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

jthornber · snitm · commit 2eae9e4489b4 · 2016-03-10T17:12:09.000-05:00
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: 8a01a6a ("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
@@ -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);
 }

Original file line number	Diff line number	Diff line change
`@@ -1981,5 +1981,8 @@ bool dm_pool_metadata_needs_check(struct dm_pool_metadata *pmd)`
`1981`	`1981`
`1982`	`1982`	`void dm_pool_issue_prefetches(struct dm_pool_metadata *pmd)`
`1983`	`1983`	`{`
`1984`		`- dm_tm_issue_prefetches(pmd->tm);`
	`1984`	`+ down_read(&pmd->root_lock);`
	`1985`	`+ if (!pmd->fail_io)`
	`1986`	`+ dm_tm_issue_prefetches(pmd->tm);`
	`1987`	`+ up_read(&pmd->root_lock);`
`1985`	`1988`	`}`