ext4: make some fast commit functions reuse extents path

The ext4_find_extent() can update the extent path so that it does not have
to allocate and free the path repeatedly, thus reducing the consumption of
memory allocation and freeing in the following functions:

    ext4_ext_clear_bb
    ext4_ext_replay_set_iblocks
    ext4_fc_replay_add_range
    ext4_fc_set_bitmaps_and_counters

No functional changes. Note that ext4_find_extent() does not support error
pointers, so in this case set path to NULL first.
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/20240822023545.1994557-25-libaokun@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents.c

@@ -6033,12 +6033,9 @@ int ext4_ext_replay_set_iblocks(struct inode *inode)
 	if (IS_ERR(path))
 		return PTR_ERR(path);
 	ex = path[path->p_depth].p_ext;
-	if (!ex) {
-		ext4_free_ext_path(path);
+	if (!ex)
 		goto out;
-	}
 	end = le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex);
-	ext4_free_ext_path(path);
 
 	/* Count the number of data blocks */
 	cur = 0;
@@ -6064,32 +6061,28 @@ int ext4_ext_replay_set_iblocks(struct inode *inode)
 	ret = skip_hole(inode, &cur);
 	if (ret < 0)
 		goto out;
-	path = ext4_find_extent(inode, cur, NULL, 0);
+	path = ext4_find_extent(inode, cur, path, 0);
 	if (IS_ERR(path))
 		goto out;
 	numblks += path->p_depth;
-	ext4_free_ext_path(path);
 	while (cur < end) {
-		path = ext4_find_extent(inode, cur, NULL, 0);
+		path = ext4_find_extent(inode, cur, path, 0);
 		if (IS_ERR(path))
 			break;
 		ex = path[path->p_depth].p_ext;
-		if (!ex) {
-			ext4_free_ext_path(path);
-			return 0;
-		}
+		if (!ex)
+			goto cleanup;
+
 		cur = max(cur + 1, le32_to_cpu(ex->ee_block) +
 					ext4_ext_get_actual_len(ex));
 		ret = skip_hole(inode, &cur);
-		if (ret < 0) {
-			ext4_free_ext_path(path);
+		if (ret < 0)
 			break;
-		}
-		path2 = ext4_find_extent(inode, cur, NULL, 0);
-		if (IS_ERR(path2)) {
-			ext4_free_ext_path(path);
+
+		path2 = ext4_find_extent(inode, cur, path2, 0);
+		if (IS_ERR(path2))
 			break;
-		}
+
 		for (i = 0; i <= max(path->p_depth, path2->p_depth); i++) {
 			cmp1 = cmp2 = 0;
 			if (i <= path->p_depth)
@@ -6101,13 +6094,14 @@ int ext4_ext_replay_set_iblocks(struct inode *inode)
 			if (cmp1 != cmp2 && cmp2 != 0)
 				numblks++;
 		}
-		ext4_free_ext_path(path);
-		ext4_free_ext_path(path2);
 	}
 
 out:
 	inode->i_blocks = numblks << (inode->i_sb->s_blocksize_bits - 9);
 	ext4_mark_inode_dirty(NULL, inode);
+cleanup:
+	ext4_free_ext_path(path);
+	ext4_free_ext_path(path2);
 	return 0;
 }
 
@@ -6128,12 +6122,9 @@ int ext4_ext_clear_bb(struct inode *inode)
 	if (IS_ERR(path))
 		return PTR_ERR(path);
 	ex = path[path->p_depth].p_ext;
-	if (!ex) {
-		ext4_free_ext_path(path);
-		return 0;
-	}
+	if (!ex)
+		goto out;
 	end = le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex);
-	ext4_free_ext_path(path);
 
 	cur = 0;
 	while (cur < end) {
@@ -6143,16 +6134,16 @@ int ext4_ext_clear_bb(struct inode *inode)
 		if (ret < 0)
 			break;
 		if (ret > 0) {
-			path = ext4_find_extent(inode, map.m_lblk, NULL, 0);
-			if (!IS_ERR_OR_NULL(path)) {
+			path = ext4_find_extent(inode, map.m_lblk, path, 0);
+			if (!IS_ERR(path)) {
 				for (j = 0; j < path->p_depth; j++) {
-
 					ext4_mb_mark_bb(inode->i_sb,
 							path[j].p_block, 1, false);
 					ext4_fc_record_regions(inode->i_sb, inode->i_ino,
 							0, path[j].p_block, 1, 1);
 				}
-				ext4_free_ext_path(path);
+			} else {
+				path = NULL;
 			}
 			ext4_mb_mark_bb(inode->i_sb, map.m_pblk, map.m_len, false);
 			ext4_fc_record_regions(inode->i_sb, inode->i_ino,
@@ -6161,5 +6152,7 @@ int ext4_ext_clear_bb(struct inode *inode)
 		cur = cur + map.m_len;
 	}
 
+out:
+	ext4_free_ext_path(path);
 	return 0;
 }

fs/ext4/fast_commit.c

@@ -1792,7 +1792,7 @@ static int ext4_fc_replay_add_range(struct super_block *sb,
 
 		if (ret == 0) {
 			/* Range is not mapped */
-			path = ext4_find_extent(inode, cur, NULL, 0);
+			path = ext4_find_extent(inode, cur, path, 0);
 			if (IS_ERR(path))
 				goto out;
 			memset(&newex, 0, sizeof(newex));
@@ -1808,7 +1808,6 @@ static int ext4_fc_replay_add_range(struct super_block *sb,
 			up_write((&EXT4_I(inode)->i_data_sem));
 			if (IS_ERR(path))
 				goto out;
-			ext4_free_ext_path(path);
 			goto next;
 		}
 
@@ -1856,6 +1855,7 @@ static int ext4_fc_replay_add_range(struct super_block *sb,
 	ext4_ext_replay_shrink_inode(inode, i_size_read(inode) >>
 					sb->s_blocksize_bits);
 out:
+	ext4_free_ext_path(path);
 	iput(inode);
 	return 0;
 }
@@ -1956,12 +1956,13 @@ static void ext4_fc_set_bitmaps_and_counters(struct super_block *sb)
 				break;
 
 			if (ret > 0) {
-				path = ext4_find_extent(inode, map.m_lblk, NULL, 0);
+				path = ext4_find_extent(inode, map.m_lblk, path, 0);
 				if (!IS_ERR(path)) {
 					for (j = 0; j < path->p_depth; j++)
 						ext4_mb_mark_bb(inode->i_sb,
 							path[j].p_block, 1, true);
-					ext4_free_ext_path(path);
+				} else {
+					path = NULL;
 				}
 				cur += ret;
 				ext4_mb_mark_bb(inode->i_sb, map.m_pblk,
@@ -1972,6 +1973,8 @@ static void ext4_fc_set_bitmaps_and_counters(struct super_block *sb)
 		}
 		iput(inode);
 	}
+
+	ext4_free_ext_path(path);
 }
 
 /*