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[unix-history] / usr / src / sys / kern / vfs_bio.c
/*
* Copyright (c) 1982, 1986 Regents of the University of California.
* All rights reserved. The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*
* @(#)vfs_bio.c 7.4 (Berkeley) %G%
*/
#include "param.h"
#include "systm.h"
#include "dir.h"
#include "user.h"
#include "buf.h"
#include "conf.h"
#include "proc.h"
#include "seg.h"
#include "vm.h"
#include "trace.h"
#include "machine/pte.h"
/*
* Read in (if necessary) the block and return a buffer pointer.
*/
struct buf *
#ifdef SECSIZE
bread(dev, blkno, size, secsize)
#else SECSIZE
bread(dev, blkno, size)
#endif SECSIZE
dev_t dev;
daddr_t blkno;
int size;
#ifdef SECSIZE
long secsize;
#endif SECSIZE
{
register struct buf *bp;
if (size == 0)
panic("bread: size 0");
#ifdef SECSIZE
bp = getblk(dev, blkno, size, secsize);
#else SECSIZE
bp = getblk(dev, blkno, size);
#endif SECSIZE
if (bp->b_flags&(B_DONE|B_DELWRI)) {
trace(TR_BREADHIT, pack(dev, size), blkno);
return (bp);
}
bp->b_flags |= B_READ;
if (bp->b_bcount > bp->b_bufsize)
panic("bread");
(*bdevsw[major(dev)].d_strategy)(bp);
trace(TR_BREADMISS, pack(dev, size), blkno);
u.u_ru.ru_inblock++; /* pay for read */
biowait(bp);
return (bp);
}
/*
* Read in the block, like bread, but also start I/O on the
* read-ahead block (which is not allocated to the caller)
*/
struct buf *
#ifdef SECSIZE
breada(dev, blkno, size, secsize, rablkno, rabsize)
#else SECSIZE
breada(dev, blkno, size, rablkno, rabsize)
#endif SECSIZE
dev_t dev;
daddr_t blkno; int size;
#ifdef SECSIZE
long secsize;
#endif SECSIZE
daddr_t rablkno; int rabsize;
{
register struct buf *bp, *rabp;
bp = NULL;
/*
* If the block isn't in core, then allocate
* a buffer and initiate i/o (getblk checks
* for a cache hit).
*/
if (!incore(dev, blkno)) {
#ifdef SECSIZE
bp = getblk(dev, blkno, size, secsize);
#else SECSIZE
bp = getblk(dev, 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("breada");
(*bdevsw[major(dev)].d_strategy)(bp);
trace(TR_BREADMISS, pack(dev, size), blkno);
u.u_ru.ru_inblock++; /* pay for read */
} else
trace(TR_BREADHIT, pack(dev, size), blkno);
}
/*
* If there's a read-ahead block, start i/o
* on it also (as above).
*/
if (rablkno && !incore(dev, rablkno)) {
#ifdef SECSIZE
rabp = getblk(dev, rablkno, rabsize, secsize);
#else SECSIZE
rabp = getblk(dev, rablkno, rabsize);
#endif SECSIZE
if (rabp->b_flags & (B_DONE|B_DELWRI)) {
brelse(rabp);
trace(TR_BREADHITRA, pack(dev, rabsize), blkno);
} else {
rabp->b_flags |= B_READ|B_ASYNC;
if (rabp->b_bcount > rabp->b_bufsize)
panic("breadrabp");
(*bdevsw[major(dev)].d_strategy)(rabp);
trace(TR_BREADMISSRA, pack(dev, rabsize), rablock);
u.u_ru.ru_inblock++; /* pay in advance */
}
}
/*
* If block was in core, let bread get it.
* If block wasn't in core, then the read was started
* above, and just wait for it.
*/
if (bp == NULL)
#ifdef SECSIZE
return (bread(dev, blkno, size, secsize));
#else SECSIZE
return (bread(dev, blkno, size));
#endif SECSIZE
biowait(bp);
return (bp);
}
/*
* Write the buffer, waiting for completion.
* Then release the buffer.
*/
bwrite(bp)
register struct buf *bp;
{
register flag;
flag = bp->b_flags;
bp->b_flags &= ~(B_READ | B_DONE | B_ERROR | B_DELWRI);
if ((flag&B_DELWRI) == 0)
u.u_ru.ru_oublock++; /* noone paid yet */
trace(TR_BWRITE, pack(bp->b_dev, bp->b_bcount), bp->b_blkno);
if (bp->b_bcount > bp->b_bufsize)
panic("bwrite");
(*bdevsw[major(bp->b_dev)].d_strategy)(bp);
/*
* If the write was synchronous, then await i/o completion.
