bitmaps patches for 2020-09-21

- Eric Blake: Improve 'qemu-img bitmap --merge' by not opening backing images
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Merge remote-tracking branch 'remotes/ericb/tags/pull-bitmaps-2020-09-21' into staging

bitmaps patches for 2020-09-21

- Eric Blake: Improve 'qemu-img bitmap --merge' by not opening backing images

# gpg: Signature made Tue 22 Sep 2020 01:58:31 BST
# gpg:                using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg:                 aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2  F3AA A7A1 6B4A 2527 436A

* remotes/ericb/tags/pull-bitmaps-2020-09-21:
  qemu-img: Support bitmap --merge into backing image

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

qemu-img.c

@@ -4779,14 +4779,19 @@ static int img_bitmap(int argc, char **argv)
     filename = argv[optind];
     bitmap = argv[optind + 1];
 
-    blk = img_open(image_opts, filename, fmt, BDRV_O_RDWR, false, false,
+    /*
-                   false);
+     * No need to open backing chains; we will be manipulating bitmaps
+     * directly in this image without reference to image contents.
+     */
+    blk = img_open(image_opts, filename, fmt, BDRV_O_RDWR | BDRV_O_NO_BACKING,
+                   false, false, false);
     if (!blk) {
         goto out;
     }
     bs = blk_bs(blk);
     if (src_filename) {
-        src = img_open(false, src_filename, src_fmt, 0, false, false, false);
+        src = img_open(false, src_filename, src_fmt, BDRV_O_NO_BACKING,
+                       false, false, false);
         if (!src) {
             goto out;
         }

tests/qemu-iotests/291

@@ -91,6 +91,15 @@ $QEMU_IMG bitmap --remove --image-opts \
     driver=$IMGFMT,file.driver=file,file.filename="$TEST_IMG" tmp
 _img_info --format-specific
 
+echo
+echo "=== Merge from top layer into backing image ==="
+echo
+
+$QEMU_IMG rebase -u -F qcow2 -b "$TEST_IMG.base" "$TEST_IMG"
+$QEMU_IMG bitmap --add --merge b2 -b "$TEST_IMG" -F $IMGFMT \
+     -f $IMGFMT "$TEST_IMG.base" b3
+_img_info --format-specific --backing-chain
+
 echo
 echo "=== Check bitmap contents ==="
 echo
@@ -107,6 +116,9 @@ $QEMU_IMG map --output=json --image-opts \
 nbd_server_start_unix_socket -r -f qcow2 -B b2 "$TEST_IMG"
 $QEMU_IMG map --output=json --image-opts \
     "$IMG,x-dirty-bitmap=qemu:dirty-bitmap:b2" | _filter_qemu_img_map
+nbd_server_start_unix_socket -r -f qcow2 -B b3 "$TEST_IMG"
+$QEMU_IMG map --output=json --image-opts \
+    "$IMG,x-dirty-bitmap=qemu:dirty-bitmap:b3" | _filter_qemu_img_map
 
 # success, all done
 echo '*** done'

tests/qemu-iotests/291.out

@@ -68,6 +68,59 @@ Format specific information:
     corrupt: false
     extended l2: false
 
+=== Merge from top layer into backing image ===
+
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 10 MiB (10485760 bytes)
+cluster_size: 65536
+backing file: TEST_DIR/t.IMGFMT.base
+backing file format: IMGFMT
+Format specific information:
+    compat: 1.1
+    compression type: zlib
+    lazy refcounts: false
+    bitmaps:
+        [0]:
+            flags:
+            name: b1
+            granularity: 524288
+        [1]:
+            flags:
+                [0]: auto
+            name: b2
+            granularity: 65536
+        [2]:
+            flags:
+            name: b0
+            granularity: 65536
+    refcount bits: 16
+    corrupt: false
+    extended l2: false
+
+image: TEST_DIR/t.IMGFMT.base
+file format: IMGFMT
+virtual size: 10 MiB (10485760 bytes)
+cluster_size: 65536
+Format specific information:
+    compat: 1.1
+    compression type: zlib
+    lazy refcounts: false
+    bitmaps:
+        [0]:
+            flags:
+                [0]: auto
+            name: b0
+            granularity: 65536
+        [1]:
+            flags:
+                [0]: auto
+            name: b3
+            granularity: 65536
+    refcount bits: 16
+    corrupt: false
+    extended l2: false
+
 === Check bitmap contents ===
 
 [{ "start": 0, "length": 3145728, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
@@ -79,4 +132,7 @@ Format specific information:
 [{ "start": 0, "length": 2097152, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
 { "start": 2097152, "length": 1048576, "depth": 0, "zero": false, "data": false},
 { "start": 3145728, "length": 7340032, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
+[{ "start": 0, "length": 2097152, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 2097152, "length": 1048576, "depth": 0, "zero": false, "data": false},
+{ "start": 3145728, "length": 7340032, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
 *** done