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use new queue primitives
[unix-history] / usr / src / sys / kern / vfs_bio.c
/*-
* Copyright (c) 1982, 1986, 1989 The Regents of the University of California.
* All rights reserved.
*
* This module is believed to contain source code proprietary to AT&T.
* Use and redistribution is subject to the Berkeley Software License
* Agreement and your Software Agreement with AT&T (Western Electric).
*
* @(#)vfs_bio.c 7.55 (Berkeley) %G%
*/
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/trace.h>
#include <sys/resourcevar.h>
#include <sys/malloc.h>
#include <libkern/libkern.h>
/*
* Definitions for the buffer hash lists.
*/
#define BUFHASH(dvp, lbn) \
(&bufhashtbl[((int)(dvp) / sizeof(*(dvp)) + (int)(lbn)) & bufhash])
struct list_entry *bufhashtbl, invalhash;
u_long bufhash;
/*
* Insq/Remq for the buffer hash lists.
*/
#define binshash(bp, dp) list_enter_head(dp, bp, struct buf *, b_hash)
#define bremhash(bp) list_remove(bp, struct buf *, b_hash)
/*
* Definitions for the buffer free lists.
*/
#define BQUEUES 4 /* number of free buffer queues */
#define BQ_LOCKED 0 /* super-blocks &c */
#define BQ_LRU 1 /* lru, useful buffers */
#define BQ_AGE 2 /* rubbish */
#define BQ_EMPTY 3 /* buffer headers with no memory */
struct queue_entry bufqueues[BQUEUES];
int needbuffer;
/*
* Insq/Remq for the buffer free lists.
*/
#define binsheadfree(bp, dp) \
queue_enter_head(dp, bp, struct buf *, b_freelist)
#define binstailfree(bp, dp) \
queue_enter_tail(dp, bp, struct buf *, b_freelist)
void
bremfree(bp)
struct buf *bp;
{
struct queue_entry *dp;
/*
* We only calculate the head of the freelist when removing
* the last element of the list as that is the only time that
* it is needed (e.g. to reset the tail pointer).
*/
if (bp->b_freelist.qe_next == NULL) {
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
if (dp->qe_prev == &bp->b_freelist.qe_next)
break;
if (dp == &bufqueues[BQUEUES])
panic("bremfree: lost tail");
}
queue_remove(dp, bp, struct buf *, b_freelist);
}
/*
* Initialize buffers and hash links for buffers.
*/
void
bufinit()
{
register struct buf *bp;
struct queue_entry *dp;
register int i;
int base, residual;
for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
queue_init(dp);
bufhashtbl = (struct list_entry *)hashinit(nbuf, M_CACHE, &bufhash);
base = bufpages / nbuf;
residual = bufpages % nbuf;
for (i = 0; i < nbuf; i++) {
bp = &buf[i];
bzero((char *)bp, sizeof *bp);
bp->b_dev = NODEV;
bp->b_rcred = NOCRED;
bp->b_wcred = NOCRED;
bp->b_un.b_addr = buffers + i * MAXBSIZE;
if (i < residual)
bp->b_bufsize = (base + 1) * CLBYTES;
else
bp->b_bufsize = base * CLBYTES;
bp->b_flags = B_INVAL;
dp = bp->b_bufsize ? &bufqueues[BQ_AGE] : &bufqueues[BQ_EMPTY];
binsheadfree(bp, dp);
binshash(bp, &invalhash);
}
}
/*
* Find the block in the buffer pool.
* If the buffer is not present, allocate a new buffer and load
* its contents according to the filesystem fill routine.
*/
bread(vp, blkno, size, cred, bpp)
struct vnode *vp;
daddr_t blkno;
int size;
struct ucred *cred;
struct buf **bpp;
#ifdef SECSIZE
long secsize;
#endif SECSIZE
{
struct proc *p = curproc; /* XXX */
register struct buf *bp;
if (size == 0)
panic("bread: size 0");
#ifdef SECSIZE
bp = getblk(dev, blkno, size, secsize);
#else SECSIZE
*bpp = bp = getblk(vp, blkno, size);
#endif SECSIZE
if (bp->b_flags & (B_DONE | B_DELWRI)) {
trace(TR_BREADHIT, pack(vp, size), blkno);
return (0);
}
bp->b_flags |= B_READ;
if (bp->b_bcount > bp->b_bufsize)
panic("bread");
if (bp->b_rcred == NOCRED && cred != NOCRED) {
crhold(cred);
bp->b_rcred = cred;
}
VOP_STRATEGY(bp);
trace(TR_BREADMISS, pack(vp, size), blkno);
p->p_stats->p_ru.ru_inblock++; /* pay for read */
return (biowait(bp));
}
/*
* Operates like bread, but also starts I/O on the N specified
* read-ahead blocks.
