From: Hugh Dickins <hughd@google.com>
To: Alistair Popple <apopple@nvidia.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Yang Shi <shy828301@gmail.com>,
Wang Yugui <wangyugui@e16-tech.com>,
Matthew Wilcox <willy@infradead.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Ralph Campbell <rcampbell@nvidia.com>, Zi Yan <ziy@nvidia.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Minchan Kim <minchan@kernel.org>, Jue Wang <juew@google.com>,
Peter Xu <peterx@redhat.com>, Jan Kara <jack@suse.cz>,
Shakeel Butt <shakeelb@google.com>,
Oscar Salvador <osalvador@suse.de>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 00/10] mm/thp: fix THP splitting unmap BUGs and related
Date: Thu, 10 Jun 2021 17:15:51 -0700 (PDT) [thread overview]
Message-ID: <b27e866-a06c-d32-20aa-3b16f58549@google.com> (raw)
In-Reply-To: <2014832.e7zRqyNrDn@nvdebian>
On Fri, 11 Jun 2021, Alistair Popple wrote:
> On Friday, 11 June 2021 8:15:05 AM AEST Andrew Morton wrote:
> > On Tue, 8 Jun 2021 20:57:34 -0700 (PDT) Hugh Dickins <hughd@google.com> wrote:
> >
> > > These are against 5.13-rc5: expect mmotm conflicts with a couple of
> > > Alistair Popple's "Add support for SVM atomics in Nouveau" series:
> > > mm-remove-special-swap-entry-functions.patch
> > > mm-rmap-split-try_to_munlock-from-try_to_unmap.patch
> >
> > I came unstuck at "mm/rmap: split migration into its own function".
Sorry about that, I hadn't yet gotten to trying my latest with mmotm.
And I think my previous mmotm-adjust.tar must have been incomplete;
and even if it were complete, would no longer apply properly anyway.
> >
> > --- mm/huge_memory.c~mm-rmap-split-migration-into-its-own-function
> > +++ mm/huge_memory.c
> > @@ -2345,16 +2345,21 @@ void vma_adjust_trans_huge(struct vm_are
> >
> > static void unmap_page(struct page *page)
> > {
> > - enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK |
> > - TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
> > + enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
> > bool unmap_success;
> >
> > VM_BUG_ON_PAGE(!PageHead(page), page);
> >
> > if (PageAnon(page))
> > - ttu_flags |= TTU_SPLIT_FREEZE;
> > -
> > - unmap_success = try_to_unmap(page, ttu_flags);
> > + unmap_success = try_to_migrate(page, ttu_flags);
> > + else
> > + /*
> > + * Don't install migration entries for file backed pages. This
> > + * helps handle cases when i_size is in the middle of the page
> > + * as there is no need to unmap pages beyond i_size manually.
> > + */
> > + unmap_success = try_to_unmap(page, ttu_flags |
> > + TTU_IGNORE_MLOCK);
> > VM_BUG_ON_PAGE(!unmap_success, page);
> > }
> >
> >
> > Sigh. I have a few todo's against Alastair's "Add support for SVM
> > atomics in Nouveau v9". Including
Sigh shared!
> >
> > https://lkml.kernel.org/r/20210525183710.fa2m2sbfixnhz7g5@revolver
> > https://lkml.kernel.org/r/20210604204934.sbspsmwdqdtmz73d@revolver
> > https://lkml.kernel.org/r/YK6mbf967dV0ljHn@t490s
> > https://lkml.kernel.org/r/2005328.bFqPmhE5MS@nvdebian
> > https://lkml.kernel.org/r/202105262107.LkxpsZsV-lkp@intel.com
> > https://lkml.kernel.org/r/YK6hYGEx+XzeZELV@t490s
> >
> > So I think I'll drop that series and shall ask for it to be redone
> > against this lot, please.
Thank you, Andrew: that's certainly easiest for you and for me:
and I think the right thing to do for now.
> >
>
> I believe v10 of the series posted earlier this week should address those
> todo's. I will double check though and resend based on top of mmotm. Thanks.
