From b277da0a8a594308e17881f4926879bd5fca2a2d Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Sat, 4 Oct 2014 10:55:32 -0600 Subject: block: disable entropy contributions for nonrot devices Clear QUEUE_FLAG_ADD_RANDOM in all block drivers that set QUEUE_FLAG_NONROT. Historically, all block devices have automatically made entropy contributions. But as previously stated in commit e2e1a148 ("block: add sysfs knob for turning off disk entropy contributions"): - 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. There are more reliable sources for randomness than non-rotational block devices. From a security perspective it is better to err on the side of caution than to allow entropy contributions from unreliable "random" sources. Signed-off-by: Mike Snitzer Signed-off-by: Jens Axboe --- drivers/md/bcache/super.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/md/bcache/super.c') diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index d4713d098a39..4dd2bb7167f0 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -842,6 +842,7 @@ static int bcache_device_init(struct bcache_device *d, unsigned block_size, q->limits.logical_block_size = block_size; q->limits.physical_block_size = block_size; set_bit(QUEUE_FLAG_NONROT, &d->disk->queue->queue_flags); + clear_bit(QUEUE_FLAG_ADD_RANDOM, &d->disk->queue->queue_flags); set_bit(QUEUE_FLAG_DISCARD, &d->disk->queue->queue_flags); blk_queue_flush(q, REQ_FLUSH|REQ_FUA); -- cgit