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From: Yang Shi <shy828301@gmail.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Shakeel Butt <shakeelb@google.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Michal Hocko <mhocko@suse.com>, Rik van Riel <riel@surriel.com>,
	Christoph Hellwig <hch@infradead.org>,
	Matthew Wilcox <willy@infradead.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Alexey Gladkov <legion@kernel.org>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	Matthew Auld <matthew.auld@intel.com>,
	Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-api@vger.kernel.org, Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH 04/16] huge tmpfs: revert shmem's use of transhuge_vma_enabled()
Date: Mon, 2 Aug 2021 13:39:00 -0700	[thread overview]
Message-ID: <CAHbLzkqTHcXqxUYzu98Ea_EzEaQ+eLPDmgyoSQEcC3MoEqchmg@mail.gmail.com> (raw)
In-Reply-To: <55526ab1-4280-9538-51d7-6669b8a97f@google.com>

On Sat, Jul 31, 2021 at 9:01 PM Hugh Dickins <hughd@google.com> wrote:
>
> On Fri, 30 Jul 2021, Yang Shi wrote:
> > On Fri, Jul 30, 2021 at 12:36 AM Hugh Dickins <hughd@google.com> wrote:
> > >
> > > 5.14 commit e6be37b2e7bd ("mm/huge_memory.c: add missing read-only THP
> > > checking in transparent_hugepage_enabled()") added transhuge_vma_enabled()
> > > as a wrapper for two very different checks: shmem_huge_enabled() prefers
> > > to show those two checks explicitly, as before.
> >
> > Basically I have no objection to separating them again. But IMHO they
> > seem not very different. Or just makes things easier for the following
> > patches?
>
> Well, it made it easier to apply the patch I'd prepared earlier,
> but that was not the point; and I thought it best to be upfront
> about the reversion, rather than hiding it in the movement.
>
> The end result of the two checks is the same (don't try for huge pages),
> and they have been grouped together because they occurred together in
> several places, and both rely on "vma".
>
> But one check is whether the app has marked that address range not to use
> THPs; and the other check is whether the process is running in a hierarchy
> that has been marked never to use THPs (which just uses vma to get to mm
> to get to mm->flags (whether current->mm would be more relevant is not an
> argument I want to get into, I'm not at all sure)).
>
> To me those are very different; and I'm particularly concerned to make
> MMF_DISABLE_THP references visible, since it did not exist when Kirill
> and I first implemented shmem huge pages, and I've tended to forget it:
> but consider it more in this series.

Yes, I agree one checks vma the other one checks mm, they are
different from this perspective. Anyway, as I said I have no objection
to this change. You could add Reviewed-by: Yang Shi
<shy828301@gmail.com>

>
> Hugh
>
> >
> > >
> > > Signed-off-by: Hugh Dickins <hughd@google.com>
> > > ---
> > >  mm/shmem.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/mm/shmem.c b/mm/shmem.c
> > > index ce3ccaac54d6..c6fa6f4f2db8 100644
> > > --- a/mm/shmem.c
> > > +++ b/mm/shmem.c
> > > @@ -4003,7 +4003,8 @@ bool shmem_huge_enabled(struct vm_area_struct *vma)
> > >         loff_t i_size;
> > >         pgoff_t off;
> > >
> > > -       if (!transhuge_vma_enabled(vma, vma->vm_flags))
> > > +       if ((vma->vm_flags & VM_NOHUGEPAGE) ||
> > > +           test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
> > >                 return false;
> > >         if (shmem_huge == SHMEM_HUGE_FORCE)
> > >                 return true;
> > > --
> > > 2.26.2

