Btrfs: remove non-sense btrfs_error_discard_extent() function

It doesn't do anything special, it just calls btrfs_discard_extent(),
so just remove it.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/ctree.h

@@ -3481,7 +3481,7 @@ void btrfs_put_block_group_cache(struct btrfs_fs_info *info);
 u64 btrfs_account_ro_block_groups_free_space(struct btrfs_space_info *sinfo);
 int btrfs_error_unpin_extent_range(struct btrfs_root *root,
 				   u64 start, u64 end);
-int btrfs_error_discard_extent(struct btrfs_root *root, u64 bytenr,
+int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
 			 u64 num_bytes, u64 *actual_bytes);
 int btrfs_force_chunk_alloc(struct btrfs_trans_handle *trans,
 			    struct btrfs_root *root, u64 type);

fs/btrfs/extent-tree.c

@@ -1889,7 +1889,7 @@ static int btrfs_issue_discard(struct block_device *bdev,
 	return blkdev_issue_discard(bdev, start >> 9, len >> 9, GFP_NOFS, 0);
 }
 
-static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
+int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
 			 u64 num_bytes, u64 *actual_bytes)
 {
 	int ret;
@@ -9698,12 +9698,6 @@ int btrfs_error_unpin_extent_range(struct btrfs_root *root, u64 start, u64 end)
 	return unpin_extent_range(root, start, end, false);
 }
 
-int btrfs_error_discard_extent(struct btrfs_root *root, u64 bytenr,
-			       u64 num_bytes, u64 *actual_bytes)
-{
-	return btrfs_discard_extent(root, bytenr, num_bytes, actual_bytes);
-}
-
 int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;

fs/btrfs/free-space-cache.c

@@ -2966,7 +2966,7 @@ static int do_trimming(struct btrfs_block_group_cache *block_group,
 	spin_unlock(&block_group->lock);
 	spin_unlock(&space_info->lock);
 
-	ret = btrfs_error_discard_extent(fs_info->extent_root,
+	ret = btrfs_discard_extent(fs_info->extent_root,
 				   start, bytes, &trimmed);
 	if (!ret)
 		*total_trimmed += trimmed;