diff options
Diffstat (limited to 'sys/kern/vfs_bio.c')
| -rw-r--r-- | sys/kern/vfs_bio.c | 3395 |
1 files changed, 3395 insertions, 0 deletions
diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c new file mode 100644 index 0000000..30dc753 --- /dev/null +++ b/sys/kern/vfs_bio.c @@ -0,0 +1,3395 @@ +/* + * Copyright (c) 1994,1997 John S. Dyson + * All rights reserved. + * + * 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 immediately at the beginning of the file, without modification, + * this list of conditions, and the following disclaimer. + * 2. Absolutely no warranty of function or purpose is made by the author + * John S. Dyson. + * + * $FreeBSD$ + */ + +/* + * this file contains a new buffer I/O scheme implementing a coherent + * VM object and buffer cache scheme. Pains have been taken to make + * sure that the performance degradation associated with schemes such + * as this is not realized. + * + * Author: John S. Dyson + * Significant help during the development and debugging phases + * had been provided by David Greenman, also of the FreeBSD core team. + * + * see man buf(9) for more info. + */ + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/stdint.h> +#include <sys/bio.h> +#include <sys/buf.h> +#include <sys/eventhandler.h> +#include <sys/lock.h> +#include <sys/malloc.h> +#include <sys/mount.h> +#include <sys/mutex.h> +#include <sys/kernel.h> +#include <sys/kthread.h> +#include <sys/ktr.h> +#include <sys/proc.h> +#include <sys/reboot.h> +#include <sys/resourcevar.h> +#include <sys/sysctl.h> +#include <sys/vmmeter.h> +#include <sys/vnode.h> +#include <vm/vm.h> +#include <vm/vm_param.h> +#include <vm/vm_kern.h> +#include <vm/vm_pageout.h> +#include <vm/vm_page.h> +#include <vm/vm_object.h> +#include <vm/vm_extern.h> +#include <vm/vm_map.h> + +static MALLOC_DEFINE(M_BIOBUF, "BIO buffer", "BIO buffer"); + +struct bio_ops bioops; /* I/O operation notification */ + +struct buf_ops buf_ops_bio = { + "buf_ops_bio", + bwrite +}; + +/* + * XXX buf is global because kern_shutdown.c and ffs_checkoverlap has + * carnal knowledge of buffers. This knowledge should be moved to vfs_bio.c. + */ +struct buf *buf; /* buffer header pool */ +struct mtx buftimelock; /* Interlock on setting prio and timo */ + +static void vm_hold_free_pages(struct buf * bp, vm_offset_t from, + vm_offset_t to); +static void vm_hold_load_pages(struct buf * bp, vm_offset_t from, + vm_offset_t to); +static void vfs_page_set_valid(struct buf *bp, vm_ooffset_t off, + int pageno, vm_page_t m); +static void vfs_clean_pages(struct buf * bp); +static void vfs_setdirty(struct buf *bp); +static void vfs_vmio_release(struct buf *bp); +static void vfs_backgroundwritedone(struct buf *bp); +static int flushbufqueues(void); +static void buf_daemon(void); + +int vmiodirenable = TRUE; +SYSCTL_INT(_vfs, OID_AUTO, vmiodirenable, CTLFLAG_RW, &vmiodirenable, 0, + "Use the VM system for directory writes"); +int runningbufspace; +SYSCTL_INT(_vfs, OID_AUTO, runningbufspace, CTLFLAG_RD, &runningbufspace, 0, + "Amount of presently outstanding async buffer io"); +static int bufspace; +SYSCTL_INT(_vfs, OID_AUTO, bufspace, CTLFLAG_RD, &bufspace, 0, + "KVA memory used for bufs"); +static int maxbufspace; +SYSCTL_INT(_vfs, OID_AUTO, maxbufspace, CTLFLAG_RD, &maxbufspace, 0, + "Maximum allowed value of bufspace (including buf_daemon)"); +static int bufmallocspace; +SYSCTL_INT(_vfs, OID_AUTO, bufmallocspace, CTLFLAG_RD, &bufmallocspace, 0, + "Amount of malloced memory for buffers"); +static int maxbufmallocspace; +SYSCTL_INT(_vfs, OID_AUTO, maxmallocbufspace, CTLFLAG_RW, &maxbufmallocspace, 0, + "Maximum amount of malloced memory for buffers"); +static int lobufspace; +SYSCTL_INT(_vfs, OID_AUTO, lobufspace, CTLFLAG_RD, &lobufspace, 0, + "Minimum amount of buffers we want to have"); +static int hibufspace; +SYSCTL_INT(_vfs, OID_AUTO, hibufspace, CTLFLAG_RD, &hibufspace, 0, + "Maximum allowed value of bufspace (excluding buf_daemon)"); +static int bufreusecnt; +SYSCTL_INT(_vfs, OID_AUTO, bufreusecnt, CTLFLAG_RW, &bufreusecnt, 0, + "Number of times we have reused a buffer"); +static int buffreekvacnt; +SYSCTL_INT(_vfs, OID_AUTO, buffreekvacnt, CTLFLAG_RW, &buffreekvacnt, 0, + "Number of times we have freed the KVA space from some buffer"); +static int bufdefragcnt; +SYSCTL_INT(_vfs, OID_AUTO, bufdefragcnt, CTLFLAG_RW, &bufdefragcnt, 0, + "Number of times we have had to repeat buffer allocation to defragment"); +static int lorunningspace; +SYSCTL_INT(_vfs, OID_AUTO, lorunningspace, CTLFLAG_RW, &lorunningspace, 0, + "Minimum preferred space used for in-progress I/O"); +static int hirunningspace; +SYSCTL_INT(_vfs, OID_AUTO, hirunningspace, CTLFLAG_RW, &hirunningspace, 0, + "Maximum amount of space to use for in-progress I/O"); +static int numdirtybuffers; +SYSCTL_INT(_vfs, OID_AUTO, numdirtybuffers, CTLFLAG_RD, &numdirtybuffers, 0, + "Number of buffers that are dirty (has unwritten changes) at the moment"); +static int lodirtybuffers; +SYSCTL_INT(_vfs, OID_AUTO, lodirtybuffers, CTLFLAG_RW, &lodirtybuffers, 0, + "How many buffers we want to have free before bufdaemon can sleep"); +static int hidirtybuffers; +SYSCTL_INT(_vfs, OID_AUTO, hidirtybuffers, CTLFLAG_RW, &hidirtybuffers, 0, + "When the number of dirty buffers is considered severe"); +static int numfreebuffers; +SYSCTL_INT(_vfs, OID_AUTO, numfreebuffers, CTLFLAG_RD, &numfreebuffers, 0, + "Number of free buffers"); +static int lofreebuffers; +SYSCTL_INT(_vfs, OID_AUTO, lofreebuffers, CTLFLAG_RW, &lofreebuffers, 0, + "XXX Unused"); +static int hifreebuffers; +SYSCTL_INT(_vfs, OID_AUTO, hifreebuffers, CTLFLAG_RW, &hifreebuffers, 0, + "XXX Complicatedly unused"); +static int getnewbufcalls; +SYSCTL_INT(_vfs, OID_AUTO, getnewbufcalls, CTLFLAG_RW, &getnewbufcalls, 0, + "Number of calls to getnewbuf"); +static int getnewbufrestarts; +SYSCTL_INT(_vfs, OID_AUTO, getnewbufrestarts, CTLFLAG_RW, &getnewbufrestarts, 0, + "Number of times getnewbuf has had to restart a buffer aquisition"); +static int dobkgrdwrite = 1; +SYSCTL_INT(_debug, OID_AUTO, dobkgrdwrite, CTLFLAG_RW, &dobkgrdwrite, 0, + "Do background writes (honoring the BX_BKGRDWRITE flag)?"); + +/* + * Wakeup point for bufdaemon, as well as indicator of whether it is already + * active. Set to 1 when the bufdaemon is already "on" the queue, 0 when it + * is idling. + */ +static int bd_request; + +/* + * bogus page -- for I/O to/from partially complete buffers + * this is a temporary solution to the problem, but it is not + * really that bad. it would be better to split the buffer + * for input in the case of buffers partially already in memory, + * but the code is intricate enough already. + */ +vm_page_t bogus_page; + +/* + * Offset for bogus_page. + * XXX bogus_offset should be local to bufinit + */ +static vm_offset_t bogus_offset; + +/* + * Synchronization (sleep/wakeup) variable for active buffer space requests. + * Set when wait starts, cleared prior to wakeup(). + * Used in runningbufwakeup() and waitrunningbufspace(). + */ +static int runningbufreq; + +/* + * Synchronization (sleep/wakeup) variable for buffer requests. + * Can contain the VFS_BIO_NEED flags defined below; setting/clearing is done + * by and/or. + * Used in numdirtywakeup(), bufspacewakeup(), bufcountwakeup(), bwillwrite(), + * getnewbuf(), and getblk(). + */ +static int needsbuffer; + +/* + * Mask for index into the buffer hash table, which needs to be power of 2 in + * size. Set in kern_vfs_bio_buffer_alloc. + */ +static int bufhashmask; + +/* + * Hash table for all buffers, with a linked list hanging from each table + * entry. Set in kern_vfs_bio_buffer_alloc, initialized in buf_init. + */ +static LIST_HEAD(bufhashhdr, buf) *bufhashtbl; + +/* + * Somewhere to store buffers when they are not in another list, to always + * have them in a list (and thus being able to use the same set of operations + * on them.) + */ +static struct bufhashhdr invalhash; + +/* + * Definitions for the buffer free lists. + */ +#define BUFFER_QUEUES 6 /* number of free buffer queues */ + +#define QUEUE_NONE 0 /* on no queue */ +#define QUEUE_LOCKED 1 /* locked buffers */ +#define QUEUE_CLEAN 2 /* non-B_DELWRI buffers */ +#define QUEUE_DIRTY 3 /* B_DELWRI buffers */ +#define QUEUE_EMPTYKVA 4 /* empty buffer headers w/KVA assignment */ +#define QUEUE_EMPTY 5 /* empty buffer headers */ + +/* Queues for free buffers with various properties */ +static TAILQ_HEAD(bqueues, buf) bufqueues[BUFFER_QUEUES] = { { 0 } }; +/* + * Single global constant for BUF_WMESG, to avoid getting multiple references. + * buf_wmesg is referred from macros. + */ +const char *buf_wmesg = BUF_WMESG; + +#define VFS_BIO_NEED_ANY 0x01 /* any freeable buffer */ +#define VFS_BIO_NEED_DIRTYFLUSH 0x02 /* waiting for dirty buffer flush */ +#define VFS_BIO_NEED_FREE 0x04 /* wait for free bufs, hi hysteresis */ +#define VFS_BIO_NEED_BUFSPACE 0x08 /* wait for buf space, lo hysteresis */ + +/* + * Buffer hash table code. Note that the logical block scans linearly, which + * gives us some L1 cache locality. + */ + +static __inline +struct bufhashhdr * +bufhash(struct vnode *vnp, daddr_t bn) +{ + return(&bufhashtbl[(((uintptr_t)(vnp) >> 7) + (int)bn) & bufhashmask]); +} + +/* + * numdirtywakeup: + * + * If someone is blocked due to there being too many dirty buffers, + * and numdirtybuffers is now reasonable, wake them up. + */ + +static __inline void +numdirtywakeup(int level) +{ + if (numdirtybuffers <= level) { + if (needsbuffer & VFS_BIO_NEED_DIRTYFLUSH) { + needsbuffer &= ~VFS_BIO_NEED_DIRTYFLUSH; + wakeup(&needsbuffer); + } + } +} + +/* + * bufspacewakeup: + * + * Called when buffer space is potentially available for recovery. + * getnewbuf() will block on this flag when it is unable to free + * sufficient buffer space. Buffer space becomes recoverable when + * bp's get placed back in the queues. + */ + +static __inline void +bufspacewakeup(void) +{ + /* + * If someone is waiting for BUF space, wake them up. Even + * though we haven't freed the kva space yet, the waiting + * process will be able to now. + */ + if (needsbuffer & VFS_BIO_NEED_BUFSPACE) { + needsbuffer &= ~VFS_BIO_NEED_BUFSPACE; + wakeup(&needsbuffer); + } +} + +/* + * runningbufwakeup() - in-progress I/O accounting. + * + */ +static __inline void +runningbufwakeup(struct buf *bp) +{ + if (bp->b_runningbufspace) { + runningbufspace -= bp->b_runningbufspace; + bp->b_runningbufspace = 0; + if (runningbufreq && runningbufspace <= lorunningspace) { + runningbufreq = 0; + wakeup(&runningbufreq); + } + } +} + +/* + * bufcountwakeup: + * + * Called when a buffer has been added to one of the free queues to + * account for the buffer and to wakeup anyone waiting for free buffers. + * This typically occurs when large amounts of metadata are being handled + * by the buffer cache ( else buffer space runs out first, usually ). + */ + +static __inline void +bufcountwakeup(void) +{ + ++numfreebuffers; + if (needsbuffer) { + needsbuffer &= ~VFS_BIO_NEED_ANY; + if (numfreebuffers >= hifreebuffers) + needsbuffer &= ~VFS_BIO_NEED_FREE; + wakeup(&needsbuffer); + } +} + +/* + * waitrunningbufspace() + * + * runningbufspace is a measure of the amount of I/O currently + * running. This routine is used in async-write situations to + * prevent creating huge backups of pending writes to a device. + * Only