Re: [GIT PULL] overlayfs update for 4.9

From: Miklos Szeredi
Date: Thu Oct 06 2016 - 04:01:43 EST

On Thu, Oct 6, 2016 at 1:49 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Oct 05, 2016 at 09:52:10PM +0200, Miklos Szeredi wrote:
>> Hi Al,
>> Please pull from:
>> git:// overlayfs-viro
>> This has an assortment of fixes and cleanups for overlayfs.
>> It also touches the VFS:
>> - add the vfs_get_link() helper for calling i_op->get_link();
>> - fix mnt_want_write_file() to freeze protect the underlying sb instead of
>> overlay sb;
>> - allow vfs_clone_file_range() to be called by overlayfs.
> Could you explain why e.g. fsetxattr() needs a different treatment in
> "vfs: mnt_want_write_file() should freeze protect underlying sb"?

Because setxattr is an i_op, not a f_op, so it's overlayfs that's
going to be called and will do the freeze protect on underlying layer
(not to mention, that it might be a different underlying sb that will
get the freeze protection in the end, due to copy up)