linux-kernel - Re: [RFC PATCH 0/2] Add flag as THP allocation hint for memfd

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Date:   Mon, 20 Feb 2023 11:04:12 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     Ackerley Tng <ackerleytng@...gle.com>
Cc:     kvm@...r.kernel.org, linux-api@...r.kernel.org,
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Subject: Re: [RFC PATCH 0/2] Add flag as THP allocation hint for
 memfd_restricted() syscall

On Sat, Feb 18, 2023 at 12:43:00AM +0000, Ackerley Tng wrote:
> Hello,
>
> This patchset builds upon the memfd_restricted() system call that has
> been discussed in the ‘KVM: mm: fd-based approach for supporting KVM’
> patch series, at
> https://lore.kernel.org/lkml/20221202061347.1070246-1-chao.p.peng@linux.intel.com/T/#m7e944d7892afdd1d62a03a287bd488c56e377b0c
>
> The tree can be found at:
> https://github.com/googleprodkernel/linux-cc/tree/restrictedmem-rmfd-hugepage
>
> Following the RFC to provide mount for memfd_restricted() syscall at
> https://lore.kernel.org/lkml/cover.1676507663.git.ackerleytng@google.com/T/#u,
> this patchset adds the RMFD_HUGEPAGE flag to the memfd_restricted()
> syscall, which will hint the kernel to use Transparent HugePages to
> back restrictedmem pages.
>
> This supplements the interface proposed earlier, which requires the
> creation of a tmpfs mount to be passed to memfd_restricted(), with a
> more direct per-file hint.
>
> Dependencies:
>
> + Sean’s iteration of the ‘KVM: mm: fd-based approach for supporting
>   KVM’ patch series at
>   https://github.com/sean-jc/linux/tree/x86/upm_base_support
> + Proposed fix for restrictedmem_getattr() as mentioned on the mailing
>   list at
>   https://lore.kernel.org/lkml/diqzzga0fv96.fsf@ackerleytng-cloudtop-sg.c.googlers.com/
> + Hugh’s patch:
>   https://lore.kernel.org/lkml/c140f56a-1aa3-f7ae-b7d1-93da7d5a3572@google.com/,
>   which provides functionality in shmem that reads the VM_HUGEPAGE
>   flag in key functions shmem_is_huge() and shmem_get_inode()

Will Hugh's patch be merged into 6.3 ? I didn't find it in 6.2-rc8.
IMHO this patch won't work without Hugh's patch, or at least need
another way, e.g. HMEM_SB(inode->i_sb)->huge.

>
> Future work/TODOs:
> + man page for the memfd_restricted() syscall
> + Support for per file NUMA binding hints
>
> Ackerley Tng (2):
>   mm: restrictedmem: Add flag as THP allocation hint for
>     memfd_restricted() syscall
>   selftests: restrictedmem: Add selftest for RMFD_HUGEPAGE
>
>  include/uapi/linux/restrictedmem.h            |  1 +
>  mm/restrictedmem.c                            | 27 ++++++++++++-------
>  .../restrictedmem_hugepage_test.c             | 25 +++++++++++++++++
>  3 files changed, 43 insertions(+), 10 deletions(-)
>
> --
> 2.39.2.637.g21b0678d19-goog
>