linux-kernel - [PATCH 4.2.y-ckt 096/218] dm thin metadata: don't issue prefetches if a transaction abort has failed

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Message-Id: <1459455431-12687-97-git-send-email-kamal@canonical.com>
Date:	Thu, 31 Mar 2016 13:15:09 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Joe Thornber <ejt@...hat.com>, Mike Snitzer <snitzer@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 096/218] dm thin metadata: don't issue prefetches if a transaction abort has failed

4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Joe Thornber <ejt@...hat.com>

commit 2eae9e4489b4cf83213fa3bd508b5afca3f01780 upstream.

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")
Signed-off-by: Joe Thornber <ejt@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/md/dm-thin-metadata.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 4479e90..dbce0df 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1935,5 +1935,8 @@ 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);
 }
-- 
2.7.4