ext4: get rid of ppath in ext4_ext_insert_extent()

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_ext_insert_extent(), the following is done
here:

 * Free the extents path when an error is encountered.
 * Its caller needs to update ppath if it uses ppath.
 * Free path when npath is used, free npath when it is not used.
 * The got_allocated_blocks label in ext4_ext_map_blocks() does not
   update err now, so err is updated to 0 if the err returned by
   ext4_ext_search_right() is greater than 0 and is about to enter
   got_allocated_blocks.

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/20240822023545.1994557-15-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -3710,9 +3710,10 @@ extern int ext4_map_blocks(handle_t *handle, struct inode *inode,
 extern int ext4_ext_calc_credits_for_single_extent(struct inode *inode,
 						   int num,
 						   struct ext4_ext_path *path);
-extern int ext4_ext_insert_extent(handle_t *, struct inode *,
+extern struct ext4_ext_path *ext4_ext_insert_extent(
-				  struct ext4_ext_path **,
+				handle_t *handle, struct inode *inode,
-				  struct ext4_extent *, int);
+				struct ext4_ext_path *path,
+				struct ext4_extent *newext, int gb_flags);
 extern struct ext4_ext_path *ext4_find_extent(struct inode *, ext4_lblk_t,
 					      struct ext4_ext_path *,
 					      int flags);

fs/ext4/extents.c

@@ -1975,16 +1975,15 @@ out:
  * inserts requested extent as new one into the tree,
  * creating new leaf in the no-space case.
  */
-int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
+struct ext4_ext_path *
-				struct ext4_ext_path **ppath,
+ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
-				struct ext4_extent *newext, int gb_flags)
+		       struct ext4_ext_path *path,
+		       struct ext4_extent *newext, int gb_flags)
 {
-	struct ext4_ext_path *path = *ppath;
 	struct ext4_extent_header *eh;
 	struct ext4_extent *ex, *fex;
 	struct ext4_extent *nearex; /* nearest extent */
-	struct ext4_ext_path *npath = NULL;
+	int depth, len, err = 0;
-	int depth, len, err;
 	ext4_lblk_t next;
 	int mb_flags = 0, unwritten;
 
@@ -1992,14 +1991,16 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
 		mb_flags |= EXT4_MB_DELALLOC_RESERVED;
 	if (unlikely(ext4_ext_get_actual_len(newext) == 0)) {
 		EXT4_ERROR_INODE(inode, "ext4_ext_get_actual_len(newext) == 0");
-		return -EFSCORRUPTED;
+		err = -EFSCORRUPTED;
+		goto errout;
 	}
 	depth = ext_depth(inode);
 	ex = path[depth].p_ext;
 	eh = path[depth].p_hdr;
 	if (unlikely(path[depth].p_hdr == NULL)) {
 		EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
-		return -EFSCORRUPTED;
+		err = -EFSCORRUPTED;
+		goto errout;
 	}
 
 	/* try to insert block into found extent and return */
@@ -2037,7 +2038,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
 			err = ext4_ext_get_access(handle, inode,
 						  path + depth);
 			if (err)
-				return err;
+				goto errout;
 			unwritten = ext4_ext_is_unwritten(ex);
 			ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
 					+ ext4_ext_get_actual_len(newext));
@@ -2062,7 +2063,7 @@ prepend:
 			err = ext4_ext_get_access(handle, inode,
 						  path + depth);
 			if (err)
-				return err;
+				goto errout;
 
 			unwritten = ext4_ext_is_unwritten(ex);
 			ex->ee_block = newext->ee_block;
@@ -2087,21 +2088,26 @@ prepend:
 	if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block))
 		next = ext4_ext_next_leaf_block(path);
 	if (next != EXT_MAX_BLOCKS) {
+		struct ext4_ext_path *npath;
+
 		ext_debug(inode, "next leaf block - %u\n", next);
-		BUG_ON(npath != NULL);
 		npath = ext4_find_extent(inode, next, NULL, gb_flags);
-		if (IS_ERR(npath))
+		if (IS_ERR(npath)) {
-			return PTR_ERR(npath);
+			err = PTR_ERR(npath);
+			goto errout;
+		}
 		BUG_ON(npath->p_depth != path->p_depth);
 		eh = npath[depth].p_hdr;
 		if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max)) {
 			ext_debug(inode, "next leaf isn't full(%d)\n",
 				  le16_to_cpu(eh->eh_entries));
+			ext4_free_ext_path(path);
 			path = npath;
 			goto has_space;
 		}
 		ext_debug(inode, "next leaf has no free space(%d,%d)\n",
 			  le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
+		ext4_free_ext_path(npath);
 	}
 
 	/*
@@ -2112,12 +2118,8 @@ prepend:
 		mb_flags |= EXT4_MB_USE_RESERVED;
 	path = ext4_ext_create_new_leaf(handle, inode, mb_flags, gb_flags,
 					path, newext);
-	if (IS_ERR(path)) {
+	if (IS_ERR(path))
-		*ppath = NULL;
+		return path;
-		err = PTR_ERR(path);
-		goto cleanup;
-	}
-	*ppath = path;
 	depth = ext_depth(inode);
 	eh = path[depth].p_hdr;
 
