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freebsd-dev/sys/kern/vfs_bio.c
John Dyson 5fe17eeb8a General fixes to the vfs clustring code: 
1) Make cluster buffer list be a non-malloced chain.  This eliminates
yet another 'evil' M_WAITOK and generally cleans up the code.
2) Fix write clustering for ext2fs.  It was just broken.  Also, ffs
clustering had an efficiency problem that more bawrites were happening
than should have been.
3) Make changes to buf.h to support the above, plus remove b_pfcent
at the request of David Greenman.
Reviewed by: davidg (partially)
1995-11-19 19:54:31 +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 1.70 1995/11/18 23:33:48 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/proc.h>
#include <sys/vnode.h>
#include <vm/vm.h>
#include <vm/vm_kern.h>
#include <vm/vm_pageout.h>
#include <vm/vm_page.h>
#include <vm/vm_object.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>
/*
* System initialization
*/
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;
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);
static __inline struct buf * gbincore(struct vnode * vp, daddr_t blkno);
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];
/*
* 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, 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);
} else if (bp->b_flags & B_VMIO) {
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_offset_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 (!vp->v_mount)
panic("brelse: missing mount info");
if (bp->b_npages) {
obj = (vm_object_t) vp->v_object;
foff = trunc_page(vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno);
for (i = 0; i < bp->b_npages; i++) {
m = bp->b_pages[i];
if (m == bogus_page) {
m = vm_page_lookup(obj, foff);
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 = (m->offset + PAGE_SIZE) - 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, 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) {
wakeup(m);
m->flags &= ~PG_WANTED;
}
if ((m->busy == 0) && ((m->flags & PG_BUSY) == 0)) {
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.
*/
static __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) {
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.
*/
void
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;
s = splbio();
if (vp->v_mount && (vp->v_flag & VVMIO) &&
(bp->b_flags & (B_CLUSTEROK | B_INVAL)) == B_CLUSTEROK) {
int size = vp->v_mount->mnt_stat.f_iosize;
int 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_BSIZE))
break;
} else {
break;
}
}
ncl = i;
/*
* this is a possible cluster write
*/
if (ncl != 1) {
cluster_wbuild(vp, size, lblkno, ncl);
splx(s);
return;
}
}
bremfree(bp);
splx(s);
/*
* default (old) behavior, writing out only one block
*/
bp->b_flags |= B_BUSY | B_ASYNC;
(void) VOP_BWRITE(bp);
}
/*
* Find a buffer header which is available for use.
*/
static struct buf *
getnewbuf(int slpflag, int slptimeo, int doingvmio)
{
struct buf *bp;
int s;
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 | slpflag, "newbuf", slptimeo);
splx(s);
return (0);
}
/* if we are a delayed write, convert to an async write */
if ((bp->b_flags & (B_DELWRI | B_INVAL)) == B_DELWRI) {
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;
if (bufspace >= maxbufspace) {
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 off, toff, tinc;
vm_page_t m;
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, trunc_page(toff + off));
if (!m)
return 0;
if (vm_page_is_valid(m, 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_SIZE;
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) * PAGE_SIZE;
offset = boffset + bp->b_pages[0]->offset;
if (offset >= object->size) {
boffset = object->size - bp->b_pages[0]->offset;
}
if (bp->b_dirtyend < boffset) {
bp->b_dirtyend = boffset;
}
}
}
/*
* 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|B_INVAL)) {
bp->b_flags |= B_WANTED;
if (!tsleep(bp, PRIBIO | 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;
}
}
}
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) * DEV_BSIZE;
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) * DEV_BSIZE;
desiredpages = round_page(newbsize) / PAGE_SIZE;
if (newbsize < bp->b_bufsize) {
if (desiredpages < bp->b_npages) {
pmap_qremove((vm_offset_t) trunc_page(bp->b_data) +
desiredpages * PAGE_SIZE, (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, off, toff, objoff;
int pageindex, curbpnpages;
struct vnode *vp;
int bsize;
vp = bp->b_vp;
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 = 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_SIZE;
objoff = trunc_page(toff + off);
if (pageindex < curbpnpages) {
m = bp->b_pages[pageindex];
if (m->offset != objoff)
panic("allocbuf: page changed offset??!!!?");
bytesinpage = tinc;
if (tinc > (newbsize - toff))
bytesinpage = newbsize - toff;
if (!vm_page_is_valid(m, toff + off, 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, PRIBIO, "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, toff + off, 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;
}
}
}
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_offset_t foff;
vm_page_t m;
vm_object_t obj;
int iosize;
struct vnode *vp = bp->b_vp;
foff = 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, 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 (trunc_page(foff) != m->offset) {
printf("biodone: foff(%d)/m->offset(%d) mismatch\n", foff, m->offset);
}
#endif
resid = (m->offset + PAGE_SIZE) - 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, 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, "
"off: %ld, foff: %ld, "
"resid: %d, index: %d\n",
m->offset, foff, resid, i);
printf(" iosize: %ld, lblkno: %ld, flags: 0x%x, npages: %d\n",
bp->b_vp->v_mount->mnt_stat.f_iosize,
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 {
bp->b_flags &= ~B_WANTED;
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;
void
vfs_update()
{
(void) spl0();
while (1) {
tsleep(&vfs_update_wakeup, PRIBIO, "update",
hz * vfs_update_interval);
vfs_update_wakeup = 0;
sync(curproc, NULL, NULL);
}
}
/*
* 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_offset_t foff;
foff = trunc_page(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, foff + i * PAGE_SIZE);
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_offset_t foff = bp->b_vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
int iocount = bp->b_bufsize;
vfs_setdirty(bp);
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
int resid = (m->offset + PAGE_SIZE) - 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,
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_offset_t foff =
bp->b_vp->v_mount->mnt_stat.f_iosize * bp->b_lblkno;
int iocount = bp->b_bufsize;
for (i = 0; i < bp->b_npages; i++) {
vm_page_t m = bp->b_pages[i];
int resid = (m->offset + PAGE_SIZE) - foff;
if (resid > iocount)
resid = iocount;
if (resid > 0) {
vm_page_set_validclean(m,
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 j;
if( bp->b_pages[0]->valid != VM_PAGE_BITS_ALL) {
bzero(bp->b_data, bp->b_bufsize);
}
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_SIZE, 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_SIZE + 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,
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_SIZE] = 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) {
p = bp->b_pages[((caddr_t) pg - bp->b_data) / PAGE_SIZE];
bp->b_pages[((caddr_t) pg - bp->b_data) / PAGE_SIZE] = 0;
pmap_kremove(pg);
vm_page_free(p);
--bp->b_npages;
}
}
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