asynchronous writes are governed by this function. + * + * Reads will adjust runningbufspace, but will not block based on it. + * The read load has a side effect of reducing the allowed write load. + * + * This does NOT turn an async write into a sync write. It waits + * for earlier writes to complete and generally returns before the + * caller's write has reached the device. + */ +static __inline void +waitrunningbufspace(void) +{ + /* + * XXX race against wakeup interrupt, currently + * protected by Giant. FIXME! + */ + while (runningbufspace > hirunningspace) { + ++runningbufreq; + tsleep(&runningbufreq, PVM, "wdrain", 0); + } +} + + +/* + * vfs_buf_test_cache: + * + * Called when a buffer is extended. This function clears the B_CACHE + * bit if the newly extended portion of the buffer does not contain + * valid data. + */ +static __inline__ +void +vfs_buf_test_cache(struct buf *bp, + vm_ooffset_t foff, vm_offset_t off, vm_offset_t size, + vm_page_t m) +{ + GIANT_REQUIRED; + + if (bp->b_flags & B_CACHE) { + int base = (foff + off) & PAGE_MASK; + if (vm_page_is_valid(m, base, size) == 0) + bp->b_flags &= ~B_CACHE; + } +} + +/* Wake up the buffer deamon if necessary */ +static __inline__ +void +bd_wakeup(int dirtybuflevel) +{ + if (bd_request == 0 && numdirtybuffers >= dirtybuflevel) { + bd_request = 1; + wakeup(&bd_request); + } +} + +/* + * bd_speedup - speedup the buffer cache flushing code + */ + +static __inline__ +void +bd_speedup(void) +{ + bd_wakeup(1); +} + +/* + * Calculating buffer cache scaling values and reserve space for buffer + * headers. This is called during low level kernel initialization and + * may be called more then once. We CANNOT write to the memory area + * being reserved at this time. + */ +caddr_t +kern_vfs_bio_buffer_alloc(caddr_t v, int physmem_est) +{ + /* + * physmem_est is in pages. Convert it to kilobytes (assumes + * PAGE_SIZE is >= 1K) + */ + physmem_est = physmem_est * (PAGE_SIZE / 1024); + + /* + * The nominal buffer size (and minimum KVA allocation) is BKVASIZE. + * For the first 64MB of ram nominally allocate sufficient buffers to + * cover 1/4 of our ram. Beyond the first 64MB allocate additional + * buffers to cover 1/20 of our ram over 64MB. When auto-sizing + * the buffer cache we limit the eventual kva reservation to + * maxbcache bytes. + * + * factor represents the 1/4 x ram conversion. + */ + if (nbuf == 0) { + int factor = 4 * BKVASIZE / 1024; + + nbuf = 50; + if (physmem_est > 4096) + nbuf += min((physmem_est - 4096) / factor, + 65536 / factor); + if (physmem_est > 65536) + nbuf += (physmem_est - 65536) * 2 / (factor * 5); + + if (maxbcache && nbuf > maxbcache / BKVASIZE) + nbuf = maxbcache / BKVASIZE; + } + +#if 0 + /* + * Do not allow the buffer_map to be more then 1/2 the size of the + * kernel_map. + */ + if (nbuf > (kernel_map->max_offset - kernel_map->min_offset) / + (BKVASIZE * 2)) { + nbuf = (kernel_map->max_offset - kernel_map->min_offset) / + (BKVASIZE * 2); + printf("Warning: nbufs capped at %d\n", nbuf); + } +#endif + + /* + * swbufs are used as temporary holders for I/O, such as paging I/O. + * We have no less then 16 and no more then 256. + */ + nswbuf = max(min(nbuf/4, 256), 16); + + /* + * Reserve space for the buffer cache buffers + */ + swbuf = (void *)v; + v = (caddr_t)(swbuf + nswbuf); + buf = (void *)v; + v = (caddr_t)(buf + nbuf); + + /* + * Calculate the hash table size and reserve space + */ + for (bufhashmask = 8; bufhashmask < nbuf / 4; bufhashmask <<= 1) + ; + bufhashtbl = (void *)v; + v = (caddr_t)(bufhashtbl + bufhashmask); + --bufhashmask; + + return(v); +} + +/* Initialize the buffer subsystem. Called before use of any buffers. */ +void +bufinit(void) +{ + struct buf *bp; + int i; + + GIANT_REQUIRED; + + LIST_INIT(&invalhash); + mtx_init(&buftimelock, "buftime lock", NULL, MTX_DEF); + + for (i = 0; i <= bufhashmask; i++) + LIST_INIT(&bufhashtbl[i]); + + /* next, make a null set of free lists */ + for (i = 0; i < BUFFER_QUEUES; i++) + TAILQ_INIT(&bufqueues[i]); + + /* finally, initialize each buffer header and stick on empty q */ + for (i = 0; i < nbuf; i++) { + bp = &buf[i]; + bzero(bp, sizeof *bp); + bp->b_flags = B_INVAL; /* we're just an empty header */ + bp->b_dev = NODEV; + bp->b_rcred = NOCRED; + bp->b_wcred = NOCRED; + bp->b_qindex = QUEUE_EMPTY; + bp->b_xflags = 0; + LIST_INIT(&bp->b_dep); + BUF_LOCKINIT(bp); + TAILQ_INSERT_TAIL(&bufqueues[QUEUE_EMPTY], bp, b_freelist); + LIST_INSERT_HEAD(&invalhash, bp, b_hash); + } + + /* + * maxbufspace is the absolute maximum amount of buffer space we are + * allowed to reserve in KVM and in real terms. The absolute maximum + * is nominally used by buf_daemon. hibufspace is the nominal maximum + * used by most other processes. The differential is required to + * ensure that buf_daemon is able to run when other processes might + * be blocked waiting for buffer space. + * + * maxbufspace is based on BKVASIZE. Allocating buffers larger then + * this may result in KVM fragmentation which is not handled optimally + * by the system. + */ + maxbufspace = nbuf * BKVASIZE; + hibufspace = imax(3 * maxbufspace / 4, maxbufspace - MAXBSIZE * 10); + lobufspace = hibufspace - MAXBSIZE; + + lorunningspace = 512 * 1024; + hirunningspace = 1024 * 1024; + +/* + * Limit the amount of malloc memory since it is wired permanently into + * the kernel space. Even though this is accounted for in the buffer + * allocation, we don't want the malloced region to grow uncontrolled. + * The malloc scheme improves memory utilization significantly on average + * (small) directories. + */ + maxbufmallocspace = hibufspace / 20; + +/* + * Reduce the chance of a deadlock occuring by limiting the number + * of delayed-write dirty buffers we allow to stack up. + */ + hidirtybuffers = nbuf / 4 + 20; + numdirtybuffers = 0; +/* + * To support extreme low-memory systems, make sure hidirtybuffers cannot + * eat up all available buffer space. This occurs when our minimum cannot + * be met. We try to size hidirtybuffers to 3/4 our buffer space assuming + * BKVASIZE'd (8K) buffers. + */ + while (hidirtybuffers * BKVASIZE > 3 * hibufspace / 4) { + hidirtybuffers >>= 1; + } + lodirtybuffers = hidirtybuffers / 2; + +/* + * Try to keep the number of free buffers in the specified range, + * and give special processes (e.g. like buf_daemon) access to an + * emergency reserve. + */ + lofreebuffers = nbuf / 18 + 5; + hifreebuffers = 2 * lofreebuffers; + numfreebuffers = nbuf; + +/* + * Maximum number of async ops initiated per buf_daemon loop. This is + * somewhat of a hack at the moment, we really need to limit ourselves + * based on the number of bytes of I/O in-transit that were initiated + * from buf_daemon. + */ + + bogus_offset = kmem_alloc_pageable(kernel_map, PAGE_SIZE); + bogus_page = vm_page_alloc(kernel_object, + ((bogus_offset - VM_MIN_KERNEL_ADDRESS) >> PAGE_SHIFT), + VM_ALLOC_NORMAL); + cnt.v_wire_count++; +} + +/* + * bfreekva() - free the kva allocation for a buffer. + * + * Must be called at splbio() or higher as this is the only locking for + * buffer_map. + * + * Since this call frees up buffer space, we call bufspacewakeup(). + */ +static void +bfreekva(struct buf * bp) +{ + GIANT_REQUIRED; + + if (bp->b_kvasize) { + ++buffreekvacnt; + bufspace -= bp->b_kvasize; + vm_map_delete(buffer_map, + (vm_offset_t) bp->b_kvabase, + (vm_offset_t) bp->b_kvabase + bp->b_kvasize + ); + bp->b_kvasize = 0; + bufspacewakeup(); + } +} + +/* + * bremfree: + * + * Remove the buffer from the appropriate free list. + */ +void +bremfree(struct buf * bp) +{ + int s = splbio(); + int old_qindex = bp->b_qindex; + + GIANT_REQUIRED; + + if (bp->b_qindex != QUEUE_NONE) { + KASSERT(BUF_REFCNT(bp) == 1, ("bremfree: bp %p not locked",bp)); + TAILQ_REMOVE(&bufqueues[bp->b_qindex], bp, b_freelist); + bp->b_qindex = QUEUE_NONE; + } else { + if (BUF_REFCNT(bp) <= 1) + panic("bremfree: removing a buffer not on a queue"); + } + + /* + * Fixup numfreebuffers count. If the buffer is invalid or not + * delayed-write, and it was on the EMPTY, LRU, or AGE queues, + * the buffer was free and we must decrement numfreebuffers. + */ + if ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0) { + switch(old_qindex) { + case QUEUE_DIRTY: + case QUEUE_CLEAN: + case QUEUE_EMPTY: + case QUEUE_EMPTYKVA: + --numfreebuffers; + break; + default: + break; + } + } + splx(s); +} + + +/* + * Get a buffer with the specified data. Look in the cache first. We + * must clear BIO_ERROR and B_INVAL prior to initiating I/O. If B_CACHE + * is set, the buffer is valid and we do not have to do anything ( see + * getblk() ). This is really just a special case of breadn(). + */ +int +bread(struct vnode * vp, daddr_t blkno, int size, struct ucred * cred, + struct buf ** bpp) +{ + + return (breadn(vp, blkno, size, 0, 0, 0, cred, bpp)); +} + +/* + * Operates like bread, but also starts asynchronous I/O on + * read-ahead blocks. We must clear BIO_ERROR and B_INVAL prior + * to initiating I/O . If B_CACHE is set, the buffer is valid + * and we do not have to do anything. + */ +int +breadn(struct vnode * vp, daddr_t blkno, int size, + daddr_t * rablkno, int *rabsize, + int cnt, struct ucred * cred, struct buf ** bpp) +{ + struct buf *bp, *rabp; + int i; + int rv = 0, readwait = 0; + + *bpp = bp = getblk(vp, blkno, size, 0, 0); + + /* if not found in cache, do some I/O */ + if ((bp->b_flags & B_CACHE) == 0) { + if (curthread != PCPU_GET(idlethread)) + curthread->td_proc->p_stats->p_ru.ru_inblock++; + bp->b_iocmd = BIO_READ; + bp->b_flags &= ~B_INVAL; + bp->b_ioflags &= ~BIO_ERROR; + if (bp->b_rcred == NOCRED && cred != NOCRED) + bp->b_rcred = crhold(cred); + vfs_busy_pages(bp, 0); + VOP_STRATEGY(vp, bp); + ++readwait; + } + + for (i = 0; i < cnt; i++, rablkno++, rabsize++) { + if (inmem(vp, *rablkno)) + continue; + rabp = getblk(vp, *rablkno, *rabsize, 0, 0); + + if ((rabp->b_flags & B_CACHE) == 0) { + if (curthread != PCPU_GET(idlethread)) + curthread->td_proc->p_stats->p_ru.ru_inblock++; + rabp->b_flags |= B_ASYNC; + rabp->b_flags &= ~B_INVAL; + rabp->b_ioflags &= ~BIO_ERROR; + rabp->b_iocmd = BIO_READ; + if (rabp->b_rcred == NOCRED && cred != NOCRED) + rabp->b_rcred = crhold(cred); + vfs_busy_pages(rabp, 0); + BUF_KERNPROC(rabp); + VOP_STRATEGY(vp, rabp); + } else { + brelse(rabp); + } + } + + if (readwait) { + rv = bufwait(bp); + } + return (rv); +} + +/* + * Write, release buffer on completion. (Done by iodone + * if async). Do not bother writing anything if the buffer + * is invalid. + * + * Note that we set B_CACHE here, indicating that buffer is + * fully valid and thus cacheable. This is true even of NFS + * now so we set it generally. This could be set either here + * or in biodone() since the I/O is synchronous. We put it + * here. + */ + +int +bwrite(struct buf * bp) +{ + int oldflags, s; + struct buf *newbp; + + if (bp->b_flags & B_INVAL) { + brelse(bp); + return (0); + } + + oldflags = bp->b_flags; + + if (BUF_REFCNT(bp) == 0) + panic("bwrite: buffer is not busy???"); + s = splbio(); + /* + * If a background write is already in progress, delay + * writing this block if it is asynchronous. Otherwise + * wait for the background write to complete. + */ + if (bp->b_xflags & BX_BKGRDINPROG) { + if (bp->b_flags & B_ASYNC) { + splx(s); + bdwrite(bp); + return (0); + } + bp->b_xflags |= BX_BKGRDWAIT; + tsleep(&bp->b_xflags, PRIBIO, "bwrbg", 0); + if (bp->b_xflags & BX_BKGRDINPROG) + panic("bwrite: still writing"); + } + + /* Mark the buffer clean */ + bundirty(bp); + + /* + * If this buffer is marked for background writing and we + * do not have to wait for it, make a copy and write the + * copy so as to leave this buffer ready for further use. + * + * This optimization eats a lot of memory. If we have a page + * or buffer shortfall we can't do it. + */ + if (dobkgrdwrite && (bp->b_xflags & BX_BKGRDWRITE) && + (bp->b_flags & B_ASYNC) && + !vm_page_count_severe() && + !buf_dirty_count_severe()) { + if (bp->b_iodone != NULL) { + printf("bp->b_iodone = %p\n", bp->b_iodone); + panic("bwrite: need chained iodone"); + } + + /* get a new block */ + newbp = geteblk(bp->b_bufsize); + + /* set it to be identical to the old block */ + memcpy(newbp->b_data, bp->b_data, bp->b_bufsize); + bgetvp(bp->b_vp, newbp); + newbp->b_lblkno = bp->b_lblkno; + newbp->b_blkno = bp->b_blkno; + newbp->b_offset = bp->b_offset; + newbp->b_iodone = vfs_backgroundwritedone; + newbp->b_flags |= B_ASYNC; + newbp->b_flags &= ~B_INVAL; + + /* move over the dependencies */ + if (LIST_FIRST(&bp->b_dep) != NULL) + buf_movedeps(bp, newbp); + + /* + * Initiate write on the copy, release the original to + * the B_LOCKED queue so that it cannot go away until + * the background write completes. If not locked it could go + * away and then be reconstituted while it was being written. + * If the reconstituted buffer were written, we could end up + * with two background copies being written at the same time. + */ + bp->b_xflags |= BX_BKGRDINPROG; + bp->b_flags |= B_LOCKED; + bqrelse(bp); + bp = newbp; + } + + bp->b_flags &= ~B_DONE; + bp->b_ioflags &= ~BIO_ERROR; + bp->b_flags |= B_WRITEINPROG | B_CACHE; + bp->b_iocmd = BIO_WRITE; + + bp->b_vp->v_numoutput++; + vfs_busy_pages(bp, 1); + + /* + * Normal bwrites pipeline writes + */ + bp->b_runningbufspace = bp->b_bufsize; + runningbufspace += bp->b_runningbufspace; + + if (curthread != PCPU_GET(idlethread)) + curthread->td_proc->p_stats->p_ru.ru_oublock++; + splx(s); + if (oldflags & B_ASYNC) + BUF_KERNPROC(bp); + BUF_STRATEGY(bp); + + if ((oldflags & B_ASYNC) == 0) { + int rtval = bufwait(bp); + brelse(bp); + return (rtval); + } else if ((oldflags & B_NOWDRAIN) == 0) { + /* + * don't allow the async write to saturate the I/O + * system. Deadlocks can occur only if a device strategy + * routine (like in MD) turns around and issues another + * high-level write, in which case B_NOWDRAIN is expected + * to be set. Otherwise we will not deadlock here because + * we are blocking waiting for I/O that is already in-progress + * to complete. + */ + waitrunningbufspace(); + } + + return (0); +} + +/* + * Complete a background write started from bwrite. + */ +static void +vfs_backgroundwritedone(bp) + struct buf *bp; +{ + struct buf *origbp; + + /* + * Find the original buffer that we are writing. + */ + if ((origbp = gbincore(bp->b_vp, bp->b_lblkno)) == NULL) + panic("backgroundwritedone: lost buffer"); + /* + * Process dependencies then return any unfinished ones. + */ + if (LIST_FIRST(&bp->b_dep) != NULL) + buf_complete(bp); + if (LIST_FIRST(&bp->b_dep) != NULL) + buf_movedeps(bp, origbp); + /* + * Clear the BX_BKGRDINPROG flag in the original buffer + * and awaken it if it is waiting for the write to complete. + * If BX_BKGRDINPROG is not set in the original buffer it must + * have been released and re-instantiated - which is not legal. + */ + KASSERT((origbp->b_xflags & BX_BKGRDINPROG), + ("backgroundwritedone: lost buffer2")); + origbp->b_xflags &= ~BX_BKGRDINPROG; + if (origbp->b_xflags & BX_BKGRDWAIT) { + origbp->b_xflags &= ~BX_BKGRDWAIT; + wakeup(&origbp->b_xflags); + } + /* + * Clear the B_LOCKED flag and remove it from the locked + * queue if it currently resides there. + */ + origbp->b_flags &= ~B_LOCKED; + if (BUF_LOCK(origbp, LK_EXCLUSIVE | LK_NOWAIT) == 0) { + bremfree(origbp); + bqrelse(origbp); + } + /* + * This buffer is marked B_NOCACHE, so when it is released + * by biodone, it will be tossed. We mark it with BIO_READ + * to avoid biodone doing a second vwakeup. + */ + bp->b_flags |= B_NOCACHE; + bp->b_iocmd = BIO_READ; + bp->b_flags &= ~(B_CACHE | B_DONE); + bp->b_iodone = 0; + bufdone(bp); +} + +/* + * Delayed write. (Buffer is marked dirty). Do not bother writing + * anything if the buffer is marked invalid. + * + * Note that since the buffer must be completely valid, we can safely + * set B_CACHE. In fact, we have to set B_CACHE here rather then in + * biodone() in order to prevent getblk from writing the buffer + * out synchronously. + */ +void +bdwrite(struct buf * bp) +{ + GIANT_REQUIRED; + + if (BUF_REFCNT(bp) == 0) + panic("bdwrite: buffer is not busy"); + + if (bp->b_flags & B_INVAL) { + brelse(bp); + return; + } + bdirty(bp); + + /* + * Set B_CACHE, indicating that the buffer is fully valid. This is + * true even of NFS now. + */ + bp->b_flags |= B_CACHE; + + /* + * This bmap keeps the system from needing to do the bmap later, + * perhaps when the system is attempting to do a sync. Since it + * is likely that the indirect block -- or whatever other datastructure + * that the filesystem needs is still in memory now, it is a good + * thing to do this. Note also, that if the pageout daemon is + * requesting a sync -- there might not be enough memory to do + * the bmap then... So, this is important to do. + */ + if (bp->b_lblkno == bp->b_blkno) { + VOP_BMAP(bp->b_vp, bp->b_lblkno, NULL, &bp->b_blkno, NULL, NULL); + } + + /* + * Set the *dirty* buffer range based upon the VM system dirty pages. + */ + vfs_setdirty(bp); + + /* + * We need to do this here to satisfy the vnode_pager and the + * pageout daemon, so that it thinks that the pages have been + * "cleaned". Note that since the pages are in a delayed write + * buffer -- the VFS layer "will" see that the pages get written + * out on the next sync, or perhaps the cluster will be completed. + */ + vfs_clean_pages(bp); + bqrelse(bp); + + /* + * Wakeup the buffer flushing daemon if we have a lot of dirty + * buffers (midpoint between our recovery point and our stall + * point). + */ + bd_wakeup((lodirtybuffers + hidirtybuffers) / 2); + + /* + * note: we cannot initiate I/O from a bdwrite even if we wanted to, + * due to the softdep code. + */ +} + +/* + * bdirty: + * + * Turn buffer into delayed write request. We must clear BIO_READ and + * B_RELBUF, and we must set B_DELWRI. We reassign the buffer to + * itself to properly update it in the dirty/clean lists. We mark it + * B_DONE to ensure that any asynchronization of the buffer properly + * clears B_DONE ( else a panic will occur later ). + * + * bdirty() is kinda like bdwrite() - we have to clear B_INVAL which + * might have been set pre-getblk(). Unlike bwrite/bdwrite, bdirty() + * should only be called if the buffer is known-good. + * + * Since the buffer is not on a queue, we do not update the numfreebuffers + * count. + * + * Must be called at splbio(). + * The buffer must be on QUEUE_NONE. + */ +void +bdirty(bp) + struct buf *bp; +{ + KASSERT(bp->b_qindex == QUEUE_NONE, + ("bdirty: buffer %p still on queue %d", bp, bp->b_qindex)); + bp->b_flags &= ~(B_RELBUF); + bp->b_iocmd = BIO_WRITE; + + if ((bp->b_flags & B_DELWRI) == 0) { + bp->b_flags |= B_DONE | B_DELWRI; + reassignbuf(bp, bp->b_vp); + ++numdirtybuffers; + bd_wakeup((lodirtybuffers + hidirtybuffers) / 2); + } +} + +/* + * bundirty: + * + * Clear B_DELWRI for buffer. + * + * Since the buffer is not on a queue, we do not update the numfreebuffers + * count. + * + * Must be called at splbio(). + * The buffer must be on QUEUE_NONE. + */ + +void +bundirty(bp) + struct buf *bp; +{ + KASSERT(bp->b_qindex == QUEUE_NONE, + ("bundirty: buffer %p still on queue %d", bp, bp->b_qindex)); + + if (bp->b_flags & B_DELWRI) { + bp->b_flags &= ~B_DELWRI; + reassignbuf(bp, bp->b_vp); + --numdirtybuffers; + numdirtywakeup(lodirtybuffers); + } + /* + * Since it is now being written, we can clear its deferred write flag. + */ + bp->b_flags &= ~B_DEFERRED; +} + +/* + * bawrite: + * + * Asynchronous write. Start output on a buffer, but do not wait for + * it to complete. The buffer is released when the output completes. + * + * bwrite() ( or the VOP routine anyway ) is responsible for handling + * B_INVAL buffers. Not us. + */ +void +bawrite(struct buf * bp) +{ + bp->b_flags |= B_ASYNC; + (void) BUF_WRITE(bp); +} + +/* + * bwillwrite: + * + * Called prior to the locking of any vnodes when we are expecting to + * write. We do not want to starve the buffer cache with too many + * dirty buffers so we block here. By blocking prior to the locking + * of any vnodes we attempt to avoid the situation where a locked vnode + * prevents the various system daemons from flushing related buffers. + */ + +void +bwillwrite(void) +{ + if (numdirtybuffers >= hidirtybuffers) { + int s; + + mtx_lock(&Giant); + s = splbio(); + while (numdirtybuffers >= hidirtybuffers) { + bd_wakeup(1); + needsbuffer |= VFS_BIO_NEED_DIRTYFLUSH; + tsleep(&needsbuffer, (PRIBIO + 4), "flswai", 0); + } + splx(s); + mtx_unlock(&Giant); + } +} + +/* + * Return true if we have too many dirty buffers. + */ +int +buf_dirty_count_severe(void) +{ + return(numdirtybuffers >= hidirtybuffers); +} + +/* + * brelse: + * + * Release a busy buffer and, if requested, free its resources. The + * buffer will be stashed in the appropriate bufqueue[] allowing it + * to be accessed later as a cache entity or reused for other purposes. + */ +void +brelse(struct buf * bp) +{ + int s; + + GIANT_REQUIRED; + + KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), + ("brelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp)); + + s = splbio(); + + if (bp->b_flags & B_LOCKED) + bp->b_ioflags &= ~BIO_ERROR; + + if (bp->b_iocmd == BIO_WRITE && + (bp->b_ioflags & BIO_ERROR) && + !(bp->b_flags & B_INVAL)) { + /* + * Failed write, redirty. Must clear BIO_ERROR to prevent + * pages from being scrapped. If B_INVAL is set then + * this case is not run and the next case is run to + * destroy the buffer. B_INVAL can occur if the buffer + * is outside the range supported by the underlying device. + */ + bp->b_ioflags &= ~BIO_ERROR; + bdirty(bp); + } else if ((bp->b_flags & (B_NOCACHE | B_INVAL)) || + (bp->b_ioflags & BIO_ERROR) || + bp->b_iocmd == BIO_DELETE || (bp->b_bufsize <= 0)) { + /* + * Either a failed I/O or we were asked to free or not + * cache the buffer. + */ + bp->b_flags |= B_INVAL; + if (LIST_FIRST(&bp->b_dep) != NULL) + buf_deallocate(bp); + if (bp->b_flags & B_DELWRI) { + --numdirtybuffers; + numdirtywakeup(lodirtybuffers); + } + bp->b_flags &= ~(B_DELWRI | B_CACHE); + if ((bp->b_flags & B_VMIO) == 0) { + if (bp->b_bufsize) + allocbuf(bp, 0); + if (bp->b_vp) + brelvp(bp); + } + } + + /* + * We must clear B_RELBUF if B_DELWRI is set. If vfs_vmio_release() + * is called with B_DELWRI set, the underlying pages may wind up + * getting freed causing a previous write (bdwrite()) to get 'lost' + * because pages associated with a B_DELWRI bp are marked clean. + * + * We still allow the B_INVAL case to call vfs_vmio_release(), even + * if B_DELWRI is set. + * + * If B_DELWRI is not set we may have to set B_RELBUF if we are low + * on pages to return pages to the VM page queues. + */ + if (bp->b_flags & B_DELWRI) + bp->b_flags &= ~B_RELBUF; + else if (vm_page_count_severe() && !