3 files changed, 29 insertions, 2 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 66bac226944e..059dfa048cc0 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1782,6 +1782,9 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
 
 
                 for (i = 0; i < multi->num_stripes; i++, stripe++) {
+                        if (!stripe->dev->can_discard)
+                                continue;
+
                         ret = btrfs_issue_discard(stripe->dev->bdev,
                                                   stripe->physical,
                                                   stripe->length);
@@ -1789,11 +1792,16 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
                                 discarded_bytes += stripe->length;
                         else if (ret != -EOPNOTSUPP)
                                 break;
+
+                        /*
+                         * Just in case we get back EOPNOTSUPP for some reason,
+                         * just ignore the return value so we don't screw up
+                         * people calling discard_extent.
+                         */
+                        ret = 0;
                 }
                 kfree(multi);
         }
-        if (discarded_bytes && ret == -EOPNOTSUPP)
-                ret = 0;
 
         if (actual_bytes)
                 *actual_bytes = discarded_bytes;
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3c5f2fcd82c1..a595f8775c37 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -517,6 +517,9 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
                         fs_devices->rw_devices--;
                 }
 
+                if (device->can_discard)
+                        fs_devices->num_can_discard--;
+
                 new_device = kmalloc(sizeof(*new_device), GFP_NOFS);
                 BUG_ON(!new_device);
                 memcpy(new_device, device, sizeof(*new_device));
@@ -525,6 +528,7 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
                 new_device->bdev = NULL;
                 new_device->writeable = 0;
                 new_device->in_fs_metadata = 0;
+                new_device->can_discard = 0;
                 list_replace_rcu(&device->dev_list, &new_device->dev_list);
 
                 call_rcu(&device->rcu, free_device);
@@ -564,6 +568,7 @@ int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                                 fmode_t flags, void *holder)
 {
+        struct request_queue *q;
         struct block_device *bdev;
         struct list_head *head = &fs_devices->devices;
         struct btrfs_device *device;
@@ -620,6 +625,12 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                         seeding = 0;
                 }
 
+                q = bdev_get_queue(bdev);
+                if (blk_queue_discard(q)) {
+                        device->can_discard = 1;
+                        fs_devices->num_can_discard++;
+                }
+
                 device->bdev = bdev;
                 device->in_fs_metadata = 0;
                 device->mode = flags;
@@ -1560,6 +1571,7 @@ error:
 
 int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 {
+        struct request_queue *q;
         struct btrfs_trans_handle *trans;
         struct btrfs_device *device;
         struct block_device *bdev;
@@ -1629,6 +1641,9 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 
         lock_chunks(root);
 
+        q = bdev_get_queue(bdev);
+        if (blk_queue_discard(q))
+                device->can_discard = 1;
         device->writeable = 1;
         device->work.func = pending_bios_fn;
         generate_random_uuid(device->uuid);
@@ -1664,6 +1679,8 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
         root->fs_info->fs_devices->num_devices++;
         root->fs_info->fs_devices->open_devices++;
         root->fs_info->fs_devices->rw_devices++;
+        if (device->can_discard)
+                root->fs_info->fs_devices->num_can_discard++;
         root->fs_info->fs_devices->total_rw_bytes += device->total_bytes;
 
         if (!blk_queue_nonrot(bdev_get_queue(bdev)))
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 7c12d61ae7ae..6d866db4e177 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -48,6 +48,7 @@ struct btrfs_device {
         int writeable;
         int in_fs_metadata;
         int missing;
+        int can_discard;
 
         spinlock_t io_lock;
 
@@ -104,6 +105,7 @@ struct btrfs_fs_devices {
         u64 rw_devices;
         u64 missing_devices;
         u64 total_rw_bytes;
+        u64 num_can_discard;
         struct block_device *latest_bdev;
 
         /* all of the devices in the FS, protected by a mutex