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freebsd-dev/sys/kern/vfs_bio.c
John Dyson beb2f78fb0 This should have fixed some conditions that could cause the 
"getblk" hang.  The B_WANTED flag was being cleared gratuitously,
also the optimization of gbincore for ignoring the B_INVAL flag was
incorrect.  There is no place in the code where buffers are on the
hash list that are B_INVAL and not B_BUSY.
1995-12-12 04:18:10 +00:00

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/*
* Copyright (c) 1994 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. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Absolutely no warranty of function or purpose is made by the author
* John S. Dyson.
* 4. This work was done expressly for inclusion into FreeBSD. Other use
* is allowed if this notation is included.
* 5. Modifications may be freely made to this file if the above conditions
* are met.
*
* $Id: vfs_bio.c,v 1.76 1995/12/11 04:56:05 dyson Exp $
*/
/*
* 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.
*/
#define VMIO
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_prot.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 <sys/buf.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include <sys/resourcevar.h>
#include <sys/proc.h>
#include <miscfs/specfs/specdev.h>
static void vfs_update __P((void));
struct proc *updateproc;
static struct kproc_desc up_kp = {
"update",
vfs_update,
&updateproc
};
SYSINIT_KT(update, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &up_kp)
struct buf *buf; /* buffer header pool */
struct swqueue bswlist;
int count_lock_queue __P((void));
void vm_hold_free_pages(struct buf * bp, vm_offset_t from, vm_offset_t to);
void vm_hold_load_pages(struct buf * bp, vm_offset_t from, vm_offset_t to);
void vfs_clean_pages(struct buf * bp);
static void vfs_setdirty(struct buf *bp);
int needsbuffer;
/*
* Internal update daemon, process 3
* The variable vfs_update_wakeup allows for internal syncs.
*/
int vfs_update_wakeup;
/*
* buffers base kva
*/
caddr_t buffers_kva;
/*
* 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;
vm_offset_t bogus_offset;
int bufspace, maxbufspace;
struct bufhashhdr bufhashtbl[BUFHSZ], invalhash;
struct bqueues bufqueues[BUFFER_QUEUES];
#define BUF_MAXUSE 8
/*
* Initialize buffer headers and related structures.
*/
void
bufinit()
{
struct buf *bp;
int i;
TAILQ_INIT(&bswlist);
LIST_INIT(&invalhash);
/* first, make a null hash table */
for (i = 0; i < BUFHSZ; i++)
LIST_INIT(&bufhashtbl[i]);
/* next, make a null set of free lists */
for (i = 0; i < BUFFER_QUEUES; i++)
TAILQ_INIT(&bufqueues[i]);
buffers_kva = (caddr_t) kmem_alloc_pageable(buffer_map, MAXBSIZE * nbuf);
/* 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_vnbufs.le_next = NOLIST;
bp->b_data = buffers_kva + i * MAXBSIZE;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_EMPTY], bp, b_freelist);
LIST_INSERT_HEAD(&invalhash, bp, b_hash);
}
/*
* maxbufspace is currently calculated to support all filesystem blocks
* to be 8K. If you happen to use a 16K filesystem, the size of the buffer
* cache is still the same as it would be for 8K filesystems. This
* keeps the size of the buffer cache "in check" for big block filesystems.
*/
maxbufspace = 2 * (nbuf + 8) * PAGE_SIZE;
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);
}
/*
* remove the buffer from the appropriate free list
*/
void
bremfree(struct buf * bp)
{
int s = splbio();
if (bp->b_qindex != QUEUE_NONE) {
TAILQ_REMOVE(&bufqueues[bp->b_qindex], bp, b_freelist);
bp->b_qindex = QUEUE_NONE;
} else {
panic("bremfree: removing a buffer when not on a queue");
}
splx(s);
}
/*
* Get a buffer with the specified data. Look in the cache first.
*/
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++;
bp->b_flags |= B_READ;
bp->b_flags &= ~(B_DONE | 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(bp);
return (biowait(bp));
}
return (0);
}
/*
* Operates like bread, but also starts asynchronous I/O on
* read-ahead blocks.
*/
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_DONE | 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(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_DONE | B_ERROR | B_INVAL);
if (rabp->b_rcred == NOCRED) {
if (cred != NOCRED)
crhold(cred);
rabp->b_rcred = cred;
}
vfs_busy_pages(rabp, 0);
VOP_STRATEGY(rabp);
} else {
brelse(rabp);
}
}
if (readwait) {
rv = biowait(bp);
}
return (rv);
}
/*
* Write, release buffer on completion. (Done by iodone
* if async.)
