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qcow2: Keep unknown extra snapshot data

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The qcow2 specification says to ignore unknown extra data fields in
snapshot table entries.  Currently, we discard it whenever we update the
image, which is a bit different from "ignore".

This patch makes the qcow2 driver keep all unknown extra data fields
when updating an image's snapshot table.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20191011152814.14791-5-mreitz@redhat.com
[mreitz: Adjusted comments as proposed by Eric]
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2019-10-11 17:28:02 +02:00
parent ecf6c7c0c1
commit fcf9a6b728
2 changed files with 58 additions and 10 deletions
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7
block/qcow2.h
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@ -61,6 +61,9 @@
* space for snapshot names and IDs */
#define QCOW_MAX_SNAPSHOTS_SIZE (1024 * QCOW_MAX_SNAPSHOTS)
/* Maximum amount of extra data per snapshot table entry to accept */
#define QCOW_MAX_SNAPSHOT_EXTRA_DATA 1024
/* Bitmap header extension constraints */
#define QCOW2_MAX_BITMAPS 65535
#define QCOW2_MAX_BITMAP_DIRECTORY_SIZE (1024 * QCOW2_MAX_BITMAPS)
@ -181,6 +184,10 @@ typedef struct QCowSnapshot {
uint32_t date_sec;
uint32_t date_nsec;
uint64_t vm_clock_nsec;
/* Size of all extra data, including QCowSnapshotExtraData if available */
uint32_t extra_data_size;
/* Data beyond QCowSnapshotExtraData, if any */
void *unknown_extra_data;
} QCowSnapshot;
struct Qcow2Cache;