*/
breadn(vp, blkno, size, rablkno, rabsize, num, cred, bpp)
struct vnode *vp;
daddr_t blkno; int size;
#ifdef SECSIZE
long secsize;
#endif SECSIZE
daddr_t rablkno[]; int rabsize[];
int num;
struct ucred *cred;
struct buf **bpp;
{
struct proc *p = curproc; /* XXX */
register struct buf *bp, *rabp;
register int i;
bp = NULL;
/*
* If the block is not memory resident,
* allocate a buffer and start I/O.
*/
if (!incore(vp, blkno)) {
*bpp = bp = getblk(vp, blkno, size);
#endif SECSIZE
if ((bp->b_flags & (B_DONE | B_DELWRI)) == 0) {
bp->b_flags |= B_READ;
if (bp->b_bcount > bp->b_bufsize)
panic("breadn");
if (bp->b_rcred == NOCRED && cred != NOCRED) {
crhold(cred);
bp->b_rcred = cred;
}
VOP_STRATEGY(bp);
trace(TR_BREADMISS, pack(vp, size), blkno);
p->p_stats->p_ru.ru_inblock++; /* pay for read */
} else {
trace(TR_BREADHIT, pack(vp, size), blkno);
}
}
/*
* If there's read-ahead block(s), start I/O
* on them also (as above).
*/
for (i = 0; i < num; i++) {
if (incore(vp, rablkno[i]))
continue;
rabp = getblk(vp, rablkno[i], rabsize[i]);
#endif SECSIZE
if (rabp->b_flags & (B_DONE | B_DELWRI)) {
brelse(rabp);
trace(TR_BREADHITRA, pack(vp, rabsize[i]), rablkno[i]);
} else {
rabp->b_flags |= B_ASYNC | B_READ;
if (rabp->b_bcount > rabp->b_bufsize)
panic("breadrabp");
if (rabp->b_rcred == NOCRED && cred != NOCRED) {
crhold(cred);
rabp->b_rcred = cred;
}
VOP_STRATEGY(rabp);
trace(TR_BREADMISSRA, pack(vp, rabsize[i]), rablkno[i]);
p->p_stats->p_ru.ru_inblock++; /* pay in advance */
}
}
/*
* If block was memory resident, let bread get it.
* If block was not memory resident, the read was
* started above, so just wait for the read to complete.
*/
if (bp == NULL)
#ifdef SECSIZE
return (bread(dev, blkno, size, secsize));
#else SECSIZE
return (bread(vp, blkno, size, cred, bpp));
return (biowait(bp));
}
/*
* Synchronous write.
* Release buffer on completion.
*/
bwrite(bp)
register struct buf *bp;
{
struct proc *p = curproc; /* XXX */
register int flag;
int s, error = 0;
flag = bp->b_flags;
bp->b_flags &= ~(B_READ | B_DONE | B_ERROR | B_DELWRI);
if (flag & B_ASYNC) {
if ((flag & B_DELWRI) == 0)
p->p_stats->p_ru.ru_oublock++; /* no one paid yet */
else
reassignbuf(bp, bp->b_vp);
}
trace(TR_BWRITE, pack(bp->b_vp, bp->b_bcount), bp->b_lblkno);
if (bp->b_bcount > bp->b_bufsize)
panic("bwrite");
s = splbio();
bp->b_vp->v_numoutput++;
splx(s);
VOP_STRATEGY(bp);
/*
* If the write was synchronous, then await I/O completion.
* If the write was "delayed", then we put the buffer on
* the queue of blocks awaiting I/O completion status.
