btrfs: drop btrfs_device::can_discard to query directly

We can query the bdev directly when needed at btrfs_discard_extent()
so drop btrfs_device::can_discard.
Signed-off-by: NAnand Jain <anand.jain@oracle.com>
Suggested-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/extent-tree.c

@@ -2145,7 +2145,10 @@ int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
 
 		for (i = 0; i < bbio->num_stripes; i++, stripe++) {
 			u64 bytes;
-			if (!stripe->dev->can_discard)
+			struct request_queue *req_q;
+
+			req_q = bdev_get_queue(stripe->dev->bdev);
+			if (!blk_queue_discard(req_q))
 				continue;
 
 			ret = btrfs_issue_discard(stripe->dev->bdev,

fs/btrfs/volumes.c

@@ -698,8 +698,6 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
 	}
 
 	q = bdev_get_queue(bdev);
-	if (blk_queue_discard(q))
-		device->can_discard = 1;
 	if (!blk_queue_nonrot(q))
 		fs_devices->rotating = 1;
 
@@ -2433,8 +2431,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	}
 
 	q = bdev_get_queue(bdev);
-	if (blk_queue_discard(q))
-		device->can_discard = 1;
 	device->writeable = 1;
 	device->generation = trans->transid;
 	device->io_width = fs_info->sectorsize;
@@ -2585,7 +2581,6 @@ int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 				  struct btrfs_device *srcdev,
 				  struct btrfs_device **device_out)
 {
-	struct request_queue *q;
 	struct btrfs_device *device;
 	struct block_device *bdev;
 	struct list_head *devices;
@@ -2642,9 +2637,6 @@ int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	}
 	rcu_assign_pointer(device->name, name);
 
-	q = bdev_get_queue(bdev);
-	if (blk_queue_discard(q))
-		device->can_discard = 1;
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 	device->writeable = 1;
 	device->generation = 0;

fs/btrfs/volumes.h

@@ -72,7 +72,6 @@ struct btrfs_device {
 	int writeable;
 	int in_fs_metadata;
 	int missing;
-	int can_discard;
 	int is_tgtdev_for_dev_replace;
 	blk_status_t last_flush_error;
 	int flush_bio_sent;