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freebsd/sys/kern/vfs_bio.c
Matthew Dillon 8f95b97072 Reimplement buf_daemon / getnewbuf() interaction for dealing with 
stressful situations.  buf_daemon now makes a distinction between
    being woken up and its sleep timing out, and as a consequence is now
    much better able to dynamically tune itself to its environment.

Reviewed by:	Alfred Perlstein <bright@wintelcom.net>
1999-12-20 20:28:40 +00:00

3090 lines
78 KiB
C
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/*
* 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/kernel.h>
#include <sys/sysctl.h>
#include <sys/proc.h>
#include <sys/kthread.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/lock.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>
#include <sys/buf.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/resourcevar.h>
#include <sys/conf.h>
static MALLOC_DEFINE(M_BIOBUF, "BIO buffer", "BIO buffer");
struct bio_ops bioops; /* I/O operation notification */
struct buf *buf; /* buffer header pool */
struct swqueue bswlist;
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 int flushbufqueues(void);
static int bd_request;
static void buf_daemon __P((void));
/*
* 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;
int runningbufspace;
int vmiodirenable = FALSE;
int buf_maxio = DFLTPHYS;
static vm_offset_t bogus_offset;
static int bufspace, maxbufspace, vmiospace,
bufmallocspace, maxbufmallocspace, hibufspace;
static int maxbdrun;
static int needsbuffer;
static int numdirtybuffers, hidirtybuffers;
static int numfreebuffers, lofreebuffers, hifreebuffers;
static int getnewbufcalls;
static int getnewbufrestarts;
static int kvafreespace;
SYSCTL_INT(_vfs, OID_AUTO, numdirtybuffers, CTLFLAG_RD,
&numdirtybuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, hidirtybuffers, CTLFLAG_RW,
&hidirtybuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, numfreebuffers, CTLFLAG_RD,
&numfreebuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, lofreebuffers, CTLFLAG_RW,
&lofreebuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, hifreebuffers, CTLFLAG_RW,
&hifreebuffers, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, runningbufspace, CTLFLAG_RD,
&runningbufspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, maxbufspace, CTLFLAG_RW,
&maxbufspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, hibufspace, CTLFLAG_RD,
&hibufspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, bufspace, CTLFLAG_RD,
&bufspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, maxbdrun, CTLFLAG_RW,
&maxbdrun, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, vmiospace, CTLFLAG_RD,
&vmiospace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, maxmallocbufspace, CTLFLAG_RW,
&maxbufmallocspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, bufmallocspace, CTLFLAG_RD,
&bufmallocspace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, kvafreespace, CTLFLAG_RD,
&kvafreespace, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufcalls, CTLFLAG_RW,
&getnewbufcalls, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, getnewbufrestarts, CTLFLAG_RW,
&getnewbufrestarts, 0, "");
SYSCTL_INT(_vfs, OID_AUTO, vmiodirenable, CTLFLAG_RW,
&vmiodirenable, 0, "");
static int bufhashmask;
static LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash;
struct bqueues bufqueues[BUFFER_QUEUES] = { { 0 } };
char *buf_wmesg = BUF_WMESG;
extern int vm_swap_size;
#define BUF_MAXUSE 24
#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 */
#define VFS_BIO_NEED_KVASPACE 0x10 /* wait for buffer_map space, emerg */
/*
* 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]);
}
/*
* kvaspacewakeup:
*
* Called when kva space is potential available for recovery or when
* kva space is recovered in the buffer_map. This function wakes up
* anyone waiting for buffer_map kva space. Even though the buffer_map
* is larger then maxbufspace, this situation will typically occur
* when the buffer_map gets fragmented.
*/
static __inline void
kvaspacewakeup(void)
{
/*
* If someone is waiting for KVA 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_KVASPACE) {
needsbuffer &= ~VFS_BIO_NEED_KVASPACE;
wakeup(&needsbuffer);
}
}
/*
* 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(void)
{
if (numdirtybuffers < hidirtybuffers) {
if (needsbuffer & VFS_BIO_NEED_DIRTYFLUSH) {
needsbuffer &= ~VFS_BIO_NEED_DIRTYFLUSH;
wakeup(&needsbuffer);
}
}
}
/*
* bufspacewakeup:
*
* Called when buffer space is potentially available for recovery or when
* buffer space is recovered. 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);
}
}
/*
* 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);
}
}
/*
* 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)
{
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;
}
}
static __inline__
void
bd_wakeup(int dirtybuflevel)
{
if (numdirtybuffers >= dirtybuflevel && bd_request == 0) {
bd_request = 1;
wakeup(&bd_request);
}
}
/*
* bd_speedup - speedup the buffer cache flushing code
*/
static __inline__
void
bd_speedup(void)
{
bd_wakeup(1);
}
/*
* Initialize buffer headers and related structures.