* If the write was "delayed", then we put the buffer on
* the q of blocks awaiting i/o completion status.
*/
if ((flag&B_ASYNC) == 0) {
biowait(bp);
brelse(bp);
} else if (flag & B_DELWRI)
bp->b_flags |= B_AGE;
}
/*
* Release the buffer, marking it so that if it is grabbed
* for another purpose it will be written out before being
* given up (e.g. when writing a partial block where it is
* assumed that another write for the same block will soon follow).
* This can't be done for magtape, since writes must be done
* in the same order as requested.
*/
bdwrite(bp)
register struct buf *bp;
{
if ((bp->b_flags&B_DELWRI) == 0)
u.u_ru.ru_oublock++; /* noone paid yet */
if (bdevsw[major(bp->b_dev)].d_flags & B_TAPE)
bawrite(bp);
else {
bp->b_flags |= B_DELWRI | B_DONE;
brelse(bp);
}
}
/*
* Release the buffer, start I/O on it, but don't wait for completion.
*/
bawrite(bp)
register struct buf *bp;
{
bp->b_flags |= B_ASYNC;
bwrite(bp);
}
/*
* Release the buffer, with no I/O implied.
*/
brelse(bp)
register struct buf *bp;
{
register struct buf *flist;
register s;
trace(TR_BRELSE, pack(bp->b_dev, bp->b_bufsize), bp->b_blkno);
/*
* If someone's waiting for the buffer, or
* is waiting for a buffer wake 'em up.
*/
if (bp->b_flags&B_WANTED)
wakeup((caddr_t)bp);
if (bfreelist[0].b_flags&B_WANTED) {
bfreelist[0].b_flags &= ~B_WANTED;
wakeup((caddr_t)bfreelist);
}
if (bp->b_flags&B_ERROR)
if (bp->b_flags & B_LOCKED)
bp->b_flags &= ~B_ERROR; /* try again later */
else
bp->b_dev = NODEV; /* no assoc */
/*
* Stick the buffer back on a free list.
*/
s = splbio();
if (bp->b_bufsize <= 0) {
/* block has no buffer ... put at front of unused buffer list */
flist = &bfreelist[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 = &bfreelist[BQ_AGE];
binsheadfree(bp, flist);
} else {
if (bp->b_flags & B_LOCKED)
flist = &bfreelist[BQ_LOCKED];
else if (bp->b_flags & B_AGE)
flist = &bfreelist[BQ_AGE];
else
flist = &bfreelist[BQ_LRU];
binstailfree(bp, flist);
}
bp->b_flags &= ~(B_WANTED|B_BUSY|B_ASYNC|B_AGE);
splx(s);
}
/*
* See if the block is associated with some buffer
* (mainly to avoid getting hung up on a wait in breada)
*/
incore(dev, blkno)
dev_t dev;
daddr_t blkno;
{
register struct buf *bp;
register struct buf *dp;
dp = BUFHASH(dev, blkno);
for (bp = dp->b_forw; bp != dp; bp = bp->b_forw)
if (bp->b_blkno == blkno && bp->b_dev == dev &&
(bp->b_flags & B_INVAL) == 0)
return (1);
return (0);
}
struct buf *
#ifdef SECSIZE
baddr(dev, blkno, size, secsize)
#else SECSIZE
baddr(dev, blkno, size)
#endif SECSIZE
dev_t dev;
daddr_t blkno;
int size;
#ifdef SECSIZE
long secsize;
#endif SECSIZE
{
if (incore(dev, blkno))
#ifdef SECSIZE
return (bread(dev, blkno, size, secsize));
#else SECSIZE
return (bread(dev, blkno, size));
#endif SECSIZE
return (0);
}
/*
* Assign a buffer for the given block. If the appropriate
* block is already associated, return it; otherwise search
* for the oldest non-busy buffer and reassign it.
*
* If we find the buffer, but it is dirty (marked DELWRI) and
* its size is changing, we must write it out first. When the
* buffer is shrinking, the write is done by brealloc to avoid
* losing the unwritten data. When the buffer is growing, the
* write is done by getblk, so that bread will not read stale
* disk data over the modified data in the buffer.
*
* We use splx here because this routine may be called
* on the interrupt stack during a dump, and we don't
* want to lower the ipl back to 0.
