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Shutemov" To: Song Liu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, matthew.wilcox@oracle.com, kernel-team@fb.com, william.kucharski@oracle.com, kirill.shutemov@linux.intel.com, Johannes Weiner , Hugh Dickins Subject: Re: [PATCH] mm,thp: recheck each page before collapsing file THP Message-ID: <20191018133444.iif7b33muxmus6lb@box> References: <20191018050832.1251306-1-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191018050832.1251306-1-songliubraving@fb.com> User-Agent: NeoMutt/20180716 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 17, 2019 at 10:08:32PM -0700, Song Liu wrote: > In collapse_file(), after locking the page, it is necessary to recheck > that the page is up-to-date, clean, and pointing to the proper mapping. > If any check fails, abort the collapse. > > Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") > Cc: Kirill A. Shutemov > Cc: Johannes Weiner > Cc: Hugh Dickins > Cc: William Kucharski > Cc: Andrew Morton > Signed-off-by: Song Liu > --- > mm/khugepaged.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 0a1b4b484ac5..7da49b643c4d 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1619,6 +1619,14 @@ static void collapse_file(struct mm_struct *mm, > result = SCAN_PAGE_LOCK; > goto xa_locked; > } > + > + /* double check the page is correct and clean */ > + if (unlikely(!PageUptodate(page)) || > + unlikely(PageDirty(page)) || > + unlikely(page->mapping != mapping)) { > + result = SCAN_FAIL; > + goto out_unlock; > + } > } > > /* Hm. But why only for !is_shmem? Or I read it wrong? -- Kirill A. Shutemov