*/
caddr_t
bufhashinit(caddr_t vaddr)
{
/* first, make a null hash table */
for (bufhashmask = 8; bufhashmask < nbuf / 4; bufhashmask <<= 1)
;
bufhashtbl = (void *)vaddr;
vaddr = vaddr + sizeof(*bufhashtbl) * bufhashmask;
--bufhashmask;
return(vaddr);
}
void
bufinit(void)
{
struct buf *bp;
int i;
TAILQ_INIT(&bswlist);
LIST_INIT(&invalhash);
simple_lock_init(&buftimelock);
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 currently calculated to be maximally efficient
* when the filesystem block size is DFLTBSIZE or DFLTBSIZE*2
* (4K or 8K). To reduce the number of stall points our calculation
* is based on DFLTBSIZE which should reduce the chances of actually
* running out of buffer headers. The maxbufspace calculation is also
* based on DFLTBSIZE (4K) instead of BKVASIZE (8K) in order to
* reduce the chance that a KVA allocation will fail due to
* fragmentation. While this does not usually create a stall,
* the KVA map allocation/free functions are O(N) rather then O(1)
* so running them constantly would result in inefficient O(N*M)
* buffer cache operation.
*/
maxbufspace = (nbuf + 8) * DFLTBSIZE;
hibufspace = imax(3 * maxbufspace / 4, maxbufspace - MAXBSIZE * 5);
/*
* 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. We also reduce buf_maxio in this case (used
* by the clustering code) in an attempt to further reduce the load on
* the buffer cache.
*/
while (hidirtybuffers * BKVASIZE > 3 * hibufspace / 4) {
hidirtybuffers >>= 1;
buf_maxio >>= 1;
}
/*
* Temporary, BKVASIZE may be manipulated soon, make sure we don't
* do something illegal. XXX
*/
#if BKVASIZE < MAXBSIZE
if (buf_maxio < BKVASIZE * 2)
buf_maxio = BKVASIZE * 2;
#else
if (buf_maxio < MAXBSIZE)
buf_maxio = MAXBSIZE;
#endif
/*
* Try to keep the number of free buffers in the specified range,
* and give the syncer 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.
*/
if ((maxbdrun = nswbuf / 4) < 4)
maxbdrun = 4;
kvafreespace = 0;
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++;
}
/*
* Free the kva allocation for a buffer
* Must be called only at splbio or higher,
* as this is the only locking for buffer_map.
*/
static void
bfreekva(struct buf * bp)
{
if (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;
kvaspacewakeup();
}
}
/*
* bremfree:
*
* Remove the buffer from the appropriate free list.
*/
void
bremfree(struct buf * bp)
{
int s = splbio();
int old_qindex = bp->b_qindex;
if (bp->b_qindex != QUEUE_NONE) {
if (bp->b_qindex == QUEUE_EMPTYKVA) {
kvafreespace -= bp->b_kvasize;
}
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;
runningbufspace += bp->b_bufsize;
} else {
#if !defined(MAX_PERF)
if (BUF_REFCNT(bp) <= 1)
panic("bremfree: removing a buffer not on a queue");
#endif
}
/*
* 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 B_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() ).
