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Subject: [Qemu-devel] [PULL 05/29] qcow2: Repair unaligned preallocated zero
clusters
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From: Max Reitz <mreitz@redhat.com>
We can easily repair unaligned preallocated zero clusters by discarding
them, so why not do it?
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20171110203759.14018-2-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
block/qcow2-refcount.c | 70 ++++++++++++++++++++++++++++++++++++++----=
----
tests/qemu-iotests/060 | 3 +-
tests/qemu-iotests/060.out | 9 ++++++
3 files changed, 69 insertions(+), 13 deletions(-)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 3de1ab51ba..92701ab7af 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -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_off=
set,
- int flags)
+ int flags, BdrvCheckMode fix)
{
BDRVQcow2State *s =3D bs->opaque;
uint64_t *l2_table, l2_entry;
@@ -1579,6 +1579,57 @@ static int check_refcounts_l2(BlockDriverState *bs, =
BdrvCheckResult *res,
next_contiguous_offset =3D offset + s->cluster_size;
}
=20
+ /* Correct offsets are cluster aligned */
+ if (offset_into_cluster(s, offset)) {
+ if (qcow2_get_cluster_type(l2_entry) =3D=3D
+ QCOW2_CLUSTER_ZERO_ALLOC)
+ {
+ fprintf(stderr, "%s offset=3D%" 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 =3D
+ l2_offset + (uint64_t)i * sizeof(uint64_t);
+
+ l2_entry =3D QCOW_OFLAG_ZERO;
+ l2_table[i] =3D cpu_to_be64(l2_entry);
+ ret =3D 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 chec=
king
+ * this L2 table */
+ goto fail;
+ }
+
+ ret =3D 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=3D%" PRIx64 ": Data clus=
ter is "
+ "not properly aligned; L2 entry corrupted.\n", off=
set);
+ res->corruptions++;
+ }
+ }
+
/* Mark cluster as used */
ret =3D 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=3D%" PRIx64 ": Cluster is no=
t "
- "properly aligned; L2 entry corrupted.\n", offset);
- res->corruptions++;
- }
break;
}
=20
@@ -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 =3D bs->opaque;
uint64_t *l1_table =3D NULL, l2_offset, l1_size2;
@@ -1681,7 +1725,8 @@ static int check_refcounts_l1(BlockDriverState *bs,
=20
/* Process and check L2 entries */
ret =3D 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,
=20
/* current L1 table */
ret =3D check_refcounts_l1(bs, res, refcount_table, nb_clusters,
- s->l1_table_offset, s->l1_size, CHECK_FRAG_IN=
FO);
+ s->l1_table_offset, s->l1_size, CHECK_FRAG_IN=
FO,
+ fix);
if (ret < 0) {
return ret;
}
@@ -1966,7 +2012,7 @@ static int calculate_refcounts(BlockDriverState *bs, =
BdrvCheckResult *res,
for (i =3D 0; i < s->nb_snapshots; i++) {
sn =3D s->snapshots + i;
ret =3D 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;
}
diff --git a/tests/qemu-iotests/060 b/tests/qemu-iotests/060
index 14797dd3b0..6c7407f499 100755
--- a/tests/qemu-iotests/060
+++ b/tests/qemu-iotests/060
@@ -335,7 +335,8 @@ poke_file "$TEST_IMG" "$l2_offset" "\x80\x00\x00\x00\x0=
0\x00\x2a\x01"
# Let's write to it!
$QEMU_IO -c "write 0 64k" "$TEST_IMG" | _filter_qemu_io
=20
-# Can't repair this yet (TODO: We can just deallocate the cluster)
+echo '--- Repairing ---'
+_check_test_img -r all
=20
echo
echo '=3D=3D=3D Discarding with an unaligned refblock =3D=3D=3D'
diff --git a/tests/qemu-iotests/060.out b/tests/qemu-iotests/060.out
index c4cb7c665e..25d5c3938b 100644
--- a/tests/qemu-iotests/060.out
+++ b/tests/qemu-iotests/060.out
@@ -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 u=
naligned (guest offset: 0); further corruption events will be suppressed
write failed: Input/output error
+--- Repairing ---
+Repairing offset=3D2a00: 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.
=20
=3D=3D=3D Discarding with an unaligned refblock =3D=3D=3D
=20
--=20
2.13.6