From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57558) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cJPsq-0007tg-Ix for qemu-devel@nongnu.org; Tue, 20 Dec 2016 14:15:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cJPsp-0007LH-K7 for qemu-devel@nongnu.org; Tue, 20 Dec 2016 14:15:32 -0500 From: Eric Blake Date: Tue, 20 Dec 2016 13:15:17 -0600 Message-Id: <20161220191523.5779-2-eblake@redhat.com> In-Reply-To: <20161220191523.5779-1-eblake@redhat.com> References: <20161220191523.5779-1-eblake@redhat.com> Subject: [Qemu-devel] [PATCH v4 1/7] qcow2: Assert that cluster operations are aligned List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Max Reitz , "open list:qcow2" qcow2_discard_clusters() is set up to silently ignore sub-cluster head or tail on unaligned requests. However, it is easy to audit the various callers: qcow2_snapshot_create() has always passed aligned data since the call was introduced in 1ebf561; qcow2_co_pdiscard() has passed aligned clusters since commit ecdbead taught the block layer the preferred discard alignment (the block layer can still pass sub-cluster values, but those are handled directly in qcow2_co_pdiscard()); and qcow2_make_empty() was fixed to pass aligned clusters in commit a3e1505. Replace rounding with assertions to hold us to the tighter contract, eliminating the now-impossible case of an early exit for a sub-cluster request. qcow2_zero_clusters() has always been called with cluster-aligned arguments from its lone caller qcow2_co_pwrite_zeroes() (like qcow2_co_pdiscard(), the caller takes care of sub-cluster requests from the block layer; and qcow2_zero_clusters() would have misbehaved on unaligned requests), but it deserves the same assertion for symmetry. Signed-off-by: Eric Blake --- v4: new patch --- block/qcow2-cluster.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 928c1e2..3304a15 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -1521,13 +1521,9 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset, end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS); - /* Round start up and end down */ - offset = align_offset(offset, s->cluster_size); - end_offset = start_of_cluster(s, end_offset); - - if (offset > end_offset) { - return 0; - } + /* Caller must pass aligned values */ + assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); + assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size)); nb_clusters = size_to_clusters(s, end_offset - offset); @@ -1602,6 +1598,10 @@ int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors, uint64_t nb_clusters; int ret; + /* Caller must pass aligned values */ + assert(QEMU_IS_ALIGNED(offset, s->cluster_size)); + assert(QEMU_IS_ALIGNED(nb_sectors, s->cluster_size >> BDRV_SECTOR_BITS)); + /* The zero flag is only supported by version 3 and newer */ if (s->qcow_version < 3) { return -ENOTSUP; -- 2.9.3