(bp->b_xflags & BX_BKGRDINPROG)) + bp->b_flags |= B_RELBUF; + + /* + * VMIO buffer rundown. It is not very necessary to keep a VMIO buffer + * constituted, not even NFS buffers now. Two flags effect this. If + * B_INVAL, the struct buf is invalidated but the VM object is kept + * around ( i.e. so it is trivial to reconstitute the buffer later ). + * + * If BIO_ERROR or B_NOCACHE is set, pages in the VM object will be + * invalidated. BIO_ERROR cannot be set for a failed write unless the + * buffer is also B_INVAL because it hits the re-dirtying code above. + * + * Normally we can do this whether a buffer is B_DELWRI or not. If + * the buffer is an NFS buffer, it is tracking piecemeal writes or + * the commit state and we cannot afford to lose the buffer. If the + * buffer has a background write in progress, we need to keep it + * around to prevent it from being reconstituted and starting a second + * background write. + */ + if ((bp->b_flags & B_VMIO) + && !(bp->b_vp->v_tag == VT_NFS && + !vn_isdisk(bp->b_vp, NULL) && + (bp->b_flags & B_DELWRI)) + ) { + + int i, j, resid; + vm_page_t m; + off_t foff; + vm_pindex_t poff; + vm_object_t obj; + struct vnode *vp; + + vp = bp->b_vp; + + /* + * Get the base offset and length of the buffer. Note that + * in the VMIO case if the buffer block size is not + * page-aligned then b_data pointer may not be page-aligned. + * But our b_pages[] array *IS* page aligned. + * + * block sizes less then DEV_BSIZE (usually 512) are not + * supported due to the page granularity bits (m->valid, + * m->dirty, etc...). + * + * See man buf(9) for more information + */ + resid = bp->b_bufsize; + foff = bp->b_offset; + + for (i = 0; i < bp->b_npages; i++) { + int had_bogus = 0; + + m = bp->b_pages[i]; + vm_page_flag_clear(m, PG_ZERO); + + /* + * If we hit a bogus page, fixup *all* the bogus pages + * now. + */ + if (m == bogus_page) { + VOP_GETVOBJECT(vp, &obj); + poff = OFF_TO_IDX(bp->b_offset); + had_bogus = 1; + + for (j = i; j < bp->b_npages; j++) { + vm_page_t mtmp; + mtmp = bp->b_pages[j]; + if (mtmp == bogus_page) { + mtmp = vm_page_lookup(obj, poff + j); + if (!mtmp) { + panic("brelse: page missing\n"); + } + bp->b_pages[j] = mtmp; + } + } + + if ((bp->b_flags & B_INVAL) == 0) { + pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages); + } + m = bp->b_pages[i]; + } + if ((bp->b_flags & B_NOCACHE) || (bp->b_ioflags & BIO_ERROR)) { + int poffset = foff & PAGE_MASK; + int presid = resid > (PAGE_SIZE - poffset) ? + (PAGE_SIZE - poffset) : resid; + + KASSERT(presid >= 0, ("brelse: extra page")); + vm_page_set_invalid(m, poffset, presid); + if (had_bogus) + printf("avoided corruption bug in bogus_page/brelse code\n"); + } + resid -= PAGE_SIZE - (foff & PAGE_MASK); + foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK; + } + + if (bp->b_flags & (B_INVAL | B_RELBUF)) + vfs_vmio_release(bp); + + } else if (bp->b_flags & B_VMIO) { + + if (bp->b_flags & (B_INVAL | B_RELBUF)) { + vfs_vmio_release(bp); + } + + } + + if (bp->b_qindex != QUEUE_NONE) + panic("brelse: free buffer onto another queue???"); + if (BUF_REFCNT(bp) > 1) { + /* do not release to free list */ + BUF_UNLOCK(bp); + splx(s); + return; + } + + /* enqueue */ + + /* buffers with no memory */ + if (bp->b_bufsize == 0) { + bp->b_flags |= B_INVAL; + bp->b_xflags &= ~BX_BKGRDWRITE; + if (bp->b_xflags & BX_BKGRDINPROG) + panic("losing buffer 1"); + if (bp->b_kvasize) { + bp->b_qindex = QUEUE_EMPTYKVA; + } else { + bp->b_qindex = QUEUE_EMPTY; + } + TAILQ_INSERT_HEAD(&bufqueues[bp->b_qindex], bp, b_freelist); + LIST_REMOVE(bp, b_hash); + LIST_INSERT_HEAD(&invalhash, bp, b_hash); + bp->b_dev = NODEV; + /* buffers with junk contents */ + } else if (bp->b_flags & (B_INVAL | B_NOCACHE | B_RELBUF) || + (bp->b_ioflags & BIO_ERROR)) { + bp->b_flags |= B_INVAL; + bp->b_xflags &= ~BX_BKGRDWRITE; + if (bp->b_xflags & BX_BKGRDINPROG) + panic("losing buffer 2"); + bp->b_qindex = QUEUE_CLEAN; + TAILQ_INSERT_HEAD(&bufqueues[QUEUE_CLEAN], bp, b_freelist); + LIST_REMOVE(bp, b_hash); + LIST_INSERT_HEAD(&invalhash, bp, b_hash); + bp->b_dev = NODEV; + + /* buffers that are locked */ + } else if (bp->b_flags & B_LOCKED) { + bp->b_qindex = QUEUE_LOCKED; + TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LOCKED], bp, b_freelist); + + /* remaining buffers */ + } else { + if (bp->b_flags & B_DELWRI) + bp->b_qindex = QUEUE_DIRTY; + else + bp->b_qindex = QUEUE_CLEAN; + if (bp->b_flags & B_AGE) + TAILQ_INSERT_HEAD(&bufqueues[bp->b_qindex], bp, b_freelist); + else + TAILQ_INSERT_TAIL(&bufqueues[bp->b_qindex], bp, b_freelist); + } + + /* + * If B_INVAL, clear B_DELWRI. We've already placed the buffer + * on the correct queue. + */ + if ((bp->b_flags & (B_INVAL|B_DELWRI)) == (B_INVAL|B_DELWRI)) + bundirty(bp); + + /* + * Fixup numfreebuffers count. The bp is on an appropriate queue + * unless locked. We then bump numfreebuffers if it is not B_DELWRI. + * We've already handled the B_INVAL case ( B_DELWRI will be clear + * if B_INVAL is set ). + */ + + if ((bp->b_flags & B_LOCKED) == 0 && !(bp->b_flags & B_DELWRI)) + bufcountwakeup(); + + /* + * Something we can maybe free or reuse + */ + if (bp->b_bufsize || bp->b_kvasize) + bufspacewakeup(); + + /* unlock */ + BUF_UNLOCK(bp); + bp->b_flags &= ~(B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF | + B_DIRECT | B_NOWDRAIN); + if ((bp->b_flags & B_DELWRI) == 0 && (bp->b_xflags & BX_VNDIRTY)) + panic("brelse: not dirty"); + splx(s); +} + +/* + * Release a buffer back to the appropriate queue but do not try to free + * it. The buffer is expected to be used again soon. + * + * bqrelse() is used by bdwrite() to requeue a delayed write, and used by + * biodone() to requeue an async I/O on completion. It is also used when + * known good buffers need to be requeued but we think we may need the data + * again soon. + * + * XXX we should be able to leave the B_RELBUF hint set on completion. + */ +void +bqrelse(struct buf * bp) +{ + int s; + + s = splbio(); + + KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), ("bqrelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp)); + + if (bp->b_qindex != QUEUE_NONE) + panic("bqrelse: free buffer onto another queue???"); + if (BUF_REFCNT(bp) > 1) { + /* do not release to free list */ + BUF_UNLOCK(bp); + splx(s); + return; + } + if (bp->b_flags & B_LOCKED) { + bp->b_ioflags &= ~BIO_ERROR; + bp->b_qindex = QUEUE_LOCKED; + TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LOCKED], bp, b_freelist); + /* buffers with stale but valid contents */ + } else if (bp->b_flags & B_DELWRI) { + bp->b_qindex = QUEUE_DIRTY; + TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], bp, b_freelist); + } else if (vm_page_count_severe()) { + /* + * We are too low on memory, we have to try to free the + * buffer (most importantly: the wired pages making up its + * backing store) *now*. + */ + splx(s); + brelse(bp); + return; + } else { + bp->b_qindex = QUEUE_CLEAN; + TAILQ_INSERT_TAIL(&bufqueues[QUEUE_CLEAN], bp, b_freelist); + } + + if ((bp->b_flags & B_LOCKED) == 0 && + ((bp->b_flags & B_INVAL) || !(bp->b_flags & B_DELWRI))) { + bufcountwakeup(); + } + + /* + * Something we can maybe free or reuse. + */ + if (bp->b_bufsize && !(bp->b_flags & B_DELWRI)) + bufspacewakeup(); + + /* unlock */ + BUF_UNLOCK(bp); + bp->b_flags &= ~(B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF); + if ((bp->b_flags & B_DELWRI) == 0 && (bp->b_xflags & BX_VNDIRTY)) + panic("bqrelse: not dirty"); + splx(s); +} + +/* Give pages used by the bp back to the VM system (where possible) */ +static void +vfs_vmio_release(bp) + struct buf *bp; +{ + int i; + vm_page_t m; + + GIANT_REQUIRED; + + for (i = 0; i < bp->b_npages; i++) { + m = bp->b_pages[i]; + bp->b_pages[i] = NULL; + /* + * In order to keep page LRU ordering consistent, put + * everything on the inactive queue. + */ + vm_page_unwire(m, 0); + /* + * We don't mess with busy pages, it is + * the responsibility of the process that + * busied the pages to deal with them. + */ + if ((m->flags & PG_BUSY) || (m->busy != 0)) + continue; + + if (m->wire_count == 0) { + vm_page_flag_clear(m, PG_ZERO); + /* + * Might as well free the page if we can and it has + * no valid data. We also free the page if the + * buffer was used for direct I/O + */ + if ((bp->b_flags & B_ASYNC) == 0 && !m->valid && + m->hold_count == 0) { + vm_page_busy(m); + vm_page_protect(m, VM_PROT_NONE); + vm_page_free(m); + } else if (bp->b_flags & B_DIRECT) { + vm_page_try_to_free(m); + } else if (vm_page_count_severe()) { + vm_page_try_to_cache(m); + } + } + } + pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages); + + if (bp->b_bufsize) { + bufspacewakeup(); + bp->b_bufsize = 0; + } + bp->b_npages = 0; + bp->b_flags &= ~B_VMIO; + if (bp->b_vp) + brelvp(bp); +} + +/* + * Check to see if a block is currently memory resident. + */ +struct buf * +gbincore(struct vnode * vp, daddr_t blkno) +{ + struct buf *bp; + struct bufhashhdr *bh; + + bh = bufhash(vp, blkno); + + /* Search hash chain */ + LIST_FOREACH(bp, bh, b_hash) { + /* hit */ + if (bp->b_vp == vp && bp->b_lblkno == blkno && + (bp->b_flags & B_INVAL) == 0) { + break; + } + } + return (bp); +} + +/* + * vfs_bio_awrite: + * + * Implement clustered async writes for clearing out B_DELWRI buffers. + * This is much better then the old way of writing only one buffer at + * a time. Note that we may not be presented with the buffers in the + * correct order, so we search for the cluster in both directions. + */ +int +vfs_bio_awrite(struct buf * bp) +{ + int i; + int j; + daddr_t lblkno = bp->b_lblkno; + struct vnode *vp = bp->b_vp; + int s; + int ncl; + struct buf *bpa; + int nwritten; + int size; + int maxcl; + + s = splbio(); + /* + * right now we support clustered writing only to regular files. If + * we find a clusterable block we could be in the middle of a cluster + * rather then at the beginning. + */ + if ((vp->v_type == VREG) && + (vp->v_mount != 0) && /* Only on nodes that have the size info */ + (bp->b_flags & (B_CLUSTEROK | B_INVAL)) == B_CLUSTEROK) { + + size = vp->v_mount->mnt_stat.f_iosize; + maxcl = MAXPHYS / size; + + for (i = 1; i < maxcl; i++) { + if ((bpa = gbincore(vp, lblkno + i)) && + BUF_REFCNT(bpa) == 0 && + ((bpa->b_flags & (B_DELWRI | B_CLUSTEROK | B_INVAL)) == + (B_DELWRI | B_CLUSTEROK)) && + (bpa->b_bufsize == size)) { + if ((bpa->b_blkno == bpa->b_lblkno) || + (bpa->b_blkno != + bp->b_blkno + ((i * size) >> DEV_BSHIFT))) + break; + } else { + break; + } + } + for (j = 1; i + j <= maxcl && j <= lblkno; j++) { + if ((bpa = gbincore(vp, lblkno - j)) && + BUF_REFCNT(bpa) == 0 && + ((bpa->b_flags & (B_DELWRI | B_CLUSTEROK | B_INVAL)) == + (B_DELWRI | B_CLUSTEROK)) && + (bpa->b_bufsize == size)) { + if ((bpa->b_blkno == bpa->b_lblkno) || + (bpa->b_blkno != + bp->b_blkno - ((j * size) >> DEV_BSHIFT))) + break; + } else { + break; + } + } + --j; + ncl = i + j; + /* + * this is a possible cluster write + */ + if (ncl != 1) { + nwritten = cluster_wbuild(vp, size, lblkno - j, ncl); + splx(s); + return nwritten; + } + } + + BUF_LOCK(bp, LK_EXCLUSIVE); + bremfree(bp); + bp->b_flags |= B_ASYNC; + + splx(s); + /* + * default (old) behavior, writing out only one block + * + * XXX returns b_bufsize instead of b_bcount for