*/
int
bwrite(struct buf * bp)
{
int oldflags = bp->b_flags;
if (bp->b_flags & B_INVAL) {
brelse(bp);
return (0);
}
if (!(bp->b_flags & B_BUSY))
panic("bwrite: buffer is not busy???");
bp->b_flags &= ~(B_READ | B_DONE | B_ERROR | B_DELWRI);
bp->b_flags |= B_WRITEINPROG;
if ((oldflags & (B_ASYNC|B_DELWRI)) == (B_ASYNC|B_DELWRI)) {
reassignbuf(bp, bp->b_vp);
}
bp->b_vp->v_numoutput++;
vfs_busy_pages(bp, 1);
if (curproc != NULL)
curproc->p_stats->p_ru.ru_oublock++;
VOP_STRATEGY(bp);
if ((oldflags & B_ASYNC) == 0) {
int rtval = biowait(bp);
if (oldflags & B_DELWRI) {
reassignbuf(bp, bp->b_vp);
}
brelse(bp);
return (rtval);
}
return (0);
}
int
vn_bwrite(ap)
struct vop_bwrite_args *ap;
{
return (bwrite(ap->a_bp));
}
/*
* Delayed write. (Buffer is marked dirty).
*/
void
bdwrite(struct buf * bp)
{
if ((bp->b_flags & B_BUSY) == 0) {
panic("bdwrite: buffer is not busy");
}
if (bp->b_flags & B_INVAL) {
brelse(bp);
return;
}
if (bp->b_flags & B_TAPE) {
bawrite(bp);
return;
}
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);
}
/*
* 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);
brelse(bp);
return;
}
/*
* Asynchronous write.
* Start output on a buffer, but do not wait for it to complete.
* The buffer is released when the output completes.
*/
void
bawrite(struct buf * bp)
{
bp->b_flags |= B_ASYNC;
(void) VOP_BWRITE(bp);
}
/*
* Release a buffer.
*/
void
brelse(struct buf * bp)
{
int s;
if (bp->b_flags & B_CLUSTER) {
relpbuf(bp);
return;
}
/* anyone need a "free" block? */
s = splbio();
if (needsbuffer) {
needsbuffer = 0;
wakeup(&needsbuffer);
}
/* anyone need this block? */
if (bp->b_flags & B_WANTED) {
bp->b_flags &= ~(B_WANTED | B_AGE);
wakeup(bp);
}
if (bp->b_flags & B_LOCKED)
bp->b_flags &= ~B_ERROR;
if ((bp->b_flags & (B_NOCACHE | B_INVAL | B_ERROR)) ||
(bp->b_bufsize <= 0)) {
bp->b_flags |= B_INVAL;
bp->b_flags &= ~(B_DELWRI | B_CACHE);
if (((bp->b_flags & B_VMIO) == 0) && bp->b_vp)
brelvp(bp);
}
/*
* VMIO buffer rundown. It is not very necessary to keep a VMIO buffer
* constituted, so the B_INVAL flag is used to *invalidate* the buffer,
* but the VM object is kept around. The B_NOCACHE flag is used to
* invalidate the pages in the VM object.
*/
if (bp->b_flags & B_VMIO) {
vm_ooffset_t foff;
vm_object_t obj;
int i, resid;
vm_page_t m;
struct vnode *vp;
int iototal = bp->b_bufsize;
vp = bp->b_vp;
if (!vp)
panic("brelse: missing vp");
if (bp->b_npages) {
vm_pindex_t poff;
obj = (vm_object_t) vp->v_object;
if (vp->v_type == VBLK)
foff = ((vm_ooffset_t) bp->b_lblkno) << DEV_BSHIFT;
else
foff = (vm_ooffset_t) vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
poff = OFF_TO_IDX(foff);
for (i = 0; i < bp->b_npages; i++) {
m = bp->b_pages[i];
if (m == bogus_page) {
m = vm_page_lookup(obj, poff + i);
if (!m) {
panic("brelse: page missing\n");
}
bp->b_pages[i] = m;
pmap_qenter(trunc_page(bp->b_data),
bp->b_pages, bp->b_npages);
}
resid = IDX_TO_OFF(m->pindex+1) - foff;
if (resid > iototal)
resid = iototal;
if (resid > 0) {
/*
* Don't invalidate the page if the local machine has already
* modified it. This is the lesser of two evils, and should
* be fixed.
