * * This implementation adds support for multiple 2q caches. * * If we have more than one 2q cache, as bufs fall off the cold queue * for recyclying, bufs that have been warm before (which retain the * B_WARM flag in addition to B_COLD) can be put into the hot queue of * a second level 2Q cache. buffers which are only B_COLD are * recycled. Bufs falling off the last cache's cold queue are always * recycled. * */ /* * this function is called when a hot or warm queue may have exceeded its * size limit. it will move a buf to the coldqueue. */ int chillbufs(struct bufcache *cache, struct bufqueue *queue, int64_t *queuepages); void bufcache_init(void) { int i; for (i=0; i < NUM_CACHES; i++) { TAILQ_INIT(&cleancache[i].hotqueue); TAILQ_INIT(&cleancache[i].coldqueue); TAILQ_INIT(&cleancache[i].warmqueue); } TAILQ_INIT(&dirtyqueue); } /* * if the buffer caches have shrunk, we may need to rebalance our queues. */ void bufcache_adjust(void) { int i; for (i=0; i < NUM_CACHES; i++) { while (chillbufs(&cleancache[i], &cleancache[i].warmqueue, &cleancache[i].warmbufpages) || chillbufs(&cleancache[i], &cleancache[i].hotqueue, &cleancache[i].hotbufpages)) ; } } /* * Get a clean buffer from the cache. if "discard" is set do not promote * previously warm buffers as normal, because we are tossing everything * away such as in a hibernation */ struct buf * bufcache_getcleanbuf(int cachenum, int discard) { struct buf *bp = NULL; struct bufcache *cache = &cleancache[cachenum]; splassert(IPL_BIO); /* try cold queue */ while ((bp = TAILQ_FIRST(&cache->coldqueue))) { if ((!discard) && cachenum < NUM_CACHES - 1 && ISSET(bp->b_flags, B_WARM)) { /* * If this buffer was warm before, move it to * the hot queue in the next cache */ TAILQ_REMOVE(&cache->coldqueue, bp, b_freelist); CLR(bp->b_flags, B_WARM); CLR(bp->b_flags, B_COLD); int64_t pages = atop(bp->b_bufsize); KASSERT(bp->cache == cachenum); if (bp->cache == 0) buf_flip_high(bp); bp->cache++; struct bufcache *newcache = &cleancache[bp->cache]; newcache->cachepages += pages; newcache->hotbufpages += pages; chillbufs(newcache, &newcache->hotqueue, &newcache->hotbufpages); TAILQ_INSERT_TAIL(&newcache->hotqueue, bp, b_freelist); } else /* buffer is cold - give it up */ return bp; } if ((bp = TAILQ_FIRST(&cache->warmqueue))) return bp; if ((bp = TAILQ_FIRST(&cache->hotqueue))) return bp; return bp; } struct buf * bufcache_getcleanbuf_range(int start, int end, int discard) { int i, j = start, q = end; struct buf *bp = NULL; /* * XXX in theory we could promote warm buffers into a previous queue * so in the pathological case of where we go through all the caches * without getting a buffer we have to start at the beginning again. */ while (j <= q) { for (i = q; i >= j; i--) if ((bp = bufcache_getcleanbuf(i, discard))) return(bp); j++; } return bp; } struct buf * bufcache_getanycleanbuf(void) { return bufcache_getcleanbuf_range(DMA_CACHE, NUM_CACHES -1, 0); } struct buf * bufcache_getdirtybuf(void) { return TAILQ_FIRST(&dirtyqueue); } void bufcache_take(struct buf *bp) { struct bufqueue *queue; int64_t pages; splassert(IPL_BIO); KASSERT(ISSET(bp->b_flags, B_BC)); KASSERT(bp->cache >= DMA_CACHE); KASSERT((bp->cache < NUM_CACHES)); pages = atop(bp->b_bufsize); struct bufcache *cache = &cleancache[bp->cache]; if (!ISSET(bp->b_flags, B_DELWRI)) { if (ISSET(bp->b_flags, B_COLD)) { queue = &cache->coldqueue; } else if (ISSET(bp->b_flags, B_WARM)) { queue = &cache->warmqueue; cache->warmbufpages -= pages; } else { queue = &cache->hotqueue; cache->hotbufpages -= pages; } bcstats.numcleanpages -= pages; cache->cachepages -= pages; } else { queue = &dirtyqueue; bcstats.numdirtypages -= pages; bcstats.delwribufs--; } TAILQ_REMOVE(queue, bp, b_freelist); } /* move buffers from a hot or warm queue to a cold queue in a cache */ int chillbufs(struct bufcache *cache, struct bufqueue *queue, int64_t *queuepages) { struct buf *bp; int64_t limit, pages; /* * The warm and hot queues are allowed to be up to one third each. * We impose a minimum size of 96 to prevent too much "wobbling". */ limit = cache->cachepages / 3; if (*queuepages > 96 && *queuepages > limit) { bp = TAILQ_FIRST(queue); if (!bp) panic("inconsistent bufpage counts"); pages = atop(bp->b_bufsize); *queuepages -= pages; TAILQ_REMOVE(queue, bp, b_freelist); /* we do not clear B_WARM */ SET(bp->b_flags, B_COLD); TAILQ_INSERT_TAIL(&cache->coldqueue, bp, b_freelist); return 1; } return 0; } void bufcache_release(struct buf *bp) { struct bufqueue *queue; int64_t pages; struct bufcache *cache = &cleancache[bp->cache]; pages = atop(bp->b_bufsize); KASSERT(ISSET(bp->b_flags, B_BC)); KASSERT((ISSET(bp->b_flags, B_DMA) && bp->cache == 0) || ((!ISSET(bp->b_flags, B_DMA)) && bp->cache > 0)); if (!ISSET(bp->b_flags, B_DELWRI)) { int64_t *queuepages; if (ISSET(bp->b_flags, B_WARM | B_COLD)) { SET(bp->b_flags, B_WARM); CLR(bp->b_flags, B_COLD); queue = &cache->warmqueue; queuepages = &cache->warmbufpages; } else { queue = &cache->hotqueue; queuepages = &cache->hotbufpages; } *queuepages += pages; bcstats.numcleanpages += pages; cache->cachepages += pages; chillbufs(cache, queue, queuepages); } else { queue = &dirtyqueue; bcstats.numdirtypages += pages; bcstats.delwribufs++; } TAILQ_INSERT_TAIL(queue, bp, b_freelist); } #ifdef HIBERNATE /* * Nuke the buffer cache from orbit when hibernating. We do not want to save * any clean cache pages to swap and read them back. the original disk files * are just as good. */ void hibernate_suspend_bufcache(void) { struct buf *bp; int s; s = splbio(); /* Chuck away all the cache pages.. discard bufs, do not promote */ while ((bp = bufcache_getcleanbuf_range(DMA_CACHE, NUM_CACHES - 1, 1))) { bufcache_take(bp); if (bp->b_vp) { RB_REMOVE(buf_rb_bufs, &bp->b_vp->v_bufs_tree, bp); brelvp(bp); } buf_put(bp); } splx(s); } void hibernate_resume_bufcache(void) { /* XXX Nothing needed here for now */ } #endif /* HIBERNATE */