nwritten? + */ + nwritten = bp->b_bufsize; + (void) BUF_WRITE(bp); + + return nwritten; +} + +/* + * getnewbuf: + * + * Find and initialize a new buffer header, freeing up existing buffers + * in the bufqueues as necessary. The new buffer is returned locked. + * + * Important: B_INVAL is not set. If the caller wishes to throw the + * buffer away, the caller must set B_INVAL prior to calling brelse(). + * + * We block if: + * We have insufficient buffer headers + * We have insufficient buffer space + * buffer_map is too fragmented ( space reservation fails ) + * If we have to flush dirty buffers ( but we try to avoid this ) + * + * To avoid VFS layer recursion we do not flush dirty buffers ourselves. + * Instead we ask the buf daemon to do it for us. We attempt to + * avoid piecemeal wakeups of the pageout daemon. + */ + +static struct buf * +getnewbuf(int slpflag, int slptimeo, int size, int maxsize) +{ + struct buf *bp; + struct buf *nbp; + int defrag = 0; + int nqindex; + static int flushingbufs; + + GIANT_REQUIRED; + + /* + * We can't afford to block since we might be holding a vnode lock, + * which may prevent system daemons from running. We deal with + * low-memory situations by proactively returning memory and running + * async I/O rather then sync I/O. + */ + + ++getnewbufcalls; + --getnewbufrestarts; +restart: + ++getnewbufrestarts; + + /* + * Setup for scan. If we do not have enough free buffers, + * we setup a degenerate case that immediately fails. Note + * that if we are specially marked process, we are allowed to + * dip into our reserves. + * + * The scanning sequence is nominally: EMPTY->EMPTYKVA->CLEAN + * + * We start with EMPTYKVA. If the list is empty we backup to EMPTY. + * However, there are a number of cases (defragging, reusing, ...) + * where we cannot backup. + */ + nqindex = QUEUE_EMPTYKVA; + nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTYKVA]); + + if (nbp == NULL) { + /* + * If no EMPTYKVA buffers and we are either + * defragging or reusing, locate a CLEAN buffer + * to free or reuse. If bufspace useage is low + * skip this step so we can allocate a new buffer. + */ + if (defrag || bufspace >= lobufspace) { + nqindex = QUEUE_CLEAN; + nbp = TAILQ_FIRST(&bufqueues[QUEUE_CLEAN]); + } + + /* + * If we could not find or were not allowed to reuse a + * CLEAN buffer, check to see if it is ok to use an EMPTY + * buffer. We can only use an EMPTY buffer if allocating + * its KVA would not otherwise run us out of buffer space. + */ + if (nbp == NULL && defrag == 0 && + bufspace + maxsize < hibufspace) { + nqindex = QUEUE_EMPTY; + nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTY]); + } + } + + /* + * Run scan, possibly freeing data and/or kva mappings on the fly + * depending. + */ + + while ((bp = nbp) != NULL) { + int qindex = nqindex; + + /* + * Calculate next bp ( we can only use it if we do not block + * or do other fancy things ). + */ + if ((nbp = TAILQ_NEXT(bp, b_freelist)) == NULL) { + switch(qindex) { + case QUEUE_EMPTY: + nqindex = QUEUE_EMPTYKVA; + if ((nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTYKVA]))) + break; + /* fall through */ + case QUEUE_EMPTYKVA: + nqindex = QUEUE_CLEAN; + if ((nbp = TAILQ_FIRST(&bufqueues[QUEUE_CLEAN]))) + break; + /* fall through */ + case QUEUE_CLEAN: + /* + * nbp is NULL. + */ + break; + } + } + + /* + * Sanity Checks + */ + KASSERT(bp->b_qindex == qindex, ("getnewbuf: inconsistant queue %d bp %p", qindex, bp)); + + /* + * Note: we no longer distinguish between VMIO and non-VMIO + * buffers. + */ + + KASSERT((bp->b_flags & B_DELWRI) == 0, ("delwri buffer %p found in queue %d", bp, qindex)); + + /* + * If we are defragging then we need a buffer with + * b_kvasize != 0. XXX this situation should no longer + * occur, if defrag is non-zero the buffer's b_kvasize + * should also be non-zero at this point. XXX + */ + if (defrag && bp->b_kvasize == 0) { + printf("Warning: defrag empty buffer %p\n", bp); + continue; + } + + /* + * Start freeing the bp. This is somewhat involved. nbp + * remains valid only for QUEUE_EMPTY[KVA] bp's. + */ + + if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0) + panic("getnewbuf: locked buf"); + bremfree(bp); + + if (qindex == QUEUE_CLEAN) { + if (bp->b_flags & B_VMIO) { + bp->b_flags &= ~B_ASYNC; + vfs_vmio_release(bp); + } + if (bp->b_vp) + brelvp(bp); + } + + /* + * NOTE: nbp is now entirely invalid. We can only restart + * the scan from this point on. + * + * Get the rest of the buffer freed up. b_kva* is still + * valid after this operation. + */ + + if (bp->b_rcred != NOCRED) { + crfree(bp->b_rcred); + bp->b_rcred = NOCRED; + } + if (bp->b_wcred != NOCRED) { + crfree(bp->b_wcred); + bp->b_wcred = NOCRED; + } + if (LIST_FIRST(&bp->b_dep) != NULL) + buf_deallocate(bp); + if (bp->b_xflags & BX_BKGRDINPROG) + panic("losing buffer 3"); + LIST_REMOVE(bp, b_hash); + LIST_INSERT_HEAD(&invalhash, bp, b_hash); + + if (bp->b_bufsize) + allocbuf(bp, 0); + + bp->b_flags = 0; + bp->b_ioflags = 0; + bp->b_xflags = 0; + bp->b_dev = NODEV; + bp->b_vp = NULL; + bp->b_blkno = bp->b_lblkno = 0; + bp->b_offset = NOOFFSET; + bp->b_iodone = 0; + bp->b_error = 0; + bp->b_resid = 0; + bp->b_bcount = 0; + bp->b_npages = 0; + bp->b_dirtyoff = bp->b_dirtyend = 0; + bp->b_magic = B_MAGIC_BIO; + bp->b_op = &buf_ops_bio; + + LIST_INIT(&bp->b_dep); + + /* + * If we are defragging then free the buffer. + */ + if (defrag) { + bp->b_flags |= B_INVAL; + bfreekva(bp); + brelse(bp); + defrag = 0; + goto restart; + } + + /* + * If we are overcomitted then recover the buffer and its + * KVM space. This occurs in rare situations when multiple + * processes are blocked in getnewbuf() or allocbuf(). + */ + if (bufspace >= hibufspace) + flushingbufs = 1; + if (flushingbufs && bp->b_kvasize != 0) { + bp->b_flags |= B_INVAL; + bfreekva(bp); + brelse(bp); + goto restart; + } + if (bufspace < lobufspace) + flushingbufs = 0; + break; + } + + /* + * If we exhausted our list, sleep as appropriate. We may have to + * wakeup various daemons and write out some dirty buffers. + * + * Generally we are sleeping due to insufficient buffer space. + */ + + if (bp == NULL) { + int flags; + char *waitmsg; + + if (defrag) { + flags = VFS_BIO_NEED_BUFSPACE; + waitmsg = "nbufkv"; + } else if (bufspace >= hibufspace) { + waitmsg = "nbufbs"; + flags = VFS_BIO_NEED_BUFSPACE; + } else { + waitmsg = "newbuf"; + flags = VFS_BIO_NEED_ANY; + } + + bd_speedup(); /* heeeelp */ + + needsbuffer |= flags; + while (needsbuffer & flags) { + if (tsleep(&needsbuffer, (PRIBIO + 4) | slpflag, + waitmsg, slptimeo)) + return (NULL); + } + } else { + /* + * We finally have a valid bp. We aren't quite out of the + * woods, we still have to reserve kva space. In order + * to keep fragmentation sane we only allocate kva in + * BKVASIZE chunks. + */ + maxsize = (maxsize + BKVAMASK) & ~BKVAMASK; + + if (maxsize != bp->b_kvasize) { + vm_offset_t addr = 0; + + bfreekva(bp); + + if (vm_map_findspace(buffer_map, + vm_map_min(buffer_map), maxsize, &addr)) { + /* + * Uh oh. Buffer map is to fragmented. We + * must defragment the map. + */ + ++bufdefragcnt; + defrag = 1; + bp->b_flags |= B_INVAL; + brelse(bp); + goto restart; + } + if (addr) { + vm_map_insert(buffer_map, NULL, 0, + addr, addr + maxsize, + VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT); + + bp->b_kvabase = (caddr_t) addr; + bp->b_kvasize = maxsize; + bufspace += bp->b_kvasize; + ++bufreusecnt; + } + } + bp->b_data = bp->b_kvabase; + } + return(bp); +} + +/* + * buf_daemon: + * + * buffer flushing daemon. Buffers are normally flushed by the + * update daemon but if it cannot keep up this process starts to + * take the load in an attempt to prevent getnewbuf() from blocking. + */ + +static struct proc *bufdaemonproc; + +static struct kproc_desc buf_kp = { + "bufdaemon", + buf_daemon, + &bufdaemonproc +}; +SYSINIT(bufdaemon, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST, kproc_start, &buf_kp) + +static void +buf_daemon() +{ + int s; + + mtx_lock(&Giant); + + /* + * This process needs to be suspended prior to shutdown sync. + */ + EVENTHANDLER_REGISTER(shutdown_pre_sync, kproc_shutdown, bufdaemonproc, + SHUTDOWN_PRI_LAST); + + /* + * This process is allowed to take the buffer cache to the limit + */ + s = splbio(); + + for (;;) { + kthread_suspend_check(bufdaemonproc); + + bd_request = 0; + + /* + * Do the flush. Limit the amount of in-transit I/O we + * allow to build up, otherwise we would completely saturate + * the I/O system. Wakeup any waiting processes before we + * normally would so they can run in parallel with our drain. + */ + while (numdirtybuffers > lodirtybuffers) { + if (flushbufqueues() == 0) + break; + waitrunningbufspace(); + numdirtywakeup((lodirtybuffers + hidirtybuffers) / 2); + } + + /* + * Only clear bd_request if we have reached our low water + * mark. The buf_daemon normally waits 1 second and + * then incrementally flushes any dirty buffers that have + * built up, within reason. + * + * If we were unable to hit our low water mark and couldn't + * find any flushable buffers, we sleep half a second. + * Otherwise we loop immediately. + */ + if (numdirtybuffers <= lodirtybuffers) { + /* + * We reached our low water mark, reset the + * request and sleep until we are needed again. + * The sleep is just so the suspend code works. + */ + bd_request = 0; + tsleep(&bd_request, PVM, "psleep", hz); + } else { + /* + * We couldn't find any flushable dirty buffers but + * still have too many dirty buffers, we + * have to sleep and try again. (rare) + */ + tsleep(&bd_request, PVM, "qsleep", hz / 2); + } + } +} + +/* + * flushbufqueues: + * + * Try to flush a buffer in the dirty queue. We must be careful to + * free up B_INVAL buffers instead of write them, which NFS is + * particularly sensitive to. + */ + +static int +flushbufqueues(void) +{ + struct buf *bp; + int r = 0; + + bp = TAILQ_FIRST(&bufqueues[QUEUE_DIRTY]); + + while (bp) { + KASSERT((bp->b_flags & B_DELWRI), ("unexpected clean buffer %p", bp)); + if ((bp->b_flags & B_DELWRI) != 0 && + (bp->b_xflags & BX_BKGRDINPROG) == 0) { + if (bp->b_flags & B_INVAL) { + if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0) + panic("flushbufqueues: locked buf"); + bremfree(bp); + brelse(bp); + ++r; + break; + } + if (LIST_FIRST(&bp->b_dep) != NULL && + (bp->b_flags & B_DEFERRED) == 0 && + buf_countdeps(bp, 0)) { + TAILQ_REMOVE(&bufqueues[QUEUE_DIRTY], + bp, b_freelist); + TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], + bp, b_freelist); + bp->b_flags |= B_DEFERRED; + bp = TAILQ_FIRST(&bufqueues[QUEUE_DIRTY]); + continue; + } + vfs_bio_awrite(bp); + ++r; + break; + } + bp = TAILQ_NEXT(bp, b_freelist); + } + return (r); +} + +/* + * Check to see if a block is currently memory resident. + */ +struct buf * +incore(struct vnode * vp, daddr_t blkno) +{ + struct buf *bp; + + int s = splbio(); + bp = gbincore(vp, blkno); + splx(s); + return (bp); +} + +/* + * Returns true if no I/O is needed to access the + * associated VM object. This is like incore except + * it also hunts around in the VM system for the data. + */ + +int +inmem(struct vnode * vp, daddr_t blkno) +{ + vm_object_t obj; + vm_offset_t toff, tinc, size; + vm_page_t m; + vm_ooffset_t off; + + GIANT_REQUIRED; + + if (incore(vp, blkno)) + return 1; + if (vp->v_mount == NULL) + return 0; + if (VOP_GETVOBJECT(vp, &obj) != 0 || (vp->v_flag & VOBJBUF) == 0) + return 0; + + size = PAGE_SIZE; + if (size > vp->v_mount->mnt_stat.f_iosize) + size = vp->v_mount->mnt_stat.f_iosize; + off = (vm_ooffset_t)blkno * (vm_ooffset_t)vp->v_mount->mnt_stat.f_iosize; + + for (toff = 0; toff < vp->v_mount->mnt_stat.f_iosize; toff += tinc) { + m = vm_page_lookup(obj, OFF_TO_IDX(off + toff)); + if (!m) + goto notinmem; + tinc = size; + if (tinc > PAGE_SIZE - ((toff + off) & PAGE_MASK)) + tinc = PAGE_SIZE - ((toff + off) & PAGE_MASK); + if (vm_page_is_valid(m, + (vm_offset_t) ((toff + off) & PAGE_MASK), tinc) == 0) + goto notinmem; + } + return 1; + +notinmem: + return (0); +} + +/* + * vfs_setdirty: + * + * Sets the dirty range for a buffer based on the status of the dirty + * bits in the pages comprising the buffer. + * + * The range is limited to the size of the buffer. + * + * This routine is primarily used by NFS, but is generalized for the + * B_VMIO case. + */ +static void +vfs_setdirty(struct buf *bp) +{ + int i; + vm_object_t object; + + GIANT_REQUIRED; + /* + * Degenerate case - empty buffer + */ + + if (bp->b_bufsize == 0) + return; + + /* + * We qualify the scan for modified pages on whether the + * object has been flushed yet. The OBJ_WRITEABLE flag + * is not cleared simply by protecting pages off. + */ + + if ((bp->b_flags & B_VMIO) == 0) + return; + + object = bp->b_pages[0]->object; + + if ((object->flags & OBJ_WRITEABLE) && !