*/
if (bp->b_flags & (B_NOCACHE | B_ERROR)) {
vm_page_test_dirty(m);
if (m->dirty == 0) {
vm_page_set_invalid(m, (vm_offset_t) foff, resid);
if (m->valid == 0)
vm_page_protect(m, VM_PROT_NONE);
}
}
}
foff += resid;
iototal -= resid;
}
}
if (bp->b_flags & (B_INVAL | B_RELBUF)) {
for(i = 0; i < bp->b_npages; i++) {
m = bp->b_pages[i];
--m->bmapped;
if (m->bmapped == 0) {
if (m->flags & PG_WANTED) {
m->flags &= ~PG_WANTED;
wakeup(m);
}
if ((m->busy == 0) && ((m->flags & PG_BUSY) == 0)) {
if (m->object->flags & OBJ_MIGHTBEDIRTY) {
vm_page_test_dirty(m);
}
/*
* if page isn't valid, no sense in keeping it around
*/
if (m->valid == 0) {
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
/*
* if page isn't dirty and hasn't been referenced by
* a process, then cache it
*/
} else if ((m->dirty & m->valid) == 0 &&
(m->flags & PG_REFERENCED) == 0 &&
!pmap_is_referenced(VM_PAGE_TO_PHYS(m))) {
vm_page_cache(m);
/*
* otherwise activate it
*/
} else if ((m->flags & PG_ACTIVE) == 0) {
vm_page_activate(m);
m->act_count = 0;
}
}
}
}
bufspace -= bp->b_bufsize;
pmap_qremove(trunc_page((vm_offset_t) bp->b_data), bp->b_npages);
bp->b_npages = 0;
bp->b_bufsize = 0;
bp->b_flags &= ~B_VMIO;
if (bp->b_vp)
brelvp(bp);
}
}
if (bp->b_qindex != QUEUE_NONE)
panic("brelse: free buffer onto another queue???");
/* enqueue */
/* buffers with no memory */
if (bp->b_bufsize == 0) {
bp->b_qindex = QUEUE_EMPTY;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_EMPTY], 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_ERROR | B_INVAL | B_NOCACHE | B_RELBUF)) {
bp->b_qindex = QUEUE_AGE;
TAILQ_INSERT_HEAD(&bufqueues[QUEUE_AGE], 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);
/* buffers with stale but valid contents */
} else if (bp->b_flags & B_AGE) {
bp->b_qindex = QUEUE_AGE;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_AGE], bp, b_freelist);
/* buffers with valid and quite potentially reuseable contents */
} else {
bp->b_qindex = QUEUE_LRU;
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LRU], bp, b_freelist);
}
/* unlock */
bp->b_flags &= ~(B_WANTED | B_BUSY | B_ASYNC | B_NOCACHE | B_AGE | B_RELBUF);
splx(s);
}
/*
* Check to see if a block is currently memory resident.
*/
__inline struct buf *
gbincore(struct vnode * vp, daddr_t blkno)
{
struct buf *bp;
struct bufhashhdr *bh;
bh = BUFHASH(vp, blkno);
bp = bh->lh_first;
/* Search hash chain */
while (bp != NULL) {
/* hit */
if (bp->b_vp == vp && bp->b_lblkno == blkno &&
(bp->b_flags & B_INVAL) == 0) {
break;
}
bp = bp->b_hash.le_next;
}
return (bp);
}
/*
* this routine implements clustered async writes for
* clearing out B_DELWRI buffers... This is much better
* than the old way of writing only one buffer at a time.
*/
int
vfs_bio_awrite(struct buf * bp)
{
int i;
daddr_t lblkno = bp->b_lblkno;
struct vnode *vp = bp->b_vp;
int s;
int ncl;
struct buf *bpa;
int nwritten;
s = splbio();
if (/* (vp->v_type != VBLK) && */
(bp->b_flags & (B_CLUSTEROK | B_INVAL)) == B_CLUSTEROK) {
int size;
int maxcl;
size = vp->v_mount->mnt_stat.f_iosize;
maxcl = MAXPHYS / size;
for (i = 1; i < maxcl; i++) {
if ((bpa = gbincore(vp, lblkno + i)) &&
((bpa->b_flags & (B_BUSY | 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;
}
}
ncl = i;
/*
* this is a possible cluster write
*/
if (ncl != 1) {
nwritten = cluster_wbuild(vp, size, lblkno, ncl);
splx(s);
return nwritten;
}
}
bremfree(bp);
splx(s);
/*
* default (old) behavior, writing out only one block
*/
bp->b_flags |= B_BUSY | B_ASYNC;
nwritten = bp->b_bufsize;
(void) VOP_BWRITE(bp);
return nwritten;
}
/*
* Find a buffer header which is available for use.
*/
static struct buf *
getnewbuf(int slpflag, int slptimeo, int doingvmio)
{
struct buf *bp;
int s;
int nbyteswritten = 0;
s = splbio();
start:
if (bufspace >= maxbufspace)
goto trytofreespace;
/* can we constitute a new buffer? */
if ((bp = bufqueues[QUEUE_EMPTY].tqh_first)) {
if (bp->b_qindex != QUEUE_EMPTY)
panic("getnewbuf: inconsistent EMPTY queue");
bremfree(bp);
goto fillbuf;
}
trytofreespace:
/*
* We keep the file I/O from hogging metadata I/O
* This is desirable because file data is cached in the
* VM/Buffer cache even if a buffer is freed.
