ext4: ensure enough credits in ext4_ext_shift_path_extents

hulk inclusion
category: bugfix
bugzilla: 181871, https://gitee.com/openeuler/kernel/issues/I4DP71
CVE: NA
---------------------------

Like ext4_ext_rm_leaf, we can ensure that there are enough credits
before every call that will consume credits.  As part of this fix we
fold the functionality of ext4_access_path() into
ext4_ext_shift_path_extents().  This change is needed as a preparation
for the next bugfix patch.

Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20210903062748.4118886-3-yangerkun@huawei.comSigned-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Conflicts:
	fs/ext4/extents.c
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/ext4/extents.c

@@ -5252,36 +5252,6 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	return error;
 }
 
-/*
- * ext4_access_path:
- * Function to access the path buffer for marking it dirty.
- * It also checks if there are sufficient credits left in the journal handle
- * to update path.
- */
-static int
-ext4_access_path(handle_t *handle, struct inode *inode,
-		struct ext4_ext_path *path)
-{
-	int credits, err;
-
-	if (!ext4_handle_valid(handle))
-		return 0;
-
-	/*
-	 * Check if need to extend journal credits
-	 * 3 for leaf, sb, and inode plus 2 (bmap and group
-	 * descriptor) for each block group; assume two block
-	 * groups
-	 */
-	credits = ext4_writepage_trans_blocks(inode);
-	err = ext4_datasem_ensure_credits(handle, inode, 7, credits, 0);
-	if (err < 0)
-		return err;
-
-	err = ext4_ext_get_access(handle, inode, path);
-	return err;
-}
-
 /*
  * ext4_ext_shift_path_extents:
  * Shift the extents of a path structure lying between path[depth].p_ext
@@ -5296,6 +5266,7 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
 	int depth, err = 0;
 	struct ext4_extent *ex_start, *ex_last;
 	bool update = false;
+	int credits, restart_credits;
 	depth = path->p_depth;
 
 	while (depth >= 0) {
@@ -5305,13 +5276,23 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
 				return -EFSCORRUPTED;
 
 			ex_last = EXT_LAST_EXTENT(path[depth].p_hdr);
+			/* leaf + sb + inode */
+			credits = 3;
+			if (ex_start == EXT_FIRST_EXTENT(path[depth].p_hdr)) {
+				update = true;
+				/* extent tree + sb + inode */
+				credits = depth + 2;
+			}
 
-			err = ext4_access_path(handle, inode, path + depth);
+			restart_credits = ext4_writepage_trans_blocks(inode);
+			err = ext4_datasem_ensure_credits(handle, inode, credits,
+					restart_credits, 0);
 			if (err)
 				goto out;
 
-			if (ex_start == EXT_FIRST_EXTENT(path[depth].p_hdr))
-				update = true;
+			err = ext4_ext_get_access(handle, inode, path + depth);
+			if (err)
+				goto out;
 
 			while (ex_start <= ex_last) {
 				if (SHIFT == SHIFT_LEFT) {
@@ -5342,7 +5323,7 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,
 		}
 
 		/* Update index too */
-		err = ext4_access_path(handle, inode, path + depth);
+		err = ext4_ext_get_access(handle, inode, path + depth);
 		if (err)
 			goto out;