md: fix calculation of stacking limits on level change.

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@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 7b45b5e1b31eb19184e26c5cbcea072078f56bda..e63ca864b35adb97d7a9a074c962a1a62d1aa17f 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3507,6 +3507,7 @@ 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);
        mddev_resume(mddev);
        set_bit(MD_CHANGE_DEVS, &mddev->flags);