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SubjectRe: [PATCH v4 1/2] hugetlb: use f_mode & FMODE_HUGETLBFS to identify hugetlbfs files
On Thu, Jun 11, 2020 at 05:46:43PM -0700, Mike Kravetz wrote:
> The routine is_file_hugepages() checks f_op == hugetlbfs_file_operations
> to determine if the file resides in hugetlbfs. This is problematic when
> the file is on a union or overlay. Instead, define a new file mode
> FMODE_HUGETLBFS which is set when a hugetlbfs file is opened. The mode
> can easily be copied to other 'files' derived from the original hugetlbfs
> file.
> With this change hugetlbfs_file_operations can be static as it should be.
> There is also a (duplicate) set of shm file operations used for the routine
> is_file_shm_hugepages(). Instead of setting/using special f_op's, just
> propagate the FMODE_HUGETLBFS mode. This means is_file_shm_hugepages() and
> the duplicate f_ops can be removed.
> While cleaning things up, change the name of is_file_hugepages() to
> is_file_hugetlbfs(). The term hugepages is a bit ambiguous.

I was going to have objections to this before I read it more carefully
and realised that the "shm" here is sysvipc and doesn't have anything
to do with the huge page support in shmfs.

> A subsequent patch will propagate FMODE_HUGETLBFS in overlayfs.
> Suggested-by: Al Viro <>
> Signed-off-by: Mike Kravetz <>

Reviewed-by: Matthew Wilcox (Oracle) <>

I might have suggested splitting the rename of is_file_hugetlbfs() from
the rest of this patch, but I wouldn't resend to change that.

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