*/
int
bread(struct vnode * vp, daddr_t blkno, int size, struct ucred * cred,
struct buf ** bpp)
{
struct buf *bp;
bp = getblk(vp, blkno, size, 0, 0);
*bpp = bp;
/* if not found in cache, do some I/O */
if ((bp->b_flags & B_CACHE) == 0) {
if (curproc != NULL)
curproc->p_stats->p_ru.ru_inblock++;
KASSERT(!(bp->b_flags & B_ASYNC), ("bread: illegal async bp %p", bp));
bp->b_flags |= B_READ;
bp->b_flags &= ~(B_ERROR | B_INVAL);
if (bp->b_rcred == NOCRED) {
if (cred != NOCRED)
crhold(cred);
bp->b_rcred = cred;
}
vfs_busy_pages(bp, 0);
VOP_STRATEGY(vp, bp);
return (biowait(bp));
}
return (0);
}
/*
* Operates like bread, but also starts asynchronous I/O on
* read-ahead blocks. We must clear B_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 (curproc != NULL)
curproc->p_stats->p_ru.ru_inblock++;
bp->b_flags |= B_READ;
bp->b_flags &= ~(B_ERROR | B_INVAL);
if (bp->b_rcred == NOCRED) {
if (cred != NOCRED)
crhold(cred);
bp->b_rcred = 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 (curproc != NULL)
curproc->p_stats->p_ru.ru_inblock++;
rabp->b_flags |= B_READ | B_ASYNC;
rabp->b_flags &= ~(B_ERROR | B_INVAL);
if (rabp->b_rcred == NOCRED) {
if (cred != NOCRED)
crhold(cred);
rabp->b_rcred = cred;
}
vfs_busy_pages(rabp, 0);
BUF_KERNPROC(rabp);
VOP_STRATEGY(vp, rabp);
} else {
brelse(rabp);
}
}
if (readwait) {
rv = biowait(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;
if (bp->b_flags & B_INVAL) {
brelse(bp);
return (0);
}
oldflags = bp->b_flags;
#if !defined(MAX_PERF)
if (BUF_REFCNT(bp) == 0)
panic("bwrite: buffer is not busy???");
#endif
s = splbio();
bundirty(bp);
bp->b_flags &= ~(B_READ | B_DONE | B_ERROR);
bp->b_flags |= B_WRITEINPROG | B_CACHE;
bp->b_vp->v_numoutput++;
vfs_busy_pages(bp, 1);
if (curproc != NULL)
curproc->p_stats->p_ru.ru_oublock++;
splx(s);
if (oldflags & B_ASYNC)
BUF_KERNPROC(bp);
VOP_STRATEGY(bp->b_vp, bp);
if ((oldflags & B_ASYNC) == 0) {
int rtval = biowait(bp);
brelse(bp);
return (rtval);
}
return (0);
}
/*
* 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)
{
#if !defined(MAX_PERF)
if (BUF_REFCNT(bp) == 0)
panic("bdwrite: buffer is not busy");
#endif
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 saturated the
* buffer cache.
*/
bd_wakeup(hidirtybuffers);
/*
* 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 B_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_READ|B_RELBUF);
if ((bp->b_flags & B_DELWRI) == 0) {
bp->b_flags |= B_DONE | B_DELWRI;
reassignbuf(bp, bp->b_vp);
++numdirtybuffers;
bd_wakeup(hidirtybuffers);
}
}
/*
* 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();
}
}
/*
* 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) VOP_BWRITE(bp->b_vp, bp);
}
/*
* bowrite:
*
* Ordered write. Start output on a buffer, and flag it so that the
* device will write it in the order it was queued. The buffer is
* released when the output completes. bwrite() ( or the VOP routine
* anyway ) is responsible for handling B_INVAL buffers.
*/
int
bowrite(struct buf * bp)
{
bp->b_flags |= B_ORDERED | B_ASYNC;
return (VOP_BWRITE(bp->b_vp, 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)
{
int slop = hidirtybuffers / 10;
if (numdirtybuffers > hidirtybuffers + slop) {
int s;
s = splbio();
while (numdirtybuffers > hidirtybuffers) {
bd_wakeup(hidirtybuffers);
needsbuffer |= VFS_BIO_NEED_DIRTYFLUSH;
tsleep(&needsbuffer, (PRIBIO + 4), "flswai", 0);
}
splx(s);
}
}
/*
* 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;
int kvawakeup = 0;
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_flags &= ~B_ERROR;
if ((bp->b_flags & (B_READ | B_ERROR | B_INVAL)) == B_ERROR) {
/*
* Failed write, redirty. Must clear B_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_flags &= ~B_ERROR;
bdirty(bp);
} else if ((bp->b_flags & (B_NOCACHE | B_INVAL | B_ERROR | B_FREEBUF)) ||
(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 && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
if (bp->b_flags & B_DELWRI) {
--numdirtybuffers;
numdirtywakeup();
}
bp->b_flags &= ~(B_DELWRI | B_CACHE | B_FREEBUF);
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 (bp->b_flags & B_DELWRI)
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 B_ERROR or B_NOCACHE is set, pages in the VM object will be
* invalidated. B_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 ((bp->b_flags & B_VMIO)
&& !(bp->b_vp->v_tag == VT_NFS &&
!vn_isdisk(bp->b_vp) &&
(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
* for block sizes that are less then PAGE_SIZE, the b_data
* base of the buffer does not represent exactly b_offset and
* neither b_offset nor b_size are necessarily page aligned.
* Instead, the starting position of b_offset is:
*
* b_data + (b_offset & PAGE_MASK)
*
* 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++) {
m = bp->b_pages[i];
vm_page_flag_clear(m, PG_ZERO);
if (m == bogus_page) {
obj = (vm_object_t) vp->v_object;
poff = OFF_TO_IDX(bp->b_offset);
for (j = i; j < bp->b_npages; j++) {
m = bp->b_pages[j];
if (m == bogus_page) {
m = vm_page_lookup(obj, poff + j);
#if !defined(MAX_PERF)
if (!m) {
panic("brelse: page missing\n");
}
#endif
bp->b_pages[j] = m;
}
}
if ((bp->b_flags & B_INVAL) == 0) {
pmap_qenter(trunc_page((vm_offset_t)bp->b_data), bp->b_pages, bp->b_npages);
}
}
if (bp->b_flags & (B_NOCACHE|B_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);
}
resid -= PAGE_SIZE - (foff & PAGE_MASK);
foff = (foff + PAGE_SIZE) & ~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 !defined(MAX_PERF)
if (bp->b_qindex != QUEUE_NONE)
panic("brelse: free buffer onto another queue???");
#endif
if (BUF_REFCNT(bp) > 1) {
/* Temporary panic to verify exclusive locking */
/* This panic goes away when we allow shared refs */
panic("brelse: multiple refs");
/* 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;
if (bp->b_kvasize) {
bp->b_qindex = QUEUE_EMPTYKVA;
kvawakeup = 1;
} 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;
kvafreespace += bp->b_kvasize;
/* buffers with junk contents */
} else if (bp->b_flags & (B_ERROR | B_INVAL | B_NOCACHE | B_RELBUF)) {
bp->b_flags |= B_INVAL;
bp->b_qindex = QUEUE_CLEAN;
if (bp->b_kvasize)
kvawakeup = 1;
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 {
switch(bp->b_flags & (B_DELWRI|B_AGE)) {
case B_DELWRI | B_AGE:
bp->b_qindex = QUEUE_DIRTY;
TAILQ_INSERT_HEAD(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
break;
case B_DELWRI:
bp->b_qindex = QUEUE_DIRTY;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_DIRTY], bp, b_freelist);
break;
case B_AGE:
bp->b_qindex = QUEUE_CLEAN;
TAILQ_INSERT_HEAD(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
if (bp->b_kvasize)
kvawakeup = 1;
break;
default:
bp->b_qindex = QUEUE_CLEAN;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
if (bp->b_kvasize)
kvawakeup = 1;
break;
}
}
/*
* 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)) {
bp->b_flags &= ~B_DELWRI;
--numdirtybuffers;
numdirtywakeup();
}
runningbufspace -= bp->b_bufsize;
/*
* 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.
*/
if (bp->b_bufsize)
bufspacewakeup();
if (kvawakeup)
kvaspacewakeup();
/* unlock */
BUF_UNLOCK(bp);
bp->b_flags &= ~(B_ORDERED | B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF);
splx(s);
}
/*
* Release a buffer back to the appropriate queue but do not try to free
* it.
*
* 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.
