[PATCH 4.9 027/164] dm cache metadata: fail operations if fail_io mode has been established

[Greg Kroah-Hartman]

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

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

From: Mike Snitzer <snitzer@xxxxxxxxxx>

commit 10add84e276432d9dd8044679a1028dd4084117e upstream.

Otherwise it is possible to trigger crashes due to the metadata being
inaccessible yet these methods don't safely account for that possibility
without these checks.

Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/dm-cache-metadata.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -1383,17 +1383,19 @@ void dm_cache_metadata_set_stats(struct
 
 int dm_cache_commit(struct dm_cache_metadata *cmd, bool clean_shutdown)
 {
-	int r;
+	int r = -EINVAL;
 	flags_mutator mutator = (clean_shutdown ? set_clean_shutdown :
 				 clear_clean_shutdown);
 
 	WRITE_LOCK(cmd);
+	if (cmd->fail_io)
+		goto out;
+
 	r = __commit_transaction(cmd, mutator);
 	if (r)
 		goto out;
 
 	r = __begin_transaction(cmd);
-
 out:
 	WRITE_UNLOCK(cmd);
 	return r;
@@ -1405,7 +1407,8 @@ int dm_cache_get_free_metadata_block_cou
 	int r = -EINVAL;
 
 	READ_LOCK(cmd);
-	r = dm_sm_get_nr_free(cmd->metadata_sm, result);
+	if (!cmd->fail_io)
+		r = dm_sm_get_nr_free(cmd->metadata_sm, result);
 	READ_UNLOCK(cmd);
 
 	return r;
@@ -1417,7 +1420,8 @@ int dm_cache_get_metadata_dev_size(struc
 	int r = -EINVAL;
 
 	READ_LOCK(cmd);
-	r = dm_sm_get_nr_blocks(cmd->metadata_sm, result);
+	if (!cmd->fail_io)
+		r = dm_sm_get_nr_blocks(cmd->metadata_sm, result);
 	READ_UNLOCK(cmd);
 
 	return r;