[SRU][N][PATCH 1/1] ext4: get rid of ppath in get_ext_path()

[Manuel Diewald]

From: Baokun Li <libaokun1 at huawei.com>

BugLink: https://bugs.launchpad.net/bugs/2158377

The use of path and ppath is now very confusing, so to make the code more
readable, pass path between functions uniformly, and get rid of ppath.

After getting rid of ppath in get_ext_path(), its caller may pass an error
pointer to ext4_free_ext_path(), so it needs to teach ext4_free_ext_path()
and ext4_ext_drop_refs() to skip the error pointer. No functional changes.

Signed-off-by: Baokun Li <libaokun1 at huawei.com>
Reviewed-by: Jan Kara <jack at suse.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin at linux.ibm.com>
Tested-by: Ojaswin Mujoo <ojaswin at linux.ibm.com>
Link: https://patch.msgid.link/20240822023545.1994557-13-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
(cherry picked from commit 6b854d552711aa33f59eda334e6d94a00d8825bb)
Signed-off-by: Manuel Diewald <manuel.diewald at canonical.com>
---
 fs/ext4/extents.c     |  5 +++--
 fs/ext4/move_extent.c | 34 +++++++++++++++++-----------------
 2 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 537b3f5795282..c1df5908be9e0 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -110,7 +110,7 @@ static void ext4_ext_drop_refs(struct ext4_ext_path *path)
 {
 	int depth, i;
 
-	if (!path)
+	if (IS_ERR_OR_NULL(path))
 		return;
 	depth = path->p_depth;
 	for (i = 0; i <= depth; i++, path++) {
@@ -121,6 +121,8 @@ static void ext4_ext_drop_refs(struct ext4_ext_path *path)
 
 void ext4_free_ext_path(struct ext4_ext_path *path)
 {
+	if (IS_ERR_OR_NULL(path))
+		return;
 	ext4_ext_drop_refs(path);
 	kfree(path);
 }
@@ -4191,7 +4193,6 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 	path = ext4_find_extent(inode, map->m_lblk, NULL, 0);
 	if (IS_ERR(path)) {
 		err = PTR_ERR(path);
-		path = NULL;
 		goto out;
 	}
 
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index e684654543199..681b48edc63f5 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -17,27 +17,23 @@
  * get_ext_path() - Find an extent path for designated logical block number.
  * @inode:	inode to be searched
  * @lblock:	logical block number to find an extent path
- * @ppath:	pointer to an extent path pointer (for output)
+ * @path:	pointer to an extent path
  *
- * ext4_find_extent wrapper. Return 0 on success, or a negative error value
- * on failure.
+ * ext4_find_extent wrapper. Return an extent path pointer on success,
+ * or an error pointer on failure.
  */
-static inline int
+static inline struct ext4_ext_path *
 get_ext_path(struct inode *inode, ext4_lblk_t lblock,
-		struct ext4_ext_path **ppath)
+	     struct ext4_ext_path *path)
 {
-	struct ext4_ext_path *path = *ppath;
-
-	*ppath = NULL;
 	path = ext4_find_extent(inode, lblock, path, EXT4_EX_NOCACHE);
 	if (IS_ERR(path))
-		return PTR_ERR(path);
+		return path;
 	if (path[ext_depth(inode)].p_ext == NULL) {
 		ext4_free_ext_path(path);
-		return -ENODATA;
+		return ERR_PTR(-ENODATA);
 	}
-	*ppath = path;
-	return 0;
+	return path;
 }
 
 /**
@@ -95,9 +91,11 @@ mext_check_coverage(struct inode *inode, ext4_lblk_t from, ext4_lblk_t count,
 	int ret = 0;
 	ext4_lblk_t last = from + count;
 	while (from < last) {
-		*err = get_ext_path(inode, from, &path);
-		if (*err)
-			goto out;
+		path = get_ext_path(inode, from, path);
+		if (IS_ERR(path)) {
+			*err = PTR_ERR(path);
+			return ret;
+		}
 		ext = path[ext_depth(inode)].p_ext;
 		if (unwritten != ext4_ext_is_unwritten(ext))
 			goto out;
@@ -633,9 +631,11 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
 		int offset_in_page;
 		int unwritten, cur_len;
 
-		ret = get_ext_path(orig_inode, o_start, &path);
-		if (ret)
+		path = get_ext_path(orig_inode, o_start, path);
+		if (IS_ERR(path)) {
+			ret = PTR_ERR(path);
 			goto out;
+		}
 		ex = path[path->p_depth].p_ext;
 		cur_blk = le32_to_cpu(ex->ee_block);
 		cur_len = ext4_ext_get_actual_len(ex);
-- 
2.34.1