Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263723AbTEMXIa (ORCPT ); Tue, 13 May 2003 19:08:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263726AbTEMXIa (ORCPT ); Tue, 13 May 2003 19:08:30 -0400 Received: from holomorphy.com ([66.224.33.161]:7870 "EHLO holomorphy") by vger.kernel.org with ESMTP id S263723AbTEMXI2 (ORCPT ); Tue, 13 May 2003 19:08:28 -0400 Date: Tue, 13 May 2003 16:20:38 -0700 From: William Lee Irwin III To: Dave McCracken Cc: Mika Penttil? , Linux Memory Management , Linux Kernel Subject: Re: Race between vmtruncate and mapped areas? Message-ID: <20030513232038.GB8978@holomorphy.com> Mail-Followup-To: William Lee Irwin III , Dave McCracken , Mika Penttil? , Linux Memory Management , Linux Kernel References: <154080000.1052858685@baldur.austin.ibm.com> <3EC15C6D.1040403@kolumbus.fi> <199610000.1052864784@baldur.austin.ibm.com> <20030513224929.GX8978@holomorphy.com> <220550000.1052866808@baldur.austin.ibm.com> <20030513231139.GZ8978@holomorphy.com> <247390000.1052867776@baldur.austin.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <247390000.1052867776@baldur.austin.ibm.com> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1187 Lines: 25 On Tuesday, May 13, 2003 16:11:39 -0700 William Lee Irwin III wrote: >> Okay, what's stopping filemap_nopage() from fetching the page from >> pagecache after one of the mm->mmap_sem's is dropped but before >> truncate_inode_pages() removes the page? The fault path is only locked >> out for one mm during one part of the operation. I can see taking >> ->i_sem in do_no_page() fixing it, but not ->mmap_sem in vmtruncate() >> (but of course that's _far_ too heavy-handed to merge at all). On Tue, May 13, 2003 at 06:16:16PM -0500, Dave McCracken wrote: > mmap_sem is held for read across the entire fault, so by the time > vmtruncate_list() can call zap_page_range() the page has been instantiated > in the page table and will get removed. That's not quite the answer, inode->i_size is. The mmap_sem works because then ->i_size can't be sampled by filemap_nopage() before the pagetable wiping operation starts. -- wli - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/