[PATCH] r/o bind mounts: make access() use new r/o helper
It is OK to let access() go without using a mnt_want/drop_write() pair because
it doesn't actually do writes to the filesystem, and it is inherently racy
anyway. This is a rare case when it is OK to use __mnt_is_readonly()
directly.
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/open.c b/fs/open.c
index 4d690e3..e58382d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -459,8 +459,17 @@
if(res || !(mode & S_IWOTH) ||
special_file(nd.path.dentry->d_inode->i_mode))
goto out_path_release;
-
- if(IS_RDONLY(nd.path.dentry->d_inode))
+ /*
+ * This is a rare case where using __mnt_is_readonly()
+ * is OK without a mnt_want/drop_write() pair. Since
+ * no actual write to the fs is performed here, we do
+ * not need to telegraph to that to anyone.
+ *
+ * By doing this, we accept that this access is
+ * inherently racy and know that the fs may change
+ * state before we even see this result.
+ */
+ if (__mnt_is_readonly(nd.path.mnt))
res = -EROFS;
out_path_release: