From: NeilBrown <neilb@suse.de>
Date: Mon, 15 Dec 2014 01:56:57 +0000 (+1100)
Subject: md: make merge_bvec_fn more robust in face of personality changes.
X-Git-Tag: fixes-v4.0-rc1~120^2~19
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=64590f45ddc7147fa1968147a1f5b5c436b728fe;p=pandora-kernel.git

md: make merge_bvec_fn more robust in face of personality changes.

There is no locking around calls to merge_bvec_fn(), so
it is possible that calls which coincide with a level (or personality)
change could go wrong.

So create a central dispatch point for these functions and use
rcu_read_lock().
If the array is suspended, reject any merge that can be rejected.
If not, we know it is safe to call the function.

Signed-off-by: NeilBrown <neilb@suse.de>
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