*/
if ((flag & B_ASYNC) == 0) {
error = biowait(bp);
if ((flag&B_DELWRI) == 0)
p->p_stats->p_ru.ru_oublock++; /* no one paid yet */
else
reassignbuf(bp, bp->b_vp);
brelse(bp);
} else if (flag & B_DELWRI) {
s = splbio();
bp->b_flags |= B_AGE;
splx(s);
}
return (error);
}
int
vn_bwrite(ap)
struct vop_bwrite_args *ap;
{
return (bwrite(ap->a_bp));
}
/*
* Delayed write.
*
* The buffer is marked dirty, but is not queued for I/O.
* This routine should be used when the buffer is expected
* to be modified again soon, typically a small write that
* partially fills a buffer.
*
* NB: magnetic tapes cannot be delayed; they must be
* written in the order that the writes are requested.
*/
bdwrite(bp)
register struct buf *bp;
{
struct proc *p = curproc; /* XXX */
if ((bp->b_flags & B_DELWRI) == 0) {
bp->b_flags |= B_DELWRI;
reassignbuf(bp, bp->b_vp);
p->p_stats->p_ru.ru_oublock++; /* no one paid yet */
}
/*
* If this is a tape drive, the write must be initiated.
*/
if (bdevsw[major(bp->b_dev)].d_flags & B_TAPE)
bawrite(bp);
} else {
bp->b_flags |= (B_DONE | B_DELWRI);
brelse(bp);
}
}
/*
* Asynchronous write.
* Start I/O on a buffer, but do not wait for it to complete.
* The buffer is released when the I/O completes.
*/
bawrite(bp)
register struct buf *bp;
{
/*
* Setting the ASYNC flag causes bwrite to return
* after starting the I/O.
*/
bp->b_flags |= B_ASYNC;
(void) bwrite(bp);
}
/*
* Release a buffer.
* Even if the buffer is dirty, no I/O is started.
*/
brelse(bp)
register struct buf *bp;
{
register struct queue_entry *flist;
int s;
trace(TR_BRELSE, pack(bp->b_vp, bp->b_bufsize), bp->b_lblkno);
/*
* If a process is waiting for the buffer, or
* is waiting for a free buffer, awaken it.
*/
if (bp->b_flags & B_WANTED)
wakeup((caddr_t)bp);
if (needbuffer) {
needbuffer = 0;
wakeup((caddr_t)&needbuffer);
}
/*
* Retry I/O for locked buffers rather than invalidating them.
*/
s = splbio();
if ((bp->b_flags & B_ERROR) && (bp->b_flags & B_LOCKED))
bp->b_flags &= ~B_ERROR;
/*
* Disassociate buffers that are no longer valid.
*/
if (bp->b_flags & (B_NOCACHE | B_ERROR))
bp->b_flags |= B_INVAL;
if ((bp->b_bufsize <= 0) || (bp->b_flags & (B_ERROR | B_INVAL))) {
if (bp->b_vp)
brelvp(bp);
bp->b_flags &= ~B_DELWRI;
}
/*
* Stick the buffer back on a free list.
*/
if (bp->b_bufsize <= 0) {
/* block has no buffer ... put at front of unused buffer list */
flist = &bufqueues[BQ_EMPTY];
binsheadfree(bp, flist);
} else if (bp->b_flags & (B_ERROR | B_INVAL)) {
/* block has no info ... put at front of most free list */
flist = &bufqueues[BQ_AGE];
binsheadfree(bp, flist);
} else {
if (bp->b_flags & B_LOCKED)
flist = &bufqueues[BQ_LOCKED];
else if (bp->b_flags & B_AGE)
flist = &bufqueues[BQ_AGE];
else
flist = &bufqueues[BQ_LRU];
binstailfree(bp, flist);
}
bp->b_flags &= ~(B_WANTED | B_BUSY | B_ASYNC | B_AGE | B_NOCACHE);
splx(s);
}
/*
* Check to see if a block is currently memory resident.
*/
incore(vp, blkno)
struct vnode *vp;
daddr_t blkno;
{
register struct buf *bp;
for (bp = BUFHASH(vp, blkno)->le_next; bp; bp = bp->b_hash.qe_next)
if (bp->b_lblkno == blkno && bp->b_vp == vp &&
(bp->b_flags & B_INVAL) == 0)
return (1);
return (0);
}
/*
* Check to see if a block is currently memory resident.
