1 files changed, 23 insertions, 2 deletions

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index fa211d80fc0a..21014836bdbf 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -138,6 +138,7 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
         struct linear_conf *conf;
         struct md_rdev *rdev;
         int i, cnt;
+        bool discard_supported = false;
 
         conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(struct dev_info),
                         GFP_KERNEL);
@@ -171,6 +172,8 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
                 conf->array_sectors += rdev->sectors;
                 cnt++;
 
+                if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+                        discard_supported = true;
         }
         if (cnt != raid_disks) {
                 printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
@@ -178,6 +181,11 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
                 goto out;
         }
 
+        if (!discard_supported)
+                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+        else
+                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
         /*
          * Here we calculate the device offsets.
          */
@@ -244,7 +252,9 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
         if (!newconf)
                 return -ENOMEM;
 
-        oldconf = rcu_dereference(mddev->private);
+        oldconf = rcu_dereference_protected(mddev->private,
+                                            lockdep_is_held(
+                                                    &mddev->reconfig_mutex));
         mddev->raid_disks++;
         rcu_assign_pointer(mddev->private, newconf);
         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
@@ -256,7 +266,10 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
 
 static int linear_stop (struct mddev *mddev)
 {
-        struct linear_conf *conf = mddev->private;
+        struct linear_conf *conf =
+                rcu_dereference_protected(mddev->private,
+                                          lockdep_is_held(
+                                                  &mddev->reconfig_mutex));
 
         /*
          * We do not require rcu protection here since
@@ -326,6 +339,14 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio)
         bio->bi_sector = bio->bi_sector - start_sector
                 + tmp_dev->rdev->data_offset;
         rcu_read_unlock();
+
+        if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+                     !blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
+                /* Just ignore it */
+                bio_endio(bio, 0);
+                return;
+        }
+
         generic_make_request(bio);
 }