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qcow2: Switch is_zero_sectors() to byte-based

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We are gradually converting to byte-based interfaces, as they are
easier to reason about than sector-based.  Convert another internal
function (no semantic change), and rename it to is_zero() in the
process.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2017-10-11 22:47:00 -05:00 • committed by Kevin Wolf
parent 7cfd527525
commit f06f6b66c7
1 changed files with 19 additions and 14 deletions
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33
block/qcow2.c
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@ -2972,21 +2972,29 @@ finish:
} }
static bool is_zero_sectors(BlockDriverState *bs, int64_t start, static bool is_zero(BlockDriverState *bs, int64_t offset, int64_t bytes)
uint32_t count)
{ {
int nr; int nr;
int64_t res; int64_t res;
int64_t start;
if (start + count > bs->total_sectors) { /* TODO: Widening to sector boundaries should only be needed as
count = bs->total_sectors - start; * long as we can't query finer granularity. */
start = QEMU_ALIGN_DOWN(offset, BDRV_SECTOR_SIZE);
bytes = QEMU_ALIGN_UP(offset + bytes, BDRV_SECTOR_SIZE) - start;
/* Clamp to image length, before checking status of underlying sectors */
if (start + bytes > bs->total_sectors * BDRV_SECTOR_SIZE) {
bytes = bs->total_sectors * BDRV_SECTOR_SIZE - start;
} }
if (!count) { if (!bytes) {
return true; return true;
} }
res = bdrv_get_block_status_above(bs, NULL, start, count, &nr, NULL); res = bdrv_get_block_status_above(bs, NULL, start >> BDRV_SECTOR_BITS,
return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == count; bytes >> BDRV_SECTOR_BITS, &nr, NULL);
return res >= 0 && (res & BDRV_BLOCK_ZERO) &&
nr * BDRV_SECTOR_SIZE == bytes;
} }
static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs, static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs,
@ -3004,24 +3012,21 @@ static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs,
} }
if (head || tail) { if (head || tail) {
int64_t cl_start = (offset - head) >> BDRV_SECTOR_BITS;
uint64_t off; uint64_t off;
unsigned int nr; unsigned int nr;
assert(head + bytes <= s->cluster_size); assert(head + bytes <= s->cluster_size);
/* check whether remainder of cluster already reads as zero */ /* check whether remainder of cluster already reads as zero */
if (!(is_zero_sectors(bs, cl_start, if (!(is_zero(bs, offset - head, head) &&
DIV_ROUND_UP(head, BDRV_SECTOR_SIZE)) && is_zero(bs, offset + bytes,
is_zero_sectors(bs, (offset + bytes) >> BDRV_SECTOR_BITS, tail ? s->cluster_size - tail : 0))) {
DIV_ROUND_UP(-tail & (s->cluster_size - 1),
BDRV_SECTOR_SIZE)))) {
return -ENOTSUP; return -ENOTSUP;
} }
qemu_co_mutex_lock(&s->lock); qemu_co_mutex_lock(&s->lock);
/* We can have new write after previous check */ /* We can have new write after previous check */
offset = cl_start << BDRV_SECTOR_BITS; offset = QEMU_ALIGN_DOWN(offset, s->cluster_size);
bytes = s->cluster_size; bytes = s->cluster_size;
nr = s->cluster_size; nr = s->cluster_size;
ret = qcow2_get_cluster_offset(bs, offset, &nr, &off); ret = qcow2_get_cluster_offset(bs, offset, &nr, &off);