qcow2: Repair unaligned preallocated zero clusters (ac5b787a) · Commits · SUMMER2020 / students / proj-2021291

block/qcow2-refcount.c

+58 −12

Original line number	Diff line number	Diff line
		@@ -1508,7 +1508,7 @@ enum {
		static int check_refcounts_l2(BlockDriverState bs, BdrvCheckResult res,
		void **refcount_table,
		int64_t *refcount_table_size, int64_t l2_offset,
		int flags)
		int flags, BdrvCheckMode fix)
		{
		BDRVQcow2State *s = bs->opaque;
		uint64_t *l2_table, l2_entry;
		@@ -1579,6 +1579,57 @@ static int check_refcounts_l2(BlockDriverState bs, BdrvCheckResult res,
		next_contiguous_offset = offset + s->cluster_size;
		}

		/* Correct offsets are cluster aligned */
		if (offset_into_cluster(s, offset)) {
		if (qcow2_get_cluster_type(l2_entry) ==
		QCOW2_CLUSTER_ZERO_ALLOC)
		{
		fprintf(stderr, "%s offset=%" PRIx64 ": Preallocated zero "
		"cluster is not properly aligned; L2 entry "
		"corrupted.\n",
		fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR",
		offset);
		if (fix & BDRV_FIX_ERRORS) {
		uint64_t l2e_offset =
		l2_offset + (uint64_t)i * sizeof(uint64_t);

		l2_entry = QCOW_OFLAG_ZERO;
		l2_table[i] = cpu_to_be64(l2_entry);
		ret = qcow2_pre_write_overlap_check(bs,
		QCOW2_OL_ACTIVE_L2 \| QCOW2_OL_INACTIVE_L2,
		l2e_offset, sizeof(uint64_t));
		if (ret < 0) {
		fprintf(stderr, "ERROR: Overlap check failed\n");
		res->check_errors++;
		/* Something is seriously wrong, so abort checking
		* this L2 table */
		goto fail;
		}

		ret = bdrv_pwrite_sync(bs->file, l2e_offset,
		&l2_table[i], sizeof(uint64_t));
		if (ret < 0) {
		fprintf(stderr, "ERROR: Failed to overwrite L2 "
		"table entry: %s\n", strerror(-ret));
		res->check_errors++;
		/* Do not abort, continue checking the rest of this
		* L2 table's entries */
		} else {
		res->corruptions_fixed++;
		/* Skip marking the cluster as used
		* (it is unused now) */
		continue;
		}
		} else {
		res->corruptions++;
		}
		} else {
		fprintf(stderr, "ERROR offset=%" PRIx64 ": Data cluster is "
		"not properly aligned; L2 entry corrupted.\n", offset);
		res->corruptions++;
		}
		}

		/* Mark cluster as used */
		ret = qcow2_inc_refcounts_imrt(bs, res,
		refcount_table, refcount_table_size,
		@@ -1586,13 +1637,6 @@ static int check_refcounts_l2(BlockDriverState bs, BdrvCheckResult res,
		if (ret < 0) {
		goto fail;
		}

		/* Correct offsets are cluster aligned */
		if (offset_into_cluster(s, offset)) {
		fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
		"properly aligned; L2 entry corrupted.\n", offset);
		res->corruptions++;
		}
		break;
		}

		@@ -1626,7 +1670,7 @@ static int check_refcounts_l1(BlockDriverState *bs,
		void **refcount_table,
		int64_t *refcount_table_size,
		int64_t l1_table_offset, int l1_size,
		int flags)
		int flags, BdrvCheckMode fix)
		{
		BDRVQcow2State *s = bs->opaque;
		uint64_t *l1_table = NULL, l2_offset, l1_size2;
		@@ -1681,7 +1725,8 @@ static int check_refcounts_l1(BlockDriverState *bs,

		/* Process and check L2 entries */
		ret = check_refcounts_l2(bs, res, refcount_table,
		refcount_table_size, l2_offset, flags);
		refcount_table_size, l2_offset, flags,
		fix);
		if (ret < 0) {
		goto fail;
		}
		@@ -1957,7 +2002,8 @@ static int calculate_refcounts(BlockDriverState bs, BdrvCheckResult res,

		/* current L1 table */
		ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
		s->l1_table_offset, s->l1_size, CHECK_FRAG_INFO);
		s->l1_table_offset, s->l1_size, CHECK_FRAG_INFO,
		fix);
		if (ret < 0) {
		return ret;
		}
		@@ -1966,7 +2012,7 @@ static int calculate_refcounts(BlockDriverState bs, BdrvCheckResult res,
		for (i = 0; i < s->nb_snapshots; i++) {
		sn = s->snapshots + i;
		ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
		sn->l1_table_offset, sn->l1_size, 0);
		sn->l1_table_offset, sn->l1_size, 0, fix);
		if (ret < 0) {
		return ret;
		}

tests/qemu-iotests/060

+2 −1

Original line number	Diff line number	Diff line
		@@ -335,7 +335,8 @@ poke_file "$TEST_IMG" "$l2_offset" "\x80\x00\x00\x00\x00\x00\x2a\x01"
		# Let's write to it!
		$QEMU_IO -c "write 0 64k" "$TEST_IMG" \| _filter_qemu_io

		# Can't repair this yet (TODO: We can just deallocate the cluster)
		echo '--- Repairing ---'
		_check_test_img -r all

		echo
		echo '=== Discarding with an unaligned refblock ==='

tests/qemu-iotests/060.out

+9 −0

Original line number	Diff line number	Diff line
		@@ -317,6 +317,15 @@ discard 65536/65536 bytes at offset 0
		64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
		qcow2: Marking image as corrupt: Preallocated zero cluster offset 0x2a00 unaligned (guest offset: 0); further corruption events will be suppressed
		write failed: Input/output error
		--- Repairing ---
		Repairing offset=2a00: Preallocated zero cluster is not properly aligned; L2 entry corrupted.
		The following inconsistencies were found and repaired:

		0 leaked clusters
		1 corruptions

		Double checking the fixed image now...
		No errors were found on the image.

		=== Discarding with an unaligned refblock ===