*/
if ((bp = bufqueues[QUEUE_AGE].tqh_first)) {
if (bp->b_qindex != QUEUE_AGE)
panic("getnewbuf: inconsistent AGE queue");
} else if ((bp = bufqueues[QUEUE_LRU].tqh_first)) {
if (bp->b_qindex != QUEUE_LRU)
panic("getnewbuf: inconsistent LRU queue");
}
if (!bp) {
/* wait for a free buffer of any kind */
needsbuffer = 1;
tsleep(&needsbuffer,
(PRIBIO + 1) | slpflag, "newbuf", slptimeo);
splx(s);
return (0);
}
if ((bp->b_qindex == QUEUE_LRU) && (bp->b_usecount > 0)) {
--bp->b_usecount;
TAILQ_REMOVE(&bufqueues[QUEUE_LRU], bp, b_freelist);
if (bufqueues[QUEUE_LRU].tqh_first != NULL) {
TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LRU], bp, b_freelist);
goto start;
}
}
/* if we are a delayed write, convert to an async write */
if ((bp->b_flags & (B_DELWRI | B_INVAL)) == B_DELWRI) {
nbyteswritten += vfs_bio_awrite(bp);
if (!slpflag && !slptimeo) {
splx(s);
return (0);
}
goto start;
}
if (bp->b_flags & B_WANTED) {
bp->b_flags &= ~B_WANTED;
wakeup(bp);
}
bremfree(bp);
if (bp->b_flags & B_VMIO) {
bp->b_flags |= B_RELBUF | B_BUSY | B_DONE;
brelse(bp);
bremfree(bp);
}
if (bp->b_vp)
brelvp(bp);
/* we are not free, nor do we contain interesting data */
if (bp->b_rcred != NOCRED)
crfree(bp->b_rcred);
if (bp->b_wcred != NOCRED)
crfree(bp->b_wcred);
fillbuf:
bp->b_flags |= B_BUSY;
LIST_REMOVE(bp, b_hash);
LIST_INSERT_HEAD(&invalhash, bp, b_hash);
splx(s);
if (bp->b_bufsize) {
allocbuf(bp, 0);
}
bp->b_flags = B_BUSY;
bp->b_dev = NODEV;
bp->b_vp = NULL;
bp->b_blkno = bp->b_lblkno = 0;
bp->b_iodone = 0;
bp->b_error = 0;
bp->b_resid = 0;
bp->b_bcount = 0;
bp->b_npages = 0;
bp->b_wcred = bp->b_rcred = NOCRED;
bp->b_data = buffers_kva + (bp - buf) * MAXBSIZE;
bp->b_dirtyoff = bp->b_dirtyend = 0;
bp->b_validoff = bp->b_validend = 0;
bp->b_usecount = 2;
if (bufspace >= maxbufspace + nbyteswritten) {
s = splbio();
bp->b_flags |= B_INVAL;
brelse(bp);
goto trytofreespace;
}
return (bp);
}
/*
* Check to see if a block is currently memory resident.
*/
struct buf *
incore(struct vnode * vp, daddr_t blkno)
{
struct buf *bp;
struct bufhashhdr *bh;
int s = splbio();
bh = BUFHASH(vp, blkno);
bp = bh->lh_first;
/* Search hash chain */
while (bp != NULL) {
/* hit */
if (bp->b_vp == vp && bp->b_lblkno == blkno &&
(bp->b_flags & B_INVAL) == 0) {
break;
}
bp = bp->b_hash.le_next;
}
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;
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 & VVMIO) == 0)
return 0;
obj = vp->v_object;
tinc = PAGE_SIZE;
if (tinc > vp->v_mount->mnt_stat.f_iosize)
tinc = vp->v_mount->mnt_stat.f_iosize;
off = blkno * 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;
if (vm_page_is_valid(m, (vm_offset_t) (toff + off), tinc) == 0)
return 0;
}
return 1;
}
/*
* now we set the dirty range for the buffer --
* for NFS -- if the file is mapped and pages have
* been written to, let it know. We want the
* entire range of the buffer to be marked dirty if
* any of the pages have been written to for consistancy
* with the b_validoff, b_validend set in the nfs write
* code, and used by the nfs read code.
