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[Qemu-devel] [PATCH V5 3/4] Add backing drive while performing backup.
From: |
Ian Main |
Subject: |
[Qemu-devel] [PATCH V5 3/4] Add backing drive while performing backup. |
Date: |
Fri, 19 Jul 2013 10:03:30 -0700 |
This patch adds the original source drive as a backing drive to our target
image so that the target image will appear complete during backup. This
is especially useful for SYNC_MODE_NONE as it allows export via NBD to
have a complete point-in-time snapshot available for export.
Signed-off-by: Ian Main <address@hidden>
---
block/backup.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/block/backup.c b/block/backup.c
index 68abd23..e086e76 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -323,6 +323,10 @@ static void coroutine_fn backup_run(void *opaque)
hbitmap_free(job->bitmap);
+ /* Set the target backing drive back to NULL before calling delete or
+ * it will also delete the underlying drive. */
+ target->backing_hd = NULL;
+
bdrv_iostatus_disable(target);
bdrv_delete(target);
@@ -362,6 +366,15 @@ void backup_start(BlockDriverState *bs, BlockDriverState
*target,
return;
}
+ /* Manually set the backing hd to be the backup source drive so
+ * that all reads done while we are backing up will be passed
+ * on to the original source drive. This allows reading from the
+ * image while the backup is in progress, or in the case of
+ * SYNC_MODE_NONE allows a complete image to be present for export.
+ * Note that we do this for all modes including SYNC_MODE_TOP as
+ * even then it allows on-the-fly reading. */
+ target->backing_hd = bs;
+
job->on_source_error = on_source_error;
job->on_target_error = on_target_error;
job->target = target;
--
1.8.1.4
[Qemu-devel] [PATCH V5 3/4] Add backing drive while performing backup.,
Ian Main <=
[Qemu-devel] [PATCH V5 4/4] Change default to qcow2 for sync mode none., Ian Main, 2013/07/19