@@ -2126,7 +2128,7 @@ has_space:
 
 	err = ext4_ext_get_access(handle, inode, path + depth);
 	if (err)
-		goto cleanup;
+		goto errout;
 
 	if (!nearex) {
 		/* there is no extent in this leaf, create first one */
@@ -2184,17 +2186,20 @@ merge:
 	if (!(gb_flags & EXT4_GET_BLOCKS_PRE_IO))
 		ext4_ext_try_to_merge(handle, inode, path, nearex);
 
-
 	/* time to correct all indexes above */
 	err = ext4_ext_correct_indexes(handle, inode, path);
 	if (err)
-		goto cleanup;
+		goto errout;
 
 	err = ext4_ext_dirty(handle, inode, path + path->p_depth);
+	if (err)
+		goto errout;
 
-cleanup:
+	return path;
-	ext4_free_ext_path(npath);
+
-	return err;
+errout:
+	ext4_free_ext_path(path);
+	return ERR_PTR(err);
 }
 
 static int ext4_fill_es_cache_info(struct inode *inode,
@@ -3249,24 +3254,29 @@ static int ext4_split_extent_at(handle_t *handle,
 	if (split_flag & EXT4_EXT_MARK_UNWRIT2)
 		ext4_ext_mark_unwritten(ex2);
 
-	err = ext4_ext_insert_extent(handle, inode, ppath, &newex, flags);
+	path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
-	if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM)
+	if (!IS_ERR(path)) {
+		*ppath = path;
 		goto out;
+	}
+	*ppath = NULL;
+	err = PTR_ERR(path);
+	if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM)
+		return err;
 
 	/*
-	 * Update path is required because previous ext4_ext_insert_extent()
+	 * Get a new path to try to zeroout or fix the extent length.
-	 * may have freed or reallocated the path. Using EXT4_EX_NOFAIL
+	 * Using EXT4_EX_NOFAIL guarantees that ext4_find_extent()
-	 * guarantees that ext4_find_extent() will not return -ENOMEM,
+	 * will not return -ENOMEM, otherwise -ENOMEM will cause a
-	 * otherwise -ENOMEM will cause a retry in do_writepages(), and a
+	 * retry in do_writepages(), and a WARN_ON may be triggered
-	 * WARN_ON may be triggered in ext4_da_update_reserve_space() due to
+	 * in ext4_da_update_reserve_space() due to an incorrect
-	 * an incorrect ee_len causing the i_reserved_data_blocks exception.
+	 * ee_len causing the i_reserved_data_blocks exception.
 	 */
-	path = ext4_find_extent(inode, ee_block, *ppath,
+	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));
-		*ppath = NULL;
 		return PTR_ERR(path);
 	}
 	depth = ext_depth(inode);
@@ -3325,7 +3335,7 @@ fix_extent_len:
 	ext4_ext_dirty(handle, inode, path + path->p_depth);
 	return err;
 out:
-	ext4_ext_show_leaf(inode, *ppath);
+	ext4_ext_show_leaf(inode, path);
 	return err;
 }
 
@@ -4315,6 +4325,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 	    get_implied_cluster_alloc(inode->i_sb, map, &ex2, path)) {
 		ar.len = allocated = map->m_len;
 		newblock = map->m_pblk;
+		err = 0;
 		goto got_allocated_blocks;
 	}
 
@@ -4387,8 +4398,9 @@ got_allocated_blocks:
 		map->m_flags |= EXT4_MAP_UNWRITTEN;
 	}
 
-	err = ext4_ext_insert_extent(handle, inode, &path, &newex, flags);
+	path = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
-	if (err) {
+	if (IS_ERR(path)) {
+		err = PTR_ERR(path);
 		if (allocated_clusters) {
 			int fb_flags = 0;
 

fs/ext4/fast_commit.c

@@ -1803,12 +1803,12 @@ static int ext4_fc_replay_add_range(struct super_block *sb,
 			if (ext4_ext_is_unwritten(ex))
 				ext4_ext_mark_unwritten(&newex);
 			down_write(&EXT4_I(inode)->i_data_sem);
-			ret = ext4_ext_insert_extent(
+			path = ext4_ext_insert_extent(NULL, inode,
-				NULL, inode, &path, &newex, 0);
+						      path, &newex, 0);
 			up_write((&EXT4_I(inode)->i_data_sem));
-			ext4_free_ext_path(path);
+			if (IS_ERR(path))
-			if (ret)
 				goto out;
+			ext4_free_ext_path(path);
 			goto next;
 		}
 

fs/ext4/migrate.c

@@ -37,7 +37,6 @@ static int finish_range(handle_t *handle, struct inode *inode,
 	path = ext4_find_extent(inode, lb->first_block, NULL, 0);
 	if (IS_ERR(path)) {
 		retval = PTR_ERR(path);
-		path = NULL;
 		goto err_out;
 	}
 
@@ -53,7 +52,9 @@ static int finish_range(handle_t *handle, struct inode *inode,
 	retval = ext4_datasem_ensure_credits(handle, inode, needed, needed, 0);
 	if (retval < 0)
 		goto err_out;
-	retval = ext4_ext_insert_extent(handle, inode, &path, &newext, 0);
+	path = ext4_ext_insert_extent(handle, inode, path, &newext, 0);
+	if (IS_ERR(path))
+		retval = PTR_ERR(path);
 err_out:
 	up_write((&EXT4_I(inode)->i_data_sem));
 	ext4_free_ext_path(path);