dm: lock limits when reading them

Lock queue limits when reading them, so that we don't read halfway
modified values.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 69d4a0e0e613ac667b24cd2d93c913cfd9f1e3c0..933e01f3fab40d71ad8b3964d1552eb66475b7fa 100644 (file)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -431,6 +431,7 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
                return 0;
        }
 
+       mutex_lock(&q->limits_lock);
        if (blk_stack_limits(limits, &q->limits,
                        get_start_sect(bdev) + start) < 0)
                DMWARN("%s: adding target device %pg caused an alignment inconsistency: "
@@ -448,6 +449,7 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
         */
        if (!dm_target_has_integrity(ti->type))
                queue_limits_stack_integrity_bdev(limits, bdev);
+       mutex_unlock(&q->limits_lock);
        return 0;
 }
 
@@ -1734,8 +1736,12 @@ static int device_not_write_zeroes_capable(struct dm_target *ti, struct dm_dev *
                                           sector_t start, sector_t len, void *data)
 {
        struct request_queue *q = bdev_get_queue(dev->bdev);
+       int b;
 
-       return !q->limits.max_write_zeroes_sectors;
+       mutex_lock(&q->limits_lock);
+       b = !q->limits.max_write_zeroes_sectors;
+       mutex_unlock(&q->limits_lock);
+       return b;
 }
 
 static bool dm_table_supports_write_zeroes(struct dm_table *t)