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authorMike Snitzer <snitzer@redhat.com>2014-10-04 10:55:32 -0600
committerJens Axboe <axboe@fb.com>2014-10-04 10:55:32 -0600
commitb277da0a8a594308e17881f4926879bd5fca2a2d (patch)
tree1af7df6ade218a4b246dd43a0771701a672c6cb8 /drivers/scsi
parent7b7b7f7e024460cb7d77f8f96b6eb1a8803f94d9 (diff)
downloadlinux-b277da0a8a594308e17881f4926879bd5fca2a2d.tar.bz2
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 <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'drivers/scsi')
-rw-r--r--drivers/scsi/sd.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 2c2041ca4b70..fe67f5c107a2 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2660,8 +2660,10 @@ static void sd_read_block_characteristics(struct scsi_disk *sdkp)
rot = get_unaligned_be16(&buffer[4]);
- if (rot == 1)
+ if (rot == 1) {
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, sdkp->disk->queue);
+ queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, sdkp->disk->queue);
+ }
out:
kfree(buffer);