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

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On 09/11/2015 02:13 PM, Sheng Yong wrote:
Hi, Dongsheng

On 9/11/2015 1:01 PM, Dongsheng Yang wrote:
On 09/11/2015 05:09 PM, Sheng Yong wrote:
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.

Why not, I think we can use it.
First of all, thanks for your review :)

It seems xattr handler will be removed because of dead code of security xattr.
And if we do so, I think it's better to do that for all xattr, but not just
security and ACL, and generic_[set|get]xattr should be set in inode_operations
instead of ubifs_[get|set]xattr.

Security handler is different with acl handler. Please read the
security_getxattr(), it just return ubifs_getxattr(). That means
we can use ubifs_getxattr() immediately. So we can remove the
security_handler for ubifs.

But acl is different, we need to call a special ubifs_get_acl()
here. Then I found you get the handler by youself in the
ubifs_get|set_xattr() and call handler->set() by youself.

That's not good idea. Please Just set the handler and call
generic_setxattr().

Yang

thanks,
Sheng

Yang

Signed-off-by: Sheng Yong <shengyong1@xxxxxxxxxx>
---
   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);




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