* If it is resident, return it. If it is not resident,
* allocate a new buffer and assign it to the block.
*/
struct buf *
#ifdef SECSIZE
getblk(dev, blkno, size, secsize)
#else SECSIZE
getblk(vp, blkno, size)
register struct vnode *vp;
daddr_t blkno;
int size;
#ifdef SECSIZE
long secsize;
#endif SECSIZE
{
register struct buf *bp;
struct list_entry *dp;
int s;
if (size > MAXBSIZE)
panic("getblk: size too big");
/*
* Search the cache for the block. If the buffer is found,
* but it is currently locked, the we must wait for it to
* become available.
*/
dp = BUFHASH(vp, blkno);
loop:
for (bp = dp->le_next; bp; bp = bp->b_hash.qe_next) {
if (bp->b_lblkno != blkno || bp->b_vp != vp ||
(bp->b_flags & B_INVAL))
continue;
s = splbio();
if (bp->b_flags & B_BUSY) {
bp->b_flags |= B_WANTED;
sleep((caddr_t)bp, PRIBIO + 1);
splx(s);
goto loop;
}
bremfree(bp);
bp->b_flags |= B_BUSY;
splx(s);
if (bp->b_bcount != size) {
printf("getblk: stray size");
bp->b_flags |= B_INVAL;
bwrite(bp);
goto loop;
}
bp->b_flags |= B_CACHE;
return (bp);
}
bp = getnewbuf();
bremhash(bp);
bgetvp(vp, bp);
bp->b_bcount = 0;
bp->b_lblkno = blkno;
#ifdef SECSIZE
bp->b_blksize = secsize;
#endif SECSIZE
bp->b_blkno = blkno;
bp->b_error = 0;
bp->b_resid = 0;
binshash(bp, dp);
allocbuf(bp, size);
return (bp);
}
/*
* Allocate a buffer.
* The caller will assign it to a block.
*/
struct buf *
geteblk(size)
int size;
{
register struct buf *bp;
if (size > MAXBSIZE)
panic("geteblk: size too big");
bp = getnewbuf();
bp->b_flags |= B_INVAL;
bremhash(bp);
binshash(bp, &invalhash);
bp->b_bcount = 0;
#ifdef SECSIZE
bp->b_blksize = DEV_BSIZE;
#endif SECSIZE
bp->b_error = 0;
bp->b_resid = 0;
allocbuf(bp, size);
return (bp);
}
/*
* Expand or contract the actual memory allocated to a buffer.
* If no memory is available, release buffer and take error exit.
*/
allocbuf(tp, size)
register struct buf *tp;
int size;
{
register struct buf *bp, *ep;
int sizealloc, take, s;
sizealloc = roundup(size, CLBYTES);
/*
* Buffer size does not change
*/
if (sizealloc == tp->b_bufsize)
goto out;
/*
* Buffer size is shrinking.
* Place excess space in a buffer header taken from the
* BQ_EMPTY buffer list and placed on the "most free" list.
* If no extra buffer headers are available, leave the
* extra space in the present buffer.
*/
if (sizealloc < tp->b_bufsize) {
if ((ep = bufqueues[BQ_EMPTY].qe_next) == NULL)
goto out;
s = splbio();
bremfree(ep);
ep->b_flags |= B_BUSY;
splx(s);
pagemove(tp->b_un.b_addr + sizealloc, ep->b_un.b_addr,
(int)tp->b_bufsize - sizealloc);
ep->b_bufsize = tp->b_bufsize - sizealloc;
tp->b_bufsize = sizealloc;
ep->b_flags |= B_INVAL;
ep->b_bcount = 0;
brelse(ep);
goto out;
}
/*
* More buffer space is needed. Get it out of buffers on
* the "most free" list, placing the empty headers on the
* BQ_EMPTY buffer header list.
*/
while (tp->b_bufsize < sizealloc) {
take = sizealloc - tp->b_bufsize;
bp = getnewbuf();
if (take >= bp->b_bufsize)
take = bp->b_bufsize;
pagemove(&bp->b_un.b_addr[bp->b_bufsize - take],
&tp->b_un.b_addr[tp->b_bufsize], take);
tp->b_bufsize += take;
bp->b_bufsize = bp->b_bufsize - take;
if (bp->b_bcount > bp->b_bufsize)
bp->b_bcount = bp->b_bufsize;
if (bp->b_bufsize <= 0) {
bremhash(bp);
binshash(bp, &invalhash);
bp->b_dev = NODEV;
bp->b_error = 0;
bp->b_flags |= B_INVAL;
}
brelse(bp);
}
out:
tp->b_bcount = size;
return (1);
}
/*
* Find a buffer which is available for use.