*/
static void
vfs_setdirty(struct buf *bp) {
int i;
vm_object_t object;
vm_offset_t boffset, offset;
/*
* 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) &&
((object = bp->b_pages[0]->object)->flags & (OBJ_WRITEABLE|OBJ_CLEANING))) {
/*
* 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_test_dirty(bp->b_pages[i]);
/*
* scan forwards for the first page modified
*/
for (i = 0; i < bp->b_npages; i++) {
if (bp->b_pages[i]->dirty) {
break;
}
}
boffset = (i << PAGE_SHIFT);
if (boffset < bp->b_dirtyoff) {
bp->b_dirtyoff = boffset;
}
/*
* scan backwards for the last page modified
*/
for (i = bp->b_npages - 1; i >= 0; --i) {
if (bp->b_pages[i]->dirty) {
break;
}
}
boffset = (i + 1);
offset = boffset + bp->b_pages[0]->pindex;
if (offset >= object->size)
boffset = object->size - bp->b_pages[0]->pindex;
if (bp->b_dirtyend < (boffset << PAGE_SHIFT))
bp->b_dirtyend = (boffset << PAGE_SHIFT);
}
}
/*
* Get a block given a specified block and offset into a file/device.
*/
struct buf *
getblk(struct vnode * vp, daddr_t blkno, int size, int slpflag, int slptimeo)
{
struct buf *bp;
int s;
struct bufhashhdr *bh;
s = splbio();
loop:
if ((bp = gbincore(vp, blkno))) {
if (bp->b_flags & B_BUSY) {
bp->b_flags |= B_WANTED;
if (bp->b_usecount < BUF_MAXUSE)
++bp->b_usecount;
if (!tsleep(bp,
(PRIBIO + 1) | slpflag, "getblk", slptimeo))
goto loop;
splx(s);
return (struct buf *) NULL;
}
bp->b_flags |= B_BUSY | B_CACHE;
bremfree(bp);
/*
* check for size inconsistancies (note that they shouldn't happen
* but do when filesystems don't handle the size changes correctly.)
* We are conservative on metadata and don't just extend the buffer
* but write and re-constitute it.
*/
if (bp->b_bcount != size) {
if (bp->b_flags & B_VMIO) {
allocbuf(bp, size);
} else {
bp->b_flags |= B_NOCACHE;
VOP_BWRITE(bp);
goto loop;
}
}
/*
* make sure that all pages in the buffer are valid, if they
* aren't, clear the cache flag.
* ASSUMPTION:
* if the buffer is greater than 1 page in size, it is assumed
* that the buffer address starts on a page boundary...
*/
if (bp->b_flags & B_VMIO) {
int szleft, i;
szleft = size;
for (i=0;i<bp->b_npages;i++) {
if (szleft > PAGE_SIZE) {
if ((bp->b_pages[i]->valid & VM_PAGE_BITS_ALL) !=
VM_PAGE_BITS_ALL) {
bp->b_flags &= ~(B_CACHE|B_DONE);
break;
}
szleft -= PAGE_SIZE;
} else {
if (!vm_page_is_valid(bp->b_pages[i],
(((vm_offset_t) bp->b_data) & PAGE_MASK),
szleft)) {
bp->b_flags &= ~(B_CACHE|B_DONE);
break;
}
szleft = 0;
}
}
}
if (bp->b_usecount < BUF_MAXUSE)
++bp->b_usecount;
splx(s);
return (bp);
} else {
vm_object_t obj;
int doingvmio;
if ((obj = vp->v_object) && (vp->v_flag & VVMIO)) {
doingvmio = 1;
} else {
doingvmio = 0;
}
if ((bp = getnewbuf(slpflag, slptimeo, doingvmio)) == 0) {
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.
* Normally the vnode is locked so this isn't a problem.
* VBLK type I/O requests, however, don't lock the vnode.
*/
if (!VOP_ISLOCKED(vp) && 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;
bgetvp(vp, bp);
LIST_REMOVE(bp, b_hash);
bh = BUFHASH(vp, blkno);
LIST_INSERT_HEAD(bh, bp, b_hash);
if (doingvmio) {
bp->b_flags |= (B_VMIO | B_CACHE);
#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;
}
splx(s);
allocbuf(bp, size);
return (bp);
}
}
/*
* Get an empty, disassociated buffer of given size.
*/
struct buf *
geteblk(int size)
{
struct buf *bp;
while ((bp = getnewbuf(0, 0, 0)) == 0);
allocbuf(bp, size);
bp->b_flags |= B_INVAL;
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).
*
* Note that this code is tricky, and has many complications to resolve
* deadlock or inconsistant data situations. Tread lightly!!!
*
* Modify the length of a buffer's underlying buffer storage without
* destroying information (unless, of course the buffer is shrinking).
