ovl: factor out ovl_free_entry() and ovl_stack_*() helpers

In preparation for moving lowerstack into ovl_inode.

Note that in ovl_lookup() the temp stack dentry refs are now cloned
into the final ovl_lowerstack instead of being transferred, so cleanup
always needs to call ovl_stack_free(stack).
Reviewed-by: Alexander Larsson <alexl@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/namei.c

@@ -907,8 +907,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 
 	if (!d.stop && ovl_numlower(poe)) {
 		err = -ENOMEM;
-		stack = kcalloc(ofs->numlayer - 1, sizeof(struct ovl_path),
-				GFP_KERNEL);
+		stack = ovl_stack_alloc(ofs->numlayer - 1);
 		if (!stack)
 			goto out_put_upper;
 	}
@@ -1073,7 +1072,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	if (!oe)
 		goto out_put;
 
-	memcpy(ovl_lowerstack(oe), stack, sizeof(struct ovl_path) * ctr);
+	ovl_stack_cpy(ovl_lowerstack(oe), stack, ctr);
 	dentry->d_fsdata = oe;
 
 	if (upperopaque)
@@ -1131,18 +1130,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		kfree(origin_path);
 	}
 	dput(index);
-	kfree(stack);
+	ovl_stack_free(stack, ctr);
 	kfree(d.redirect);
 	return d_splice_alias(inode, dentry);
 
 out_free_oe:
 	dentry->d_fsdata = NULL;
-	kfree(oe);
+	ovl_free_entry(oe);
 out_put:
 	dput(index);
-	for (i = 0; i < ctr; i++)
-		dput(stack[i].dentry);
-	kfree(stack);
+	ovl_stack_free(stack, ctr);
 out_put_upper:
 	if (origin_path) {
 		dput(origin_path->dentry);

fs/overlayfs/overlayfs.h

@@ -373,7 +373,12 @@ int ovl_can_decode_fh(struct super_block *sb);
 struct dentry *ovl_indexdir(struct super_block *sb);
 bool ovl_index_all(struct super_block *sb);
 bool ovl_verify_lower(struct super_block *sb);
+struct ovl_path *ovl_stack_alloc(unsigned int n);
+void ovl_stack_cpy(struct ovl_path *dst, struct ovl_path *src, unsigned int n);
+void ovl_stack_put(struct ovl_path *stack, unsigned int n);
+void ovl_stack_free(struct ovl_path *stack, unsigned int n);
 struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
+void ovl_free_entry(struct ovl_entry *oe);
 bool ovl_dentry_remote(struct dentry *dentry);
 void ovl_dentry_update_reval(struct dentry *dentry, struct dentry *realdentry);
 void ovl_dentry_init_reval(struct dentry *dentry, struct dentry *upperdentry);

fs/overlayfs/ovl_entry.h

@@ -127,8 +127,6 @@ static inline struct ovl_path *ovl_lowerstack(struct ovl_entry *oe)
 	return ovl_numlower(oe) ? oe->__lowerstack : NULL;
 }
 
-struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
-
 static inline struct ovl_entry *OVL_E(struct dentry *dentry)
 {
 	return (struct ovl_entry *) dentry->d_fsdata;

fs/overlayfs/super.c

@@ -54,15 +54,6 @@ module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
 MODULE_PARM_DESC(xino_auto,
 		 "Auto enable xino feature");
 
-static void ovl_entry_stack_free(struct ovl_entry *oe)
-{
-	struct ovl_path *lowerstack = ovl_lowerstack(oe);
-	unsigned int i;
-
-	for (i = 0; i < ovl_numlower(oe); i++)
-		dput(lowerstack[i].dentry);
-}
-
 static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
 module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
 MODULE_PARM_DESC(metacopy,
@@ -73,7 +64,7 @@ static void ovl_dentry_release(struct dentry *dentry)
 	struct ovl_entry *oe = dentry->d_fsdata;
 
 	if (oe) {
-		ovl_entry_stack_free(oe);
+		ovl_stack_put(ovl_lowerstack(oe), ovl_numlower(oe));
 		kfree_rcu(oe, rcu);
 	}
 }
@@ -2070,8 +2061,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	return 0;
 
 out_free_oe:
-	ovl_entry_stack_free(oe);
-	kfree(oe);
+	ovl_free_entry(oe);
 out_err:
 	kfree(splitlower);
 	path_put(&upperpath);

fs/overlayfs/util.c

@@ -83,6 +83,34 @@ bool ovl_verify_lower(struct super_block *sb)
 	return ofs->config.nfs_export && ofs->config.index;
 }
 
+struct ovl_path *ovl_stack_alloc(unsigned int n)
+{
+	return kcalloc(n, sizeof(struct ovl_path), GFP_KERNEL);
+}
+
+void ovl_stack_cpy(struct ovl_path *dst, struct ovl_path *src, unsigned int n)
+{
+	unsigned int i;
+
+	memcpy(dst, src, sizeof(struct ovl_path) * n);
+	for (i = 0; i < n; i++)
+		dget(src[i].dentry);
+}
+
+void ovl_stack_put(struct ovl_path *stack, unsigned int n)
+{
+	unsigned int i;
+
+	for (i = 0; stack && i < n; i++)
+		dput(stack[i].dentry);
+}
+
+void ovl_stack_free(struct ovl_path *stack, unsigned int n)
+{
+	ovl_stack_put(stack, n);
+	kfree(stack);
+}
+
 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
 {
 	size_t size = offsetof(struct ovl_entry, __lowerstack[numlower]);
@@ -94,6 +122,12 @@ struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
 	return oe;
 }
 
+void ovl_free_entry(struct ovl_entry *oe)
+{
+	ovl_stack_put(ovl_lowerstack(oe), ovl_numlower(oe));
+	kfree(oe);
+}
+
 #define OVL_D_REVALIDATE (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE)
 
 bool ovl_dentry_remote(struct dentry *dentry)