From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 1 Oct 2014 17:29:48 +0000 (-0400)
Subject: dm bufio: when done scanning return from __scan immediately
X-Git-Tag: fixes-against-v3.18-rc2~51^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0e825862f3c04cee40e25f55680333728a4ffa9b;p=pandora-kernel.git

dm bufio: when done scanning return from __scan immediately

When __scan frees the required number of buffer entries that the
shrinker requested (nr_to_scan becomes zero) it must return.  Before
this fix the __scan code exited only the inner loop and continued in the
outer loop -- which could result in reduced performance due to extra
buffers being freed (e.g. unnecessarily evicted thinp metadata needing
to be synchronously re-read into bufio's cache).

Also, move dm_bufio_cond_resched to __scan's inner loop, so that
iterating the bufio client's lru lists doesn't result in scheduling
latency.

Reported-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.2+
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