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authorStefan Hajnoczi <stefanha@linux.vnet.ibm.com>2012-08-28 14:04:27 +0100
committerKevin Wolf <kwolf@redhat.com>2012-08-29 15:23:35 +0200
commitef72f76e58107bd4096018c3db2912d28249308e (patch)
treea4601e141bf87c772980c1aef6c0fd462dc3fe87
parent18fec301cd2a38f72a5eeba2656a0c5b4fa69fb7 (diff)
downloadqemu-arm-ef72f76e58107bd4096018c3db2912d28249308e.tar.gz
qed: refuse unaligned zero writes with a backing file
Zero writes have cluster granularity in QED. Therefore they can only be used to zero entire clusters. If the zero write request leaves sectors untouched, zeroing the entire cluster would obscure the backing file. Instead return -ENOTSUP, which is handled by block.c:bdrv_co_do_write_zeroes() and falls back to a regular write. The qemu-iotests 034 test cases covers this scenario. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/qed.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/block/qed.c b/block/qed.c
index a02dbfd72d..21cb239870 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1363,10 +1363,21 @@ static int coroutine_fn bdrv_qed_co_write_zeroes(BlockDriverState *bs,
int nb_sectors)
{
BlockDriverAIOCB *blockacb;
+ BDRVQEDState *s = bs->opaque;
QEDWriteZeroesCB cb = { .done = false };
QEMUIOVector qiov;
struct iovec iov;
+ /* Refuse if there are untouched backing file sectors */
+ if (bs->backing_hd) {
+ if (qed_offset_into_cluster(s, sector_num * BDRV_SECTOR_SIZE) != 0) {
+ return -ENOTSUP;
+ }
+ if (qed_offset_into_cluster(s, nb_sectors * BDRV_SECTOR_SIZE) != 0) {
+ return -ENOTSUP;
+ }
+ }
+
/* Zero writes start without an I/O buffer. If a buffer becomes necessary
* then it will be allocated during request processing.
*/