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

[Al Viro]

On Wed, Jun 10, 2020 at 05:13:52PM -0700, Mike Kravetz wrote:

> To address this issue,
> - Add a new file operation f_real while will return the underlying file.
>   Only overlayfs provides a function for this operation.
> - Add a new routine real_file() which can be used by core code get an
>   underlying file.
> - Update is_file_hugepages to get the real file.

Egads...  So to find out whether it's a hugetlb you would
	* check if a method is NULL
	* if not, call it
	* ... and check if the method table of the result is hugetlbfs one?

Here's a radical suggestion: FMODE_HUGEPAGES.  Just have it set by
->open() and let is_file_hugepages() check it.  In ->f_mode.  And
make the bloody hugetlbfs_file_operations static, while we are at it.