Patch "raid5: Set R5_Expanded on parity devices as well as data." has been added to the 3.18-stable tree

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

raid5: Set R5_Expanded on parity devices as well as data.

to the 3.18-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:
raid5-set-r5_expanded-on-parity-devices-as-well-as-data.patch
and it can be found in the queue-3.18 subdirectory.

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

From: NeilBrown <[email protected]>
Date: Tue, 17 Oct 2017 16:18:36 +1100
Subject: raid5: Set R5_Expanded on parity devices as well as data.

From: NeilBrown <[email protected]>

[ Upstream commit 235b6003fb28f0dd8e7ed8fbdb088bb548291766 ]

When reshaping a fully degraded raid5/raid6 to a larger nubmer of devices, the new device(s) are not in-sync and so that can make the newly grown stripe appear to be "failed".
To avoid this, we set the R5_Expanded flag to say "Even though this device is not fully in-sync, this block is safe so don't treat the device as failed for this stripe". This flag is set for data devices, not not for parity devices.

Consequently, if you have a RAID6 with two devices that are partly recovered and a spare, and start a reshape to include the spare, then when the reshape gets past the point where the recovery was up to, it will think the stripes are failed and will get into an infinite loop, failing to make progress.

So when contructing parity on an EXPAND_READY stripe, set R5_Expanded.

---
 drivers/md/raid5.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

@@ -1454,8 +1454,11 @@ static void ops_complete_reconstruct(voi
 		struct r5dev *dev = &sh->dev[i];
 
 		if (dev->written || i == pd_idx || i == qd_idx) {
-			if (!discard && !test_bit(R5_SkipCopy, &dev->flags))
+			if (!discard && !test_bit(R5_SkipCopy, &dev->flags)) {
 				set_bit(R5_UPTODATE, &dev->flags);
+				if (test_bit(STRIPE_EXPAND_READY, &sh->state))
+					set_bit(R5_Expanded, &dev->flags);
+			}
 			if (fua)
 				set_bit(R5_WantFUA, &dev->flags);
 			if (sync)

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

queue-3.18/autofs-fix-careless-error-in-recent-commit.patch queue-3.18/raid5-set-r5_expanded-on-parity-devices-as-well-as-data.patch queue-3.18/nfsd-fix-nfsd_reset_versions-for-nfsv4.patch queue-3.18/nfsd-fix-nfsd_minorversion-..-nfsd_avail.patch