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Shutemov" To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, William Kucharski Subject: Re: [PATCH 12/15] mm: Support removing arbitrary sized pages from mapping Message-ID: <20191001103939.gglcqk2gzezkrpnc@box> References: <20190925005214.27240-1-willy@infradead.org> <20190925005214.27240-13-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190925005214.27240-13-willy@infradead.org> 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 Tue, Sep 24, 2019 at 05:52:11PM -0700, Matthew Wilcox wrote: > From: William Kucharski > > __remove_mapping() assumes that pages can only be either base pages > or HPAGE_PMD_SIZE. Ask the page what size it is. You also fixes the issue CONFIG_READ_ONLY_THP_FOR_FS=y with this patch. The new feature makes the refcount calculation relevant not only for PageSwapCache(). It should go to v5.4. > > Signed-off-by: William Kucharski > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/vmscan.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index a7f9f379e523..9f44868e640b 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -932,10 +932,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page, > * Note that if SetPageDirty is always performed via set_page_dirty, > * and thus under the i_pages lock, then this ordering is not required. > */ > - if (unlikely(PageTransHuge(page)) && PageSwapCache(page)) > - refcount = 1 + HPAGE_PMD_NR; > - else > - refcount = 2; > + refcount = 1 + compound_nr(page); > if (!page_ref_freeze(page, refcount)) > goto cannot_free; > /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */ > -- > 2.23.0 > > -- Kirill A. Shutemov