From: Jens Axboe <jaxboe@fusionio.com>
Date: Wed, 9 Jun 2010 08:42:09 +0000 (+0200)
Subject: block: add sysfs knob for turning off disk entropy contributions
X-Git-Tag: v2.6.36-rc1~288^2~142
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e2e1a148bc45855816ae6b4692ce29d0020fa22e;p=pandora-kernel.git

block: add sysfs knob for turning off disk entropy contributions

There are two reasons for doing this:

- On SSD disks, the completion times aren't as random as they
  are for rotational drives. So it's questionable whether they
  should contribute to the random pool in the first place.

- Calling add_disk_randomness() has a lot of overhead.

This adds /sys/block/<dev>/queue/add_random that will allow you to
switch off on a per-device basis. The default setting is on, so there
should be no functional changes from this patch.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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