dm thin metadata: don't issue prefetches if a transaction abort has failed

If a transaction abort has failed then we can no longer use the metadata
device.  Typically this happens if the superblock is unreadable.

This fix addresses a crash seen during metadata device failure testing.

Fixes: 8a01a6af75 ("dm thin: prefetch missing metadata pages")
Cc: stable@vger.kernel.org # 3.19+
Signed-off-by: Joe Thornber <ejt@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 dc947f5..43824d7 100644 (file)
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1981,5 +1981,8 @@ bool dm_pool_metadata_needs_check(struct dm_pool_metadata *pmd)
 
 void dm_pool_issue_prefetches(struct dm_pool_metadata *pmd)
 {
-       dm_tm_issue_prefetches(pmd->tm);
+       down_read(&pmd->root_lock);
+       if (!pmd->fail_io)
+               dm_tm_issue_prefetches(pmd->tm);
+       up_read(&pmd->root_lock);
 }