vmdk: Fix partial overwrite of zero cluster
When overwriting a zero cluster, we must not perform copy-on-write from the backing file, but from a zeroed buffer. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20200430133007.170335-4-kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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parent
2821c1cc0f
commit
4823cde58e
18
block/vmdk.c
18
block/vmdk.c
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@ -1340,7 +1340,9 @@ static void vmdk_refresh_limits(BlockDriverState *bs, Error **errp)
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* get_whole_cluster
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* get_whole_cluster
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*
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*
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* Copy backing file's cluster that covers @sector_num, otherwise write zero,
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* Copy backing file's cluster that covers @sector_num, otherwise write zero,
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* to the cluster at @cluster_sector_num.
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* to the cluster at @cluster_sector_num. If @zeroed is true, we're overwriting
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* a zeroed cluster in the current layer and must not copy data from the
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* backing file.
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*
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*
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* If @skip_start_sector < @skip_end_sector, the relative range
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* If @skip_start_sector < @skip_end_sector, the relative range
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* [@skip_start_sector, @skip_end_sector) is not copied or written, and leave
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* [@skip_start_sector, @skip_end_sector) is not copied or written, and leave
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@ -1351,18 +1353,21 @@ static int get_whole_cluster(BlockDriverState *bs,
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uint64_t cluster_offset,
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uint64_t cluster_offset,
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uint64_t offset,
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uint64_t offset,
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uint64_t skip_start_bytes,
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uint64_t skip_start_bytes,
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uint64_t skip_end_bytes)
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uint64_t skip_end_bytes,
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bool zeroed)
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{
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{
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int ret = VMDK_OK;
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int ret = VMDK_OK;
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int64_t cluster_bytes;
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int64_t cluster_bytes;
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uint8_t *whole_grain;
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uint8_t *whole_grain;
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bool copy_from_backing;
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/* For COW, align request sector_num to cluster start */
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/* For COW, align request sector_num to cluster start */
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cluster_bytes = extent->cluster_sectors << BDRV_SECTOR_BITS;
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cluster_bytes = extent->cluster_sectors << BDRV_SECTOR_BITS;
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offset = QEMU_ALIGN_DOWN(offset, cluster_bytes);
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offset = QEMU_ALIGN_DOWN(offset, cluster_bytes);
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whole_grain = qemu_blockalign(bs, cluster_bytes);
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whole_grain = qemu_blockalign(bs, cluster_bytes);
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copy_from_backing = bs->backing && !zeroed;
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if (!bs->backing) {
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if (!copy_from_backing) {
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memset(whole_grain, 0, skip_start_bytes);
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memset(whole_grain, 0, skip_start_bytes);
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memset(whole_grain + skip_end_bytes, 0, cluster_bytes - skip_end_bytes);
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memset(whole_grain + skip_end_bytes, 0, cluster_bytes - skip_end_bytes);
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}
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}
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@ -1377,7 +1382,7 @@ static int get_whole_cluster(BlockDriverState *bs,
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/* Read backing data before skip range */
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/* Read backing data before skip range */
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if (skip_start_bytes > 0) {
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if (skip_start_bytes > 0) {
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if (bs->backing) {
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if (copy_from_backing) {
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/* qcow2 emits this on bs->file instead of bs->backing */
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/* qcow2 emits this on bs->file instead of bs->backing */
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BLKDBG_EVENT(extent->file, BLKDBG_COW_READ);
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BLKDBG_EVENT(extent->file, BLKDBG_COW_READ);
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ret = bdrv_pread(bs->backing, offset, whole_grain,
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ret = bdrv_pread(bs->backing, offset, whole_grain,
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@ -1397,7 +1402,7 @@ static int get_whole_cluster(BlockDriverState *bs,
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}
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}
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/* Read backing data after skip range */
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/* Read backing data after skip range */
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if (skip_end_bytes < cluster_bytes) {
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if (skip_end_bytes < cluster_bytes) {
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if (bs->backing) {
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if (copy_from_backing) {
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/* qcow2 emits this on bs->file instead of bs->backing */
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/* qcow2 emits this on bs->file instead of bs->backing */
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BLKDBG_EVENT(extent->file, BLKDBG_COW_READ);
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BLKDBG_EVENT(extent->file, BLKDBG_COW_READ);
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ret = bdrv_pread(bs->backing, offset + skip_end_bytes,
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ret = bdrv_pread(bs->backing, offset + skip_end_bytes,
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@ -1631,7 +1636,8 @@ static int get_cluster_offset(BlockDriverState *bs,
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* or inappropriate VM shutdown.
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* or inappropriate VM shutdown.
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*/
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*/
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ret = get_whole_cluster(bs, extent, cluster_sector * BDRV_SECTOR_SIZE,
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ret = get_whole_cluster(bs, extent, cluster_sector * BDRV_SECTOR_SIZE,
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offset, skip_start_bytes, skip_end_bytes);
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offset, skip_start_bytes, skip_end_bytes,
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zeroed);
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if (ret) {
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if (ret) {
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return ret;
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return ret;
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}
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}
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