Now that we have adjusted the majority of the calls this function makes to be byte-based, it is easier to read the code if it makes passes over the image using bytes rather than sectors.
iotests 165 was rather weak - on a default 64k-cluster image, where bitmap granularity also defaults to 64k bytes, a single cluster of the bitmap table thus covers (64*1024*8) bits which each cover 64k bytes, or 32G of image space. But the test only uses a 1G image, so it cannot trigger any more than one loop of the code in store_bitmap_data(); and it was writing to the first cluster. In order to test that we are properly aligning which portions of the bitmap are being written to the file, we really want to test a case where the first dirty bit returned by bdrv_dirty_iter_next() is not aligned to the start of a cluster, which we can do by modifying the test to write data that doesn't happen to fall in the first cluster of the image. Signed-off-by: Eric Blake <ebl...@redhat.com> --- v9: update iotests to show why aligning down is needed [Kevin], R-b dropped v8: no change v7: rebase to earlier change, make rounding of offset obvious (no semantic change, so R-b kept) [Kevin] v5-v6: no change v4: new patch --- block/qcow2-bitmap.c | 31 ++++++++++++++++--------------- tests/qemu-iotests/165 | 2 +- 2 files changed, 17 insertions(+), 16 deletions(-) diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c index 692ce0de88..df957c66d5 100644 --- a/block/qcow2-bitmap.c +++ b/block/qcow2-bitmap.c @@ -1072,10 +1072,9 @@ static uint64_t *store_bitmap_data(BlockDriverState *bs, { int ret; BDRVQcow2State *s = bs->opaque; - int64_t sector; - uint64_t limit, sbc; + int64_t offset; + uint64_t limit; uint64_t bm_size = bdrv_dirty_bitmap_size(bitmap); - uint64_t bm_sectors = DIV_ROUND_UP(bm_size, BDRV_SECTOR_SIZE); const char *bm_name = bdrv_dirty_bitmap_name(bitmap); uint8_t *buf = NULL; BdrvDirtyBitmapIter *dbi; @@ -1100,18 +1099,22 @@ static uint64_t *store_bitmap_data(BlockDriverState *bs, dbi = bdrv_dirty_iter_new(bitmap); buf = g_malloc(s->cluster_size); limit = bytes_covered_by_bitmap_cluster(s, bitmap); - sbc = limit >> BDRV_SECTOR_BITS; assert(DIV_ROUND_UP(bm_size, limit) == tb_size); - while ((sector = bdrv_dirty_iter_next(dbi) >> BDRV_SECTOR_BITS) >= 0) { - uint64_t cluster = sector / sbc; + while ((offset = bdrv_dirty_iter_next(dbi)) >= 0) { + uint64_t cluster = offset / limit; uint64_t end, write_size; int64_t off; - sector = cluster * sbc; - end = MIN(bm_sectors, sector + sbc); - write_size = bdrv_dirty_bitmap_serialization_size(bitmap, - sector * BDRV_SECTOR_SIZE, (end - sector) * BDRV_SECTOR_SIZE); + /* + * We found the first dirty offset, but want to write out the + * entire cluster of the bitmap that includes that offset, + * including any leading zero bits. + */ + offset = QEMU_ALIGN_DOWN(offset, limit); + end = MIN(bm_size, offset + limit); + write_size = bdrv_dirty_bitmap_serialization_size(bitmap, offset, + end - offset); assert(write_size <= s->cluster_size); off = qcow2_alloc_clusters(bs, s->cluster_size); @@ -1123,9 +1126,7 @@ static uint64_t *store_bitmap_data(BlockDriverState *bs, } tb[cluster] = off; - bdrv_dirty_bitmap_serialize_part(bitmap, buf, - sector * BDRV_SECTOR_SIZE, - (end - sector) * BDRV_SECTOR_SIZE); + bdrv_dirty_bitmap_serialize_part(bitmap, buf, offset, end - offset); if (write_size < s->cluster_size) { memset(buf + write_size, 0, s->cluster_size - write_size); } @@ -1143,11 +1144,11 @@ static uint64_t *store_bitmap_data(BlockDriverState *bs, goto fail; } - if (end >= bm_sectors) { + if (end >= bm_size) { break; } - bdrv_set_dirty_iter(dbi, end * BDRV_SECTOR_SIZE); + bdrv_set_dirty_iter(dbi, end); } *bitmap_table_size = tb_size; diff --git a/tests/qemu-iotests/165 b/tests/qemu-iotests/165 index 74d7b79a0b..a3932db3de 100755 --- a/tests/qemu-iotests/165 +++ b/tests/qemu-iotests/165 @@ -27,7 +27,7 @@ disk = os.path.join(iotests.test_dir, 'disk') disk_size = 0x40000000 # 1G # regions for qemu_io: (start, count) in bytes -regions1 = ((0, 0x100000), +regions1 = ((0x0fff00, 0x10000), (0x200000, 0x100000)) regions2 = ((0x10000000, 0x20000), -- 2.13.5