Received: from eggs.gnu.org ([2001:4830:134:3::10]:36819) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dVSa2-0004pQ-OQ for qemu-devel@nongnu.org; Wed, 12 Jul 2017 21:06:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dVSa1-0001YH-Tu for qemu-devel@nongnu.org; Wed, 12 Jul 2017 21:06:10 -0400 From: Eric Blake Date: Wed, 12 Jul 2017 20:05:40 -0500 Message-Id: <20170713010555.6769-4-eblake@redhat.com> In-Reply-To: <20170713010555.6769-1-eblake@redhat.com> References: <20170713010555.6769-1-eblake@redhat.com> Subject: [Qemu-devel] [PATCH v5 03/18] qcow2: Ensure bitmap serialization is aligned List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, jsnow@redhat.com, qemu-block@nongnu.org, vsementsov@virtuozzo.com, Max Reitz When subdividing a bitmap serialization, the code in hbitmap.c enforces that start/count parameters are aligned (except that count can end early at end-of-bitmap). We exposed this required alignment through bdrv_dirty_bitmap_serialization_align(), but forgot to actually check that we comply with it. Fortunately, qcow2 is never dividing bitmap serialization smaller than one cluster (which is a minimum of 512 bytes); so we are always compliant with the serialization alignment (which insists that we partition at least 64 bits per chunk) because we are doing at least 4k bits per chunk. Still, it's safer to add an assertion (for the unlikely case that we'd ever support a cluster smaller than 512 bytes, or if the hbitmap implementation changes what it considers to be aligned), rather than leaving bdrv_dirty_bitmap_serialization_align() without a caller. Signed-off-by: Eric Blake Reviewed-by: John Snow --- v5: no change v4: new patch --- block/qcow2-bitmap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c index 3e8735a..5aa0b8d 100644 --- a/block/qcow2-bitmap.c +++ b/block/qcow2-bitmap.c @@ -274,10 +274,13 @@ static int free_bitmap_clusters(BlockDriverState *bs, Qcow2BitmapTable *tb) static uint64_t sectors_covered_by_bitmap_cluster(const BDRVQcow2State *s, const BdrvDirtyBitmap *bitmap) { - uint32_t sector_granularity = + uint64_t sector_granularity = bdrv_dirty_bitmap_granularity(bitmap) >> BDRV_SECTOR_BITS; + uint64_t sbc = sector_granularity * (s->cluster_size << 3); - return (uint64_t)sector_granularity * (s->cluster_size << 3); + assert(QEMU_IS_ALIGNED(sbc, + bdrv_dirty_bitmap_serialization_align(bitmap))); + return sbc; } /* load_bitmap_data -- 2.9.4