COW: Extend checking allocated bits to beyond one sector
cow_co_is_allocated() only checks one sector's worth of allocated bits before returning. This is allowed but (slightly) inefficient, so extend it to check all of the file's metadata sectors. Signed-off-by: Charlie Shepherd <charlie@ctshepherd.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> [kwolf: silenced compiler warning (-Wmaybe-uninitialized for changed)] Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
parent
14b98fdaf3
commit
091b1108ca
36
block/cow.c
36
block/cow.c
|
@ -152,18 +152,34 @@ static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs,
|
||||||
{
|
{
|
||||||
int64_t bitnum = sector_num + sizeof(struct cow_header_v2) * 8;
|
int64_t bitnum = sector_num + sizeof(struct cow_header_v2) * 8;
|
||||||
uint64_t offset = (bitnum / 8) & -BDRV_SECTOR_SIZE;
|
uint64_t offset = (bitnum / 8) & -BDRV_SECTOR_SIZE;
|
||||||
uint8_t bitmap[BDRV_SECTOR_SIZE];
|
bool first = true;
|
||||||
int ret;
|
int changed = 0, same = 0;
|
||||||
int changed;
|
|
||||||
|
|
||||||
ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
|
do {
|
||||||
if (ret < 0) {
|
int ret;
|
||||||
return ret;
|
uint8_t bitmap[BDRV_SECTOR_SIZE];
|
||||||
}
|
|
||||||
|
|
||||||
bitnum &= BITS_PER_BITMAP_SECTOR - 1;
|
bitnum &= BITS_PER_BITMAP_SECTOR - 1;
|
||||||
changed = cow_test_bit(bitnum, bitmap);
|
int sector_bits = MIN(nb_sectors, BITS_PER_BITMAP_SECTOR - bitnum);
|
||||||
*num_same = cow_find_streak(bitmap, changed, bitnum, nb_sectors);
|
|
||||||
|
ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
|
||||||
|
if (ret < 0) {
|
||||||
|
return ret;
|
||||||
|
}
|
||||||
|
|
||||||
|
if (first) {
|
||||||
|
changed = cow_test_bit(bitnum, bitmap);
|
||||||
|
first = false;
|
||||||
|
}
|
||||||
|
|
||||||
|
same += cow_find_streak(bitmap, changed, bitnum, nb_sectors);
|
||||||
|
|
||||||
|
bitnum += sector_bits;
|
||||||
|
nb_sectors -= sector_bits;
|
||||||
|
offset += BDRV_SECTOR_SIZE;
|
||||||
|
} while (nb_sectors);
|
||||||
|
|
||||||
|
*num_same = same;
|
||||||
return changed;
|
return changed;
|
||||||
}
|
}
|
||||||
|
|
||||||
|
|
Loading…
Reference in a new issue