Sorry to give you the bother, Alistair: it's worked out as a bad moment
to rewrite swapops.h and rmap.c, I'm afraid.
And the only help I've had time to give you was pointing Peter at your
series - many thanks to Peter, and to Shakeel.
Several times I've been on the point of asking you to keep the familiar
migration_entry_to_page(), along with your new pfn_swap_entry_to_page();
but each time I've looked, seen that it's hard to retain it sensibly at
the same time as overdue cleanup of the device_private_entry_to_page()s.
So I guess I'm resigned to losing it; but there are at least three
bugs currently under discussion or fixes in flight, which border on
migration_entry_to_page() - Jann Horn's smaps syzbot bug, Xu Yu's
__migration_entry_wait() fix, my __split_huge_pmd_locked() fix
(and page_vma_mapped_walk() cleanup).
And regarding huge_memory.c's unmap_page(): I did not recognize the
"helps handle cases when i_size" comment you added there. What I
ended up with (and thought was in mmotm-adjust.tar but seems not):
/*
* Anon pages need migration entries to preserve them, but file
* pages can simply be left unmapped, then faulted back on demand.
* If that is ever changed (perhaps for mlock), update remap_page().
*/
if (PageAnon(page))
try_to_migrate(page, ttu_flags);
else
try_to_unmap(page, ttu_flags | TTU_IGNORE_MLOCK);
with
/* If try_to_migrate() is used on file, remove this check */
in remap_page() to replace the
/* If TTU_SPLIT_FREEZE is ever extended to file, remove this check */
comment my series puts there (since you delete TTU_SPLIT_FREEZE altogether).
Hugh
next prev parent reply other threads:[~2021-06-11 0:16 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <af88612-1473-2eaa-903-8d1a448b26@google.com>
2021-06-09 4:08 ` [PATCH v2 02/10] mm/thp: make is_huge_zero_pmd() safe and quicker Hugh Dickins
2021-06-09 10:22 ` Kirill A. Shutemov
2021-06-09 16:56 ` Yang Shi
2021-06-09 4:14 ` [PATCH v2 04/10] mm/thp: fix vma_address() if virtual address below file offset Hugh Dickins
2021-06-09 4:16 ` [PATCH v2 05/10] mm/thp: fix page_address_in_vma() on file THP tails Hugh Dickins
2021-06-09 4:19 ` [PATCH v2 06/10] mm/thp: unmap_mapping_page() to fix THP truncate_cleanup_page() Hugh Dickins
2021-06-09 17:02 ` Yang Shi
2021-06-09 21:11 ` Hugh Dickins
2021-06-09 21:16 ` [PATCH v3 " Hugh Dickins
2021-06-09 21:51 ` Yang Shi
2021-06-09 4:22 ` [PATCH v2 07/10] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Hugh Dickins
2021-06-09 4:25 ` [PATCH v2 08/10] mm: rmap: make try_to_unmap() void function Hugh Dickins
2021-06-10 7:57 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-09 4:27 ` [PATCH v2 09/10] mm/thp: remap_page() is only needed on anonymous THP Hugh Dickins
2021-06-09 4:30 ` [PATCH v2 10/10] mm: hwpoison_user_mappings() try_to_unmap() with TTU_SYNC Hugh Dickins
2021-06-09 10:27 ` Kirill A. Shutemov
2021-06-10 7:38 ` HORIGUCHI NAOYA(堀口 直也)
[not found] ` <20210610151505.d0124033e55bda07fa3d4408@linux-foundation.org>
[not found] ` <2014832.e7zRqyNrDn@nvdebian>
2021-06-11 0:15 ` Hugh Dickins [this message]
2021-06-11 7:28 ` [PATCH v2 00/10] mm/thp: fix THP splitting unmap BUGs and related Alistair Popple
2021-06-11 20:56 ` Hugh Dickins
2021-06-12 7:34 ` Alistair Popple
2021-06-12 8:20 ` Hugh Dickins
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