From: Dave Hansen may_open() calls vfs_permission() before it does checks for IS_RDONLY(inode). It checks _again_ inside of vfs_permission(). The check inside of vfs_permission() is going away eventually. With the mnt_want/drop_write() functions, all of the r/o checks (except for this one) are consistently done before calling permission(). Because of this, I'd like to use permission() to hold a debugging check to make sure that the mnt_want/drop_write() calls are actually being made. So, to do this: 1. remove the IS_RDONLY() check from permission() 2. enforce that you must mnt_want_write() before even calling permission() 3. actually add the debugging check to permission() We need to rearrange may_open() to do r/o checks before calling permission(). Here's the patch. Signed-off-by: Dave Hansen Cc: Christoph Hellwig Signed-off-by: Andrew Morton --- fs/namei.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff -puN fs/namei.c~r-o-bind-mounts-rearrange-may_open-to-be-r-o-friendly fs/namei.c --- a/fs/namei.c~r-o-bind-mounts-rearrange-may_open-to-be-r-o-friendly +++ a/fs/namei.c @@ -1605,10 +1605,6 @@ int may_open(struct nameidata *nd, int a if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE)) return -EISDIR; - error = vfs_permission(nd, acc_mode); - if (error) - return error; - /* * FIFO's, sockets and device files are special: they don't * actually live on the filesystem itself, and as such you @@ -1623,6 +1619,10 @@ int may_open(struct nameidata *nd, int a flag &= ~O_TRUNC; } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE)) return -EROFS; + + error = vfs_permission(nd, acc_mode); + if (error) + return error; /* * An append-only file must be opened in append mode for writing. */ _