/*
* Read a disk block.
* This algorithm described in Bach (p.54).
*/
int
bread(struct vnode *vp, daddr_t blkno, int size, struct buf **bpp)
{
struct buf *bp;
/* Get buffer for block. */
bp = *bpp = bio_doread(vp, blkno, size, 0);
/* Wait for the read to complete, and return result. */
return (biowait(bp));
}
/*
* Read-ahead multiple disk blocks. The first is sync, the rest async.
* Trivial modification to the breada algorithm presented in Bach (p.55).
*/
int
breadn(struct vnode *vp, daddr_t blkno, int size, daddr_t rablks[],
int rasizes[], int nrablks, struct ucred *cred, struct buf **bpp)
{
struct buf *bp;
int i;
bp = *bpp = bio_doread(vp, blkno, size, 0);
/*
* For each of the read-ahead blocks, start a read, if necessary.
*/
for (i = 0; i < nrablks; i++) {
/* If it's in the cache, just go on to next one. */
if (incore(vp, rablks[i]))
continue;
/* Get a buffer for the read-ahead block */
(void) bio_doread(vp, rablks[i], rasizes[i], B_ASYNC);
}
/* Otherwise, we had to start a read for it; wait until it's valid. */
return (biowait(bp));
}
int
bread_cluster(struct vnode *vp, daddr_t blkno, int size, struct buf **rbpp)
{
struct buf *bp, **xbpp;
int howmany, maxra, i, inc;
daddr_t sblkno;
*rbpp = bio_doread(vp, blkno, size, 0);
if (size != round_page(size))
goto out;
if (VOP_BMAP(vp, blkno + 1, NULL, &sblkno, &maxra))
goto out;
maxra++;
if (sblkno == -1 || maxra < 2)
goto out;
howmany = MAXPHYS / size;
if (howmany > maxra)
howmany = maxra;
xbpp = malloc((howmany + 1) * sizeof(struct buf *), M_TEMP, M_NOWAIT);
if (xbpp == NULL)
goto out;
for (i = howmany - 1; i >= 0; i--) {
size_t sz;
/*
* First buffer allocates big enough size to cover what
* all the other buffers need.
*/
sz = i == 0 ? howmany * size : 0;
xbpp[i] = buf_get(vp, blkno + i + 1, sz);
if (xbpp[i] == NULL) {
for (++i; i < howmany; i++) {
SET(xbpp[i]->b_flags, B_INVAL);
brelse(xbpp[i]);
}
free(xbpp, M_TEMP);
goto out;
}
}
bp = xbpp[0];
xbpp[howmany] = 0;
inc = btodb(size);
for (i = 1; i < howmany; i++) {
bcstats.pendingreads++;
bcstats.numreads++;
SET(xbpp[i]->b_flags, B_READ | B_ASYNC);
xbpp[i]->b_blkno = sblkno + (i * inc);
xbpp[i]->b_bufsize = xbpp[i]->b_bcount = size;
xbpp[i]->b_data = NULL;
xbpp[i]->b_pobj = bp->b_pobj;
xbpp[i]->b_poffs = bp->b_poffs + (i * size);
}
KASSERT(bp->b_lblkno == blkno + 1);
KASSERT(bp->b_vp == vp);
bp->b_blkno = sblkno;
SET(bp->b_flags, B_READ | B_ASYNC | B_CALL);
bp->b_saveaddr = (void *)xbpp;
bp->b_iodone = bread_cluster_callback;
bcstats.pendingreads++;
bcstats.numreads++;
VOP_STRATEGY(bp);
curproc->p_ru.ru_inblock++;
out:
return (biowait(*rbpp));
}
