Patch "dm cache metadata: fail operations if fail_io mode has been established" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

dm cache metadata: fail operations if fail_io mode has been established

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
dm-cache-metadata-fail-operations-if-fail_io-mode-has-been-established.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mike Snitzer <[email protected]>
Date: Fri, 5 May 2017 14:40:13 -0400
Subject: dm cache metadata: fail operations if fail_io mode has been established

From: Mike Snitzer <[email protected]>

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.

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

@@ -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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/dm-btree-fix-for-dm_btree_find_lowest_key.patch queue-4.9/dm-bufio-avoid-a-possible-abba-deadlock.patch queue-4.9/dm-cache-metadata-fail-operations-if-fail_io-mode-has-been-established.patch queue-4.9/dm-raid-select-the-kconfig-option-config_md_raid0.patch queue-4.9/dm-bufio-make-the-parameter-retain_bytes-unsigned-long.patch queue-4.9/dm-space-map-disk-fix-some-book-keeping-in-the-disk-space-map.patch queue-4.9/dm-mpath-split-and-rename-activate_path-to-prepare-for-its-expanded-use.patch queue-4.9/dm-bufio-check-new-buffer-allocation-watermark-every-30-seconds.patch queue-4.9/dm-thin-metadata-call-precommit-before-saving-the-roots.patch