[PATCH] move read-only and immutable checks into permission()

Currently it's up to the filesystem ->permission method to check whether
the filesystem is readonly or the file marked immutable.  But this is
really a VFS decision, and the distintion becomes more important when
moving to per-mountpoint read only flags.

For most filesystems that have been using generic_permission this is not
change in behaviour.  For those that we're missing the check (cifs without
CIFS_MOUNT_NO_PERM and coda [1]) this is a bugfix.

Both reiserfs and xfs have this check still in their ->permission routine
because they call it from other places aswell.  I'll try switching them
over to generic_permission and will take care of this one.

[1] coda_ioctl_permission always returns 0, aka always grants access,
    which looks more than fishy to me.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/namei.c

@@ -169,21 +169,6 @@ int generic_permission(struct inode *inode, int mask,
 {
 	umode_t			mode = inode->i_mode;
 
-	if (mask & MAY_WRITE) {
-		/*
-		 * Nobody gets write access to a read-only fs.
-		 */
-		if (IS_RDONLY(inode) &&
-		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
-			return -EROFS;
-
-		/*
-		 * Nobody gets write access to an immutable file.
-		 */
-		if (IS_IMMUTABLE(inode))
-			return -EACCES;
-	}
-
 	if (current->fsuid == inode->i_uid)
 		mode >>= 6;
 	else {
@@ -225,14 +210,30 @@ int generic_permission(struct inode *inode, int mask,
 	return -EACCES;
 }
 
-int permission(struct inode * inode,int mask, struct nameidata *nd)
+int permission(struct inode *inode, int mask, struct nameidata *nd)
 {
-	int retval;
-	int submask;
+	int retval, submask;
+
+	if (mask & MAY_WRITE) {
+		umode_t mode = inode->i_mode;
+
+		/*
+		 * Nobody gets write access to a read-only fs.
+		 */
+		if (IS_RDONLY(inode) &&
+		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+			return -EROFS;
+
+		/*
+		 * Nobody gets write access to an immutable file.
+		 */
+		if (IS_IMMUTABLE(inode))
+			return -EACCES;
+	}
+
 
 	/* Ordinary permission routines do not understand MAY_APPEND. */
 	submask = mask & ~MAY_APPEND;
-
 	if (inode->i_op && inode->i_op->permission)
 		retval = inode->i_op->permission(inode, submask, nd);
 	else

fs/nfs/dir.c

@@ -1498,29 +1498,11 @@ static int nfs_do_access(struct inode *inode, struct rpc_cred *cred, int mask)
 int nfs_permission(struct inode *inode, int mask, struct nameidata *nd)
 {
 	struct rpc_cred *cred;
-	int mode = inode->i_mode;
 	int res;
 
 	if (mask == 0)
 		return 0;
-	if (mask & MAY_WRITE) {
-		/*
-		 *
-		 * Nobody gets write access to a read-only fs.
-		 *
-		 */
-		if (IS_RDONLY(inode) &&
-		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
-			return -EROFS;
 
-		/*
-		 *
-		 * Nobody gets write access to an immutable file.
-		 *
-		 */
-		if (IS_IMMUTABLE(inode))
-			return -EACCES;
-	}
 	/* Are we checking permissions on anything other than lookup/execute? */
 	if ((mask & MAY_EXEC) == 0) {
 		/* We only need to check permissions on file open() and access() */