*/
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 !defined(MAX_PERF)
if (bp->b_qindex != QUEUE_NONE)
panic("bqrelse: free buffer onto another queue???");
#endif
if (BUF_REFCNT(bp) > 1) {
/* do not release to free list */
panic("bqrelse: multiple refs");
BUF_UNLOCK(bp);
splx(s);
return;
}
if (bp->b_flags & B_LOCKED) {
bp->b_flags &= ~B_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 {
bp->b_qindex = QUEUE_CLEAN;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_CLEAN], bp, b_freelist);
}
runningbufspace -= bp->b_bufsize;
if ((bp->b_flags & B_LOCKED) == 0 &&
((bp->b_flags & B_INVAL) || !(bp->b_flags & B_DELWRI))) {
bufcountwakeup();
}
/*
* Something we can maybe wakeup
*/
if (bp->b_bufsize && !(bp->b_flags & B_DELWRI))
bufspacewakeup();
/* unlock */
BUF_UNLOCK(bp);
bp->b_flags &= ~(B_ORDERED | B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF);
splx(s);
}
static void
vfs_vmio_release(bp)
struct buf *bp;
{
int i, s;
vm_page_t m;
s = splvm();
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.
*/
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);
}
}
}
bufspace -= bp->b_bufsize;
vmiospace -= bp->b_bufsize;
runningbufspace -= bp->b_bufsize;
splx(s);
pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
if (bp->b_bufsize)
bufspacewakeup();
bp->b_npages = 0;
bp->b_bufsize = 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) VOP_BWRITE(bp->b_vp, 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;
struct buf *dbp;
int outofspace;
int nqindex;
int defrag = 0;
++getnewbufcalls;
--getnewbufrestarts;
restart:
++getnewbufrestarts;
/*
* Calculate whether we are out of buffer space. This state is
* recalculated on every restart. If we are out of space, we
* have to turn off defragmentation. Setting defrag to -1 when
* outofspace is positive means "defrag while freeing buffers".
* The looping conditional will be muffed up if defrag is left
* positive when outofspace is positive.
*/
dbp = NULL;
outofspace = 0;
if (bufspace >= hibufspace) {
if ((curproc && (curproc->p_flag & P_BUFEXHAUST) == 0) ||
bufspace >= maxbufspace) {
outofspace = 1;
if (defrag > 0)
defrag = -1;
}
}
/*
* defrag state is semi-persistant. 1 means we are flagged for
* defragging. -1 means we actually defragged something.
*/
/* nop */
/*
* 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.
*
* Normally we want to find an EMPTYKVA buffer. That is, a
* buffer with kva already allocated. If there are no EMPTYKVA
* buffers we back up to the truely EMPTY buffers. When defragging
* we do not bother backing up since we have to locate buffers with
* kva to defrag. If we are out of space we skip both EMPTY and
* EMPTYKVA and dig right into the CLEAN queue.
*
* In this manner we avoid scanning unnecessary buffers. It is very
* important for us to do this because the buffer cache is almost
* constantly out of space or in need of defragmentation.
*/
if (curproc && (curproc->p_flag & P_BUFEXHAUST) == 0 &&
numfreebuffers < lofreebuffers) {
nqindex = QUEUE_CLEAN;
nbp = NULL;
} else {
nqindex = QUEUE_EMPTYKVA;
nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTYKVA]);
if (nbp == NULL) {
if (defrag <= 0) {
nqindex = QUEUE_EMPTY;
nbp = TAILQ_FIRST(&bufqueues[QUEUE_EMPTY]);
}
}
if (outofspace || nbp == NULL) {
nqindex = QUEUE_CLEAN;
nbp = TAILQ_FIRST(&bufqueues[QUEUE_CLEAN]);
}
}
/*
* 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 and the buffer isn't useful for fixing
* that problem we continue. If we are out of space and the
* buffer isn't useful for fixing that problem we continue.
*/
if (defrag > 0 && bp->b_kvasize == 0)
continue;
if (outofspace > 0 && bp->b_bufsize == 0)
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 && bioops.io_deallocate)
(*bioops.io_deallocate)(bp);
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_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;
LIST_INIT(&bp->b_dep);
/*
* Ok, now that we have a free buffer, if we are defragging
* we have to recover the kvaspace. If we are out of space
* we have to free the buffer (which we just did), but we
* do not have to recover kva space unless we hit a defrag
* hicup. Being able to avoid freeing the kva space leads
* to a significant reduction in overhead.
*/
if (defrag > 0) {
defrag = -1;
bp->b_flags |= B_INVAL;
bfreekva(bp);
brelse(bp);
goto restart;
}
if (outofspace > 0) {
outofspace = -1;
bp->b_flags |= B_INVAL;
if (defrag < 0)
bfreekva(bp);
brelse(bp);
goto restart;
}
/*
* We are done
*/
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 > 0) {
flags = VFS_BIO_NEED_KVASPACE;
waitmsg = "nbufkv";
} else if (outofspace > 0) {
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.
