ext4: refactor ext4_swap_extents() to reuse extents path

The ext4_find_extent() can update the extent path so it doesn't have to
allocate and free path repeatedly, thus reducing the consumption of memory
allocation and freeing in ext4_swap_extents().

Signed-off-by: Baokun Li <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Reviewed-by: Ojaswin Mujoo <[email protected]>
Tested-by: Ojaswin Mujoo <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>

Author: LiBaokun96

fs/ext4/extents.c

@@ -5663,25 +5663,21 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 		int e1_len, e2_len, len;
 		int split = 0;
 
-		path1 = ext4_find_extent(inode1, lblk1, NULL, EXT4_EX_NOCACHE);
+		path1 = ext4_find_extent(inode1, lblk1, path1, EXT4_EX_NOCACHE);
 		if (IS_ERR(path1)) {
 			*erp = PTR_ERR(path1);
-			path1 = NULL;
-		finish:
-			count = 0;
-			goto repeat;
+			goto errout;
 		}
-		path2 = ext4_find_extent(inode2, lblk2, NULL, EXT4_EX_NOCACHE);
+		path2 = ext4_find_extent(inode2, lblk2, path2, EXT4_EX_NOCACHE);
 		if (IS_ERR(path2)) {
 			*erp = PTR_ERR(path2);
-			path2 = NULL;
-			goto finish;
+			goto errout;
 		}
 		ex1 = path1[path1->p_depth].p_ext;
 		ex2 = path2[path2->p_depth].p_ext;
 		/* Do we have something to swap ? */
 		if (unlikely(!ex2 || !ex1))
-			goto finish;
+			goto errout;
 
 		e1_blk = le32_to_cpu(ex1->ee_block);
 		e2_blk = le32_to_cpu(ex2->ee_block);
@@ -5703,7 +5699,7 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 				next2 = e2_blk;
 			/* Do we have something to swap */
 			if (next1 == EXT_MAX_BLOCKS || next2 == EXT_MAX_BLOCKS)
-				goto finish;
+				goto errout;
 			/* Move to the rightest boundary */
 			len = next1 - lblk1;
 			if (len < next2 - lblk2)
@@ -5713,7 +5709,7 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 			lblk1 += len;
 			lblk2 += len;
 			count -= len;
-			goto repeat;
+			continue;
 		}
 
 		/* Prepare left boundary */
@@ -5723,7 +5719,7 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 							   path1, lblk1, 0);
 			if (IS_ERR(path1)) {
 				*erp = PTR_ERR(path1);
-				goto finish;
+				goto errout;
 			}
 		}
 		if (e2_blk < lblk2) {
@@ -5732,13 +5728,13 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 							   path2, lblk2, 0);
 			if (IS_ERR(path2)) {
 				*erp = PTR_ERR(path2);
-				goto finish;
+				goto errout;
 			}
 		}
 		/* ext4_split_extent_at() may result in leaf extent split,
 		 * path must to be revalidated. */
 		if (split)
-			goto repeat;
+			continue;
 
 		/* Prepare right boundary */
 		len = count;
@@ -5753,7 +5749,7 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 							path1, lblk1 + len, 0);
 			if (IS_ERR(path1)) {
 				*erp = PTR_ERR(path1);
-				goto finish;
+				goto errout;
 			}
 		}
 		if (len != e2_len) {
@@ -5762,21 +5758,21 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 							path2, lblk2 + len, 0);
 			if (IS_ERR(path2)) {
 				*erp = PTR_ERR(path2);
-				goto finish;
+				goto errout;
 			}
 		}
 		/* ext4_split_extent_at() may result in leaf extent split,
 		 * path must to be revalidated. */
 		if (split)
-			goto repeat;
+			continue;
 
 		BUG_ON(e2_len != e1_len);
 		*erp = ext4_ext_get_access(handle, inode1, path1 + path1->p_depth);
 		if (unlikely(*erp))
-			goto finish;
+			goto errout;
 		*erp = ext4_ext_get_access(handle, inode2, path2 + path2->p_depth);
 		if (unlikely(*erp))
-			goto finish;
+			goto errout;
 
 		/* Both extents are fully inside boundaries. Swap it now */
 		tmp_ex = *ex1;
@@ -5794,7 +5790,7 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 		*erp = ext4_ext_dirty(handle, inode2, path2 +
 				      path2->p_depth);
 		if (unlikely(*erp))
-			goto finish;
+			goto errout;
 		*erp = ext4_ext_dirty(handle, inode1, path1 +
 				      path1->p_depth);
 		/*
@@ -5804,17 +5800,17 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
 		 * aborted anyway.
 		 */
 		if (unlikely(*erp))
-			goto finish;
+			goto errout;
+
 		lblk1 += len;
 		lblk2 += len;
 		replaced_count += len;
 		count -= len;
-
-	repeat:
-		ext4_free_ext_path(path1);
-		ext4_free_ext_path(path2);
-		path1 = path2 = NULL;
 	}
+
+errout:
+	ext4_free_ext_path(path1);
+	ext4_free_ext_path(path2);
 	return replaced_count;
 }