[RFC PATCH v3 1/5] UBIFS: ACL: introduce init/set/get functions for ACL

[Sheng Yong <shengyong1@huawei.com>]

This patch introduce a new file `acl.c', which implements:
  * initializing ACL for new file according to the directory's default ACL,
  * getting ACL which finds the ACL releated xattr and converts it to ACL,
  * setting ACL function which converts ACL to xattr and creates/changes/
    removes the xattr.

On flash ACL format is based on POSIX ACL structures, and POSIX generic
functions, posix_acl_[to|from]_xattr, are called to do the ACL conversion
between in-memory and on-flash ACL.

The ACL xattr handler is not implemented, because UBIFS does not use it.

Signed-off-by: Sheng Yong <shengyong1@huawei.com>
---
 fs/ubifs/acl.c   | 141 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/ubifs/ubifs.h |  14 ++++++
 2 files changed, 155 insertions(+)
 create mode 100644 fs/ubifs/acl.c

diff --git a/fs/ubifs/acl.c b/fs/ubifs/acl.c
new file mode 100644
index 0000000..bf37875
--- /dev/null
+++ b/fs/ubifs/acl.c
@@ -0,0 +1,141 @@
+/*
+ * This file is part of UBIFS.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ */
+
+#include <linux/fs.h>
+#include <linux/xattr.h>
+#include <linux/posix_acl_xattr.h>
+
+#include "ubifs.h"
+
+struct posix_acl *ubifs_get_acl(struct inode *inode, int type)
+{
+	struct posix_acl *acl;
+	char *name, *value = NULL;
+	int size = 0;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		name = XATTR_NAME_POSIX_ACL_ACCESS;
+		break;
+	case ACL_TYPE_DEFAULT:
+		name = XATTR_NAME_POSIX_ACL_DEFAULT;
+		break;
+	default:
+		BUG();
+	}
+
+	size = ubifs_do_getxattr(inode, name, NULL, 0);
+	if (size > 0) {
+		value = kmalloc(size, GFP_KERNEL);
+		if (!value)
+			return ERR_PTR(-ENOMEM);
+		size = ubifs_do_getxattr(inode, name, value, size);
+	}
+	if (size > 0)
+		acl = posix_acl_from_xattr(&init_user_ns, value, size);
+	else if (size == -ENODATA)
+		acl = NULL;
+	else
+		acl = ERR_PTR(size);
+
+	kfree(value);
+	if (!IS_ERR(acl))
+		set_cached_acl(inode, type, acl);
+
+	return acl;
+}
+
+int ubifs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
+{
+	char *name;
+	void *value = NULL;
+	size_t size = 0;
+	int flag = 0, err;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		name = XATTR_NAME_POSIX_ACL_ACCESS;
+		if (acl) {
+			err = posix_acl_equiv_mode(acl, &inode->i_mode);
+			if (err < 0)
+				return err;
+			if (err == 0)
+				acl = NULL;
+		}
+		break;
+
+	case ACL_TYPE_DEFAULT:
+		name = XATTR_NAME_POSIX_ACL_DEFAULT;
+		if (!S_ISDIR(inode->i_mode))
+			return acl ? -EACCES : 0;
+		break;
+
+	default:
+		BUG();
+	}
+
+	if (acl) {
+		size = posix_acl_xattr_size(acl->a_count);
+		value = kmalloc(size, GFP_NOFS);
+		if (!value)
+			return -ENOMEM;
+
+		err = posix_acl_to_xattr(&init_user_ns, acl, value, size);
+		if (err < 0) {
+			kfree(value);
+			return err;
+		}
+	}
+
+	if (size == 0)
+		flag = XATTR_REPLACE;
+	err = ubifs_do_setxattr(inode, name, value, size, flag);
+
+	kfree(value);
+	if (!err)
+		set_cached_acl(inode, type, acl);
+
+	return err;
+}
+
+/*
+ * Initialize the ACLs of a new inode.
+ */
+int ubifs_init_acl(struct inode *dir, struct inode *inode)
+{
+	struct posix_acl *default_acl, *acl;
+	int err;
+
+	err = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
+	if (err)
+		return err;
+
+	if (default_acl) {
+		mutex_lock(&inode->i_mutex);
+		err = ubifs_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
+		mutex_unlock(&inode->i_mutex);
+		posix_acl_release(default_acl);
+	}
+
+	if (acl) {
+		if (!err) {
+			mutex_lock(&inode->i_mutex);
+			err = ubifs_set_acl(inode, acl, ACL_TYPE_ACCESS);
+			mutex_unlock(&inode->i_mutex);
+		}
+		posix_acl_release(acl);
+	}
+
+	return err;
+}
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 62aa1a5..b9ddc8d 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1767,6 +1767,20 @@ int ubifs_removexattr(struct dentry *dentry, const char *name);
 int ubifs_init_security(struct inode *dentry, struct inode *inode,
 			const struct qstr *qstr);
 
+/* acl.c */
+#ifdef CONFIG_UBIFS_FS_POSIX_ACL
+int ubifs_init_acl(struct inode *dir, struct inode *inode);
+int ubifs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
+struct posix_acl *ubifs_get_acl(struct inode *inode, int type);
+#else
+static inline int ubifs_init_acl(struct inode *inode, struct inode *dir)
+{
+	return 0;
+}
+#define ubifs_get_acl NULL
+#define ubifs_set_acl NULL
+#endif
+
 /* super.c */
 struct inode *ubifs_iget(struct super_block *sb, unsigned long inum);
 
-- 
1.9.1