*/
vm_offset_t addr = 0;
maxsize = (maxsize + PAGE_MASK) & ~PAGE_MASK;
if (maxsize != bp->b_kvasize) {
bfreekva(bp);
if (vm_map_findspace(buffer_map,
vm_map_min(buffer_map), maxsize, &addr)) {
/*
* Uh oh. Buffer map is to fragmented. Try
* to defragment.
*/
if (defrag <= 0) {
defrag = 1;
bp->b_flags |= B_INVAL;
brelse(bp);
goto restart;
}
/*
* Uh oh. We couldn't seem to defragment
*/
panic("getnewbuf: unreachable code reached");
}
}
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;
}
bp->b_data = bp->b_kvabase;
}
return(bp);
}
/*
* waitfreebuffers:
*
* Wait for sufficient free buffers. Only called from normal processes.
*/
static void
waitfreebuffers(int slpflag, int slptimeo)
{
while (numfreebuffers < hifreebuffers) {
if (numfreebuffers >= hifreebuffers)
break;
needsbuffer |= VFS_BIO_NEED_FREE;
if (tsleep(&needsbuffer, (PRIBIO + 4)|slpflag, "biofre", slptimeo))
break;
}
}
/*
* 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 int bd_interval;
static int bd_flushto;
static int bd_flushinc;
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;
/*
* This process is allowed to take the buffer cache to the limit
*/
curproc->p_flag |= P_BUFEXHAUST;
s = splbio();
bd_interval = 5 * hz; /* dynamically adjusted */
bd_flushto = hidirtybuffers; /* dynamically adjusted */
bd_flushinc = 1;
while (TRUE) {
bd_request = 0;
/*
* Do the flush. Limit the number of buffers we flush in one
* go. The failure condition occurs when processes are writing
* buffers faster then we can dispose of them. In this case
* we may be flushing so often that the previous set of flushes
* have not had time to complete, causing us to run out of
* physical buffers and block.
*/
{
int runcount = maxbdrun;
while (numdirtybuffers > bd_flushto && runcount) {
--runcount;
if (flushbufqueues() == 0)
break;
}
}
if (bd_request ||
tsleep(&bd_request, PVM, "psleep", bd_interval) == 0) {
/*
* Another request is pending or we were woken up
* without timing out. Flush more.
*/
--bd_flushto;
if (bd_flushto >= numdirtybuffers - 5) {
bd_flushto = numdirtybuffers - 10;
bd_flushinc = 1;
}
if (bd_flushto < 2)
bd_flushto = 2;
} else {
/*
* We slept and timed out, we can slow down.
*/
bd_flushto += bd_flushinc;
if (bd_flushto > hidirtybuffers)
bd_flushto = hidirtybuffers;
++bd_flushinc;
if (bd_flushinc > hidirtybuffers / 20 + 1)
bd_flushinc = hidirtybuffers / 20 + 1;
}
/*
* Set the interval on a linear scale based on hidirtybuffers
* with a maximum frequency of 1/10 second.
*/
bd_interval = bd_flushto * 5 * hz / hidirtybuffers;
if (bd_interval < hz / 10)
bd_interval = hz / 10;
}
}
/*
* 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) {
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;
}
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;
if (incore(vp, blkno))
return 1;
if (vp->v_mount == NULL)
return 0;
if ((vp->v_object == NULL) || (vp->v_flag & VOBJBUF) == 0)
return 0;
obj = vp->v_object;
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)
return 0;
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)
return 0;
}
return 1;
}
/*
* 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;
/*
* 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 VOP_BWRITE() 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 B_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 !defined(MAX_PERF)
if (size > MAXBSIZE)
panic("getblk: size(%d) > MAXBSIZE(%d)\n", size, MAXBSIZE);
#endif
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.
*/
if (!curproc || (curproc->p_flag & P_BUFEXHAUST)) {
if (numfreebuffers == 0) {
if (!curproc)
return NULL;
needsbuffer |= VFS_BIO_NEED_ANY;
tsleep(&needsbuffer, (PRIBIO + 4) | slpflag, "newbuf",
slptimeo);
}
} else if (numfreebuffers < lofreebuffers) {
waitfreebuffers(slpflag, slptimeo);
}
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. Ohterwise, 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;
VOP_BWRITE(bp->b_vp, 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;
VOP_BWRITE(bp->b_vp, 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.
