dm thin metadata: check if in fail_io mode when setting needs_check

Check if in fail_io mode at start of dm_pool_metadata_set_needs_check().
Otherwise dm_pool_metadata_set_needs_check()'s superblock_lock() can
crash in dm_bm_write_lock() while accessing the block manager object
that was previously destroyed as part of a failed
dm_pool_abort_metadata() that ultimately set fail_io to begin with.

Also, update DMERR() message to more accurately describe
superblock_lock() failure.

Cc: stable@vger.kernel.org
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 7f08406..4c68a7b 100644 (file)
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -2046,16 +2046,19 @@ int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
 
 int dm_pool_metadata_set_needs_check(struct dm_pool_metadata *pmd)
 {
-       int r;
+       int r = -EINVAL;
        struct dm_block *sblock;
        struct thin_disk_superblock *disk_super;
 
        pmd_write_lock(pmd);
+       if (pmd->fail_io)
+               goto out;
+
        pmd->flags |= THIN_METADATA_NEEDS_CHECK_FLAG;
 
        r = superblock_lock(pmd, &sblock);
        if (r) {
-               DMERR("couldn't read superblock");
+               DMERR("couldn't lock superblock");
                goto out;
        }