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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id a47sm13855216qtb.79.2019.04.04.14.28.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 04 Apr 2019 14:28:03 -0700 (PDT) Message-ID: <1554413282.26196.40.camel@lca.pw> Subject: Re: page cache: Store only head pages in i_pages From: Qian Cai To: "Kirill A. Shutemov" Cc: Matthew Wilcox , Huang Ying , linux-mm@kvack.org Date: Thu, 04 Apr 2019 17:28:02 -0400 In-Reply-To: <20190404134553.vuvhgmghlkiw2hgl@kshutemo-mobl1> References: <20190324030422.GE10344@bombadil.infradead.org> <20190329195941.GW10344@bombadil.infradead.org> <1553894734.26196.30.camel@lca.pw> <20190330030431.GX10344@bombadil.infradead.org> <20190330141052.GZ10344@bombadil.infradead.org> <20190331032326.GA10344@bombadil.infradead.org> <20190401091858.s7clitbvf46nomjm@kshutemo-mobl1> <20190401092716.mxw32y4sl66ywc2o@kshutemo-mobl1> <1554383410.26196.39.camel@lca.pw> <20190404134553.vuvhgmghlkiw2hgl@kshutemo-mobl1> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit 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, 2019-04-04 at 16:45 +0300, Kirill A. Shutemov wrote: > What about this: > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index f939e004c5d1..2e8438a1216a 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -335,12 +335,15 @@ static inline struct page *grab_cache_page_nowait(struct > address_space *mapping, >   >  static inline struct page *find_subpage(struct page *page, pgoff_t offset) >  { > - unsigned long index = page_index(page); > + unsigned long mask; > + > + if (PageHuge(page)) > + return page; >   >   VM_BUG_ON_PAGE(PageTail(page), page); > - VM_BUG_ON_PAGE(index > offset, page); > - VM_BUG_ON_PAGE(index + (1 << compound_order(page)) <= offset, page); > - return page - index + offset; > + > + mask = (1UL << compound_order(page)) - 1; > + return page + (offset & mask); >  } >   >  struct page *find_get_entry(struct address_space *mapping, pgoff_t offset); It works fine.