From: Matthew Wilcox <willy@infradead.org>
To: David Stevens <stevensd@chromium.org>
Cc: linux-mm@kvack.org, Peter Xu <peterx@redhat.com>,
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 1/2] mm/khugepaged: set THP as uptodate earlier for shmem
Date: Tue, 14 Feb 2023 15:44:54 +0000 [thread overview]
Message-ID: <Y+usdhfguWr/aD5x@casper.infradead.org> (raw)
In-Reply-To: <20230214075710.2401855-1-stevensd@google.com>
On Tue, Feb 14, 2023 at 04:57:09PM +0900, David Stevens wrote:
> /*
> - * At this point the hpage is locked and not up-to-date.
> - * It's safe to insert it into the page cache, because nobody would
> - * be able to map it or use it in another way until we unlock it.
> + * Mark hpage as up-to-date before inserting it into the page cache to
> + * prevent it from being mistaken for an fallocated but unwritten page.
> + * Inserting the unfinished hpage into the page cache is safe because
> + * it is locked, so nobody can map it or use it in another way until we
> + * unlock it.
No, that's not true. The data has to be there before we mark it
uptodate. See filemap_get_pages() for example, used as part of
read(). We don't lock the page unless we need to bring it uptodate
ourselves.
next prev parent reply other threads:[~2023-02-14 15:45 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-14 7:57 [PATCH 1/2] mm/khugepaged: set THP as uptodate earlier for shmem David Stevens
2023-02-14 7:57 ` [PATCH 2/2] mm/khugepaged: skip shmem with userfaultfd David Stevens
2023-02-14 22:35 ` Peter Xu
2023-02-15 1:57 ` David Stevens
2023-02-15 22:27 ` Peter Xu
2023-02-15 22:48 ` Peter Xu
2023-02-16 1:37 ` David Stevens
2023-02-16 14:41 ` Peter Xu
2023-02-16 21:58 ` Yang Shi
2023-02-16 23:07 ` Peter Xu
2023-02-16 23:52 ` Yang Shi
2023-02-17 2:00 ` David Stevens
2023-02-17 3:20 ` Yang Shi
2023-02-14 15:44 ` Matthew Wilcox [this message]
2023-02-15 1:33 ` [PATCH 1/2] mm/khugepaged: set THP as uptodate earlier for shmem David Stevens
2023-02-15 22:05 ` Peter Xu
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