Skip to content

Commit

Permalink
qcow2: introduce icount field for snapshots
Browse files Browse the repository at this point in the history 
This patch introduces the icount field for saving within the snapshot.
It is required for navigation between the snapshots in record/replay mode.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Acked-by: Kevin Wolf <kwolf@redhat.com>

--

v7 changes:
 - also fix the test which checks qcow2 snapshot extra data
Message-Id: <160174518284.12451.2301137308458777398.stgit@pasha-ThinkPad-X280>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  • Loading branch information
@Dovgalyuk @bonzini
Dovgalyuk authored and bonzini committed Oct 6, 2020
1 parent 56db119 commit bbacffc
Show file tree
Hide file tree
Showing 5 changed files with 58 additions and 23 deletions.
7 changes: 7 additions & 0 deletions block/qcow2-snapshot.c
View file
Expand Up @@ -164,6 +164,12 @@ static int qcow2_do_read_snapshots(BlockDriverState *bs, bool repair,
sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
}

if (sn->extra_data_size >= endof(QCowSnapshotExtraData, icount)) {
sn->icount = be64_to_cpu(extra.icount);
} else {
sn->icount = -1ULL;
}

if (sn->extra_data_size > sizeof(extra)) {
uint64_t extra_data_end;
size_t unknown_extra_data_size;
Expand Down Expand Up @@ -333,6 +339,7 @@ int qcow2_write_snapshots(BlockDriverState *bs)
memset(&extra, 0, sizeof(extra));
extra.vm_state_size_large = cpu_to_be64(sn->vm_state_size);
extra.disk_size = cpu_to_be64(sn->disk_size);
extra.icount = cpu_to_be64(sn->icount);

id_str_size = strlen(sn->id_str);
name_size = strlen(sn->name);
Expand Down
3 changes: 3 additions & 0 deletions block/qcow2.h
View file
Expand Up @@ -206,6 +206,7 @@ typedef struct QEMU_PACKED QCowSnapshotHeader {
typedef struct QEMU_PACKED QCowSnapshotExtraData {
uint64_t vm_state_size_large;
uint64_t disk_size;
uint64_t icount;
} QCowSnapshotExtraData;


Expand All @@ -219,6 +220,8 @@ typedef struct QCowSnapshot {
uint32_t date_sec;
uint32_t date_nsec;
uint64_t vm_clock_nsec;
/* icount value for the moment when snapshot was taken */
uint64_t icount;
/* Size of all extra data, including QCowSnapshotExtraData if available */
uint32_t extra_data_size;
/* Data beyond QCowSnapshotExtraData, if any */
Expand Down
5 changes: 5 additions & 0 deletions docs/interop/qcow2.txt
View file
Expand Up @@ -707,6 +707,11 @@ Snapshot table entry:

Byte 48 - 55: Virtual disk size of the snapshot in bytes

Byte 56 - 63: icount value which corresponds to
the record/replay instruction count
when the snapshot was taken. Set to -1
if icount was disabled

Version 3 images must include extra data at least up to
byte 55.

Expand Down
15 changes: 9 additions & 6 deletions tests/qemu-iotests/261
View file
Expand Up @@ -91,7 +91,10 @@ print_snapshot_table()
if [ $extra_len -ge 16 ]; then
echo " Disk size: $(peek_file_be "$1" $((extra_ofs + 8)) 8)"
fi
if [ $extra_len -gt 16 ]; then
if [ $extra_len -ge 24 ]; then
echo " Icount: $(peek_file_be "$1" $((extra_ofs + 16)) 8)"
fi
if [ $extra_len -gt 24 ]; then
echo ' Unknown extra data:' \
"$(peek_file_raw "$1" $((extra_ofs + 16)) $((extra_len - 16)) \
| tr -d '\0')"
Expand Down Expand Up @@ -198,12 +201,12 @@ truncate -s 0 "$TEST_DIR/sn0-extra"
truncate -s $(($(snapshot_table_entry_size "$TEST_DIR/sn0-pre") - 40)) \
"$TEST_DIR/sn0-post"

