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qcow2: Add corrupt bit

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This adds an incompatible bit indicating corruption to qcow2. Any image
with this bit set may not be written to unless for repairing (and
subsequently clearing the bit if the repair has been successful).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2013-08-30 14:34:24 +02:00 committed by Kevin Wolf
parent 449df70638
commit 69c9872653
5 changed files with 66 additions and 9 deletions
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47
block/qcow2.c
View File

@ -272,6 +272,37 @@ static int qcow2_mark_clean(BlockDriverState *bs)
return 0;
}
/*
* Marks the image as corrupt.
*/
int qcow2_mark_corrupt(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
s->incompatible_features |= QCOW2_INCOMPAT_CORRUPT;
return qcow2_update_header(bs);
}
/*
* Marks the image as consistent, i.e., unsets the corrupt bit, and flushes
* before if necessary.
*/
int qcow2_mark_consistent(BlockDriverState *bs)
{
BDRVQcowState *s = bs->opaque;
if (s->incompatible_features & QCOW2_INCOMPAT_CORRUPT) {
int ret = bdrv_flush(bs);
if (ret < 0) {
return ret;
}
s->incompatible_features &= ~QCOW2_INCOMPAT_CORRUPT;
return qcow2_update_header(bs);
}
return 0;
}
static int qcow2_check(BlockDriverState *bs, BdrvCheckResult *result,
BdrvCheckMode fix)
{
@ -402,6 +433,17 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
goto fail;
}
if (s->incompatible_features & QCOW2_INCOMPAT_CORRUPT) {
/* Corrupt images may not be written to unless they are being repaired
*/
if ((flags & BDRV_O_RDWR) && !(flags & BDRV_O_CHECK)) {
error_report("qcow2: Image is corrupt; cannot be opened "
"read/write.");
ret = -EACCES;
goto fail;
}
}
/* Check support for various header values */
if (header.refcount_order != 4) {
report_unsupported(bs, "%d bit reference counts",
@ -1129,6 +1171,11 @@ int qcow2_update_header(BlockDriverState *bs)
.bit = QCOW2_INCOMPAT_DIRTY_BITNR,
.name = "dirty bit",
},
{
.type = QCOW2_FEAT_TYPE_INCOMPATIBLE,
.bit = QCOW2_INCOMPAT_CORRUPT_BITNR,
.name = "corrupt bit",
},
{
.type = QCOW2_FEAT_TYPE_COMPATIBLE,
.bit = QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR,

7
block/qcow2.h
View File

@ -119,9 +119,12 @@ enum {
/* Incompatible feature bits */
enum {
QCOW2_INCOMPAT_DIRTY_BITNR = 0,
QCOW2_INCOMPAT_CORRUPT_BITNR = 1,
QCOW2_INCOMPAT_DIRTY = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
QCOW2_INCOMPAT_CORRUPT = 1 << QCOW2_INCOMPAT_CORRUPT_BITNR,
QCOW2_INCOMPAT_MASK = QCOW2_INCOMPAT_DIRTY,
QCOW2_INCOMPAT_MASK = QCOW2_INCOMPAT_DIRTY
| QCOW2_INCOMPAT_CORRUPT,
};
/* Compatible feature bits */
@ -361,6 +364,8 @@ int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t sector_num, int nb_sectors);
int qcow2_mark_dirty(BlockDriverState *bs);
int qcow2_mark_corrupt(BlockDriverState *bs);
int qcow2_mark_consistent(BlockDriverState *bs);
int qcow2_update_header(BlockDriverState *bs);
/* qcow2-refcount.c functions */

7
docs/specs/qcow2.txt
View File

@ -80,7 +80,12 @@ in the description of a field.
tables to repair refcounts before accessing the
image.
Bits 1-63: Reserved (set to 0)
Bit 1: Corrupt bit. If this bit is set then any data
structure may be corrupt and the image must not
be written to (unless for regaining
consistency).
Bits 2-63: Reserved (set to 0)
80 - 87: compatible_features
Bitmask of compatible features. An implementation can

12
tests/qemu-iotests/031.out
View File

@ -54,7 +54,7 @@ header_length 72
Header extension:
magic 0x6803f857
length 96
length 144
data <binary>
Header extension:
@ -68,7 +68,7 @@ No errors were found on the image.
magic 0x514649fb
version 2
backing_file_offset 0xf8
backing_file_offset 0x128
backing_file_size 0x17
cluster_bits 16
size 67108864
@ -92,7 +92,7 @@ data 'host_device'
Header extension:
magic 0x6803f857
length 96
length 144
data <binary>
Header extension:
@ -155,7 +155,7 @@ header_length 104
Header extension:
magic 0x6803f857
length 96
length 144
data <binary>
Header extension:
@ -169,7 +169,7 @@ No errors were found on the image.
magic 0x514649fb
version 3
backing_file_offset 0x118
backing_file_offset 0x148
backing_file_size 0x17
cluster_bits 16
size 67108864
@ -193,7 +193,7 @@ data 'host_device'
Header extension:
magic 0x6803f857
length 96
length 144
data <binary>
Header extension:

2
tests/qemu-iotests/036.out
View File

@ -46,7 +46,7 @@ header_length 104
Header extension:
magic 0x6803f857
length 96
length 144
data <binary>
*** done