[PATCH 3.16.y-ckt 114/135] dm thin: don't allow messages to be sent to a pool target in READ_ONLY or FAIL mode

[Luis Henriques]

3.16.7-ckt6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joe Thornber <ejt at redhat.com>

commit 2a7eaea02b99b6e267b1e89c79acc6e9a51cee3b upstream.

You can't modify the metadata in these modes.  It's better to fail these
messages immediately than let the block-manager deny write locks on
metadata blocks.  Otherwise these failed metadata changes will trigger
'needs_check' to get set in the metadata superblock -- requiring repair
using the thin_check utility.

Signed-off-by: Joe Thornber <ejt at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/dm-thin.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 408ffba7ec63..add44f5a87b1 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2913,6 +2913,12 @@ static int pool_message(struct dm_target *ti, unsigned argc, char **argv)
 	struct pool_c *pt = ti->private;
 	struct pool *pool = pt->pool;
 
+	if (get_pool_mode(pool) >= PM_READ_ONLY) {
+		DMERR("%s: unable to service pool target messages in READ_ONLY or FAIL mode",
+		      dm_device_name(pool->pool_md));
+		return -EINVAL;
+	}
+
 	if (!strcasecmp(argv[0], "create_thin"))
 		r = process_create_thin_mesg(argc, argv, pool);
 
-- 
2.1.4