[PATCH] add a file_permission helper

A few more callers of permission() just want to check for a different access
pattern on an already open file.  This patch adds a wrapper for permission()
that takes a file in preparation of per-mount read-only support and to clean
up the callers a little.  The helper is not intended for new code, everything
without the interface set in stone should use vfs_permission()

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 25e4ab4ce8b7..b69f6ebadb95 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -271,6 +271,23 @@ int vfs_permission(struct nameidata *nd, int mask)
         return permission(nd->dentry->d_inode, mask, nd);
 }
 
+/**
+ * file_permission  -  check for additional access rights to a given file
+ * @file:       file to check access rights for
+ * @mask:       right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * Used to check for read/write/execute permissions on an already opened
+ * file.
+ *
+ * Note:
+ *      Do not use this function in new code.  All access checks should
+ *      be done using vfs_permission().
+ */
+int file_permission(struct file *file, int mask)
+{
+        return permission(file->f_dentry->d_inode, mask, NULL);
+}
+
 /*
  * get_write_access() gets write permission for a file.
  * put_write_access() releases this write permission.
@@ -2551,6 +2568,7 @@ EXPORT_SYMBOL(path_release);
 EXPORT_SYMBOL(path_walk);
 EXPORT_SYMBOL(permission);
 EXPORT_SYMBOL(vfs_permission);
+EXPORT_SYMBOL(file_permission);
 EXPORT_SYMBOL(unlock_rename);
 EXPORT_SYMBOL(vfs_create);
 EXPORT_SYMBOL(vfs_follow_link);