*/
if ((bp->b_flags & (B_CACHE|B_DELWRI)) == B_DELWRI) {
VOP_BWRITE(bp->b_vp, 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))
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 = (off_t)blkno * bsize;
vmio = (vp->v_object != 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 && vp->v_type != VBLK)
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;
s = splbio();
while ((bp = getnewbuf(0, 0, size, MAXBSIZE)) == 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;
#if !defined(MAX_PERF)
if (BUF_REFCNT(bp) == 0)
panic("allocbuf: buffer not busy");
if (bp->b_kvasize < size)
panic("allocbuf: buffer too small");
#endif
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 !defined(NO_B_MALLOC)
if (bp->b_flags & B_MALLOC)
newbsize = mbsize;
else
#endif
newbsize = round_page(size);
if (newbsize < bp->b_bufsize) {
#if !defined(NO_B_MALLOC)
/*
* malloced buffers are not shrunk
*/
if (bp->b_flags & B_MALLOC) {
if (newbsize) {
bp->b_bcount = size;
} else {
free(bp->b_data, M_BIOBUF);
bufspace -= bp->b_bufsize;
bufmallocspace -= bp->b_bufsize;
runningbufspace -= bp->b_bufsize;
if (bp->b_bufsize)
bufspacewakeup();
bp->b_data = bp->b_kvabase;
bp->b_bufsize = 0;
bp->b_bcount = 0;
bp->b_flags &= ~B_MALLOC;
}
return 1;
}
#endif
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) {
#if !defined(NO_B_MALLOC)
/*
* 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;
bufspace += mbsize;
bufmallocspace += mbsize;
runningbufspace += bp->b_bufsize;
return 1;
}
#endif
origbuf = NULL;
origbufsize = 0;
#if !defined(NO_B_MALLOC)
/*
* 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;
bufspace -= bp->b_bufsize;
bufmallocspace -= bp->b_bufsize;
runningbufspace -= bp->b_bufsize;
if (bp->b_bufsize)
bufspacewakeup();
bp->b_bufsize = 0;
bp->b_flags &= ~B_MALLOC;
newbsize = round_page(newbsize);
}
#endif
vm_hold_load_pages(
bp,
(vm_offset_t) bp->b_data + bp->b_bufsize,
(vm_offset_t) bp->b_data + newbsize);
#if !defined(NO_B_MALLOC)
if (origbuf) {
bcopy(origbuf, bp->b_data, origbufsize);
free(origbuf, M_BIOBUF);
}
#endif
}
} 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 !defined(NO_B_MALLOC)
if (bp->b_flags & B_MALLOC)
panic("allocbuf: VMIO buffer can't be malloced");
#endif
/*
* 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;
obj = vp->v_object;
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) {
m = vm_page_alloc(obj, pi, VM_ALLOC_NORMAL);
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 (bp->b_flags & B_VMIO)
vmiospace += (newbsize - bp->b_bufsize);
bufspace += (newbsize - bp->b_bufsize);
runningbufspace += (newbsize - bp->b_bufsize);
if (newbsize < bp->b_bufsize)
bufspacewakeup();
bp->b_bufsize = newbsize; /* actual buffer allocation */
bp->b_bcount = size; /* requested buffer size */
return 1;
}
/*
* biowait:
*
* 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
biowait(register struct buf * bp)
{
int s;
s = splbio();
while ((bp->b_flags & B_DONE) == 0) {
#if defined(NO_SCHEDULE_MODS)
tsleep(bp, PRIBIO, "biowait", 0);
#else
if (bp->b_flags & B_READ)
tsleep(bp, PRIBIO, "biord", 0);
else
tsleep(bp, PRIBIO, "biowr", 0);
#endif
}
splx(s);
if (bp->b_flags & B_EINTR) {
bp->b_flags &= ~B_EINTR;
return (EINTR);
}
if (bp->b_flags & B_ERROR) {
return (bp->b_error ? bp->b_error : EIO);
} else {
return (0);
}
}
/*
* biodone:
*
* 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
biodone(register struct buf * bp)
{
int s;
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;
if (bp->b_flags & B_FREEBUF) {
brelse(bp);
splx(s);
return;
}
if ((bp->b_flags & B_READ) == 0) {
vwakeup(bp);
}
/* call optional completion function if requested */
if (bp->b_flags & B_CALL) {
bp->b_flags &= ~B_CALL;
(*bp->b_iodone) (bp);
splx(s);
return;
}
if (LIST_FIRST(&bp->b_dep) != NULL && bioops.io_complete)
(*bioops.io_complete)(bp);
if (bp->b_flags & B_VMIO) {
int i, resid;
vm_ooffset_t foff;
vm_page_t m;
vm_object_t obj;
int iosize;
struct vnode *vp = bp->b_vp;
