dm thin metadata: fix a race when entering fail mode

In dm_thin_find_block() the ->fail_io flag was checked outside the metadata device's root_lock, causing dm_thin_find_block() to race with the setting of this flag. Signed-off-by: Joe Thornber <[email protected]> Signed-off-by: Mike Snitzer <[email protected]>
torvalds · Jun 11, 2015 · b1f11af · b1f11af
1 parent fd46769
commit b1f11af
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
@@ -1390,10 +1390,11 @@ int dm_thin_find_block(struct dm_thin_device *td, dm_block_t block,
 	dm_block_t keys[2] = { td->id, block };
 	struct dm_btree_info *info;
 
-	if (pmd->fail_io)
-		return -EINVAL;
-
 	down_read(&pmd->root_lock);
+	if (pmd->fail_io) {
+		up_read(&pmd->root_lock);
+		return -EINVAL;
+	}
 
 	if (can_issue_io) {
 		info = &pmd->info;