linux-kernel - Re: [PATCH v5 3/3] mm/khugepaged: maintain page cache uptodate flag

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Date:   Thu, 23 Mar 2023 21:56:07 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Song Liu <songliubraving@...com>, Jiri Olsa <jolsa@...nel.org>,
        David Stevens <stevensd@...omium.org>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Xu <peterx@...hat.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Yang Shi <shy828301@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Jiaqi Yan <jiaqiyan@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] mm/khugepaged: maintain page cache uptodate flag

On Thu, Mar 23, 2023 at 12:07:46PM -0700, Hugh Dickins wrote:
> On an earlier audit, for different reasons, I did also run across
> lib/buildid.c build_id_parse() using find_get_page() without checking
> PageUptodate() - looks as if it might do the wrong thing if it races
> with khugepaged collapsing text to huge, and should probably have a
> similar fix.

That shouldn't be using find_get_page().  It should probably use
read_cache_folio() which will actually read in the data if it's not
present in the page cache, and return an ERR_PTR if the data couldn't
be read.