From: Yang Shi <shy828301@gmail.com>
To: Naoya Horiguchi <naoya.horiguchi@linux.dev>
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>,
"Peter Xu" <peterx@redhat.com>,
"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 4/5] mm: shmem: don't truncate page if memory failure happens
Date: Fri, 1 Oct 2021 14:08:41 -0700 [thread overview]
Message-ID: <CAHbLzkouad1qTUr1KPV5Ubaa74=Q4Emvg5BX4iO3p8M3kY0XFw@mail.gmail.com> (raw)
In-Reply-To: <20211001070539.GA1364952@u2004>
On Fri, Oct 1, 2021 at 12:05 AM Naoya Horiguchi
<naoya.horiguchi@linux.dev> wrote:
>
> On Thu, Sep 30, 2021 at 02:53:10PM -0700, Yang Shi wrote:
> > The current behavior of memory failure is to truncate the page cache
> > regardless of dirty or clean. If the page is dirty the later access
> > will get the obsolete data from disk without any notification to the
> > users. This may cause silent data loss. It is even worse for shmem
> > since shmem is in-memory filesystem, truncating page cache means
> > discarding data blocks. The later read would return all zero.
> >
> > The right approach is to keep the corrupted page in page cache, any
> > later access would return error for syscalls or SIGBUS for page fault,
> > until the file is truncated, hole punched or removed. The regular
> > storage backed filesystems would be more complicated so this patch
> > is focused on shmem. This also unblock the support for soft
> > offlining shmem THP.
> >
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > ---
> ...
> > @@ -894,6 +896,12 @@ static int me_pagecache_clean(struct page_state *ps, struct page *p)
> > goto out;
> > }
> >
> > + /*
> > + * The shmem page is kept in page cache instead of truncating
> > + * so need decrement the refcount from page cache.
> > + */
>
> This comment seems to me confusing because no refcount is decremented here.
> What the variable dec tries to do is to give the expected value of the
> refcount of the error page after successfull erorr handling, which differs
> according to the page state before error handling, so dec adjusts it.
>
> How about the below?
>
> + /*
> + * The shmem page is kept in page cache instead of truncating
> + * so is expected to have an extra refcount after error-handling.
> + */
Thanks for the suggestion, yes, it seems better.
>
> > + dec = shmem_mapping(mapping);
> > +
> > /*
> > * Truncation is a bit tricky. Enable it per file system for now.
> > *
> ...
> > @@ -2466,7 +2467,17 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
> > return -EPERM;
> > }
> >
> > - return shmem_getpage(inode, index, pagep, SGP_WRITE);
> > + ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
> > +
> > + if (*pagep) {
> > + if (PageHWPoison(*pagep)) {
>
> Unless you plan to add some code in the near future, how about merging
> these two if sentences?
>
> if (*pagep && PageHWPoison(*pagep)) {
Sure.
>
> Thanks,
> Naoya Horiguchi
>
> > + unlock_page(*pagep);
> > + put_page(*pagep);
> > + ret = -EIO;
> > + }
> > + }
> > +
> > + return ret;
> > }
> >
> > static int
next prev parent reply other threads:[~2021-10-01 21:08 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
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 [this message]
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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