(object->flags & OBJ_MIGHTBEDIRTY)) + printf("Warning: object %p writeable but not mightbedirty\n", object); + if (!(object->flags & OBJ_WRITEABLE) && (object->flags & OBJ_MIGHTBEDIRTY)) + printf("Warning: object %p mightbedirty but not writeable\n", object); + + if (object->flags & (OBJ_MIGHTBEDIRTY|OBJ_CLEANING)) { + vm_offset_t boffset; + vm_offset_t eoffset; + + /* + * test the pages to see if they have been modified directly + * by users through the VM system. + */ + for (i = 0; i < bp->b_npages; i++) { + vm_page_flag_clear(bp->b_pages[i], PG_ZERO); + vm_page_test_dirty(bp->b_pages[i]); + } + + /* + * Calculate the encompassing dirty range, boffset and eoffset, + * (eoffset - boffset) bytes. + */ + + for (i = 0; i < bp->b_npages; i++) { + if (bp->b_pages[i]->dirty) + break; + } + boffset = (i << PAGE_SHIFT) - (bp->b_offset & PAGE_MASK); + + for (i = bp->b_npages - 1; i >= 0; --i) { + if (bp->b_pages[i]->dirty) { + break; + } + } + eoffset = ((i + 1) << PAGE_SHIFT) - (bp->b_offset & PAGE_MASK); + + /* + * Fit it to the buffer. + */ + + if (eoffset > bp->b_bcount) + eoffset = bp->b_bcount; + + /* + * If we have a good dirty range, merge with the existing + * dirty range. + */ + + if (boffset < eoffset) { + if (bp->b_dirtyoff > boffset) + bp->b_dirtyoff = boffset; + if (bp->b_dirtyend < eoffset) + bp->b_dirtyend = eoffset; + } + } +} + +/* + * getblk: + * + * Get a block given a specified block and offset into a file/device. + * The buffers B_DONE bit will be cleared on return, making it almost + * ready for an I/O initiation. B_INVAL may or may not be set on + * return. The caller should clear B_INVAL prior to initiating a + * READ. + * + * For a non-VMIO buffer, B_CACHE is set to the opposite of B_INVAL for + * an existing buffer. + * + * For a VMIO buffer, B_CACHE is modified according to the backing VM. + * If getblk()ing a previously 0-sized invalid buffer, B_CACHE is set + * and then cleared based on the backing VM. If the previous buffer is + * non-0-sized but invalid, B_CACHE will be cleared. + * + * If getblk() must create a new buffer, the new buffer is returned with + * both B_INVAL and B_CACHE clear unless it is a VMIO buffer, in which + * case it is returned with B_INVAL clear and B_CACHE set based on the + * backing VM. + * + * getblk() also forces a BUF_WRITE() for any B_DELWRI buffer whos + * B_CACHE bit is clear. + * + * What this means, basically, is that the caller should use B_CACHE to + * determine whether the buffer is fully valid or not and should clear + * B_INVAL prior to issuing a read. If the caller intends to validate + * the buffer by loading its data area with something, the caller needs + * to clear B_INVAL. If the caller does this without issuing an I/O, + * the caller should set B_CACHE ( as an optimization ), else the caller + * should issue the I/O and biodone() will set B_CACHE if the I/O was + * a write attempt or if it was a successfull read. If the caller + * intends to issue a READ, the caller must clear B_INVAL and BIO_ERROR + * prior to issuing the READ. biodone() will *not* clear B_INVAL. + */ +struct buf * +getblk(struct vnode * vp, daddr_t blkno, int size, int slpflag, int slptimeo) +{ + struct buf *bp; + int s; + struct bufhashhdr *bh; + + if (size > MAXBSIZE) + panic("getblk: size(%d) > MAXBSIZE(%d)\n", size, MAXBSIZE); + + s = splbio(); +loop: + /* + * Block if we are low on buffers. Certain processes are allowed + * to completely exhaust the buffer cache. + * + * If this check ever becomes a bottleneck it may be better to + * move it into the else, when gbincore() fails. At the moment + * it isn't a problem. + * + * XXX remove if 0 sections (clean this up after its proven) + */ + if (numfreebuffers == 0) { + if (curthread == PCPU_GET(idlethread)) + return NULL; + needsbuffer |= VFS_BIO_NEED_ANY; + } + + if ((bp = gbincore(vp, blkno))) { + /* + * Buffer is in-core. If the buffer is not busy, it must + * be on a queue. + */ + + if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) { + if (BUF_TIMELOCK(bp, LK_EXCLUSIVE | LK_SLEEPFAIL, + "getblk", slpflag, slptimeo) == ENOLCK) + goto loop; + splx(s); + return (struct buf *) NULL; + } + + /* + * The buffer is locked. B_CACHE is cleared if the buffer is + * invalid. Otherwise, for a non-VMIO buffer, B_CACHE is set + * and for a VMIO buffer B_CACHE is adjusted according to the + * backing VM cache. + */ + if (bp->b_flags & B_INVAL) + bp->b_flags &= ~B_CACHE; + else if ((bp->b_flags & (B_VMIO | B_INVAL)) == 0) + bp->b_flags |= B_CACHE; + bremfree(bp); + + /* + * check for size inconsistancies for non-VMIO case. + */ + + if (bp->b_bcount != size) { + if ((bp->b_flags & B_VMIO) == 0 || + (size > bp->b_kvasize)) { + if (bp->b_flags & B_DELWRI) { + bp->b_flags |= B_NOCACHE; + BUF_WRITE(bp); + } else { + if ((bp->b_flags & B_VMIO) && + (LIST_FIRST(&bp->b_dep) == NULL)) { + bp->b_flags |= B_RELBUF; + brelse(bp); + } else { + bp->b_flags |= B_NOCACHE; + BUF_WRITE(bp); + } + } + goto loop; + } + } + + /* + * If the size is inconsistant in the VMIO case, we can resize + * the buffer. This might lead to B_CACHE getting set or + * cleared. If the size has not changed, B_CACHE remains + * unchanged from its previous state. + */ + + if (bp->b_bcount != size) + allocbuf(bp, size); + + KASSERT(bp->b_offset != NOOFFSET, + ("getblk: no buffer offset")); + + /* + * A buffer with B_DELWRI set and B_CACHE clear must + * be committed before we can return the buffer in + * order to prevent the caller from issuing a read + * ( due to B_CACHE not being set ) and overwriting + * it. + * + * Most callers, including NFS and FFS, need this to + * operate properly either because they assume they + * can issue a read if B_CACHE is not set, or because + * ( for example ) an uncached B_DELWRI might loop due + * to softupdates re-dirtying the buffer. In the latter + * case, B_CACHE is set after the first write completes, + * preventing further loops. + * NOTE! b*write() sets B_CACHE. If we cleared B_CACHE + * above while extending the buffer, we cannot allow the + * buffer to remain with B_CACHE set after the write + * completes or it will represent a corrupt state. To + * deal with this we set B_NOCACHE to scrap the buffer + * after the write. + * + * We might be able to do something fancy, like setting + * B_CACHE in bwrite() except if B_DELWRI is already set, + * so the below call doesn't set B_CACHE, but that gets real + * confusing. This is much easier. + */ + + if ((bp->b_flags & (B_CACHE|B_DELWRI)) == B_DELWRI) { + bp->b_flags |= B_NOCACHE; + BUF_WRITE(bp); + goto loop; + } + + splx(s); + bp->b_flags &= ~B_DONE; + } else { + /* + * Buffer is not in-core, create new buffer. The buffer + * returned by getnewbuf() is locked. Note that the returned + * buffer is also considered valid (not marked B_INVAL). + */ + int bsize, maxsize, vmio; + off_t offset; + + if (vn_isdisk(vp, NULL)) + bsize = DEV_BSIZE; + else if (vp->v_mountedhere) + bsize = vp->v_mountedhere->mnt_stat.f_iosize; + else if (vp->v_mount) + bsize = vp->v_mount->mnt_stat.f_iosize; + else + bsize = size; + + offset = blkno * bsize; + vmio = (VOP_GETVOBJECT(vp, NULL) == 0) && (vp->v_flag & VOBJBUF); + maxsize = vmio ? size + (offset & PAGE_MASK) : size; + maxsize = imax(maxsize, bsize); + + if ((bp = getnewbuf(slpflag, slptimeo, size, maxsize)) == NULL) { + if (slpflag || slptimeo) { + splx(s); + return NULL; + } + goto loop; + } + + /* + * This code is used to make sure that a buffer is not + * created while the getnewbuf routine is blocked. + * This can be a problem whether the vnode is locked or not. + * If the buffer is created out from under us, we have to + * throw away the one we just created. There is now window + * race because we are safely running at splbio() from the + * point of the duplicate buffer creation through to here, + * and we've locked the buffer. + */ + if (gbincore(vp, blkno)) { + bp->b_flags |= B_INVAL; + brelse(bp); + goto loop; + } + + /* + * Insert the buffer into the hash, so that it can + * be found by incore. + */ + bp->b_blkno = bp->b_lblkno = blkno; + bp->b_offset = offset; + + bgetvp(vp, bp); + LIST_REMOVE(bp, b_hash); + bh = bufhash(vp, blkno); + LIST_INSERT_HEAD(bh, bp, b_hash); + + /* + * set B_VMIO bit. allocbuf() the buffer bigger. Since the + * buffer size starts out as 0, B_CACHE will be set by + * allocbuf() for the VMIO case prior to it testing the + * backing store for validity. + */ + + if (vmio) { + bp->b_flags |= B_VMIO; +#if defined(VFS_BIO_DEBUG) + if (vp->v_type != VREG) + printf("getblk: vmioing file type %d???