Re: [PATCH 3/3] nfs: Store and use inode in nfs_open_context

[Miklos Szeredi <miklos@szeredi.hu>]

On Wed, Mar 2, 2016 at 4:57 PM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
> On 03/02/2016 08:43 AM, Miklos Szeredi wrote:

>> Not sure how any dentry seen by NFS became associated with overlayfs.
>> Through ->f_path by any chance?
>>
>
> Yes, NFS extracts dentry from filp->f_path.dentry in fs/nfs/inode.c
> nfs_open(). What can it use to evaluate dentry?

Commit 4bacc9c9234c ("overlayfs: Make f_path always point to the
overlay and f_inode to the underlay") broke this.  Breakage only
affects regular files.  Accessing file->f_path.dentry->d_name (and
"%pD" format etc) is OK for everything.   ->d_fsdata is not OK.

I have no idea what the plan was with filesystems that use
f_path.dentry a separate open file for them.  David?  Al?

My plan was to introduce a file_dentry() helper that MUST be used by
filesystems to get the dentry from the file and that makes sure it's
the right one (check against file_inode()).   If not, then we could
call into overlayfs to return the right one, similar to
->d_select_inode(), except we want to have a dentry and we want to
have *a particular dentry* matching file_inode() (the file could have
been copied up in the mean time).

Thanks,
Miklos

Thanks,
Miklos