*/
int
allocbuf(struct buf * bp, int size)
{
int s;
int newbsize, mbsize;
int i;
if (!(bp->b_flags & B_BUSY))
panic("allocbuf: buffer not busy");
if ((bp->b_flags & B_VMIO) == 0) {
/*
* Just get anonymous memory from the kernel
*/
mbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
newbsize = round_page(size);
if (newbsize < bp->b_bufsize) {
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) {
vm_hold_load_pages(
bp,
(vm_offset_t) bp->b_data + bp->b_bufsize,
(vm_offset_t) bp->b_data + newbsize);
}
} else {
vm_page_t m;
int desiredpages;
newbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
desiredpages = (round_page(newbsize) >> PAGE_SHIFT);
if (newbsize < bp->b_bufsize) {
if (desiredpages < bp->b_npages) {
pmap_qremove((vm_offset_t) trunc_page(bp->b_data) +
(desiredpages << PAGE_SHIFT), (bp->b_npages - desiredpages));
for (i = desiredpages; i < bp->b_npages; i++) {
m = bp->b_pages[i];
s = splhigh();
while ((m->flags & PG_BUSY) || (m->busy != 0)) {
m->flags |= PG_WANTED;
tsleep(m, PVM, "biodep", 0);
}
splx(s);
if (m->bmapped == 0) {
printf("allocbuf: bmapped is zero for page %d\n", i);
panic("allocbuf: error");
}
--m->bmapped;
if (m->bmapped == 0) {
vm_page_protect(m, VM_PROT_NONE);
vm_page_free(m);
}
bp->b_pages[i] = NULL;
}
bp->b_npages = desiredpages;
}
} else if (newbsize > bp->b_bufsize) {
vm_object_t obj;
vm_offset_t tinc, toff;
vm_ooffset_t off;
vm_pindex_t objoff;
int pageindex, curbpnpages;
struct vnode *vp;
int bsize;
vp = bp->b_vp;
if (vp->v_type == VBLK)
bsize = DEV_BSIZE;
else
bsize = vp->v_mount->mnt_stat.f_iosize;
if (bp->b_npages < desiredpages) {
obj = vp->v_object;
tinc = PAGE_SIZE;
if (tinc > bsize)
tinc = bsize;
off = (vm_ooffset_t) bp->b_lblkno * bsize;
doretry:
curbpnpages = bp->b_npages;
bp->b_flags |= B_CACHE;
for (toff = 0; toff < newbsize; toff += tinc) {
int bytesinpage;
pageindex = toff >> PAGE_SHIFT;
objoff = OFF_TO_IDX(off + toff);
if (pageindex < curbpnpages) {
m = bp->b_pages[pageindex];
if (m->pindex != objoff)
panic("allocbuf: page changed offset??!!!?");
bytesinpage = tinc;
if (tinc > (newbsize - toff))
bytesinpage = newbsize - toff;
if (!vm_page_is_valid(m,
(vm_offset_t) ((toff + off) & (PAGE_SIZE - 1)),
bytesinpage)) {
bp->b_flags &= ~B_CACHE;
}
if ((m->flags & PG_ACTIVE) == 0) {
vm_page_activate(m);
m->act_count = 0;
}
continue;
}
m = vm_page_lookup(obj, objoff);
if (!m) {
m = vm_page_alloc(obj, objoff, VM_ALLOC_NORMAL);
if (!m) {
int j;
for (j = bp->b_npages; j < pageindex; j++) {
PAGE_WAKEUP(bp->b_pages[j]);
}
VM_WAIT;
goto doretry;
}
vm_page_activate(m);
m->act_count = 0;
m->valid = 0;
bp->b_flags &= ~B_CACHE;
} else if (m->flags & PG_BUSY) {
int j;
for (j = bp->b_npages; j < pageindex; j++) {
PAGE_WAKEUP(bp->b_pages[j]);
}
s = splbio();
m->flags |= PG_WANTED;
tsleep(m, PVM, "pgtblk", 0);
splx(s);
goto doretry;
} else {
if ((curproc != pageproc) &&
(m->flags & PG_CACHE) &&
(cnt.v_free_count + cnt.v_cache_count) < cnt.v_free_min) {
pagedaemon_wakeup();
}
bytesinpage = tinc;
if (tinc > (newbsize - toff))
bytesinpage = newbsize - toff;
if (!vm_page_is_valid(m,
(vm_offset_t) ((toff + off) & (PAGE_SIZE - 1)),
bytesinpage)) {
bp->b_flags &= ~B_CACHE;
}
if ((m->flags & PG_ACTIVE) == 0) {
vm_page_activate(m);
m->act_count = 0;
}
m->flags |= PG_BUSY;
}
bp->b_pages[pageindex] = m;
curbpnpages = pageindex + 1;
}
for (i = bp->b_npages; i < curbpnpages; i++) {
m = bp->b_pages[i];
m->bmapped++;
PAGE_WAKEUP(m);
}
bp->b_npages = curbpnpages;
bp->b_data = buffers_kva + (bp - buf) * MAXBSIZE;
pmap_qenter((vm_offset_t) bp->b_data, bp->b_pages, bp->b_npages);
bp->b_data += off & (PAGE_SIZE - 1);
}
}
}
bufspace += (newbsize - bp->b_bufsize);
bp->b_bufsize = newbsize;
bp->b_bcount = size;
return 1;
}
/*
* Wait for buffer I/O completion, returning error status.
