ext4: get rid of ppath in ext4_split_extent_at()

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.

To get rid of the ppath in ext4_split_extent_at(), the following is done
here:

 * Free the extents path when an error is encountered.
 * Its caller needs to update ppath if it uses ppath.
 * Teach ext4_ext_show_leaf() to skip error pointer.

No functional changes.

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/20240822023545.1994557-16-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 47 insertions, 38 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 632f0a1a00b3..fcc06fd77af9 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -84,12 +84,11 @@ static void ext4_extent_block_csum_set(struct inode *inode,
 	et->et_checksum = ext4_extent_block_csum(inode, eh);
 }
 
-static int ext4_split_extent_at(handle_t *handle,
-			     struct inode *inode,
-			     struct ext4_ext_path **ppath,
-			     ext4_lblk_t split,
-			     int split_flag,
-			     int flags);
+static struct ext4_ext_path *ext4_split_extent_at(handle_t *handle,
+						  struct inode *inode,
+						  struct ext4_ext_path *path,
+						  ext4_lblk_t split,
+						  int split_flag, int flags);
 
 static int ext4_ext_trunc_restart_fn(struct inode *inode, int *dropped)
 {
@@ -341,9 +340,15 @@ ext4_force_split_extent_at(handle_t *handle, struct inode *inode,
 	if (nofail)
 		flags |= EXT4_GET_BLOCKS_METADATA_NOFAIL | EXT4_EX_NOFAIL;
 
-	return ext4_split_extent_at(handle, inode, ppath, lblk, unwritten ?
+	path = ext4_split_extent_at(handle, inode, path, lblk, unwritten ?
 			EXT4_EXT_MARK_UNWRIT1|EXT4_EXT_MARK_UNWRIT2 : 0,
 			flags);
+	if (IS_ERR(path)) {
+		*ppath = NULL;
+		return PTR_ERR(path);
+	}
+	*ppath = path;
+	return 0;
 }
 
 static int
@@ -694,7 +699,7 @@ static void ext4_ext_show_leaf(struct inode *inode, struct ext4_ext_path *path)
 	struct ext4_extent *ex;
 	int i;
 
-	if (!path)
+	if (IS_ERR_OR_NULL(path))
 		return;
 
 	eh = path[depth].p_hdr;
@@ -3175,16 +3180,14 @@ static int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
  *  a> the extent are splitted into two extent.
  *  b> split is not needed, and just mark the extent.
  *
- * return 0 on success.
+ * Return an extent path pointer on success, or an error pointer on failure.
  */
-static int ext4_split_extent_at(handle_t *handle,
-			     struct inode *inode,
-			     struct ext4_ext_path **ppath,
-			     ext4_lblk_t split,
-			     int split_flag,
-			     int flags)
+static struct ext4_ext_path *ext4_split_extent_at(handle_t *handle,
+						  struct inode *inode,
+						  struct ext4_ext_path *path,
+						  ext4_lblk_t split,
+						  int split_flag, int flags)
 {
-	struct ext4_ext_path *path = *ppath;
 	ext4_fsblk_t newblock;
 	ext4_lblk_t ee_block;
 	struct ext4_extent *ex, newex, orig_ex, zero_ex;
@@ -3255,14 +3258,12 @@ static int ext4_split_extent_at(handle_t *handle,
 		ext4_ext_mark_unwritten(ex2);
 
 	path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
-	if (!IS_ERR(path)) {
-		*ppath = path;
+	if (!IS_ERR(path))
 		goto out;
-	}
-	*ppath = NULL;
+
 	err = PTR_ERR(path);
 	if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM)
-		return err;
+		return path;
 
 	/*
 	 * Get a new path to try to zeroout or fix the extent length.
@@ -3272,16 +3273,14 @@ static int ext4_split_extent_at(handle_t *handle,
 	 * in ext4_da_update_reserve_space() due to an incorrect
 	 * ee_len causing the i_reserved_data_blocks exception.
 	 */
-	path = ext4_find_extent(inode, ee_block, NULL,
-				flags | EXT4_EX_NOFAIL);
+	path = ext4_find_extent(inode, ee_block, NULL, flags | EXT4_EX_NOFAIL);
 	if (IS_ERR(path)) {
 		EXT4_ERROR_INODE(inode, "Failed split extent on %u, err %ld",
 				 split, PTR_ERR(path));
-		return PTR_ERR(path);
+		return path;
 	}
 	depth = ext_depth(inode);
 	ex = path[depth].p_ext;
-	*ppath = path;
 
 	if (EXT4_EXT_MAY_ZEROOUT & split_flag) {
 		if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) {
@@ -3333,10 +3332,13 @@ fix_extent_len:
 	 * and err is a non-zero error code.
 	 */
 	ext4_ext_dirty(handle, inode, path + path->p_depth);
-	return err;
 out:
+	if (err) {
+		ext4_free_ext_path(path);
+		path = ERR_PTR(err);
+	}
 	ext4_ext_show_leaf(inode, path);
-	return err;
+	return path;
 }
 
 /*
@@ -3380,10 +3382,14 @@ static int ext4_split_extent(handle_t *handle,
 				       EXT4_EXT_MARK_UNWRIT2;
 		if (split_flag & EXT4_EXT_DATA_VALID2)
 			split_flag1 |= EXT4_EXT_DATA_VALID1;
-		err = ext4_split_extent_at(handle, inode, ppath,
+		path = ext4_split_extent_at(handle, inode, path,
 				map->m_lblk + map->m_len, split_flag1, flags1);
-		if (err)
+		if (IS_ERR(path)) {
+			err = PTR_ERR(path);
+			*ppath = NULL;
 			goto out;
+		}
+		*ppath = path;
 	} else {
 		allocated = ee_len - (map->m_lblk - ee_block);
 	}
@@ -3391,7 +3397,7 @@ static int ext4_split_extent(handle_t *handle,
 	 * Update path is required because previous ext4_split_extent_at() may
 	 * result in split of original leaf or extent zeroout.
 	 */
-	path = ext4_find_extent(inode, map->m_lblk, *ppath, flags);
+	path = ext4_find_extent(inode, map->m_lblk, path, flags);
 	if (IS_ERR(path)) {
 		*ppath = NULL;
 		return PTR_ERR(path);
@@ -3413,13 +3419,17 @@ static int ext4_split_extent(handle_t *handle,
 			split_flag1 |= split_flag & (EXT4_EXT_MAY_ZEROOUT |
 						     EXT4_EXT_MARK_UNWRIT2);
 		}
-		err = ext4_split_extent_at(handle, inode, ppath,
+		path = ext4_split_extent_at(handle, inode, path,
 				map->m_lblk, split_flag1, flags);
-		if (err)
+		if (IS_ERR(path)) {
+			err = PTR_ERR(path);
+			*ppath = NULL;
 			goto out;
+		}
+		*ppath = path;
 	}
 
-	ext4_ext_show_leaf(inode, *ppath);
+	ext4_ext_show_leaf(inode, path);
 out:
 	return err ? err : allocated;
 }
@@ -5580,22 +5590,21 @@ static int ext4_insert_range(struct file *file, loff_t offset, loff_t len)
 			if (ext4_ext_is_unwritten(extent))
 				split_flag = EXT4_EXT_MARK_UNWRIT1 |
 					EXT4_EXT_MARK_UNWRIT2;
-			ret = ext4_split_extent_at(handle, inode, &path,
+			path = ext4_split_extent_at(handle, inode, path,
 					offset_lblk, split_flag,
 					EXT4_EX_NOCACHE |
 					EXT4_GET_BLOCKS_PRE_IO |
 					EXT4_GET_BLOCKS_METADATA_NOFAIL);
 		}
 
-		ext4_free_ext_path(path);
-		if (ret < 0) {
+		if (IS_ERR(path)) {
 			up_write(&EXT4_I(inode)->i_data_sem);
+			ret = PTR_ERR(path);
 			goto out_stop;
 		}
-	} else {
-		ext4_free_ext_path(path);
 	}
 
+	ext4_free_ext_path(path);
 	ext4_es_remove_extent(inode, offset_lblk, EXT_MAX_BLOCKS - offset_lblk);
 
 	/*