  reply	other threads:[~2021-08-02 20:39 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30  7:22 [PATCH 00/16] tmpfs: HUGEPAGE and MEM_LOCK fcntls and memfds Hugh Dickins
2021-07-30  7:25 ` [PATCH 01/16] huge tmpfs: fix fallocate(vanilla) advance over huge pages Hugh Dickins
2021-07-30 21:36   ` Yang Shi
2021-08-01  3:38     ` Hugh Dickins
2021-08-02 20:36       ` Yang Shi
2021-07-30  7:28 ` [PATCH 02/16] huge tmpfs: fix split_huge_page() after FALLOC_FL_KEEP_SIZE Hugh Dickins
2021-07-30 23:48   ` Yang Shi
2021-07-30  7:30 ` [PATCH 03/16] huge tmpfs: remove shrinklist addition from shmem_setattr() Hugh Dickins
2021-07-30 21:50   ` Yang Shi
2021-07-30  7:36 ` [PATCH 04/16] huge tmpfs: revert shmem's use of transhuge_vma_enabled() Hugh Dickins
2021-07-30 21:56   ` Yang Shi
2021-08-01  4:01     ` Hugh Dickins
2021-08-02 20:39       ` Yang Shi [this message]
2021-07-30  7:39 ` [PATCH 05/16] huge tmpfs: move shmem_huge_enabled() upwards Hugh Dickins
2021-07-30 21:57   ` Yang Shi
2021-07-30  7:42 ` [PATCH 06/16] huge tmpfs: shmem_is_huge(vma, inode, index) Hugh Dickins
2021-07-30 23:34   ` Yang Shi
2021-08-01  5:22     ` Hugh Dickins
2021-08-01  5:37       ` Hugh Dickins
2021-08-02 21:14       ` Yang Shi
2021-08-04  8:28         ` Hugh Dickins
2021-08-04 19:01           ` Yang Shi
2021-08-06  5:21             ` Hugh Dickins
2021-08-06 17:41               ` Yang Shi
2021-08-05 23:04         ` Yang Shi
2021-08-06  5:43           ` Hugh Dickins
2021-08-06 17:57             ` Yang Shi
2021-08-12 18:19               ` Yang Shi
2021-07-30  7:45 ` [PATCH 07/16] memfd: memfd_create(name, MFD_HUGEPAGE) for shmem huge pages Hugh Dickins
2021-08-04 14:03   ` Kirill A. Shutemov
2021-08-06  3:33     ` Hugh Dickins
2021-07-30  7:48 ` [PATCH 08/16] huge tmpfs: fcntl(fd, F_HUGEPAGE) and fcntl(fd, F_NOHUGEPAGE) Hugh Dickins
2021-08-04 14:08   ` Kirill A. Shutemov
2021-08-06  4:34     ` Hugh Dickins
2021-07-30  7:51 ` [PATCH 09/16] huge tmpfs: decide stat.st_blksize by shmem_is_huge() Hugh Dickins
2021-07-30 23:40   ` Yang Shi
2021-07-30  7:55 ` [PATCH 10/16] tmpfs: fcntl(fd, F_MEM_LOCK) to memlock a tmpfs file Hugh Dickins
2021-08-03  1:38   ` Matthew Wilcox
2021-08-04  9:15     ` Hugh Dickins
2021-07-30  7:57 ` [PATCH 11/16] tmpfs: fcntl(fd, F_MEM_LOCKED) to test if memlocked Hugh Dickins
2021-07-30  8:00 ` [PATCH 12/16] tmpfs: refuse memlock when fallocated beyond i_size Hugh Dickins
2021-07-30  8:03 ` [PATCH 13/16] mm: bool user_shm_lock(loff_t size, struct ucounts *) Hugh Dickins
2021-07-30  8:06 ` [PATCH 14/16] mm: user_shm_lock(,,getuc) and user_shm_unlock(,,putuc) Hugh Dickins
2021-07-30  8:09 ` [PATCH 15/16] tmpfs: permit changing size of memlocked file Hugh Dickins
2021-07-30  8:13 ` [PATCH 16/16] memfd: memfd_create(name, MFD_MEM_LOCK) for memlocked shmem Hugh Dickins

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