md: fix calculation of stacking limits on level change.
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. Cc: stable@vger.kernel.org (3.3+) Reported-and-tested-by: "Baldysiak, Pawel" <pawel.baldysiak@intel.com> Signed-off-by: NeilBrown <neilb@suse.de>
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