obj = vp->v_object;
#if defined(VFS_BIO_DEBUG)
if (vp->v_usecount == 0) {
panic("biodone: zero vnode ref count");
}
if (vp->v_object == NULL) {
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 !defined(MAX_PERF)
if (!obj) {
panic("biodone: no object");
}
#endif
#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_flags & (B_READ|B_FREEBUF|B_INVAL|B_NOCACHE|B_ERROR)) == B_READ) {
bp->b_flags |= B_CACHE;
}
for (i = 0; i < bp->b_npages; i++) {
int bogusflag = 0;
m = bp->b_pages[i];
if (m == bogus_page) {
bogusflag = 1;
m = vm_page_lookup(obj, OFF_TO_IDX(foff));
if (!m) {
#if defined(VFS_BIO_DEBUG)
printf("biodone: page disappeared\n");
#endif
vm_object_pip_subtract(obj, 1);
bp->b_flags &= ~B_CACHE;
continue;
}
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
resid = IDX_TO_OFF(m->pindex + 1) - foff;
if (resid > iosize)
resid = iosize;
/*
* 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_flags & B_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) {
#if !defined(MAX_PERF)
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);
#endif
if (!vn_isdisk(vp))
#if !defined(MAX_PERF)
printf(" iosize: %ld, lblkno: %d, flags: 0x%lx, npages: %d\n",
bp->b_vp->v_mount->mnt_stat.f_iosize,
(int) bp->b_lblkno,
bp->b_flags, bp->b_npages);
else
printf(" VDEV, lblkno: %d, flags: 0x%lx, npages: %d\n",
(int) 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);
#endif
panic("biodone: page busy < 0\n");
}
vm_page_io_finish(m);
vm_object_pip_subtract(obj, 1);
foff += resid;
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_ERROR | B_RELBUF)) != 0)
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;
if (bp->b_flags & B_VMIO) {
struct vnode *vp = bp->b_vp;
vm_object_t obj = vp->v_object;
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 !defined(MAX_PERF)
if (!m) {
panic("vfs_unbusy_pages: page missing\n");
}
#endif
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;
/*
* 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) & ~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 B_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;
if (bp->b_flags & B_VMIO) {
struct vnode *vp = bp->b_vp;
vm_object_t obj = vp->v_object;
vm_ooffset_t foff;
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) & ~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;
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) & ~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 B_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;
if ((bp->b_flags & (B_VMIO | B_MALLOC)) == B_VMIO) {
bp->b_flags &= ~(B_INVAL|B_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]->flags & PG_ZERO) == 0) &&
((bp->b_pages[0]->valid & mask) != mask)) {
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_unload pages get pages into
* a buffers address space. The pages are anonymous and are
* not associated with a file object.
*/
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;
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:
p = vm_page_alloc(kernel_object,
((pg - VM_MIN_KERNEL_ADDRESS) >> PAGE_SHIFT),
VM_ALLOC_NORMAL);
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_kenter(pg, VM_PAGE_TO_PHYS(p));
bp->b_pages[index] = p;
vm_page_wakeup(p);
}
bp->b_npages = index;
}
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;
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 !defined(MAX_PERF)
if (p->busy) {
printf("vm_hold_free_pages: blkno: %d, lblkno: %d\n",
bp->b_blkno, bp->b_lblkno);
}
#endif
bp->b_pages[index] = NULL;
pmap_kremove(pg);
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>
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\nb_dev = (%d,%d), b_data = %p, "
"b_blkno = %d, b_pblkno = %d\n",
bp->b_error, bp->b_bufsize, bp->b_bcount, bp->b_resid,
major(bp->b_dev), minor(bp->b_dev),
bp->b_data, bp->b_blkno, 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 */
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