ext4: allow a NULL argument to ext4_ext_drop_refs()

Teach ext4_ext_drop_refs() to accept a NULL argument, much like
kfree().  This allows us to drop a lot of checks to make sure path is
non-NULL before calling ext4_ext_drop_refs().
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents.c

@@ -709,9 +709,11 @@ static void ext4_ext_show_move(struct inode *inode, struct ext4_ext_path *path,
 
 void ext4_ext_drop_refs(struct ext4_ext_path *path)
 {
-	int depth = path->p_depth;
-	int i;
+	int depth, i;
 
+	if (!path)
+		return;
+	depth = path->p_depth;
 	for (i = 0; i <= depth; i++, path++)
 		if (path->p_bh) {
 			brelse(path->p_bh);
@@ -2125,10 +2127,8 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
 	err = ext4_ext_dirty(handle, inode, path + path->p_depth);
 
 cleanup:
-	if (npath) {
 	ext4_ext_drop_refs(npath);
 	kfree(npath);
-	}
 	return err;
 }
 
@@ -2283,11 +2283,8 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
 		block = es.es_lblk + es.es_len;
 	}
 
-	if (path) {
 	ext4_ext_drop_refs(path);
 	kfree(path);
-	}
-
 	return err;
 }
 
@@ -3018,11 +3015,9 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start,
 		}
 	}
 out:
-	if (path) {
 	ext4_ext_drop_refs(path);
 	kfree(path);
 	path = NULL;
-	}
 	if (err == -EAGAIN)
 		goto again;
 	ext4_journal_stop(handle);
@@ -4611,10 +4606,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 	map->m_pblk = newblock;
 	map->m_len = allocated;
 out2:
-	if (path) {
 	ext4_ext_drop_refs(path);
 	kfree(path);
-	}
 
 	trace_ext4_ext_map_blocks_exit(inode, flags, map,
 				       err ? err : allocated);
@@ -5693,16 +5686,11 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 		count -= len;
 
 	repeat:
-		if (path1) {
 		ext4_ext_drop_refs(path1);
 		kfree(path1);
-			path1 = NULL;
-		}
-		if (path2) {
 		ext4_ext_drop_refs(path2);
 		kfree(path2);
-			path2 = NULL;
-		}
+		path1 = path2 = NULL;
 	}
 	return replaced_count;
 }

fs/ext4/extents_status.c

@@ -499,10 +499,8 @@ static void ext4_es_insert_extent_ext_check(struct inode *inode,
 		}
 	}
 out:
-	if (path) {
 	ext4_ext_drop_refs(path);
 	kfree(path);
-	}
 }
 
 static void ext4_es_insert_extent_ind_check(struct inode *inode,

fs/ext4/migrate.c

@@ -84,10 +84,8 @@ static int finish_range(handle_t *handle, struct inode *inode,
 	retval = ext4_ext_insert_extent(handle, inode, &path, &newext, 0);
 err_out:
 	up_write((&EXT4_I(inode)->i_data_sem));
-	if (path) {
 	ext4_ext_drop_refs(path);
 	kfree(path);
-	}
 	lb->first_pblock = 0;
 	return retval;
 }

fs/ext4/move_extent.c

@@ -113,10 +113,8 @@ mext_check_coverage(struct inode *inode, ext4_lblk_t from, ext4_lblk_t count,
 	}
 	ret = 1;
 out:
-	if (path) {
 	ext4_ext_drop_refs(path);
 	kfree(path);
-	}
 	return ret;
 }
 
@@ -711,12 +709,10 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
 		o_start += cur_len;
 		d_start += cur_len;
 	repeat:
-		if (path) {
 		ext4_ext_drop_refs(path);
 		kfree(path);
 		path = NULL;
 	}
-	}
 	*moved_len = o_start - orig_blk;
 	if (*moved_len > len)
 		*moved_len = len;
@@ -727,10 +723,8 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
 		ext4_discard_preallocations(donor_inode);
 	}
 
-	if (path) {
 	ext4_ext_drop_refs(path);
 	kfree(path);
-	}
 	ext4_double_up_write_data_sem(orig_inode, donor_inode);
 	ext4_inode_resume_unlocked_dio(orig_inode);
 	ext4_inode_resume_unlocked_dio(donor_inode);