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Research V7 development
[unix-history] / usr / sys / dev / bio.c
#include "../h/param.h"
#include "../h/systm.h"
#include "../h/dir.h"
#include "../h/user.h"
#include "../h/buf.h"
#include "../h/conf.h"
#include "../h/proc.h"
#include "../h/seg.h"
#define DISKMON 1
#ifdef DISKMON
struct {
int nbuf;
long nread;
long nreada;
long ncache;
long nwrite;
long bufcount[NBUF];
} io_info;
#endif
/*
* swap IO headers.
* they are filled in to point
* at the desired IO operation.
*/
struct buf swbuf1;
struct buf swbuf2;
/*
* The following several routines allocate and free
* buffers with various side effects. In general the
* arguments to an allocate routine are a device and
* a block number, and the value is a pointer to
* to the buffer header; the buffer is marked "busy"
* so that no one else can touch it. If the block was
* already in core, no I/O need be done; if it is
* already busy, the process waits until it becomes free.
* The following routines allocate a buffer:
* getblk
* bread
* breada
* Eventually the buffer must be released, possibly with the
* side effect of writing it out, by using one of
* bwrite
* bdwrite
* bawrite
* brelse
*/
/*
* Read in (if necessary) the block and return a buffer pointer.
*/
struct buf *
bread(dev, blkno)
dev_t dev;
daddr_t blkno;
{
register struct buf *bp;
bp = getblk(dev, blkno);
if (bp->b_flags&B_DONE) {
#ifdef DISKMON
io_info.ncache++;
#endif
return(bp);
}
bp->b_flags |= B_READ;
bp->b_bcount = BSIZE;
(*bdevsw[major(dev)].d_strategy)(bp);
#ifdef DISKMON
io_info.nread++;
#endif
iowait(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 *
breada(dev, blkno, rablkno)
dev_t dev;
daddr_t blkno, rablkno;
{
register struct buf *bp, *rabp;
bp = NULL;
if (!incore(dev, blkno)) {
bp = getblk(dev, blkno);
if ((bp->b_flags&B_DONE) == 0) {
bp->b_flags |= B_READ;
bp->b_bcount = BSIZE;
(*bdevsw[major(dev)].d_strategy)(bp);
#ifdef DISKMON
io_info.nread++;
#endif
}
}
if (rablkno && !incore(dev, rablkno)) {
rabp = getblk(dev, rablkno);
if (rabp->b_flags & B_DONE)
brelse(rabp);
else {
rabp->b_flags |= B_READ|B_ASYNC;
rabp->b_bcount = BSIZE;
(*bdevsw[major(dev)].d_strategy)(rabp);
#ifdef DISKMON
io_info.nreada++;
#endif
}
}
if(bp == NULL)
return(bread(dev, blkno));
iowait(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 | B_AGE);
bp->b_bcount = BSIZE;
#ifdef DISKMON
io_info.nwrite++;
#endif
(*bdevsw[major(bp->b_dev)].d_strategy)(bp);
if ((flag&B_ASYNC) == 0) {
iowait(bp);
brelse(bp);
} else if (flag & B_DELWRI)
bp->b_flags |= B_AGE;
else
geterror(bp);
}
/*
* 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;
{
register struct buf *dp;
dp = bdevsw[major(bp->b_dev)].d_tab;
if(dp->b_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 **backp;
register s;
if (bp->b_flags&B_WANTED)
wakeup((caddr_t)bp);
if (bfreelist.b_flags&B_WANTED) {
bfreelist.b_flags &= ~B_WANTED;
wakeup((caddr_t)&bfreelist);
}
if (bp->b_flags&B_ERROR)
bp->b_dev = NODEV; /* no assoc. on error */
s = spl6();
if(bp->b_flags & B_AGE) {
backp = &bfreelist.av_forw;
(*backp)->av_back = bp;
bp->av_forw = *backp;
*backp = bp;
bp->av_back = &bfreelist;
} else {
backp = &bfreelist.av_back;
(*backp)->av_forw = bp;
bp->av_back = *backp;
*backp = bp;
bp->av_forw = &bfreelist;
}
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 = bdevsw[major(dev)].d_tab;
for (bp=dp->b_forw; bp != dp; bp = bp->b_forw)
if (bp->b_blkno==blkno && bp->b_dev==dev)
return(1);
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.
