linux-kernel - [PATCH 3.5 55/90] md: fix calculation of stacking limits on level change.

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Message-Id: <1386264972-5399-56-git-send-email-luis.henriques@canonical.com>
Date:	Thu,  5 Dec 2013 17:35:37 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	NeilBrown <neilb@...e.de>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.5 55/90] md: fix calculation of stacking limits on level change.

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

------------------

From: NeilBrown <neilb@...e.de>

commit 02e5f5c0a0f726e66e3d8506ea1691e344277969 upstream.

The various ->run routines of md personalities assume that the 'queue'
has been initialised by the blk_set_stacking_limits() call in
md_alloc().

However when the level is changed (by level_store()) the ->run routine
for the new level is called for an array which has already had the
stacking limits modified.  This can result in incorrect final
settings.

So call blk_set_stacking_limits() before ->run in level_store().

A specific consequence of this bug is that it causes
discard_granularity to be set incorrectly when reshaping a RAID4 to a
RAID0.

This is suitable for any -stable kernel since 3.3 in which
blk_set_stacking_limits() was introduced.

Reported-and-tested-by: "Baldysiak, Pawel" <pawel.baldysiak@...el.com>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/md/md.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5f5e10e..84f0f19 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3681,6 +3681,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->in_sync = 1;
 		del_timer_sync(&mddev->safemode_timer);
 	}
+	blk_set_stacking_limits(&mddev->queue->limits);
 	pers->run(mddev);
 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
 	mddev_resume(mddev);
-- 
1.8.3.2

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