@@ -1083,7 +1083,9 @@ coroutine_fn iscsi_co_pdiscard(BlockDriverState *bs, int64_t offset, int count)
struct IscsiTask iTask;
struct unmap_list list;
- assert(is_byte_request_lun_aligned(offset, count, iscsilun));
+ if (!is_byte_request_lun_aligned(offset, count, iscsilun)) {
+ return -ENOTSUP;
+ }
if (!iscsilun->lbp.lbpu) {
/* UNMAP is not supported by the target */
@@ -2490,6 +2490,10 @@ static coroutine_fn int qcow2_co_pdiscard(BlockDriverState *bs,
int ret;
BDRVQcow2State *s = bs->opaque;
+ if (!QEMU_IS_ALIGNED(offset | count, s->cluster_size)) {
+ return -ENOTSUP;
+ }
+
qemu_co_mutex_lock(&s->lock);
ret = qcow2_discard_clusters(bs, offset, count >> BDRV_SECTOR_BITS,
QCOW2_DISCARD_REQUEST, false);
@@ -2829,8 +2829,9 @@ static coroutine_fn int sd_co_pdiscard(BlockDriverState *bs, int64_t offset,
iov.iov_len = sizeof(zero);
discard_iov.iov = &iov;
discard_iov.niov = 1;
- assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
- assert((count & (BDRV_SECTOR_SIZE - 1)) == 0);
+ if (!QEMU_IS_ALIGNED(offset | count, BDRV_SECTOR_SIZE)) {
+ return -ENOTSUP;
+ }
acb = sd_aio_setup(bs, &discard_iov, offset >> BDRV_SECTOR_BITS,
count >> BDRV_SECTOR_BITS);
acb->aiocb_type = AIOCB_DISCARD_OBJ;
Right now, the block layer rounds discard requests, so that individual drivers are able to assert that discard requests will never be unaligned. But there are some ISCSI devices that track and coalesce multiple unaligned requests, turning it into an actual discard if the requests eventually cover an entire page, which implies that it is better to always pass discard requests as low down the stack as possible. In isolation, this patch has no semantic effect, since the block layer currently never passes an unaligned request down. But the block layer already has code that silently ignores drivers that return -ENOTSUP for a discard request that cannot be honored (as well as drivers that return 0 even when nothing was done). So the next patch will update the block layer to fragment discard requests, so that clients are guaranteed that they are either dealing with an unaligned head or tail, or an aligned body, of the overall request, making it similar to the block layer semantics of write zero fragmentation. Signed-off-by: Eric Blake <eblake@redhat.com> CC: qemu-stable@nongnu.org --- block/iscsi.c | 4 +++- block/qcow2.c | 4 ++++ block/sheepdog.c | 5 +++-- 3 files changed, 10 insertions(+), 3 deletions(-)