*/
struct buf *
getblk(dev, blkno)
dev_t dev;
daddr_t blkno;
{
register struct buf *bp;
register struct buf *dp;
#ifdef DISKMON
register i;
#endif
if(major(dev) >= nblkdev)
panic("blkdev");
loop:
spl0();
dp = bdevsw[major(dev)].d_tab;
if(dp == NULL)
panic("devtab");
for (bp=dp->b_forw; bp != dp; bp = bp->b_forw) {
if (bp->b_blkno!=blkno || bp->b_dev!=dev)
continue;
spl6();
if (bp->b_flags&B_BUSY) {
bp->b_flags |= B_WANTED;
sleep((caddr_t)bp, PRIBIO+1);
goto loop;
}
spl0();
#ifdef DISKMON
i = 0;
dp = bp->av_forw;
while (dp != &bfreelist) {
i++;
dp = dp->av_forw;
}
if (i<NBUF)
io_info.bufcount[i]++;
#endif
notavail(bp);
return(bp);
}
spl6();
if (bfreelist.av_forw == &bfreelist) {
bfreelist.b_flags |= B_WANTED;
sleep((caddr_t)&bfreelist, PRIBIO+1);
goto loop;
}
spl0();
notavail(bp = bfreelist.av_forw);
if (bp->b_flags & B_DELWRI) {
bp->b_flags |= B_ASYNC;
bwrite(bp);
goto loop;
}
bp->b_flags = B_BUSY;
bp->b_back->b_forw = bp->b_forw;
bp->b_forw->b_back = bp->b_back;
bp->b_forw = dp->b_forw;
bp->b_back = dp;
dp->b_forw->b_back = bp;
dp->b_forw = bp;
bp->b_dev = dev;
bp->b_blkno = blkno;
return(bp);
}
/*
* get an empty block,
* not assigned to any particular device
*/
struct buf *
geteblk()
{
register struct buf *bp;
register struct buf *dp;
loop:
spl6();
while (bfreelist.av_forw == &bfreelist) {
bfreelist.b_flags |= B_WANTED;
sleep((caddr_t)&bfreelist, PRIBIO+1);
}
spl0();
dp = &bfreelist;
notavail(bp = bfreelist.av_forw);
if (bp->b_flags & B_DELWRI) {
bp->b_flags |= B_ASYNC;
bwrite(bp);
goto loop;
}
bp->b_flags = B_BUSY;
bp->b_back->b_forw = bp->b_forw;
bp->b_forw->b_back = bp->b_back;
bp->b_forw = dp->b_forw;
bp->b_back = dp;
dp->b_forw->b_back = bp;
dp->b_forw = bp;
bp->b_dev = (dev_t)NODEV;
return(bp);
}
/*
* Wait for I/O completion on the buffer; return errors
* to the user.
*/
iowait(bp)
register struct buf *bp;
{
spl6();
while ((bp->b_flags&B_DONE)==0)
sleep((caddr_t)bp, PRIBIO);
spl0();
geterror(bp);
}
/*
* Unlink a buffer from the available list and mark it busy.
* (internal interface)
*/
notavail(bp)
register struct buf *bp;
{
register s;
s = spl6();
bp->av_back->av_forw = bp->av_forw;
bp->av_forw->av_back = bp->av_back;
bp->b_flags |= B_BUSY;
splx(s);
}
/*
* Mark I/O complete on a buffer, release it if I/O is asynchronous,
* and wake up anyone waiting for it.
*/
iodone(bp)
register struct buf *bp;
{
if(bp->b_flags&B_MAP)
mapfree(bp);
bp->b_flags |= B_DONE;
if (bp->b_flags&B_ASYNC)
brelse(bp);
else {
bp->b_flags &= ~B_WANTED;
wakeup((caddr_t)bp);
}
}
/*
* Zero the core associated with a buffer.
