From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752141AbZBQLkM (ORCPT ); Tue, 17 Feb 2009 06:40:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754186AbZBQLjl (ORCPT ); Tue, 17 Feb 2009 06:39:41 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:34080 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754112AbZBQLjk (ORCPT ); Tue, 17 Feb 2009 06:39:40 -0500 Subject: Re: set_page_dirty races (was: Re: [patch 2/4] vfs: add set_page_dirty_notag) From: Peter Zijlstra To: Nick Piggin Cc: Edward Shishkin , Andrew Morton , Ryan Hope , Randy Dunlap , linux-kernel@vger.kernel.org, ReiserFS Mailing List In-Reply-To: <20090217112512.GD26402@wotan.suse.de> References: <49957C43.7050701@gmail.com> <1234534150.6519.101.camel@twins> <18838.49922.215481.399653@edward.zelnet.ru> <1234645893.4695.8.camel@laptop> <18841.60432.329341.514726@edward.zelnet.ru> <1234861781.4744.21.camel@laptop> <20090217093805.GB31323@wotan.suse.de> <1234865116.4744.46.camel@laptop> <20090217102443.GA26402@wotan.suse.de> <1234867200.4744.65.camel@laptop> <20090217112512.GD26402@wotan.suse.de> Content-Type: text/plain Date: Tue, 17 Feb 2009 12:39:32 +0100 Message-Id: <1234870772.4744.79.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.25.90 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2009-02-17 at 12:25 +0100, Nick Piggin wrote: > Introduce put_user_pages function. > > In order to have more flexibility to deal with issues surrounding > get_user_pages difficulties[*], introduce put_user_pages function > intended to release pages acquired by get_user_pages. For now, just > do the regular put_page thing. If all callers are converted, it could > be used to help with such races. In the meantime, it will actually > serve as a small extra piece of documentation for the code. > > [*] eg. get_user_pages caller can bypass page_mkwrite calls into the > filesystem to notify of page dirty activity if the page gets cleaned > before the caller calls its final set_page_dirty). Hmm, if we want to distinguish between .write=1 and .write=0, we would have to pass .write to pup too, right? > --- > include/linux/mm.h | 1 + > mm/memory.c | 13 ++++++++++++- > 2 files changed, 13 insertions(+), 1 deletion(-) > > Index: linux-2.6/include/linux/mm.h > =================================================================== > --- linux-2.6.orig/include/linux/mm.h > +++ linux-2.6/include/linux/mm.h > @@ -826,6 +826,7 @@ extern int access_process_vm(struct task > int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, > int len, int write, int force, struct page **pages, struct vm_area_struct **vmas); > > +void put_user_pages(struct page **pages, int nr); > extern int try_to_release_page(struct page * page, gfp_t gfp_mask); > extern void do_invalidatepage(struct page *page, unsigned long offset); > > Index: linux-2.6/mm/memory.c > =================================================================== > --- linux-2.6.orig/mm/memory.c > +++ linux-2.6/mm/memory.c > @@ -1370,9 +1370,20 @@ int get_user_pages(struct task_struct *t > start, len, flags, > pages, vmas); > } > - > EXPORT_SYMBOL(get_user_pages); > > +/* > + * put_user_pages should be used to release pages acquired with get_user_pages. > + */ > +void put_user_pages(struct page **pages, int nr) > +{ > + int i; > + > + for (i = 0; i < nr; i++) > + put_page(pages[i]); > +} > +EXPORT_SYMBOL(put_user_pages); > + > pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr, > spinlock_t **ptl) > { >