Commit c3c4555e authored by Milan Broz's avatar Milan Broz Committed by Alasdair G Kergon
Browse files

dm table: clear add_random unless all devices have it set 



Always clear QUEUE_FLAG_ADD_RANDOM if any underlying device does not
have it set. Otherwise devices with predictable characteristics may
contribute entropy.

QUEUE_FLAG_ADD_RANDOM specifies whether or not queue IO timings
contribute to the random pool.

For bio-based targets this flag is always 0 because such devices have no
real queue.

For request-based devices this flag was always set to 1 by default.

Now set it according to the flags on underlying devices. If there is at
least one device which should not contribute, set the flag to zero: If a
device, such as fast SSD storage, is not suitable for supplying entropy,
a request-based queue stacked over it will not be either.

Because the checking logic is exactly same as for the rotational flag,
share the iteration function with device_is_nonrot().

Signed-off-by: default avatarMilan Broz <mbroz@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent ba1cbad9

drivers/md/dm-table.c

+22 −4
Original line number Diff line number Diff line
@@ -1354,17 +1354,25 @@ static int device_is_nonrot(struct dm_target *ti, struct dm_dev *dev, 
	return q && blk_queue_nonrot(q);

}



static bool dm_table_is_nonrot(struct dm_table *t)

static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,

			     sector_t start, sector_t len, void *data)

{

	struct request_queue *q = bdev_get_queue(dev->bdev);



	return q && !blk_queue_add_random(q);

}



static bool dm_table_all_devices_attribute(struct dm_table *t,

					   iterate_devices_callout_fn func)

{

	struct dm_target *ti;

	unsigned i = 0;



	/* Ensure that all underlying device are non-rotational. */

	while (i < dm_table_get_num_targets(t)) {

		ti = dm_table_get_target(t, i++);



		if (!ti->type->iterate_devices ||

		    !ti->type->iterate_devices(ti, device_is_nonrot, NULL))

		    !ti->type->iterate_devices(ti, func, NULL))

			return 0;

	}
@@ -1396,13 +1404,23 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, 
	if (!dm_table_discard_zeroes_data(t))

		q->limits.discard_zeroes_data = 0;



	if (dm_table_is_nonrot(t))

	/* Ensure that all underlying devices are non-rotational. */

	if (dm_table_all_devices_attribute(t, device_is_nonrot))

		queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);

	else

		queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);



	dm_table_set_integrity(t);



	/*

	 * Determine whether or not this queue's I/O timings contribute

	 * to the entropy pool, Only request-based targets use this.

	 * Clear QUEUE_FLAG_ADD_RANDOM if any underlying device does not

	 * have it set.

	 */

	if (blk_queue_add_random(q) && dm_table_all_devices_attribute(t, device_is_not_random))

		queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, q);



	/*

	 * QUEUE_FLAG_STACKABLE must be set after all queue settings are

	 * visible to other CPUs because, once the flag is set, incoming bios

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