From: Peter Xu <peterx@redhat.com>
To: David Stevens <stevensd@chromium.org>
Cc: linux-mm@kvack.org, Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Yang Shi <shy828301@gmail.com>,
David Hildenbrand <david@redhat.com>,
Hugh Dickins <hughd@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 3/3] mm/khugepaged: maintain page cache uptodate flag
Date: Tue, 21 Feb 2023 17:18:22 -0500 [thread overview]
Message-ID: <Y/VDLvLpiHkRgVjs@x1n> (raw)
In-Reply-To: <20230217085439.2826375-4-stevensd@google.com>
On Fri, Feb 17, 2023 at 05:54:39PM +0900, David Stevens wrote:
> From: David Stevens <stevensd@chromium.org>
>
> Make sure that collapse_file doesn't interfere with checking the
> uptodate flag in the page cache by only inserting hpage into the page
> cache after it has been updated and marked uptodate. This is achieved by
> simply not replacing present pages with hpage when iterating over them
> target range. The present pages are already locked, so replacing the
> with the locked hpage before the collapse is finalized is unnecessary.
>
> This fixes a race where folio_seek_hole_data would mistake hpage for
> an fallocated but unwritten page. This race is visible to userspace via
> data temporarily disappearing from SEEK_DATA/SEEK_HOLE.
>
> Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages")
> Signed-off-by: David Stevens <stevensd@chromium.org>
Per my knowledge, this one looks all correct too.
Acked-by: Peter Xu <peterx@redhat.com>
So at least to me the whole set looks mostly good except patch 1 needs some
confirmation.
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2023-02-21 22:18 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-17 8:54 [PATCH v4 0/3] mm/khugepaged: fix khugepaged+shmem races David Stevens
2023-02-17 8:54 ` [PATCH v4 1/3] mm/khugepaged: refactor collapse_file control flow David Stevens
2023-02-17 23:44 ` Yang Shi
2023-02-21 21:54 ` Peter Xu
2023-02-21 22:28 ` Yang Shi
2023-02-22 4:08 ` David Stevens
2023-02-22 16:24 ` Peter Xu
2023-02-17 8:54 ` [PATCH v4 2/3] mm/khugepaged: skip shmem with userfaultfd David Stevens
2023-02-21 22:12 ` Peter Xu
2023-02-17 8:54 ` [PATCH v4 3/3] mm/khugepaged: maintain page cache uptodate flag David Stevens
2023-02-21 22:18 ` Peter Xu [this message]
2023-02-17 10:37 ` [PATCH v4 0/3] mm/khugepaged: fix khugepaged+shmem races Miko Larsson
2023-03-03 15:35 ` Peter Xu
2023-03-03 15:45 ` Zach O'Keefe
2023-03-03 18:55 ` Yang Shi
2023-03-03 22:52 ` Andrew Morton
2023-03-06 2:44 ` David Stevens
2023-03-06 21:25 ` Andrew Morton
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