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blockdev: move BDRV_O_NO_BACKING option forward 

For both external_snapshot_prepare and qmp_drive_mirror, we eventually
append the option BDRV_O_NO_BACKING. However, we generally do so after
we create the image.

To accommodate image creation wanting to verify that a backing file
exists or not, add this option prior to create to override checking
the existence of the backing file. This prevents QEMU from trying to
re-open a backing file that's already in use (thanks to qcow2 locking).

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
John Snow 2017-07-17 20:34:21 -04:00 committed by Kevin Wolf
parent 7c8730d45f
commit 2a32c6e82e
1 changed files with 6 additions and 5 deletions
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11
blockdev.c
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@ -1710,7 +1710,8 @@ static void external_snapshot_prepare(BlkActionState *common,
}
flags = state->old_bs->open_flags;
flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING | BDRV_O_COPY_ON_READ);
flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_COPY_ON_READ);
flags |= BDRV_O_NO_BACKING;
/* create new image w/backing file */
mode = s->has_mode ? s->mode : NEW_IMAGE_MODE_ABSOLUTE_PATHS;
@ -1735,8 +1736,6 @@ static void external_snapshot_prepare(BlkActionState *common,
qdict_put_str(options, "node-name", snapshot_node_name);
}
qdict_put_str(options, "driver", format);
flags |= BDRV_O_NO_BACKING;
}
state->new_bs = bdrv_open(new_image_file, snapshot_ref, options, flags,
@ -3548,6 +3547,9 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)
backing_mode = MIRROR_OPEN_BACKING_CHAIN;
}
/* Don't open backing image in create() */
flags |= BDRV_O_NO_BACKING;
if ((arg->sync == MIRROR_SYNC_MODE_FULL || !source)
&& arg->mode != NEW_IMAGE_MODE_EXISTING)
{
@ -3587,8 +3589,7 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)
/* Mirroring takes care of copy-on-write using the source's backing
* file.
*/
target_bs = bdrv_open(arg->target, NULL, options,
flags | BDRV_O_NO_BACKING, errp);
target_bs = bdrv_open(arg->target, NULL, options, flags, errp);
if (!target_bs) {
goto out;
}