From ef72f76e58107bd4096018c3db2912d28249308e Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 28 Aug 2012 14:04:27 +0100 Subject: 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 Reviewed-by: Paolo Bonzini Signed-off-by: Kevin Wolf --- block/qed.c | 11 +++++++++++ 1 file changed, 11 insertions(+) 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. */ -- cgit v1.2.3