Patch "rbd: require stable pages if message data CRCs are enabled" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

rbd: require stable pages if message data CRCs are enabled

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
rbd-require-stable-pages-if-message-data-crcs-are-enabled.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ronny Hegewald <[email protected]>
Date: Thu, 15 Oct 2015 18:50:46 +0000
Subject: rbd: require stable pages if message data CRCs are enabled

From: Ronny Hegewald <[email protected]>

commit bae818ee1577c27356093901a0ea48f672eda514 upstream.

rbd requires stable pages, as it performs a crc of the page data before they are send to the OSDs.

But since kernel 3.9 (patch 1d1d1a767206fbe5d4c69493b7e6d2a8d08cc0a0 "mm: only enforce stable page writes if the backing device requires it") it is not assumed anymore that block devices require stable pages.

This patch sets the necessary flag to get stable pages back for rbd.

In a ceph installation that provides multiple ext4 formatted rbd devices "bad crc" messages appeared regularly (ca 1 message every 1-2 minutes on every OSD that provided the data for the rbd) in the OSD-logs before this patch. After this patch this messages are pretty much gone (only ca 1-2 / month / OSD).

---
 drivers/block/rbd.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -3443,6 +3443,9 @@ static int rbd_init_disk(struct rbd_devi
 	blk_queue_io_opt(q, segment_size);
 
 	blk_queue_merge_bvec(q, rbd_merge_bvec);
+	if (!ceph_test_opt(rbd_dev->rbd_client->client, NOCRC))
+		q->backing_dev_info.capabilities |= BDI_CAP_STABLE_WRITES;
+
 	disk->queue = q;
 
 	q->queuedata = rbd_dev;

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/rbd-require-stable-pages-if-message-data-crcs-are-enabled.patch