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authorJens Axboe <jaxboe@fusionio.com>2010-06-09 10:42:09 +0200
committerJens Axboe <jaxboe@fusionio.com>2010-08-07 18:13:00 +0200
commite2e1a148bc45855816ae6b4692ce29d0020fa22e (patch)
treefd5ec8a580d4333b471acfe50f6f92b4cc880087 /block/blk-core.c
parent841fdffdd382722d33579a6aa1487e8a4e526dbd (diff)
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>
Diffstat (limited to 'block/blk-core.c')
-rw-r--r--block/blk-core.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index f0640d7f800f..b4131d29148c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2111,7 +2111,8 @@ static bool blk_update_bidi_request(struct request *rq, int error,
blk_update_request(rq->next_rq, error, bidi_bytes))
return true;
- add_disk_randomness(rq->rq_disk);
+ if (blk_queue_add_random(rq->q))
+ add_disk_randomness(rq->rq_disk);
return false;
}