\n", vp->v_type); +#endif + } else { + bp->b_flags &= ~B_VMIO; + } + + allocbuf(bp, size); + + splx(s); + bp->b_flags &= ~B_DONE; + } + return (bp); +} + +/* + * Get an empty, disassociated buffer of given size. The buffer is initially + * set to B_INVAL. + */ +struct buf * +geteblk(int size) +{ + struct buf *bp; + int s; + int maxsize; + + maxsize = (size + BKVAMASK) & ~BKVAMASK; + + s = splbio(); + while ((bp = getnewbuf(0, 0, size, maxsize)) == 0); + splx(s); + allocbuf(bp, size); + bp->b_flags |= B_INVAL; /* b_dep cleared by getnewbuf() */ + return (bp); +} + + +/* + * This code constitutes the buffer memory from either anonymous system + * memory (in the case of non-VMIO operations) or from an associated + * VM object (in the case of VMIO operations). This code is able to + * resize a buffer up or down. + * + * Note that this code is tricky, and has many complications to resolve + * deadlock or inconsistant data situations. Tread lightly!!! + * There are B_CACHE and B_DELWRI interactions that must be dealt with by + * the caller. Calling this code willy nilly can result in the loss of data. + * + * allocbuf() only adjusts B_CACHE for VMIO buffers. getblk() deals with + * B_CACHE for the non-VMIO case. + */ + +int +allocbuf(struct buf *bp, int size) +{ + int newbsize, mbsize; + int i; + + GIANT_REQUIRED; + + if (BUF_REFCNT(bp) == 0) + panic("allocbuf: buffer not busy"); + + if (bp->b_kvasize < size) + panic("allocbuf: buffer too small"); + + if ((bp->b_flags & B_VMIO) == 0) { + caddr_t origbuf; + int origbufsize; + /* + * Just get anonymous memory from the kernel. Don't + * mess with B_CACHE. + */ + mbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1); + if (bp->b_flags & B_MALLOC) + newbsize = mbsize; + else + newbsize = round_page(size); + + if (newbsize < bp->b_bufsize) { + /* + * malloced buffers are not shrunk + */ + if (bp->b_flags & B_MALLOC) { + if (newbsize) { + bp->b_bcount = size; + } else { + free(bp->b_data, M_BIOBUF); + if (bp->b_bufsize) { + bufmallocspace -= bp->b_bufsize; + bufspacewakeup(); + bp->b_bufsize = 0; + } + bp->b_data = bp->b_kvabase; + bp->b_bcount = 0; + bp->b_flags &= ~B_MALLOC; + } + return 1; + } + vm_hold_free_pages( + bp, + (vm_offset_t) bp->b_data + newbsize, + (vm_offset_t) bp->b_data + bp->b_bufsize); + } else if (newbsize > bp->b_bufsize) { + /* + * We only use malloced memory on the first allocation. + * and revert to page-allocated memory when the buffer + * grows. + */ + if ( (bufmallocspace < maxbufmallocspace) && + (bp->b_bufsize == 0) && + (mbsize <= PAGE_SIZE/2)) { + + bp->b_data = malloc(mbsize, M_BIOBUF, M_WAITOK); + bp->b_bufsize = mbsize; + bp->b_bcount = size; + bp->b_flags |= B_MALLOC; + bufmallocspace += mbsize; + return 1; + } + origbuf = NULL; + origbufsize = 0; + /* + * If the buffer is growing on its other-than-first allocation, + * then we revert to the page-allocation scheme. + */ + if (bp->b_flags & B_MALLOC) { + origbuf = bp->b_data; + origbufsize = bp->b_bufsize; + bp->b_data = bp->b_kvabase; + if (bp->b_bufsize) { + bufmallocspace -= bp->b_bufsize; + bufspacewakeup(); + bp->b_bufsize = 0; + } + bp->b_flags &= ~B_MALLOC; + newbsize = round_page(newbsize); + } + vm_hold_load_pages( + bp, + (vm_offset_t) bp->b_data + bp->b_bufsize, + (vm_offset_t) bp->b_data + newbsize); + if (origbuf) { + bcopy(origbuf, bp->b_data, origbufsize); + free(origbuf, M_BIOBUF); + } + } + } else { + vm_page_t m; + int desiredpages; + + newbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1); + desiredpages = (size == 0) ? 0 : + num_pages((bp->b_offset & PAGE_MASK) + newbsize); + + if (bp->b_flags & B_MALLOC) + panic("allocbuf: VMIO buffer can't be malloced"); + /* + * Set B_CACHE initially if buffer is 0 length or will become + * 0-length. + */ + if (size == 0 || bp->b_bufsize == 0) + bp->b_flags |= B_CACHE; + + if (newbsize < bp->b_bufsize) { + /* + * DEV_BSIZE aligned new buffer size is less then the + * DEV_BSIZE aligned existing buffer size. Figure out + * if we have to remove any pages. + */ + if (desiredpages < bp->b_npages) { + for (i = desiredpages; i < bp->b_npages; i++) { + /* + * the page is not freed here -- it + * is the responsibility of + * vnode_pager_setsize + */ + m = bp->b_pages[i]; + KASSERT(m != bogus_page, + ("allocbuf: bogus page found")); + while (vm_page_sleep_busy(m, TRUE, "biodep")) + ; + + bp->b_pages[i] = NULL; + vm_page_unwire(m, 0); + } + pmap_qremove((vm_offset_t) trunc_page((vm_offset_t)bp->b_data) + + (desiredpages << PAGE_SHIFT), (bp->b_npages - desiredpages)); + bp->b_npages = desiredpages; + } + } else if (size > bp->b_bcount) { + /* + * We are growing the buffer, possibly in a + * byte-granular fashion. + */ + struct vnode *vp; + vm_object_t obj; + vm_offset_t toff; + vm_offset_t tinc; + + /* + * Step 1, bring in the VM pages from the object, + * allocating them if necessary. We must clear + * B_CACHE if these pages are not valid for the + * range covered by the buffer. + */ + + vp = bp->b_vp; + VOP_GETVOBJECT(vp, &obj); + + while (bp->b_npages < desiredpages) { + vm_page_t m; + vm_pindex_t pi; + + pi = OFF_TO_IDX(bp->b_offset) + bp->b_npages; + if ((m = vm_page_lookup(obj, pi)) == NULL) { + /* + * note: must allocate system pages + * since blocking here could intefere + * with paging I/O, no matter which + * process we are. + */ + m = vm_page_alloc(obj, pi, VM_ALLOC_SYSTEM); + if (m == NULL) { + VM_WAIT; + vm_pageout_deficit += desiredpages - bp->b_npages; + } else { + vm_page_wire(m); + vm_page_wakeup(m); + bp->b_flags &= ~B_CACHE; + bp->b_pages[bp->b_npages] = m; + ++bp->b_npages; + } + continue; + } + + /* + * We found a page. If we have to sleep on it, + * retry because it might have gotten freed out + * from under us. + * + * We can only test PG_BUSY here. Blocking on + * m->busy might lead to a deadlock: + * + * vm_fault->getpages->cluster_read->allocbuf + * + */ + + if (vm_page_sleep_busy(m, FALSE, "pgtblk")) + continue; + + /* + * We have a good page. Should we wakeup the + * page daemon? + */ + if ((curproc != pageproc) && + ((m->queue - m->pc) == PQ_CACHE) && + ((cnt.v_free_count + cnt.v_cache_count) < + (cnt.v_free_min + cnt.v_cache_min))) { + pagedaemon_wakeup(); + } + vm_page_flag_clear(m, PG_ZERO); + vm_page_wire(m); + bp->b_pages[bp->b_npages] = m; + ++bp->b_npages; + } + + /* + * Step 2. We've loaded the pages into the buffer, + * we have to figure out if we can still have B_CACHE + * set. Note that B_CACHE is set according to the + * byte-granular range ( bcount and size ), new the + * aligned range ( newbsize ). + * + * The VM test is against m->valid, which is DEV_BSIZE + * aligned. Needless to say, the validity of the data + * needs to also be DEV_BSIZE aligned. Note that this + * fails with NFS if the server or some other client + * extends the file's EOF. If our buffer is resized, + * B_CACHE may remain set! XXX + */ + + toff = bp->b_bcount; + tinc = PAGE_SIZE - ((bp->b_offset + toff) & PAGE_MASK); + + while ((bp->b_flags & B_CACHE) && toff < size) { + vm_pindex_t pi; + + if (tinc > (size - toff)) + tinc = size - toff; + + pi = ((bp->b_offset & PAGE_MASK) + toff) >> + PAGE_SHIFT; + + vfs_buf_test_cache( + bp, + bp->b_offset, + toff, + tinc, + bp->b_pages[pi] + ); + toff += tinc; + tinc = PAGE_SIZE; + } + + /* + * Step 3, fixup the KVM pmap. Remember that + * bp->b_data is relative to bp->b_offset, but + * bp->b_offset may be offset into the first page. + */ + + bp->b_data = (caddr_t) + trunc_page((vm_offset_t)bp->b_data); + pmap_qenter( + (vm_offset_t)bp->b_data, + bp->b_pages, + bp->b_npages + ); + + bp->b_data = (caddr_t)((vm_offset_t)bp->b_data | + (vm_offset_t)(bp->b_offset & PAGE_MASK)); + } + } + if (newbsize < bp->b_bufsize) + bufspacewakeup(); + bp->b_bufsize = newbsize; /* actual buffer allocation */ + bp->b_bcount = size; /* requested buffer size */ + return 1; +} + +/* + * bufwait: + * + * Wait for buffer I/O completion, returning error status. The buffer + * is left locked and B_DONE on return. B_EINTR is converted into a EINTR + * error and cleared. + */ +int +bufwait(register struct buf * bp) +{ + int s; + + s = splbio(); + while ((bp->b_flags & B_DONE) == 0) { + if (bp->b_iocmd == BIO_READ) + tsleep(bp, PRIBIO, "biord", 0); + else + tsleep(bp, PRIBIO, "biowr", 0); + } + splx(s); + if (bp->b_flags & B_EINTR) { + bp->b_flags &= ~B_EINTR; + return (EINTR); + } + if (bp->b_ioflags & BIO_ERROR) { + return (bp->b_error ? bp->b_error : EIO); + } else { + return (0); + } +} + + /* + * Call back function from struct bio back up to struct buf. + * The corresponding initialization lives in sys/conf.h:DEV_STRATEGY(). + */ +void +bufdonebio(struct bio *bp) +{ + bufdone(bp->bio_caller2); +} + +/* + * bufdone: + * + * Finish I/O on a buffer, optionally calling a completion function. + * This is usually called from an interrupt so process blocking is + * not allowed. + * + * biodone is also responsible for setting B_CACHE in a B_VMIO bp. + * In a non-VMIO bp, B_CACHE will be set on the next getblk() + * assuming B_INVAL is clear. + * + * For the VMIO case, we set B_CACHE if the op was a read and no + * read error occured, or if the op was a write. B_CACHE is never + * set if the buffer is invalid or otherwise uncacheable. + * + * biodone does not mess with B_INVAL, allowing the I/O routine or the + * initiator to leave B_INVAL set to brelse the buffer out of existance + * in the biodone routine. + */ +void +bufdone(struct buf *bp) +{ + int s, error; + void (*biodone)(struct buf *); + + GIANT_REQUIRED; + + s = splbio(); + + KASSERT(BUF_REFCNT(bp) > 0, ("biodone: bp %p not busy %d", bp, BUF_REFCNT(bp))); + KASSERT(!(bp->b_flags & B_DONE), ("biodone: bp %p already done", bp)); + + bp->b_flags |= B_DONE; + runningbufwakeup(bp); + + if (bp->b_iocmd == BIO_DELETE) { + brelse(bp); + splx(s); + return; + } + + if (bp->b_iocmd == BIO_WRITE) { + vwakeup(bp); + } + + /* call optional completion function if requested */ + if (bp->b_iodone != NULL) { + biodone = bp->b_iodone; + bp->b_iodone = NULL; + (*biodone) (bp); + splx(s); + return; + } + if (LIST_FIRST(&bp->b_dep) != NULL) + buf_complete(bp); + + if (bp->b_flags & B_VMIO) { + int i; + vm_ooffset_t foff; + vm_page_t m; + vm_object_t obj; + int iosize; + struct vnode *vp = bp->b_vp; + + error = VOP_GETVOBJECT(vp, &obj); + +#if defined(VFS_BIO_DEBUG) + if (vp->v_usecount == 0) { + panic("biodone: zero vnode ref count"); + } + + if (error) { + panic("biodone: missing VM object"); + } + + if ((vp->v_flag & VOBJBUF) == 0) { + panic("biodone: vnode is not setup for merged cache"); + } +#endif + + foff = bp->b_offset; + KASSERT(bp->b_offset != NOOFFSET, + ("biodone: no buffer offset")); + + if (error) { + panic("biodone: no object"); + } +#if defined(VFS_BIO_DEBUG) + if (obj->paging_in_progress < bp->b_npages) { + printf("biodone: paging in progress(%d) < bp->b_npages(%d)\n", + obj->paging_in_progress, bp->b_npages); + } +#endif + + /* + * Set B_CACHE if the op was a normal read and no error + * occured. B_CACHE is set for writes in the b*write() + * routines. + */ + iosize = bp->b_bcount - bp->b_resid; + if (bp->b_iocmd == BIO_READ && + !(bp->b_flags & (B_INVAL|B_NOCACHE)) && + !