From: Yang Shi <shy828301@gmail.com>
To: Peter Xu <peterx@redhat.com>
Cc: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>,
"Hugh Dickins" <hughd@google.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Oscar Salvador" <osalvador@suse.de>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Linux MM" <linux-mm@kvack.org>,
"Linux FS-devel Mailing List" <linux-fsdevel@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [v3 PATCH 2/5] mm: filemap: check if THP has hwpoisoned subpage for PMD page fault
Date: Thu, 7 Oct 2021 11:19:15 -0700 [thread overview]
Message-ID: <CAHbLzkq-18rDvfVepNTfKzPbb0+Tg9S=bwFCgjXGv0RxgouptA@mail.gmail.com> (raw)
In-Reply-To: <YV8bChbXop3FuwPC@t490s>
On Thu, Oct 7, 2021 at 9:06 AM Peter Xu <peterx@redhat.com> wrote:
>
> On Wed, Oct 06, 2021 at 04:57:38PM -0700, Yang Shi wrote:
> > > For example, I see that both unpoison_memory() and soft_offline_page() will
> > > call it too, does it mean that we'll also set the bits e.g. even when we want
> > > to inject an unpoison event too?
> >
> > unpoison_memory() should be not a problem since it will just bail out
> > once THP is met as the comment says:
> >
> > /*
> > * unpoison_memory() can encounter thp only when the thp is being
> > * worked by memory_failure() and the page lock is not held yet.
> > * In such case, we yield to memory_failure() and make unpoison fail.
> > */
>
> But I still think setting the subpage-hwpoison bit hides too deep there, it'll
> be great we can keep get_hwpoison_page() as simple as a safe version of getting
> the refcount of the page we want. Or we'd still better touch up the comment
> above get_hwpoison_page() to show that side effect.
>
> >
> >
> > And I think we should set the flag for soft offline too, right? The
>
> I'm not familiar with either memory failure or soft offline, so far it looks
> right to me. However..
>
> > soft offline does set the hwpoison flag for the corrupted sub page and
> > doesn't split file THP,
>
> .. I believe this will become not true after your patch 5, right?
But THP split may fail, right?
>
> > so it should be captured by page fault as well. And yes for poison injection.
>
> One more thing: besides thp split and page free, do we need to conditionally
> drop the HasHwpoisoned bit when received an unpoison event?
It seems not to me, as the above comment from unpoison_memory() says
unpoison can encounter thp only when the thp is being worked by
memory_failure() and the page lock is not held yet. So it just bails
out.
In addition, unpoison just works for software injected errors, not
real hardware failure.
>
> If my understanding is correct, we may need to scan all the subpages there, to
> make sure HasHwpoisoned bit reflects the latest status for the thp in question.
>
> >
> > But your comment reminds me that get_hwpoison_page() is just called
> > when !MF_COUNT_INCREASED, so it means MADV_HWPOISON still could
> > escape. This needs to be covered too.
>
> Right, maybe that's also a clue that we shouldn't set the new page flag within
> get_hwpoison_page(), since get_hwpoison_page() is actually well coupled with
> MF_COUNT_INCREASED and all of them are only about refcounting of the pages.
Yeah, maybe, as long as there is not early bail out in some error
handling paths.
>
> --
> Peter Xu
>
next prev parent reply other threads:[~2021-10-07 18:19 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-30 21:53 [RFC v3 PATCH 0/5] Solve silent data loss caused by poisoned page cache (shmem/tmpfs) Yang Shi
2021-09-30 21:53 ` [v3 PATCH 1/5] mm: hwpoison: remove the unnecessary THP check Yang Shi
2021-10-06 2:35 ` Yang Shi
2021-10-06 4:00 ` Naoya Horiguchi
2021-10-06 17:56 ` Yang Shi
2021-09-30 21:53 ` [v3 PATCH 2/5] mm: filemap: check if THP has hwpoisoned subpage for PMD page fault Yang Shi
2021-10-01 7:23 ` Naoya Horiguchi
2021-10-01 21:07 ` Yang Shi
2021-10-04 14:06 ` Kirill A. Shutemov
2021-10-04 18:17 ` Yang Shi
2021-10-04 19:41 ` Kirill A. Shutemov
2021-10-04 20:13 ` Yang Shi
2021-10-06 19:54 ` Peter Xu
2021-10-06 23:41 ` Yang Shi
2021-10-07 16:14 ` Peter Xu
2021-10-07 18:28 ` Yang Shi
2021-10-08 9:35 ` Kirill A. Shutemov
2021-10-11 22:57 ` Peter Xu
2021-10-06 20:15 ` Peter Xu
2021-10-06 23:57 ` Yang Shi
2021-10-07 16:06 ` Peter Xu
2021-10-07 18:19 ` Yang Shi [this message]
2021-10-07 20:27 ` Yang Shi
2021-10-07 21:28 ` Yang Shi
2021-10-12 0:55 ` Peter Xu
2021-10-12 1:44 ` Peter Xu
2021-10-12 18:02 ` Yang Shi
2021-10-12 22:10 ` Peter Xu
2021-10-13 2:48 ` Yang Shi
2021-10-13 3:01 ` Peter Xu
2021-10-13 3:27 ` Yang Shi
2021-10-13 3:41 ` Peter Xu
2021-10-13 21:42 ` Yang Shi
2021-10-13 23:13 ` Peter Xu
2021-10-14 6:54 ` Naoya Horiguchi
2021-10-06 20:18 ` Peter Xu
2021-10-07 2:49 ` Yang Shi
2021-11-01 19:05 ` Naresh Kamboju
2021-11-01 19:26 ` Yang Shi
2021-09-30 21:53 ` [v3 PATCH 3/5] mm: hwpoison: refactor refcount check handling Yang Shi
2021-10-06 22:01 ` Peter Xu
2021-10-07 2:47 ` Yang Shi
2021-10-07 16:18 ` Peter Xu
2021-09-30 21:53 ` [v3 PATCH 4/5] mm: shmem: don't truncate page if memory failure happens Yang Shi
2021-10-01 7:05 ` Naoya Horiguchi
2021-10-01 21:08 ` Yang Shi
2021-10-12 1:57 ` Peter Xu
2021-10-12 19:17 ` Yang Shi
2021-10-12 22:26 ` Peter Xu
2021-10-13 3:00 ` Yang Shi
2021-10-13 3:06 ` Peter Xu
2021-10-13 3:29 ` Yang Shi
2021-09-30 21:53 ` [v3 PATCH 5/5] mm: hwpoison: handle non-anonymous THP correctly Yang Shi
2021-10-01 7:06 ` Naoya Horiguchi
2021-10-01 21:09 ` Yang Shi
2021-10-13 2:40 ` [RFC v3 PATCH 0/5] Solve silent data loss caused by poisoned page cache (shmem/tmpfs) Peter Xu
2021-10-13 3:09 ` Yang Shi
2021-10-13 3:24 ` Peter Xu
2021-10-14 6:54 ` Naoya Horiguchi
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