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[Qemu-devel] [PATCH v6 03/18] qcow2: Ensure bitmap serialization is alig
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH v6 03/18] qcow2: Ensure bitmap serialization is aligned |
Date: |
Wed, 30 Aug 2017 16:05:27 -0500 |
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 <address@hidden>
Reviewed-by: John Snow <address@hidden>
---
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 e8d3bdbd6e..b3ee4c794a 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
--
2.13.5
- [Qemu-devel] [PATCH v6 00/18] make dirty-bitmap byte-based, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 01/18] block: Make bdrv_img_create() size selection easier to read, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 03/18] qcow2: Ensure bitmap serialization is aligned,
Eric Blake <=
- [Qemu-devel] [PATCH v6 02/18] hbitmap: Rename serialization_granularity to serialization_align, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 04/18] dirty-bitmap: Drop unused functions, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 06/18] dirty-bitmap: Change bdrv_dirty_bitmap_*serialize*() to take bytes, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 05/18] dirty-bitmap: Change bdrv_dirty_bitmap_size() to report bytes, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 07/18] qcow2: Switch sectors_covered_by_bitmap_cluster() to byte-based, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 09/18] dirty-bitmap: Change bdrv_dirty_iter_next() to report byte offset, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 08/18] dirty-bitmap: Set iterator start by offset, not sector, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 10/18] dirty-bitmap: Change bdrv_get_dirty_count() to report bytes, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 11/18] dirty-bitmap: Change bdrv_get_dirty_locked() to take bytes, Eric Blake, 2017/08/30
- [Qemu-devel] [PATCH v6 12/18] dirty-bitmap: Change bdrv_[re]set_dirty_bitmap() to use bytes, Eric Blake, 2017/08/30