/*
* Initialize buffer headers and related structures.
*/
void bufinit()
{
struct bufhd *bh;
struct buf *bp;
/* first, make a null hash table */
for(bh = bufhash; bh < bufhash + BUFHSZ; bh++) {
bh->b_flags = 0;
bh->b_forw = (struct buf *)bh;
bh->b_back = (struct buf *)bh;
}
/* next, make a null set of free lists */
for(bp = bfreelist; bp < bfreelist + BQUEUES; bp++) {
bp->b_flags = 0;
bp->av_forw = bp;
bp->av_back = bp;
bp->b_forw = bp;
bp->b_back = bp;
}
/* finally, initialize each buffer header and stick on empty q */
for(bp = buf; bp < buf + nbuf ; bp++) {
bp->b_flags = B_HEAD | B_INVAL; /* we're just an empty header */
bp->b_dev = NODEV;
bp->b_vp = 0;
binstailfree(bp, bfreelist + BQ_EMPTY);
binshash(bp, bfreelist + BQ_EMPTY);
}
}
/*
* Release a buffer.
* Even if the buffer is dirty, no I/O is started.
*/
void
brelse(register struct buf *bp)
{
int x;
/* anyone need a "free" block? */
x=splbio();
if ((bfreelist + BQ_AGE)->b_flags & B_WANTED) {
(bfreelist + BQ_AGE) ->b_flags &= ~B_WANTED;
wakeup(bfreelist);
}
/* anyone need this very block? */
if (bp->b_flags & B_WANTED) {
bp->b_flags &= ~B_WANTED;
wakeup(bp);
}
if (bp->b_flags & (B_INVAL|B_ERROR)) {
bp->b_flags |= B_INVAL;
bp->b_flags &= ~(B_DELWRI|B_CACHE);
if(bp->b_vp)
brelvp(bp);
}
/* enqueue */
/* just an empty buffer head ... */
/*if(bp->b_flags & B_HEAD)
binsheadfree(bp, bfreelist + BQ_EMPTY)*/
/* buffers with junk contents */
/*else*/ if(bp->b_flags & (B_ERROR|B_INVAL|B_NOCACHE))
binsheadfree(bp, bfreelist + BQ_AGE)
/* buffers with stale but valid contents */
else if(bp->b_flags & B_AGE)
binstailfree(bp, bfreelist + BQ_AGE)
/* buffers with valid and quite potentially reuseable contents */
else
binstailfree(bp, bfreelist + BQ_LRU)
/* unlock */
bp->b_flags &= ~B_BUSY;
splx(x);
}
/*
* Buffer cleaning daemon.
*/
void
buf_daemon(struct proc *p)
{
int s;
struct buf *bp;
struct timeval starttime, timediff;
cleanerproc = curproc;
for (;;) {
if (numdirtypages < hidirtypages) {
tsleep(&bd_req, PRIBIO - 7, "cleaner", 0);
}
starttime = time;
s = splbio();
while ((bp = TAILQ_FIRST(&bufqueues[BQ_DIRTY]))) {
bremfree(bp);
SET(bp->b_flags, B_BUSY);
splx(s);
if (ISSET(bp->b_flags, B_INVAL)) {
brelse(bp);
s = splbio();
continue;
}
#ifdef DIAGNOSTIC
if (!ISSET(bp->b_flags, B_DELWRI))
panic("Clean buffer on BQ_DIRTY");
#endif
if (LIST_FIRST(&bp->b_dep) != NULL &&
!ISSET(bp->b_flags, B_DEFERRED) &&
buf_countdeps(bp, 0, 1)) {
SET(bp->b_flags, B_DEFERRED);
s = splbio();
numfreepages += btoc(bp->b_bufsize);
numdirtypages += btoc(bp->b_bufsize);
binstailfree(bp, &bufqueues[BQ_DIRTY]);
CLR(bp->b_flags, B_BUSY);
continue;
}
bawrite(bp);
if (numdirtypages < lodirtypages)
break;
/* Never allow processing to run for more than 1 sec */
timersub(&time, &starttime, &timediff);
if (timediff.tv_sec)
break;
s = splbio();
}
}
}
/*
* Release a buffer on to the free lists.
* Described in Bach (p. 46).
*/
void
brelse(struct buf *bp)
{
struct bqueues *bufq;
int s;
/* Block disk interrupts. */
s = splbio();
/*
* Determine which queue the buffer should be on, then put it there.
*/
/* If it's locked, don't report an error; try again later. */
if (ISSET(bp->b_flags, (B_LOCKED|B_ERROR)) == (B_LOCKED|B_ERROR))
CLR(bp->b_flags, B_ERROR);
/* If it's not cacheable, or an error, mark it invalid. */
if (ISSET(bp->b_flags, (B_NOCACHE|B_ERROR)))
SET(bp->b_flags, B_INVAL);
if ((bp->b_bufsize <= 0) || ISSET(bp->b_flags, B_INVAL)) {
/*
* If it's invalid or empty, dissociate it from its vnode
* and put on the head of the appropriate queue.
*/
if (LIST_FIRST(&bp->b_dep) != NULL)
buf_deallocate(bp);
if (ISSET(bp->b_flags, B_DELWRI)) {
CLR(bp->b_flags, B_DELWRI);
}
if (bp->b_vp) {
reassignbuf(bp);
brelvp(bp);
}
if (bp->b_bufsize <= 0) {
/* no data */
bufq = &bufqueues[BQ_EMPTY];
numemptybufs++;
} else {
/* invalid data */
bufq = &bufqueues[BQ_CLEAN];
numfreepages += btoc(bp->b_bufsize);
numcleanpages += btoc(bp->b_bufsize);
}
binsheadfree(bp, bufq);
} else {
/*
* It has valid data. Put it on the end of the appropriate
* queue, so that it'll stick around for as long as possible.
*/
if (ISSET(bp->b_flags, B_LOCKED))
/* locked in core */
bufq = &bufqueues[BQ_LOCKED];
else {
numfreepages += btoc(bp->b_bufsize);
if (!ISSET(bp->b_flags, B_DELWRI)) {
numcleanpages += btoc(bp->b_bufsize);
bufq = &bufqueues[BQ_CLEAN];
} else {
numdirtypages += btoc(bp->b_bufsize);
bufq = &bufqueues[BQ_DIRTY];
}
}
if (ISSET(bp->b_flags, B_AGE))
binsheadfree(bp, bufq);
else
binstailfree(bp, bufq);
}
/* Unlock the buffer. */
CLR(bp->b_flags, (B_AGE | B_ASYNC | B_BUSY | B_NOCACHE | B_DEFERRED));
/* Wake up syncer and cleaner processes waiting for buffers */
if (nobuffers) {
wakeup(&nobuffers);
nobuffers = 0;
}
/* Wake up any processes waiting for any buffer to become free. */
if (needbuffer && (numcleanpages > locleanpages)) {
needbuffer--;
wakeup_one(&needbuffer);
}
splx(s);
/* Wake up any processes waiting for _this_ buffer to become free. */
if (ISSET(bp->b_flags, B_WANTED)) {
CLR(bp->b_flags, B_WANTED);
wakeup(bp);
}
}