Re: [PATCH v2] ovl: provide real_file() and overlayfs get_unmapped_area()

[Al Viro]

On Wed, Jun 10, 2020 at 06:36:16PM -0700, Matthew Wilcox wrote:

> 	while (file->f_mode & FMODE_OVL_UPPER)
> 		file = file->private_data;
> 	return file;
> 
> Or are you proposing that overlayfs copy FMODE_HUGEPAGES from the
> underlying fs to the overlaying fs?

The latter - that way nobody outside of overlayfs needs to know what
its ->private_data points to, for one thing.  And it's cheaper that
way, obviously.