*/
int
biowait(register struct buf * bp)
{
int s;
s = splbio();
while ((bp->b_flags & B_DONE) == 0)
tsleep(bp, PRIBIO, "biowait", 0);
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);
}
}
/*
* Finish I/O on a buffer, calling an optional function.
* This is usually called from interrupt level, so process blocking
* is not *a good idea*.
*/
void
biodone(register struct buf * bp)
{
int s;
s = splbio();
if (!(bp->b_flags & B_BUSY))
panic("biodone: buffer not busy");
if (bp->b_flags & B_DONE) {
splx(s);
printf("biodone: buffer already done\n");
return;
}
bp->b_flags |= B_DONE;
if ((bp->b_flags & B_READ) == 0) {
vwakeup(bp);
}
#ifdef BOUNCE_BUFFERS
if (bp->b_flags & B_BOUNCE)
vm_bounce_free(bp);
#endif
/* 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 (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;
if (vp->v_type == VBLK)
foff = (vm_ooffset_t) DEV_BSIZE * bp->b_lblkno;
else
foff = (vm_ooffset_t) vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
obj = vp->v_object;
if (!obj) {
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
iosize = bp->b_bufsize;
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
--obj->paging_in_progress;
continue;
}
bp->b_pages[i] = m;
pmap_qenter(trunc_page(bp->b_data), bp->b_pages, bp->b_npages);
}
#if defined(VFS_BIO_DEBUG)
if (OFF_TO_IDX(foff) != m->pindex) {
printf("biodone: foff(%d)/m->pindex(%d) mismatch\n", 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, so we only need to do this
* here in the read case.
*/
if ((bp->b_flags & B_READ) && !bogusflag && resid > 0) {
vm_page_set_validclean(m,
(vm_offset_t) (foff & (PAGE_SIZE-1)), resid);
}
/*
* 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 (vp->v_type != VBLK)
printf(" iosize: %d, 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, mapped: %d\n",
m->valid, m->dirty, m->bmapped);
panic("biodone: page busy < 0\n");
}
--m->busy;
if ((m->busy == 0) && (m->flags & PG_WANTED)) {
m->flags &= ~PG_WANTED;
wakeup(m);
}
--obj->paging_in_progress;
foff += resid;
iosize -= resid;
}
if (obj && obj->paging_in_progress == 0 &&
(obj->flags & OBJ_PIPWNT)) {
obj->flags &= ~OBJ_PIPWNT;
wakeup(obj);
}
}
/*
* For asynchronous completions, release the buffer now. The brelse
* checks for B_WANTED and will do the wakeup there if necessary - so
* no need to do a wakeup here in the async case.
*/
if (bp->b_flags & B_ASYNC) {
brelse(bp);
} else {
wakeup(bp);
}
splx(s);
}
int
count_lock_queue()
{
int count;
struct buf *bp;
count = 0;
for (bp = bufqueues[QUEUE_LOCKED].tqh_first;
bp != NULL;
bp = bp->b_freelist.tqe_next)
count++;
return (count);
}
int vfs_update_interval = 30;
static void
vfs_update()
{
(void) spl0(); /* XXX redundant? wrong place? */
while (1) {
tsleep(&vfs_update_wakeup, PUSER, "update",
hz * vfs_update_interval);
vfs_update_wakeup = 0;
sync(curproc, NULL, NULL);
}
}
static int
sysctl_kern_updateinterval SYSCTL_HANDLER_ARGS
{
int error = sysctl_handle_int(oidp,
oidp->oid_arg1, oidp->oid_arg2, req);
if (!error)
wakeup(&vfs_update_wakeup);
return error;
}
SYSCTL_PROC(_kern, KERN_UPDATEINTERVAL, update, CTLTYPE_INT|CTLFLAG_RW,
&vfs_update_interval, 0, sysctl_kern_updateinterval, "I", "");
/*
* 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;
vm_ooffset_t foff;
foff = (vm_ooffset_t) vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
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(foff) + i);
if (!m) {
panic("vfs_unbusy_pages: page missing\n");
}
bp->b_pages[i] = m;
pmap_qenter(trunc_page(bp->b_data), bp->b_pages, bp->b_npages);
}
--obj->paging_in_progress;
--m->busy;
if ((m->busy == 0) && (m->flags & PG_WANTED)) {
m->flags &= ~PG_WANTED;
wakeup(m);
}
}
if (obj->paging_in_progress == 0 &&
(obj->flags & OBJ_PIPWNT)) {
obj->flags &= ~OBJ_PIPWNT;
wakeup(obj);
}
}
}
/*
* 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.