(bp->b_ioflags & BIO_ERROR)) { + bp->b_flags |= B_CACHE; + } + + for (i = 0; i < bp->b_npages; i++) { + int bogusflag = 0; + int resid; + + resid = ((foff + PAGE_SIZE) & ~(off_t)PAGE_MASK) - foff; + if (resid > iosize) + resid = iosize; + + /* + * cleanup bogus pages, restoring the originals + */ + m = bp->b_pages[i]; + if (m == bogus_page) { + bogusflag = 1; + m = vm_page_lookup(obj, OFF_TO_IDX(foff)); + if (m == NULL) + panic("biodone: page disappeared!"); + bp->b_pages[i] = m; + pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages); + } +#if defined(VFS_BIO_DEBUG) + if (OFF_TO_IDX(foff) != m->pindex) { + printf( +"biodone: foff(%lu)/m->pindex(%d) mismatch\n", + (unsigned long)foff, m->pindex); + } +#endif + + /* + * In the write case, the valid and clean bits are + * already changed correctly ( see bdwrite() ), so we + * only need to do this here in the read case. + */ + if ((bp->b_iocmd == BIO_READ) && !bogusflag && resid > 0) { + vfs_page_set_valid(bp, foff, i, m); + } + vm_page_flag_clear(m, PG_ZERO); + + /* + * when debugging new filesystems or buffer I/O methods, this + * is the most common error that pops up. if you see this, you + * have not set the page busy flag correctly!!! + */ + if (m->busy == 0) { + printf("biodone: page busy < 0, " + "pindex: %d, foff: 0x(%x,%x), " + "resid: %d, index: %d\n", + (int) m->pindex, (int)(foff >> 32), + (int) foff & 0xffffffff, resid, i); + if (!vn_isdisk(vp, NULL)) + printf(" iosize: %ld, lblkno: %jd, flags: 0x%lx, npages: %d\n", + bp->b_vp->v_mount->mnt_stat.f_iosize, + (intmax_t) bp->b_lblkno, + bp->b_flags, bp->b_npages); + else + printf(" VDEV, lblkno: %jd, flags: 0x%lx, npages: %d\n", + (intmax_t) bp->b_lblkno, + bp->b_flags, bp->b_npages); + printf(" valid: 0x%x, dirty: 0x%x, wired: %d\n", + m->valid, m->dirty, m->wire_count); + panic("biodone: page busy < 0\n"); + } + vm_page_io_finish(m); + vm_object_pip_subtract(obj, 1); + foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK; + iosize -= resid; + } + if (obj) + vm_object_pip_wakeupn(obj, 0); + } + + /* + * For asynchronous completions, release the buffer now. The brelse + * will do a wakeup there if necessary - so no need to do a wakeup + * here in the async case. The sync case always needs to do a wakeup. + */ + + if (bp->b_flags & B_ASYNC) { + if ((bp->b_flags & (B_NOCACHE | B_INVAL | B_RELBUF)) || (bp->b_ioflags & BIO_ERROR)) + brelse(bp); + else + bqrelse(bp); + } else { + wakeup(bp); + } + splx(s); +} + +/* + * This routine is called in lieu of iodone in the case of + * incomplete I/O. This keeps the busy status for pages + * consistant. + */ +void +vfs_unbusy_pages(struct buf * bp) +{ + int i; + + GIANT_REQUIRED; + + runningbufwakeup(bp); + if (bp->b_flags & B_VMIO) { + struct vnode *vp = bp->b_vp; + vm_object_t obj; + + VOP_GETVOBJECT(vp, &obj); + + for (i = 0; i < bp->b_npages; i++) { + vm_page_t m = bp->b_pages[i]; + + if (m == bogus_page) { + m = vm_page_lookup(obj, OFF_TO_IDX(bp->b_offset) + i); + if (!m) { + panic("vfs_unbusy_pages: page missing\n"); + } + bp->b_pages[i] = m; + pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages); + } + vm_object_pip_subtract(obj, 1); + vm_page_flag_clear(m, PG_ZERO); + vm_page_io_finish(m); + } + vm_object_pip_wakeupn(obj, 0); + } +} + +/* + * vfs_page_set_valid: + * + * Set the valid bits in a page based on the supplied offset. The + * range is restricted to the buffer's size. + * + * This routine is typically called after a read completes. + */ +static void +vfs_page_set_valid(struct buf *bp, vm_ooffset_t off, int pageno, vm_page_t m) +{ + vm_ooffset_t soff, eoff; + + GIANT_REQUIRED; + /* + * Start and end offsets in buffer. eoff - soff may not cross a + * page boundry or cross the end of the buffer. The end of the + * buffer, in this case, is our file EOF, not the allocation size + * of the buffer. + */ + soff = off; + eoff = (off + PAGE_SIZE) & ~(off_t)PAGE_MASK; + if (eoff > bp->b_offset + bp->b_bcount) + eoff = bp->b_offset + bp->b_bcount; + + /* + * Set valid range. This is typically the entire buffer and thus the + * entire page. + */ + if (eoff > soff) { + vm_page_set_validclean( + m, + (vm_offset_t) (soff & PAGE_MASK), + (vm_offset_t) (eoff - soff) + ); + } +} + +/* + * This routine is called before a device strategy routine. + * It is used to tell the VM system that paging I/O is in + * progress, and treat the pages associated with the buffer + * almost as being PG_BUSY. Also the object paging_in_progress + * flag is handled to make sure that the object doesn't become + * inconsistant. + * + * Since I/O has not been initiated yet, certain buffer flags + * such as BIO_ERROR or B_INVAL may be in an inconsistant state + * and should be ignored. + */ +void +vfs_busy_pages(struct buf * bp, int clear_modify) +{ + int i, bogus; + + GIANT_REQUIRED; + + if (bp->b_flags & B_VMIO) { + struct vnode *vp = bp->b_vp; + vm_object_t obj; + vm_ooffset_t foff; + + VOP_GETVOBJECT(vp, &obj); + foff = bp->b_offset; + KASSERT(bp->b_offset != NOOFFSET, + ("vfs_busy_pages: no buffer offset")); + vfs_setdirty(bp); + +retry: + for (i = 0; i < bp->b_npages; i++) { + vm_page_t m = bp->b_pages[i]; + if (vm_page_sleep_busy(m, FALSE, "vbpage")) + goto retry; + } + + bogus = 0; + for (i = 0; i < bp->b_npages; i++) { + vm_page_t m = bp->b_pages[i]; + + vm_page_flag_clear(m, PG_ZERO); + if ((bp->b_flags & B_CLUSTER) == 0) { + vm_object_pip_add(obj, 1); + vm_page_io_start(m); + } + + /* + * When readying a buffer for a read ( i.e + * clear_modify == 0 ), it is important to do + * bogus_page replacement for valid pages in + * partially instantiated buffers. Partially + * instantiated buffers can, in turn, occur when + * reconstituting a buffer from its VM backing store + * base. We only have to do this if B_CACHE is + * clear ( which causes the I/O to occur in the + * first place ). The replacement prevents the read + * I/O from overwriting potentially dirty VM-backed + * pages. XXX bogus page replacement is, uh, bogus. + * It may not work properly with small-block devices. + * We need to find a better way. + */ + + vm_page_protect(m, VM_PROT_NONE); + if (clear_modify) + vfs_page_set_valid(bp, foff, i, m); + else if (m->valid == VM_PAGE_BITS_ALL && + (bp->b_flags & B_CACHE) == 0) { + bp->b_pages[i] = bogus_page; + bogus++; + } + foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK; + } + if (bogus) + pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages); + } +} + +/* + * Tell the VM system that the pages associated with this buffer + * are clean. This is used for delayed writes where the data is + * going to go to disk eventually without additional VM intevention. + * + * Note that while we only really need to clean through to b_bcount, we + * just go ahead and clean through to b_bufsize. + */ +static void +vfs_clean_pages(struct buf * bp) +{ + int i; + + GIANT_REQUIRED; + + if (bp->b_flags & B_VMIO) { + vm_ooffset_t foff; + + foff = bp->b_offset; + KASSERT(bp->b_offset != NOOFFSET, + ("vfs_clean_pages: no buffer offset")); + for (i = 0; i < bp->b_npages; i++) { + vm_page_t m = bp->b_pages[i]; + vm_ooffset_t noff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK; + vm_ooffset_t eoff = noff; + + if (eoff > bp->b_offset + bp->b_bufsize) + eoff = bp->b_offset + bp->b_bufsize; + vfs_page_set_valid(bp, foff, i, m); + /* vm_page_clear_dirty(m, foff & PAGE_MASK, eoff - foff); */ + foff = noff; + } + } +} + +/* + * vfs_bio_set_validclean: + * + * Set the range within the buffer to valid and clean. The range is + * relative to the beginning of the buffer, b_offset. Note that b_offset + * itself may be offset from the beginning of the first page. + * + */ + +void +vfs_bio_set_validclean(struct buf *bp, int base, int size) +{ + if (bp->b_flags & B_VMIO) { + int i; + int n; + + /* + * Fixup base to be relative to beginning of first page. + * Set initial n to be the maximum number of bytes in the + * first page that can be validated. + */ + + base += (bp->b_offset & PAGE_MASK); + n = PAGE_SIZE - (base & PAGE_MASK); + + for (i = base / PAGE_SIZE; size > 0 && i < bp->b_npages; ++i) { + vm_page_t m = bp->b_pages[i]; + + if (n > size) + n = size; + + vm_page_set_validclean(m, base & PAGE_MASK, n); + base += n; + size -= n; + n = PAGE_SIZE; + } + } +} + +/* + * vfs_bio_clrbuf: + * + * clear a buffer. This routine essentially fakes an I/O, so we need + * to clear BIO_ERROR and B_INVAL. + * + * Note that while we only theoretically need to clear through b_bcount, + * we go ahead and clear through b_bufsize. + */ + +void +vfs_bio_clrbuf(struct buf *bp) +{ + int i, mask = 0; + caddr_t sa, ea; + + GIANT_REQUIRED; + + if ((bp->b_flags & (B_VMIO | B_MALLOC)) == B_VMIO) { + bp->b_flags &= ~B_INVAL; + bp->b_ioflags &= ~BIO_ERROR; + if( (bp->b_npages == 1) && (bp->b_bufsize < PAGE_SIZE) && + (bp->b_offset & PAGE_MASK) == 0) { + mask = (1 << (bp->b_bufsize / DEV_BSIZE)) - 1; + if ((bp->b_pages[0]->valid & mask) == mask) { + bp->b_resid = 0; + return; + } + if (((bp->b_pages[0]->flags & PG_ZERO) == 0) && + ((bp->b_pages[0]->valid & mask) == 0)) { + bzero(bp->b_data, bp->b_bufsize); + bp->b_pages[0]->valid |= mask; + bp->b_resid = 0; + return; + } + } + ea = sa = bp->b_data; + for(i=0;i<bp->b_npages;i++,sa=ea) { + int j = ((vm_offset_t)sa & PAGE_MASK) / DEV_BSIZE; + ea = (caddr_t)trunc_page((vm_offset_t)sa + PAGE_SIZE); + ea = (caddr_t)(vm_offset_t)ulmin( + (u_long)(vm_offset_t)ea, + (u_long)(vm_offset_t)bp->b_data + bp->b_bufsize); + mask = ((1 << ((ea - sa) / DEV_BSIZE)) - 1) << j; + if ((bp->b_pages[i]->valid & mask) == mask) + continue; + if ((bp->b_pages[i]->valid & mask) == 0) { + if ((bp->b_pages[i]->flags & PG_ZERO) == 0) { + bzero(sa, ea - sa); + } + } else { + for (; sa < ea; sa += DEV_BSIZE, j++) { + if (((bp->b_pages[i]->flags & PG_ZERO) == 0) && + (bp->b_pages[i]->valid & (1<<j)) == 0) + bzero(sa, DEV_BSIZE); + } + } + bp->b_pages[i]->valid |= mask; + vm_page_flag_clear(bp->b_pages[i], PG_ZERO); + } + bp->b_resid = 0; + } else { + clrbuf(bp); + } +} + +/* + * vm_hold_load_pages and vm_hold_free_pages get pages into + * a buffers address space. The pages are anonymous and are + * not associated with a file object. + */ +static void +vm_hold_load_pages(struct buf * bp, vm_offset_t from, vm_offset_t to) +{ + vm_offset_t pg; + vm_page_t p; + int index; + + GIANT_REQUIRED; + + to = round_page(to); + from = round_page(from); + index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT; + + for (pg = from; pg < to; pg += PAGE_SIZE, index++) { +tryagain: + /* + * note: must allocate system pages since blocking here + * could intefere with paging I/O, no matter which + * process we are. + */ + p = vm_page_alloc(kernel_object, + ((pg - VM_MIN_KERNEL_ADDRESS) >> PAGE_SHIFT), + VM_ALLOC_SYSTEM); + if (!p) { + vm_pageout_deficit += (to - from) >> PAGE_SHIFT; + VM_WAIT; + goto tryagain; + } + vm_page_wire(p); + p->valid = VM_PAGE_BITS_ALL; + vm_page_flag_clear(p, PG_ZERO); + pmap_qenter(pg, &p, 1); + bp->b_pages[index] = p; + vm_page_wakeup(p); + } + bp->b_npages = index; +} + +/* Return pages associated with this buf to the vm system */ +void +vm_hold_free_pages(struct buf * bp, vm_offset_t from, vm_offset_t to) +{ + vm_offset_t pg; + vm_page_t p; + int index, newnpages; + + GIANT_REQUIRED; + + from = round_page(from); + to = round_page(to); + newnpages = index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT; + + for (pg = from; pg < to; pg += PAGE_SIZE, index++) { + p = bp->b_pages[index]; + if (p && (index < bp->b_npages)) { + if (p->busy) { + printf( + "vm_hold_free_pages: blkno: %jd, lblkno: %jd\n", + (intmax_t)bp->b_blkno, + (intmax_t)bp->b_lblkno); + } + bp->b_pages[index] = NULL; + pmap_qremove(pg, 1); + vm_page_busy(p); + vm_page_unwire(p, 0); + vm_page_free(p); + } + } + bp->b_npages = newnpages; +} + + +#include "opt_ddb.h" +#ifdef DDB +#include <ddb/ddb.h> + +/* DDB command to show buffer data */ +DB_SHOW_COMMAND(buffer, db_show_buffer) +{ + /* get args */ + struct buf *bp = (struct buf *)addr; + + if (!have_addr) { + db_printf("usage: show buffer <addr>\n"); + return; + } + + db_printf("b_flags = 0x%b\n", (u_int)bp->b_flags, PRINT_BUF_FLAGS); + db_printf( + "b_error = %d, b_bufsize = %ld, b_bcount = %ld, b_resid = %ld\n" + "b_dev = (%d,%d), b_data = %p, b_blkno = %jd, b_pblkno = %jd\n", + bp->b_error, bp->b_bufsize, bp->b_bcount, bp->b_resid, + major(bp->b_dev), minor(bp->b_dev), bp->b_data, + (intmax_t)bp->b_blkno, (intmax_t)bp->b_pblkno); + if (bp->b_npages) { + int i; + db_printf("b_npages = %d, pages(OBJ, IDX, PA): ", bp->b_npages); + for (i = 0; i < bp->b_npages; i++) { + vm_page_t m; + m = bp->b_pages[i]; + db_printf("(%p, 0x%lx, 0x%lx)", (void *)m->object, + (u_long)m->pindex, (u_long)VM_PAGE_TO_PHYS(m)); + if ((i + 1) < bp->b_npages) + db_printf(","); + } + db_printf("\n"); + } +} +#endif /* DDB */ |
