uint8_t *bread(uint16_t dev, blkno_t blk, bool rewrite)
{
register bufptr bp;
if ((bp = bfind(dev, blk)) != NULL) {
if (bp->bf_busy == BF_BUSY)
panic(PANIC_WANTBSYB);
else if (bp->bf_busy == BF_FREE)
bp->bf_busy = BF_BUSY;
/* BF_SUPERBLOCK is fine */
} else {
bp = freebuf();
bp->bf_dev = dev;
bp->bf_blk = blk;
bp->bf_busy = BF_BUSY;
/* If rewrite is set, we are about to write over the entire block,
so we don't need the previous contents */
if (!rewrite) {
if (bdread(bp) == -1) {
udata.u_error = EIO;
return (NULL);
}
}
}
bp->bf_time = ++bufclock; /* Time stamp it */
return (bp->bf_data);
}
char *bread(int dev, blkno_t blk, int rewrite)
{
register bufptr bp;
/*printf("Reading block %d\n", blk);*/
bp = bfind(dev, blk);
if (bp) {
if (bp->bf_busy)
panic("want busy block");
goto done;
}
bp = freebuf();
bp->bf_dev = dev;
bp->bf_blk = blk;
/* If rewrite is set, we are about to write over the entire block,
so we don't need the previous contents */
ifnot(rewrite)
if (bdread(bp) == -1) {
udata.u_error = EIO;
return 0;
}
done:
bp->bf_busy = 1;
bp->bf_time = ++bufclock; /* Time stamp it */
return (bp->bf_data);
}
/*
* Make an entry in the buffer cache and fill it. If rewrite is
* set then we are not keeping any of the old data but overwriting
* it all.
*
* Hands back either a locked buffer, or NULL on an error.
*/
bufptr bread(uint16_t dev, blkno_t blk, bool rewrite)
{
regptr bufptr bp;
if ((bp = bfind(dev, blk)) == NULL) {
bp = freebuf();
bp->bf_dev = dev;
bp->bf_blk = blk;
/* If rewrite is set, we are about to write over the entire block,
so we don't need the previous contents */
if (!rewrite) {
if (bdread(bp) != BLKSIZE) {
udata.u_error = EIO;
/* Don't cache the failure */
bp->bf_dev = NO_DEVICE;
bp->bf_dirty = false;
bunlock(bp);
return (NULL);
}
}
}
return bp;
}
