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authorMilan Broz <mbroz@redhat.com>2012-09-26 23:45:43 +0100
committerAlasdair G Kergon <agk@redhat.com>2012-09-26 23:45:43 +0100
commitc3c4555edd10dbc0b388a0125b9c50de5e79af05 (patch)
tree6beec93488391802ad897ebeb4c208af432a5791
parentba1cbad93dd47223b1f3b8edd50dd9ef2abcb2ed (diff)
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: Milan Broz <mbroz@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Alasdair G Kergon <agk@redhat.com>
-rw-r--r--drivers/md/dm-table.c26
1 files changed, 22 insertions, 4 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f90069029aae..77b90ae66991 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -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;
}
@@ -1396,7 +1404,8 @@ 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);
@@ -1404,6 +1413,15 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *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
* are processed by request-based dm, which refers to the queue