From: Benjamin LaHaise <bcrl@kvack.org>
Date: Mon, 14 Jul 2014 16:49:26 +0000 (-0400)
Subject: aio: protect reqs_available updates from changes in interrupt handlers
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~291^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=263782c1c95bbddbb022dc092fd89a36bb8d5577;p=pandora-kernel.git

aio: protect reqs_available updates from changes in interrupt handlers

As of commit f8567a3845ac05bb28f3c1b478ef752762bd39ef it is now possible to
have put_reqs_available() called from irq context.  While put_reqs_available()
is per cpu, it did not protect itself from interrupts on the same CPU.  This
lead to aio_complete() corrupting the available io requests count when run
under a heavy O_DIRECT workloads as reported by Robert Elliott.  Fix this by
disabling irq updates around the per cpu batch updates of reqs_available.

Many thanks to Robert and folks for testing and tracking this down.

Reported-by: Robert Elliot <Elliott@hp.com>
Tested-by: Robert Elliot <Elliott@hp.com>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@infradead.org>
Cc: stable@vger.kenel.org
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