Patch "md/raid10: always set reshape_safe when initializing reshape_position." has been added to the 4.1-stable tree

Patch "md/raid10: always set reshape_safe when initializing reshape_position." has been added to the 4.1-stable tree

[gregkh]

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

    md/raid10: always set reshape_safe when initializing reshape_position.

to the 4.1-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:
     md-raid10-always-set-reshape_safe-when-initializing-reshape_position.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 299b0685e31c9f3dcc2d58ee3beca761a40b44b3 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.com>
Date: Mon, 6 Jul 2015 17:37:49 +1000
Subject: md/raid10: always set reshape_safe when initializing reshape_position.

From: NeilBrown <neilb@suse.com>

commit 299b0685e31c9f3dcc2d58ee3beca761a40b44b3 upstream.

'reshape_position' tracks where in the reshape we have reached.
'reshape_safe' tracks where in the reshape we have safely recorded
in the metadata.

These are compared to determine when to update the metadata.
So it is important that reshape_safe is initialised properly.
Currently it isn't.  When starting a reshape from the beginning
it usually has the correct value by luck.  But when reducing the
number of devices in a RAID10, it has the wrong value and this leads
to the metadata not being updated correctly.
This can lead to corruption if the reshape is not allowed to complete.

This patch is suitable for any -stable kernel which supports RAID10
reshape, which is 3.5 and later.

Fixes: 3ea7daa5d7fd ("md/raid10: add reshape support")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/raid10.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3566,6 +3566,7 @@ static struct r10conf *setup_conf(struct
 			/* far_copies must be 1 */
 			conf->prev.stride = conf->dev_sectors;
 	}
+	conf->reshape_safe = conf->reshape_progress;
 	spin_lock_init(&conf->device_lock);
 	INIT_LIST_HEAD(&conf->retry_list);
 
@@ -3770,7 +3771,6 @@ static int run(struct mddev *mddev)
 		}
 		conf->offset_diff = min_offset_diff;
 
-		conf->reshape_safe = conf->reshape_progress;
 		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
 		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
 		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
@@ -4113,6 +4113,7 @@ static int raid10_start_reshape(struct m
 		conf->reshape_progress = size;
 	} else
 		conf->reshape_progress = 0;
+	conf->reshape_safe = conf->reshape_progress;
 	spin_unlock_irq(&conf->device_lock);
 
 	if (mddev->delta_disks && mddev->bitmap) {
@@ -4180,6 +4181,7 @@ abort:
 		rdev->new_data_offset = rdev->data_offset;
 	smp_wmb();
 	conf->reshape_progress = MaxSector;
+	conf->reshape_safe = MaxSector;
 	mddev->reshape_position = MaxSector;
 	spin_unlock_irq(&conf->device_lock);
 	return ret;
@@ -4534,6 +4536,7 @@ static void end_reshape(struct r10conf *
 	md_finish_reshape(conf->mddev);
 	smp_wmb();
 	conf->reshape_progress = MaxSector;
+	conf->reshape_safe = MaxSector;
 	spin_unlock_irq(&conf->device_lock);
 
 	/* read-ahead size must cover two whole stripes, which is


Patches currently in stable-queue which might be from neilb@suse.com are

queue-4.1/md-raid5-avoid-races-when-changing-cache-size.patch
queue-4.1/md-flush-event_work-before-stopping-array.patch
queue-4.1/md-raid5-don-t-let-shrink_slab-shrink-too-far.patch
queue-4.1/nfsv4-don-t-set-setattr-for-o_rdonly-o_excl.patch
queue-4.1/md-raid10-always-set-reshape_safe-when-initializing-reshape_position.patch