linux-kernel - Re: [PATCH v1 25/32] mm: shmem: use SHMEM_F_* flags instead of VM

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Message-ID: <CA+CK2bCHFW35oudOUTykzV4zH6Hv4ChmUq=-BZAtDP_mtOwBjA@mail.gmail.com>
Date: Wed, 23 Jul 2025 14:08:02 +0000
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Pratyush Yadav <pratyush@...nel.org>
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Subject: Re: [PATCH v1 25/32] mm: shmem: use SHMEM_F_* flags instead of VM_* flags

On Thu, Jun 26, 2025 at 1:01 PM Pratyush Yadav <pratyush@...nel.org> wrote:
>
> Hi all,
>
> On Wed, Jun 25 2025, Pasha Tatashin wrote:
>
> > From: Pratyush Yadav <ptyadav@...zon.de>
> >
> > shmem_inode_info::flags can have the VM flags VM_NORESERVE and
> > VM_LOCKED. These are used to suppress pre-accounting or to lock the
> > pages in the inode respectively. Using the VM flags directly makes it
> > difficult to add shmem-specific flags that are unrelated to VM behavior
> > since one would need to find a VM flag not used by shmem and re-purpose
> > it.
> >
> > Introduce SHMEM_F_NORESERVE and SHMEM_F_LOCKED which represent the same
> > information, but their bits are independent of the VM flags. Callers can
> > still pass VM_NORESERVE to shmem_get_inode(), but it gets transformed to
> > the shmem-specific flag internally.
> >
> > No functional changes intended.
>
> I was reading through this patch again and just realized that I missed a
> spot. __shmem_file_setup() passes VM flags to shmem_{un,}acct_size(),
> even though it now expects SHMEM_F flag. Below fixup patch should fix
> that.

Added for v2.

Pasha