*/
void
vfs_busy_pages(struct buf * bp, int clear_modify)
{
int i;
if (bp->b_flags & B_VMIO) {
vm_object_t obj = bp->b_vp->v_object;
vm_ooffset_t foff;
int iocount = bp->b_bufsize;
if (bp->b_vp->v_type == VBLK)
foff = (vm_ooffset_t) DEV_BSIZE * bp->b_lblkno;
else
foff = (vm_ooffset_t) bp->b_vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
vfs_setdirty(bp);
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
int resid = IDX_TO_OFF(m->pindex + 1) - foff;
if (resid > iocount)
resid = iocount;
if ((bp->b_flags & B_CLUSTER) == 0) {
obj->paging_in_progress++;
m->busy++;
}
if (clear_modify) {
vm_page_protect(m, VM_PROT_READ);
vm_page_set_validclean(m,
(vm_offset_t) (foff & (PAGE_SIZE-1)), resid);
} else if (bp->b_bcount >= PAGE_SIZE) {
if (m->valid && (bp->b_flags & B_CACHE) == 0) {
bp->b_pages[i] = bogus_page;
pmap_qenter(trunc_page(bp->b_data), bp->b_pages, bp->b_npages);
}
}
foff += resid;
iocount -= resid;
}
}
}
/*
* 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.
*/
void
vfs_clean_pages(struct buf * bp)
{
int i;
if (bp->b_flags & B_VMIO) {
vm_ooffset_t foff;
int iocount = bp->b_bufsize;
if (bp->b_vp->v_type == VBLK)
foff = (vm_ooffset_t) DEV_BSIZE * bp->b_lblkno;
else
foff = (vm_ooffset_t) bp->b_vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
int resid = IDX_TO_OFF(m->pindex + 1) - foff;
if (resid > iocount)
resid = iocount;
if (resid > 0) {
vm_page_set_validclean(m,
((vm_offset_t) foff & (PAGE_SIZE-1)), resid);
}
foff += resid;
iocount -= resid;
}
}
}
void
vfs_bio_clrbuf(struct buf *bp) {
int i;
if( bp->b_flags & B_VMIO) {
if( (bp->b_npages == 1) && (bp->b_bufsize < PAGE_SIZE)) {
int mask;
mask = 0;
for(i=0;i<bp->b_bufsize;i+=DEV_BSIZE)
mask |= (1 << (i/DEV_BSIZE));
if( bp->b_pages[0]->valid != mask) {
bzero(bp->b_data, bp->b_bufsize);
}
bp->b_pages[0]->valid = mask;
bp->b_resid = 0;
return;
}
for(i=0;i<bp->b_npages;i++) {
if( bp->b_pages[i]->valid == VM_PAGE_BITS_ALL)
continue;
if( bp->b_pages[i]->valid == 0) {
if ((bp->b_pages[i]->flags & PG_ZERO) == 0)
bzero(bp->b_data + (i << PAGE_SHIFT), PAGE_SIZE);
} else {
int j;
for(j=0;j<PAGE_SIZE/DEV_BSIZE;j++) {
if( (bp->b_pages[i]->valid & (1<<j)) == 0)
bzero(bp->b_data + (i << PAGE_SHIFT) + j * DEV_BSIZE, DEV_BSIZE);
}
}
bp->b_pages[i]->valid = VM_PAGE_BITS_ALL;
}
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 froma, vm_offset_t toa)
{
vm_offset_t pg;
vm_page_t p;
vm_offset_t from = round_page(froma);
vm_offset_t to = round_page(toa);
for (pg = from; pg < to; pg += PAGE_SIZE) {
tryagain:
p = vm_page_alloc(kernel_object, ((pg - VM_MIN_KERNEL_ADDRESS) >> PAGE_SHIFT),
VM_ALLOC_NORMAL);
if (!p) {
VM_WAIT;
goto tryagain;
}
vm_page_wire(p);
pmap_kenter(pg, VM_PAGE_TO_PHYS(p));
bp->b_pages[((caddr_t) pg - bp->b_data) >> PAGE_SHIFT] = p;
PAGE_WAKEUP(p);
bp->b_npages++;
}
}
void
vm_hold_free_pages(struct buf * bp, vm_offset_t froma, vm_offset_t toa)
{
vm_offset_t pg;
vm_page_t p;
vm_offset_t from = round_page(froma);
vm_offset_t to = round_page(toa);
for (pg = from; pg < to; pg += PAGE_SIZE) {
int index = ((caddr_t) pg - bp->b_data) >> PAGE_SHIFT;
p = bp->b_pages[index];
bp->b_pages[index] = 0;
pmap_kremove(pg);
vm_page_free(p);
--bp->b_npages;
}
}
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