From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id E8AEE6B004D for ; Tue, 9 Jun 2009 08:11:44 -0400 (EDT) Date: Tue, 9 Jun 2009 20:47:55 +0800 From: Wu Fengguang Subject: Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3 Message-ID: <20090609124755.GA6583@localhost> References: <20090528145021.GA5503@localhost> <20090607160225.GA24315@localhost> <20090608123133.GA7944@localhost> <20090609064855.GB5490@localhost> <20090609104825.GJ14820@wotan.suse.de> <20090609121510.GB5589@localhost> <20090609121722.GC9158@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090609121722.GC9158@wotan.suse.de> Sender: owner-linux-mm@kvack.org To: Nick Piggin Cc: Nai Xia , Andi Kleen , "hugh@veritas.com" , "riel@redhat.com" , "akpm@linux-foundation.org" , "chris.mason@oracle.com" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" List-ID: On Tue, Jun 09, 2009 at 08:17:22PM +0800, Nick Piggin wrote: > On Tue, Jun 09, 2009 at 08:15:10PM +0800, Wu Fengguang wrote: > > On Tue, Jun 09, 2009 at 06:48:25PM +0800, Nick Piggin wrote: > > > On Tue, Jun 09, 2009 at 02:48:55PM +0800, Wu Fengguang wrote: > > > > On Mon, Jun 08, 2009 at 10:46:53PM +0800, Nai Xia wrote: > > > > > I meant PG_writeback stops writers to index---->struct page mapping. > > > > > > > > It's protected by the radix tree RCU locks. Period. > > > > > > > > If you are referring to the reverse mapping: page->mapping is procted > > > > by PG_lock. No one should make assumption that it won't change under > > > > page writeback. > > > > > > Well... I think probably PG_writeback should be enough. Phrased another > > > way: I think it is a very bad idea to truncate PG_writeback pages out of > > > pagecache. Does anything actually do that? > > > > There shall be no one. OK I will follow that convention.. > > > > But as I stated it is only safe do rely on the fact "no one truncates > > PG_writeback pages" in end_writeback_io handlers. And I suspect if > > there does exist such a handler, it could be trivially converted to > > take the page lock. > > Well, the writeback submitter first sets writeback, then unlocks > the page. I don't think he wants a truncate coming in at that point. OK. I think we've mostly agreed on the consequences of PG_writeback vs truncation. I'll follow the least surprise principle and stop here, hehe. Thanks, Fengguang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org