# Set sn1's extra data size to 42
poke_file "$TEST_DIR/sn1-pre" 36 '\x00\x00\x00\x2a'
truncate -s 42 "$TEST_DIR/sn1-extra"
poke_file "$TEST_DIR/sn1-extra" 16 'very important data'
# Set sn1's extra data size to 50
poke_file "$TEST_DIR/sn1-pre" 36 '\x00\x00\x00\x32'
truncate -s 50 "$TEST_DIR/sn1-extra"
poke_file "$TEST_DIR/sn1-extra" 24 'very important data'
# Grow sn1-post to pad
truncate -s $(($(snapshot_table_entry_size "$TEST_DIR/sn1-pre") - 82)) \
truncate -s $(($(snapshot_table_entry_size "$TEST_DIR/sn1-pre") - 90)) \
"$TEST_DIR/sn1-post"

# Set sn2's extra data size to 8
Expand Down
51 changes: 34 additions & 17 deletions tests/qemu-iotests/261.out
View file
Expand Up @@ -12,9 +12,10 @@ Snapshots in TEST_DIR/t.IMGFMT.v2.orig:
[1]
ID: 2
Name: sn1
Extra data size: 42
Extra data size: 50
VM state size: 0
Disk size: 67108864
Icount: 0
Unknown extra data: very important data
[2]
ID: 3
Expand All @@ -29,22 +30,25 @@ Snapshots in TEST_DIR/t.IMGFMT.v3.orig:
[0]
ID: 1
Name: sn0
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615
[1]
ID: 2
Name: sn1
Extra data size: 42
Extra data size: 50
VM state size: 0
Disk size: 67108864
Icount: 0
Unknown extra data: very important data
[2]
ID: 3
Name: sn2
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615

=== Repair botched v3 ===

Expand All @@ -61,22 +65,25 @@ Snapshots in TEST_DIR/t.IMGFMT:
[0]
ID: 1
Name: sn0
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615
[1]
ID: 2
Name: sn1
Extra data size: 42
Extra data size: 50
VM state size: 0
Disk size: 67108864
Icount: 0
Unknown extra data: very important data
[2]
ID: 3
Name: sn2
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615

=== Add new snapshot ===

Expand All @@ -85,28 +92,32 @@ Snapshots in TEST_DIR/t.IMGFMT:
[0]
ID: 1
Name: sn0
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615
[1]
ID: 2
Name: sn1
Extra data size: 42
Extra data size: 50
VM state size: 0
Disk size: 67108864
Icount: 0
Unknown extra data: very important data
[2]
ID: 3
Name: sn2
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615
[3]
ID: 4
Name: sn3
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 0

=== Remove different snapshots ===

Expand All @@ -116,48 +127,54 @@ Snapshots in TEST_DIR/t.IMGFMT:
[0]
ID: 2
Name: sn1
Extra data size: 42
Extra data size: 50
VM state size: 0
Disk size: 67108864
Icount: 0
Unknown extra data: very important data
[1]
ID: 3
Name: sn2
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615

--- sn1 ---
No errors were found on the image.
Snapshots in TEST_DIR/t.IMGFMT:
[0]
ID: 1
Name: sn0
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615
[1]
ID: 3
Name: sn2
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615

--- sn2 ---
No errors were found on the image.
Snapshots in TEST_DIR/t.IMGFMT:
[0]
ID: 1
Name: sn0
Extra data size: 16
Extra data size: 24
VM state size: 0
Disk size: 67108864
Icount: 18446744073709551615
[1]
ID: 2
Name: sn1
Extra data size: 42
Extra data size: 50
VM state size: 0
Disk size: 67108864
Icount: 0
Unknown extra data: very important data

=== Reject too much unknown extra data ===
Expand Down

0 comments on commit bbacffc

Please sign in to comment.