From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751403AbbCTIEh (ORCPT ); Fri, 20 Mar 2015 04:04:37 -0400 Received: from mta-out1.inet.fi ([62.71.2.227]:45875 "EHLO jenni2.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750966AbbCTIE2 (ORCPT ); Fri, 20 Mar 2015 04:04:28 -0400 Date: Fri, 20 Mar 2015 10:04:16 +0200 From: "Kirill A. Shutemov" To: Hillf Danton Cc: "Kirill A. Shutemov" , linux-kernel , linux-mm@kvack.org Subject: Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound pages Message-ID: <20150320080416.GA15877@node.dhcp.inet.fi> References: <010501d062df$05125160$0f36f420$@alibaba-inc.com> <010601d062df$f7b5a4d0$e720ee70$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <010601d062df$f7b5a4d0$e720ee70$@alibaba-inc.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 20, 2015 at 03:32:05PM +0800, Hillf Danton wrote: > > --- a/include/linux/page-flags.h > > +++ b/include/linux/page-flags.h > > @@ -269,7 +269,7 @@ static inline struct page *compound_head_fast(struct page *page) > > return page; > > } > > > > -TESTPAGEFLAG(Locked, locked, ANY) > > +__PAGEFLAG(Locked, locked, NO_TAIL) > > PAGEFLAG(Error, error, ANY) TESTCLEARFLAG(Error, error, ANY) > > PAGEFLAG(Referenced, referenced, ANY) TESTCLEARFLAG(Referenced, referenced, ANY) > > __SETPAGEFLAG(Referenced, referenced, ANY) > [...] > > @@ -490,9 +481,9 @@ extern int wait_on_page_bit_killable_timeout(struct page *page, > > > > static inline int wait_on_page_locked_killable(struct page *page) > > { > > - if (PageLocked(page)) > > - return wait_on_page_bit_killable(page, PG_locked); > > - return 0; > > + if (!PageLocked(page)) > > + return 0; > > I am lost here: can we feed any page to NO_TAIL operation? NO_TAIL triggers VM_BUG on set/clear, but not on checks. PageLocked() will look on head page. I tried to enforce policy for checks too, but it triggers all over the kernel. We tend to check random pages. We can try apply enforcing for *some* flags, but I didn't evaluate that. -- Kirill A. Shutemov