*/
struct buf *
#ifdef SECSIZE
getblk(dev, blkno, size, secsize)
#else SECSIZE
getblk(dev, blkno, size)
#endif SECSIZE
dev_t dev;
daddr_t blkno;
int size;
#ifdef SECSIZE
long secsize;
#endif SECSIZE
{
register struct buf *bp, *dp;
int s;
if (size > MAXBSIZE)
panic("getblk: size too big");
/*
* To prevent overflow of 32-bit ints when converting block
* numbers to byte offsets, blknos > 2^32 / DEV_BSIZE are set
* to the maximum number that can be converted to a byte offset
* without overflow. This is historic code; what bug it fixed,
* or whether it is still a reasonable thing to do is open to
* dispute. mkm 9/85
*/
if ((unsigned)blkno >= 1 << (sizeof(int)*NBBY-DEV_BSHIFT))
blkno = 1 << ((sizeof(int)*NBBY-DEV_BSHIFT) + 1);
/*
* Search the cache for the block. If we hit, but
* the buffer is in use for i/o, then we wait until
* the i/o has completed.
*/
dp = BUFHASH(dev, blkno);
loop:
for (bp = dp->b_forw; bp != dp; bp = bp->b_forw) {
if (bp->b_blkno != blkno || bp->b_dev != dev ||
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;
}
splx(s);
notavail(bp);
if (bp->b_bcount != size) {
if (bp->b_bcount < size && (bp->b_flags&B_DELWRI)) {
bp->b_flags &= ~B_ASYNC;
bwrite(bp);
goto loop;
}
if (brealloc(bp, size) == 0)
goto loop;
}
if (bp->b_bcount != size && brealloc(bp, size) == 0)
goto loop;
bp->b_flags |= B_CACHE;
return (bp);
}
if (major(dev) >= nblkdev)
panic("blkdev");
bp = getnewbuf();
bfree(bp);
bremhash(bp);
binshash(bp, dp);
bp->b_dev = dev;
#ifdef SECSIZE
bp->b_blksize = secsize;
#endif SECSIZE
bp->b_blkno = blkno;
bp->b_error = 0;
if (brealloc(bp, size) == 0)
goto loop;
return (bp);
}
/*
* get an empty block,
* not assigned to any particular device
*/
struct buf *
geteblk(size)
int size;
{
register struct buf *bp, *flist;
if (size > MAXBSIZE)
panic("geteblk: size too big");
loop:
bp = getnewbuf();
bp->b_flags |= B_INVAL;
bfree(bp);
bremhash(bp);
flist = &bfreelist[BQ_AGE];
binshash(bp, flist);
bp->b_dev = (dev_t)NODEV;
#ifdef SECSIZE
bp->b_blksize = DEV_BSIZE;
#endif SECSIZE
bp->b_error = 0;
if (brealloc(bp, size) == 0)
goto loop;
return (bp);
}
/*
* Allocate space associated with a buffer.
* If can't get space, buffer is released
*/
brealloc(bp, size)
register struct buf *bp;
int size;
{
daddr_t start, last;
register struct buf *ep;
struct buf *dp;
int s;
/*
* First need to make sure that all overlapping previous I/O
* is dispatched with.
*/
if (size == bp->b_bcount)
return (1);
if (size < bp->b_bcount) {
if (bp->b_flags & B_DELWRI) {
bwrite(bp);
return (0);
}
if (bp->b_flags & B_LOCKED)
panic("brealloc");
return (allocbuf(bp, size));
}
bp->b_flags &= ~B_DONE;
if (bp->b_dev == NODEV)
return (allocbuf(bp, size));
trace(TR_BREALLOC, pack(bp->b_dev, size), bp->b_blkno);
/*
* Search cache for any buffers that overlap the one that we
* are trying to allocate. Overlapping buffers must be marked
* invalid, after being written out if they are dirty. (indicated
* by B_DELWRI) A disk block must be mapped by at most one buffer
* at any point in time. Care must be taken to avoid deadlocking
* when two buffer are trying to get the same set of disk blocks.
*/
start = bp->b_blkno;
#ifdef SECSIZE
last = start + size/bp->b_blksize - 1;
#else SECSIZE
last = start + btodb(size) - 1;
#endif SECSIZE
dp = BUFHASH(bp->b_dev, bp->b_blkno);
loop:
for (ep = dp->b_forw; ep != dp; ep = ep->b_forw) {
if (ep == bp || ep->b_dev != bp->b_dev || (ep->b_flags&B_INVAL))
continue;
/* look for overlap */
if (ep->b_bcount == 0 || ep->b_blkno > last ||
#ifdef SECSIZE
ep->b_blkno + ep->b_bcount/ep->b_blksize <= start)
#else SECSIZE
ep->b_blkno + btodb(ep->b_bcount) <= start)
#endif SECSIZE
continue;
s = splbio();
if (ep->b_flags&B_BUSY) {
ep->b_flags |= B_WANTED;
sleep((caddr_t)ep, PRIBIO+1);
splx(s);
goto loop;
}
splx(s);
notavail(ep);
if (ep->b_flags & B_DELWRI) {
bwrite(ep);
goto loop;
}
ep->b_flags |= B_INVAL;
brelse(ep);
}
return (allocbuf(bp, size));
}
/*
* 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, *dp;
int s;
loop:
s = splbio();
for (dp = &bfreelist[BQ_AGE]; dp > bfreelist; dp--)
if (dp->av_forw != dp)
break;
if (dp == bfreelist) { /* no free blocks */
dp->b_flags |= B_WANTED;
sleep((caddr_t)dp, PRIBIO+1);
splx(s);
goto loop;
}
splx(s);
bp = dp->av_forw;
notavail(bp);
if (bp->b_flags & B_DELWRI) {
bp->b_flags |= B_ASYNC;
bwrite(bp);
goto loop;
}
trace(TR_BRELSE, pack(bp->b_dev, bp->b_bufsize), bp->b_blkno);
bp->b_flags = B_BUSY;
return (bp);
}
/*
* Wait for I/O completion on the buffer; return errors
* to the user.
