[Qemu-devel] [PATCH v2 0/2] fix 'qemu-img snapshot -a' operation for sheepdog

[Qemu-devel] [PATCH v2 0/2] fix 'qemu-img snapshot -a' operation for sheepdog

[Liu Yuan]

v2:
 - add the comment to make things more clear
 - call sd_create_branch() after s->is_snapshot = true because after calling
   sd_create_branch, it is not snapshot anymore.

Nothing big, just two simple patches to enable this commind for sheepdog.

Cc: qemu-devel@nongnu.org
Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>

Liu Yuan (2):
  sheepdog: fix snapshot tag initialization
  sheepdog: support 'qemu-img snapshot -a'

 block/sheepdog.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

-- 
1.7.9.5

[Qemu-devel] [PATCH v2 1/2] sheepdog: fix snapshot tag initialization

[Liu Yuan]

This is an old and obvious bug. We should pass snapshot_id to the
tag. Or simple command like 'qemu-img snapshot -a tag sheepdog:image' will fail

Cc: qemu-devel@nongnu.org
Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
---
 block/sheepdog.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 21a4edf..94218ac 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2063,7 +2063,7 @@ static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
     if (snapid) {
         tag[0] = 0;
     } else {
-        pstrcpy(tag, sizeof(tag), s->name);
+        pstrcpy(tag, sizeof(tag), snapshot_id);
     }
 
     ret = reload_inode(s, snapid, tag);
-- 
1.7.9.5

[Qemu-devel] [PATCH v2 2/2] sheepdog: support 'qemu-img snapshot -a'

[Liu Yuan]

Just call sd_create_branch() to rollback the image is good enough

Cc: qemu-devel@nongnu.org
Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
---
 block/sheepdog.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 94218ac..c128b37 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2071,14 +2071,21 @@ static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
         goto out;
     }
 
+    s->is_snapshot = true;
+
     if (!s->inode.vm_state_size) {
-        error_report("Invalid snapshot");
-        ret = -ENOENT;
-        goto out;
+        /*
+         * qemu-img asks us to rollback, we can't rely on the write to create
+         * the branch, so do it right now. We can call sd_create_branch() right
+         * here only when vm_state_size == 0 because it changes vdi_id
+         * internally, otherwise we will read the wrong vmstate if any.
+         */
+        ret = sd_create_branch(s);
+        if (ret) {
+            goto out;
+        }
     }
 
-    s->is_snapshot = true;
-
     g_free(old_s);
 
     return 0;
-- 
1.7.9.5