@@ -2428,43 +2428,47 @@ static bool is_zero_cluster_top_locked(BlockDriverState *bs, int64_t start)
return ret == QCOW2_CLUSTER_UNALLOCATED || ret == QCOW2_CLUSTER_ZERO;
}
-static coroutine_fn int qcow2_co_write_zeroes(BlockDriverState *bs,
- int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
+static coroutine_fn int qcow2_co_pwrite_zeroes(BlockDriverState *bs,
+ int64_t offset, int count, BdrvRequestFlags flags)
{
int ret;
BDRVQcow2State *s = bs->opaque;
- int head = sector_num % s->cluster_sectors;
- int tail = (sector_num + nb_sectors) % s->cluster_sectors;
+ int head = offset % s->cluster_size;
+ int tail = (offset + count) % s->cluster_size;
+ /* Widen the write to a full cluster, if the cluster already reads
+ * as zero. */
if (head != 0 || tail != 0) {
- int64_t cl_end = -1;
+ int64_t tail_sector = 0;
- sector_num -= head;
- nb_sectors += head;
-
- if (tail != 0) {
- nb_sectors += s->cluster_sectors - tail;
+ offset -= head;
+ count += head;
+ if (tail) {
+ count += s->cluster_size - tail;
}
- if (!is_zero_cluster(bs, sector_num)) {
+ if (!is_zero_cluster(bs, offset >> BDRV_SECTOR_BITS)) {
return -ENOTSUP;
}
- if (nb_sectors > s->cluster_sectors) {
- /* Technically the request can cover 2 clusters, f.e. 4k write
- at s->cluster_sectors - 2k offset. One of these cluster can
- be zeroed, one unallocated */
- cl_end = sector_num + nb_sectors - s->cluster_sectors;
- if (!is_zero_cluster(bs, cl_end)) {
+ if (count > s->cluster_size) {
+ /* Technically the request can cover 2 clusters, f.e. 4k
+ * write at s->cluster_sectors - 2k offset. One of these
+ * cluster can be zeroed, one unallocated. Anything larger
+ * and the front end already split it to alignment
+ * boundaries. */
+ assert(count == 2 * s->cluster_size);
+ tail_sector = (offset >> BDRV_SECTOR_BITS) + s->cluster_sectors;
+ if (!is_zero_cluster(bs, tail_sector)) {
return -ENOTSUP;
}
}
qemu_co_mutex_lock(&s->lock);
/* We can have new write after previous check */
- if (!is_zero_cluster_top_locked(bs, sector_num) ||
- (cl_end > 0 && !is_zero_cluster_top_locked(bs, cl_end))) {
+ if (!is_zero_cluster_top_locked(bs, offset >> BDRV_SECTOR_BITS) ||
+ (tail_sector && !is_zero_cluster_top_locked(bs, tail_sector))) {
qemu_co_mutex_unlock(&s->lock);
return -ENOTSUP;
}
@@ -2473,7 +2477,7 @@ static coroutine_fn int qcow2_co_write_zeroes(BlockDriverState *bs,
}
/* Whatever is left can use real zero clusters */
- ret = qcow2_zero_clusters(bs, sector_num << BDRV_SECTOR_BITS, nb_sectors);
+ ret = qcow2_zero_clusters(bs, offset, count >> BDRV_SECTOR_BITS);
qemu_co_mutex_unlock(&s->lock);
return ret;
@@ -3380,7 +3384,7 @@ BlockDriver bdrv_qcow2 = {
.bdrv_co_writev = qcow2_co_writev,
.bdrv_co_flush_to_os = qcow2_co_flush_to_os,
- .bdrv_co_write_zeroes = qcow2_co_write_zeroes,
+ .bdrv_co_pwrite_zeroes = qcow2_co_pwrite_zeroes,
.bdrv_co_discard = qcow2_co_discard,
.bdrv_truncate = qcow2_truncate,
.bdrv_write_compressed = qcow2_write_compressed,
Another step on our continuing quest to switch to byte-based interfaces. There are still opportunities to optimize the qcow2 handling of zero clusters. For example, if the backing file only has non-zero data in the portion about to be overwritten, then we could widen the request and make the entire cluster zero, rather than falling back to -ENOTSUP. But for this patch, intentionally leave the semantics unchanged, even if not optimal. Signed-off-by: Eric Blake <eblake@redhat.com> --- block/qcow2.c | 46 +++++++++++++++++++++++++--------------------- 1 file changed, 25 insertions(+), 21 deletions(-)