qcow2: introduce icount field for snapshots

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>

block/qcow2-snapshot.c

@@ -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;
@@ -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);

block/qcow2.h

@@ -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;
 
 
@@ -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 */

docs/interop/qcow2.txt

@@ -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.
 

tests/qemu-iotests/261

@@ -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)) $((extra_len - 16)) \
                    | tr -d '\0')"
@@ -198,12 +201,12 @@ truncate -s 0 "$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

tests/qemu-iotests/261.out

@@ -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
@@ -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 ===
 
@@ -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 ===
 
@@ -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 ===
 
@@ -116,16 +127,18 @@ 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.
@@ -133,15 +146,17 @@ 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.
@@ -149,15 +164,17 @@ 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 ===