qemu-img: Add convert --bitmaps option

Make it easier to copy all the persistent bitmaps of (the top layer
of) a source image along with its guest-visible contents, by adding a
boolean flag for use with qemu-img convert.  This is basically
shorthand, as the same effect could be accomplished with a series of
'qemu-img bitmap --add' and 'qemu-img bitmap --merge -b source'
commands, or by their corresponding QMP commands.

Note that this command will fail in the same scenarios where 'qemu-img
measure' omits a 'bitmaps size:' line, namely, when either the source
or the destination lacks persistent bitmap support altogether.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1779893

While touching this, clean up a couple coding issues spotted in the
same function: an extra blank line, and merging back-to-back 'if
(!skip_create)' blocks.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200521192137.1120211-5-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

1 files changed, 67 insertions, 3 deletions

diff --git a/qemu-img.c b/qemu-img.c
index 0778d8f566..d7e846e607 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -78,6 +78,7 @@ enum {
     OPTION_ENABLE = 272,
     OPTION_DISABLE = 273,
     OPTION_MERGE = 274,
+    OPTION_BITMAPS = 275,
 };
 
 typedef enum OutputFormat {
@@ -191,6 +192,7 @@ static void QEMU_NORETURN help(void)
            "       hiding corruption that has already occurred.\n"
            "\n"
            "Parameters to convert subcommand:\n"
+           "  '--bitmaps' copies all top-level persistent bitmaps to destination\n"
            "  '-m' specifies how many coroutines work in parallel during the convert\n"
            "       process (defaults to 8)\n"
            "  '-W' allow to write to the target out of order rather than sequential\n"
@@ -2139,6 +2141,39 @@ static int convert_do_copy(ImgConvertState *s)
     return s->ret;
 }
 
+static int convert_copy_bitmaps(BlockDriverState *src, BlockDriverState *dst)
+{
+    BdrvDirtyBitmap *bm;
+    Error *err = NULL;
+
+    FOR_EACH_DIRTY_BITMAP(src, bm) {
+        const char *name;
+
+        if (!bdrv_dirty_bitmap_get_persistence(bm)) {
+            continue;
+        }
+        name = bdrv_dirty_bitmap_name(bm);
+        qmp_block_dirty_bitmap_add(dst->node_name, name,
+                                   true, bdrv_dirty_bitmap_granularity(bm),
+                                   true, true,
+                                   true, !bdrv_dirty_bitmap_enabled(bm),
+                                   &err);
+        if (err) {
+            error_reportf_err(err, "Failed to create bitmap %s: ", name);
+            return -1;
+        }
+
+        do_dirty_bitmap_merge(dst->node_name, name, src->node_name, name,
+                              &err);
+        if (err) {
+            error_reportf_err(err, "Failed to populate bitmap %s: ", name);
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 #define MAX_BUF_SECTORS 32768
 
 static int img_convert(int argc, char **argv)
@@ -2160,6 +2195,7 @@ static int img_convert(int argc, char **argv)
     int64_t ret = -EINVAL;
     bool force_share = false;
     bool explict_min_sparse = false;
+    bool bitmaps = false;
 
     ImgConvertState s = (ImgConvertState) {
         /* Need at least 4k of zeros for sparse detection */
@@ -2179,6 +2215,7 @@ static int img_convert(int argc, char **argv)
             {"target-image-opts", no_argument, 0, OPTION_TARGET_IMAGE_OPTS},
             {"salvage", no_argument, 0, OPTION_SALVAGE},
             {"target-is-zero", no_argument, 0, OPTION_TARGET_IS_ZERO},
+            {"bitmaps", no_argument, 0, OPTION_BITMAPS},
             {0, 0, 0, 0}
         };
         c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WU",
@@ -2304,6 +2341,9 @@ static int img_convert(int argc, char **argv)
              */
             s.has_zero_init = true;
             break;
+        case OPTION_BITMAPS:
+            bitmaps = true;
+            break;
         }
     }
 
@@ -2365,7 +2405,6 @@ static int img_convert(int argc, char **argv)
         goto fail_getopt;
     }
 
-
     /* ret is still -EINVAL until here */
     ret = bdrv_parse_cache_mode(src_cache, &src_flags, &src_writethrough);
     if (ret < 0) {
@@ -2525,6 +2564,20 @@ static int img_convert(int argc, char **argv)
         }
     }
 
+    /* Determine if bitmaps need copying */
+    if (bitmaps) {
+        if (s.src_num > 1) {
+            error_report("Copying bitmaps only possible with single source");
+            ret = -1;
+            goto out;
+        }
+        if (!bdrv_supports_persistent_dirty_bitmap(blk_bs(s.src[0]))) {
+            error_report("Source lacks bitmap support");
+            ret = -1;
+            goto out;
+        }
+    }
+
     /*
      * The later open call will need any decryption secrets, and
      * bdrv_create() will purge "opts", so extract them now before
@@ -2533,9 +2586,7 @@ static int img_convert(int argc, char **argv)
     if (!skip_create) {
         open_opts = qdict_new();
         qemu_opt_foreach(opts, img_add_key_secrets, open_opts, &error_abort);
-    }
 
-    if (!skip_create) {
         /* Create the new image */
         ret = bdrv_create(drv, out_filename, opts, &local_err);
         if (ret < 0) {
@@ -2573,6 +2624,13 @@ static int img_convert(int argc, char **argv)
     }
     out_bs = blk_bs(s.target);
 
+    if (bitmaps && !bdrv_supports_persistent_dirty_bitmap(out_bs)) {
+        error_report("Format driver '%s' does not support bitmaps",
+                     out_bs->drv->format_name);
+        ret = -1;
+        goto out;
+    }
+
     if (s.compressed && !block_driver_can_compress(out_bs->drv)) {
         error_report("Compression not supported for this file format");
         ret = -1;
@@ -2632,6 +2690,12 @@ static int img_convert(int argc, char **argv)
     }
 
     ret = convert_do_copy(&s);
+
+    /* Now copy the bitmaps */
+    if (bitmaps && ret == 0) {
+        ret = convert_copy_bitmaps(blk_bs(s.src[0]), out_bs);
+    }
+
 out:
     if (!ret) {
         qemu_progress_print(100, 0);