ACK/APPLIED[Unstable]: [PATCH v1][SRU][EOAN] UBUNTU: SAUCE: shiftfs: rework how shiftfs opens files

[Christian Brauner]

On Tue Oct 15, 2019 at 1:25 PM Seth Forshee wrote:
> On Wed, Oct 02, 2019 at 09:57:14AM +0200, Christian Brauner wrote:
> > BugLink: https://bugs.launchpad.net/bugs/1846265
> > 
> > This commit simplifies how shiftfs open files, both regular files an
> > directories.
> > 
> > In the first iteration, we implemented a kmem cache for struct
> > shiftfs_file_info which stashed away a struct path and the struct file
> > for the underlay. The path however was never used anywhere so the struct
> > shiftfs_file_info and therefore the whole kmem cache can go away.
> > Instead we move to the same model as overlayfs and just stash away the
> > struct file for the underlay in file->private_data of the shiftfs struct
> > file.
> > Addtionally, we split the .open method for files and directories.
> > Similar to overlayfs .open for regular files uses open_with_fake_path()
> > which ensures that it doesn't contribute to the open file count (since
> > this would mean we'd count double). The .open method for directories
> > however used dentry_open() which contributes to the open file count.
> > 
> > The basic logic for opening files is unchanged. The main point is to
> > ensure that a reference to the underlay's dentry is kept through struct
> > path.
> > 
> > Various bits and pieces of this were cooked up in discussions Seth and I
> > had in Paris.
> > 
> > Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
> 
> Looks sane, scope limited to shiftfs.
> 
> Acked-by: Seth Forshee <seth.forshee at canonical.com>
> 
> Applied to unstable/master, thanks!

Thanks!
Christian