*/
clrbuf(bp)
struct buf *bp;
{
register *p;
register c;
p = bp->b_un.b_words;
c = BSIZE/sizeof(int);
do
*p++ = 0;
while (--c);
bp->b_resid = 0;
}
/*
* swap I/O
*/
swap(blkno, coreaddr, count, rdflg)
register count;
{
register struct buf *bp;
register tcount;
bp = &swbuf1;
if(bp->b_flags & B_BUSY)
if((swbuf2.b_flags&B_WANTED) == 0)
bp = &swbuf2;
spl6();
while (bp->b_flags&B_BUSY) {
bp->b_flags |= B_WANTED;
sleep((caddr_t)bp, PSWP+1);
}
while (count) {
bp->b_flags = B_BUSY | B_PHYS | rdflg;
bp->b_dev = swapdev;
tcount = count;
if (tcount >= 01700) /* prevent byte-count wrap */
tcount = 01700;
bp->b_bcount = ctob(tcount);
bp->b_blkno = swplo+blkno;
bp->b_un.b_addr = (caddr_t)(coreaddr<<6);
bp->b_xmem = (coreaddr>>10) & 077;
(*bdevsw[major(swapdev)].d_strategy)(bp);
spl6();
while((bp->b_flags&B_DONE)==0)
sleep((caddr_t)bp, PSWP);
count -= tcount;
coreaddr += tcount;
blkno += ctod(tcount);
}
if (bp->b_flags&B_WANTED)
wakeup((caddr_t)bp);
spl0();
bp->b_flags &= ~(B_BUSY|B_WANTED);
if (bp->b_flags & B_ERROR)
panic("IO err in swap");
}
/*
* 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;
loop:
spl6();
for (bp = bfreelist.av_forw; bp != &bfreelist; bp = bp->av_forw) {
if (bp->b_flags&B_DELWRI && (dev == NODEV||dev==bp->b_dev)) {
bp->b_flags |= B_ASYNC;
notavail(bp);
bwrite(bp);
goto loop;
}
}
spl0();
}
/*
* Raw I/O. The arguments are
* The strategy routine for the device
* A buffer, which will always be a special buffer
* header owned exclusively by the device for this purpose
* The device number
* Read/write flag
* Essentially all the work is computing physical addresses and
* validating them.
*/
physio(strat, bp, dev, rw)
register struct buf *bp;
int (*strat)();
{
register unsigned base;
register int nb;
int ts;
base = (unsigned)u.u_base;
/*
* Check odd base, odd count, and address wraparound
*/
if (base&01 || u.u_count&01 || base>=base+u.u_count)
goto bad;
ts = (u.u_tsize+127) & ~0177;
if (u.u_sep)
ts = 0;
nb = (base>>6) & 01777;
/*
* Check overlap with text. (ts and nb now
* in 64-byte clicks)
*/
if (nb < ts)
goto bad;
/*
* Check that transfer is either entirely in the
* data or in the stack: that is, either
* the end is in the data or the start is in the stack
* (remember wraparound was already checked).
*/
if ((((base+u.u_count)>>6)&01777) >= ts+u.u_dsize
&& nb < 1024-u.u_ssize)
goto bad;
spl6();
while (bp->b_flags&B_BUSY) {
bp->b_flags |= B_WANTED;
sleep((caddr_t)bp, PRIBIO+1);
}
bp->b_flags = B_BUSY | B_PHYS | rw;
bp->b_dev = dev;
/*
* Compute physical address by simulating
* the segmentation hardware.
*/
ts = (u.u_sep? UDSA: UISA)->r[nb>>7] + (nb&0177);
bp->b_un.b_addr = (caddr_t)((ts<<6) + (base&077));
bp->b_xmem = (ts>>10) & 077;
bp->b_blkno = u.u_offset >> BSHIFT;
bp->b_bcount = u.u_count;
bp->b_error = 0;
u.u_procp->p_flag |= SLOCK;
(*strat)(bp);
spl6();
while ((bp->b_flags&B_DONE) == 0)
sleep((caddr_t)bp, PRIBIO);
u.u_procp->p_flag &= ~SLOCK;
if (bp->b_flags&B_WANTED)
wakeup((caddr_t)bp);
spl0();
bp->b_flags &= ~(B_BUSY|B_WANTED);
u.u_count = bp->b_resid;
geterror(bp);
return;
bad:
u.u_error = EFAULT;
}
/*
* 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. Actually the latter is always true because devices
* don't yet return specific errors.
*/
geterror(bp)
register struct buf *bp;
{
if (bp->b_flags&B_ERROR)
if ((u.u_error = bp->b_error)==0)
u.u_error = EIO;
}
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.