[Qemu-devel] [PATCH v6 08/14] qemu-img: Empty image after commit

[Max Reitz]

After the top image has been committed, it should be emptied unless
specified otherwise.

Signed-off-by: Max Reitz <address@hidden>
---
 qemu-img-cmds.hx |  4 ++--
 qemu-img.c       | 34 +++++++++++++++++++++++++++++++---
 qemu-img.texi    |  6 +++++-
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index d029609..b31d81c 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -22,9 +22,9 @@ STEXI
 ETEXI
 
 DEF("commit", img_commit,
-    "commit [-q] [-f fmt] [-t cache] filename")
+    "commit [-q] [-f fmt] [-t cache] [-d] filename")
 STEXI
address@hidden commit [-q] [-f @var{fmt}] [-t @var{cache}] @var{filename}
address@hidden commit [-q] [-f @var{fmt}] [-t @var{cache}] [-d] @var{filename}
 ETEXI
 
 DEF("compare", img_compare,
diff --git a/qemu-img.c b/qemu-img.c
index f80b42c..2ffc054 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -737,14 +737,14 @@ static int img_commit(int argc, char **argv)
     int c, ret, flags;
     const char *filename, *fmt, *cache;
     BlockDriverState *bs, *base_bs;
-    bool quiet = false;
+    bool quiet = false, drop = false;
     Error *local_err = NULL;
     CommonBlockJobCBInfo cbi;
 
     fmt = NULL;
     cache = BDRV_DEFAULT_CACHE;
     for(;;) {
-        c = getopt(argc, argv, "f:ht:q");
+        c = getopt(argc, argv, "f:ht:dq");
         if (c == -1) {
             break;
         }
@@ -759,6 +759,9 @@ static int img_commit(int argc, char **argv)
         case 't':
             cache = optarg;
             break;
+        case 'd':
+            drop = true;
+            break;
         case 'q':
             quiet = true;
             break;
@@ -769,7 +772,7 @@ static int img_commit(int argc, char **argv)
     }
     filename = argv[optind++];
 
-    flags = BDRV_O_RDWR;
+    flags = BDRV_O_RDWR | BDRV_O_UNMAP;
     ret = bdrv_parse_cache_flags(cache, &flags);
     if (ret < 0) {
         error_report("Invalid cache option: %s", cache);
@@ -801,7 +804,32 @@ static int img_commit(int argc, char **argv)
         goto done;
     }
 
+    /* The block job will swap base_bs and bs (which is not what we really want
+     * here, but okay) and unref bs (and subsequently all intermediate block
+     * devices). In order to be able to empty these images afterwards, 
increment
+     * the reference counter here preemptively. */
+    if (!drop) {
+        bdrv_ref(base_bs);
+    }
+
     run_block_job(bs->job, &local_err);
+    if (local_err) {
+        goto unref_backing;
+    }
+
+    if (!drop && base_bs->drv->bdrv_make_empty) {
+        ret = base_bs->drv->bdrv_make_empty(base_bs);
+        if (ret) {
+            error_setg_errno(&local_err, -ret, "Could not empty %s",
+                             filename);
+            goto unref_backing;
+        }
+    }
+
+unref_backing:
+    if (!drop) {
+        bdrv_unref(base_bs);
+    }
 
 done:
     bdrv_unref(bs);
diff --git a/qemu-img.texi b/qemu-img.texi
index f84590e..40f0088 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -140,7 +140,7 @@ this case. @var{backing_file} will never be modified unless 
you use the
 The size can also be specified using the @var{size} option with @code{-o},
 it doesn't need to be specified separately in this case.
 
address@hidden commit [-f @var{fmt}] [-t @var{cache}] @var{filename}
address@hidden commit [-f @var{fmt}] [-t @var{cache}] [-d] @var{filename}
 
 Commit the changes recorded in @var{filename} in its base image or backing 
file.
 If the backing file is smaller than the snapshot, then the backing file will be
@@ -149,6 +149,10 @@ the backing file, the backing file will not be truncated.  
If you want the
 backing file to match the size of the smaller snapshot, you can safely truncate
 it yourself once the commit operation successfully completes.
 
+The image @var{filename} is emptied after the operation has been successful. If
+you do not need @var{filename} afterwards anymore and intend to drop it, you 
may
+skip this operation by specifying the @code{-d} flag.
+
 @item compare [-f @var{fmt}] [-F @var{fmt}] [-p] [-s] [-q] @var{filename1} 
@var{filename2}
 
 Check if two images have the same content. You can compare images with
-- 
1.9.2