*/
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 (u.u_error == 0) /* XXX */
u.u_error = geterror(bp);
}
/*
* Mark I/O complete on a buffer.
* If someone should be called, e.g. the pageout
* daemon, do so. Otherwise, wake up anyone
* waiting for it.
*/
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_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);
}
}
/*
* Insure that no part of a specified block is in an incore buffer.
#ifdef SECSIZE
* "size" is given in device blocks (the units of b_blkno).
#endif SECSIZE
#ifdef SECSIZE
* "size" is given in device blocks (the units of b_blkno).
#endif SECSIZE
*/
blkflush(dev, blkno, size)
dev_t dev;
daddr_t blkno;
#ifdef SECSIZE
int size;
#else SECSIZE
long size;
#endif SECSIZE
{
register struct buf *ep;
struct buf *dp;
daddr_t start, last;
int s;
start = blkno;
#ifdef SECSIZE
last = start + size - 1;
#else SECSIZE
last = start + btodb(size) - 1;
#endif SECSIZE
dp = BUFHASH(dev, blkno);
loop:
for (ep = dp->b_forw; ep != dp; ep = ep->b_forw) {
if (ep->b_dev != dev || (ep->b_flags&B_INVAL))
continue;
/* look for overlap */
if (ep->b_bcount == 0 || ep->b_blkno > last ||
#ifdef SECSIZE
ep->b_blkno + ep->b_bcount / ep->b_blksize <= start)
#else SECSIZE
ep->b_blkno + btodb(ep->b_bcount) <= start)
#endif SECSIZE
continue;
s = splbio();
if (ep->b_flags&B_BUSY) {
ep->b_flags |= B_WANTED;
sleep((caddr_t)ep, PRIBIO+1);
splx(s);
goto loop;
}
if (ep->b_flags & B_DELWRI) {
splx(s);
notavail(ep);
bwrite(ep);
goto loop;
}
splx(s);
}
}
/*
* Make sure all write-behind blocks
* on dev (or NODEV for all)
* are flushed out.
* (from umount and update)
*/
bflush(dev)
dev_t dev;
{
register struct buf *bp;
register struct buf *flist;
int s;
loop:
s = splbio();
for (flist = bfreelist; flist < &bfreelist[BQ_EMPTY]; flist++)
for (bp = flist->av_forw; bp != flist; bp = bp->av_forw) {
if ((bp->b_flags & B_DELWRI) == 0)
continue;
if (dev == NODEV || dev == bp->b_dev) {
bp->b_flags |= B_ASYNC;
notavail(bp);
bwrite(bp);
splx(s);
goto loop;
}
}
splx(s);
}
/*
* Pick up the device's error number and pass it to the user;
* if there is an error but the number is 0 set a generalized code.
*/
geterror(bp)
register struct buf *bp;
{
int error = 0;
if (bp->b_flags&B_ERROR)
if ((error = bp->b_error)==0)
return (EIO);
return (error);
}
/*
* Invalidate in core blocks belonging to closed or umounted filesystem
*
* This is not nicely done at all - the buffer ought to be removed from the
* hash chains & have its dev/blkno fields clobbered, but unfortunately we
* can't do that here, as it is quite possible that the block is still
* being used for i/o. Eventually, all disc drivers should be forced to
* have a close routine, which ought ensure that the queue is empty, then
* properly flush the queues. Until that happy day, this suffices for
* correctness. ... kre
*/
binval(dev)
dev_t dev;
{
register struct buf *bp;
register struct bufhd *hp;
#define dp ((struct buf *)hp)
for (hp = bufhash; hp < &bufhash[BUFHSZ]; hp++)
for (bp = dp->b_forw; bp != dp; bp = bp->b_forw)
if (bp->b_dev == dev)
bp->b_flags |= B_INVAL;
}
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.