[patch 42/56] md: Allow metadata_version to be updated forexternally managed metadata.

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.
------------------

From: NeilBrown <neilb@xxxxxxx>

commit ea43ddd8491feccf36267349748ea91b1194481e upstream.

For externally managed metadata, the 'metadata_version' sysfs
attribute is really just a channel for user-space programs to
communicate about how the array is being managed.
It can be useful for this to be changed while the array is active.

Normally changes to metadata_version are not permitted while the array
is active.  Change that so that if the metadata is externally managed,
the metadata_version can be changed to a different flavour of external
management.

Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/md/md.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2960,7 +2960,13 @@ metadata_store(mddev_t *mddev, const cha
 {
 	int major, minor;
 	char *e;
-	if (!list_empty(&mddev->disks))
+	/* Changing the details of 'external' metadata is
+	 * always permitted.  Otherwise there must be
+	 * no devices attached to the array.
+	 */
+	if (mddev->external && strncmp(buf, "external:", 9) == 0)
+		;
+	else if (!list_empty(&mddev->disks))
 		return -EBUSY;
 
 	if (cmd_match(buf, "none")) {

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