* Select something from a free list.
* Preference is to AGE list, then LRU list.
*/
struct buf *
getnewbuf()
{
register struct buf *bp;
register struct queue_entry *dp;
register struct ucred *cred;
int s;
loop:
s = splbio();
for (dp = &bufqueues[BQ_AGE]; dp > bufqueues; dp--)
if (dp->qe_next)
break;
if (dp == bufqueues) { /* no free blocks */
needbuffer = 1;
sleep((caddr_t)&needbuffer, PRIBIO + 1);
splx(s);
goto loop;
}
bp = dp->qe_next;
bremfree(bp);
bp->b_flags |= B_BUSY;
splx(s);
if (bp->b_flags & B_DELWRI) {
(void) bawrite(bp);
goto loop;
}
trace(TR_BRELSE, pack(bp->b_vp, bp->b_bufsize), bp->b_lblkno);
if (bp->b_vp)
brelvp(bp);
if (bp->b_rcred != NOCRED) {
cred = bp->b_rcred;
bp->b_rcred = NOCRED;
crfree(cred);
}
if (bp->b_wcred != NOCRED) {
cred = bp->b_wcred;
bp->b_wcred = NOCRED;
crfree(cred);
}
bp->b_flags = B_BUSY;
bp->b_dirtyoff = bp->b_dirtyend = 0;
bp->b_validoff = bp->b_validend = 0;
return (bp);
}
/*
* Wait for I/O to complete.
*
* Extract and return any errors associated with the I/O.
* If the error flag is set, but no specific error is
* given, return EIO.
*/
biowait(bp)
register struct buf *bp;
{
int s;
s = splbio();
while ((bp->b_flags & B_DONE) == 0)
sleep((caddr_t)bp, PRIBIO);
splx(s);
if ((bp->b_flags & B_ERROR) == 0)
return (0);
if (bp->b_error)
return (bp->b_error);
return (EIO);
}
/*
* Mark I/O complete on a buffer.
*
* If a callback has been requested, e.g. the pageout
* daemon, do so. Otherwise, awaken waiting processes.
*/
void
biodone(bp)
register struct buf *bp;
{
if (bp->b_flags & B_DONE)
panic("dup biodone");
bp->b_flags |= B_DONE;
if ((bp->b_flags & B_READ) == 0)
vwakeup(bp);
if (bp->b_flags & B_CALL) {
bp->b_flags &= ~B_CALL;
(*bp->b_iodone)(bp);
return;
}
if (bp->b_flags & B_ASYNC)
brelse(bp);
else {
bp->b_flags &= ~B_WANTED;
wakeup((caddr_t)bp);
}
}
#ifdef DIAGNOSTIC
/*
* Print out statistics on the current allocation of the buffer pool.
* Can be enabled to print out on every ``sync'' by setting "syncprt"
* above.
*/
void
vfs_bufstats()
{
int s, i, j, count;
register struct buf *bp;
register struct queue_entry *dp;
int counts[MAXBSIZE/CLBYTES+1];
static char *bname[BQUEUES] = { "LOCKED", "LRU", "AGE", "EMPTY" };
for (dp = bufqueues, i = 0; dp < &bufqueues[BQUEUES]; dp++, i++) {
count = 0;
for (j = 0; j <= MAXBSIZE/CLBYTES; j++)
counts[j] = 0;
s = splbio();
for (bp = dp->qe_next; bp; bp = bp->b_freelist.qe_next) {
counts[bp->b_bufsize/CLBYTES]++;
count++;
}
splx(s);
printf("%s: total-%d", bname[i], count);
for (j = 0; j <= MAXBSIZE/CLBYTES; j++)
if (counts[j] != 0)
printf(", %d-%d", j * CLBYTES, counts[j]);
printf("\n");
}
}
#endif /* DIAGNOSTIC */
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.