Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751668AbWEaQWn (ORCPT ); Wed, 31 May 2006 12:22:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751669AbWEaQWn (ORCPT ); Wed, 31 May 2006 12:22:43 -0400 Received: from smtp105.mail.mud.yahoo.com ([209.191.85.215]:51827 "HELO smtp105.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S1751635AbWEaQWm (ORCPT ); Wed, 31 May 2006 12:22:42 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=lxk/oyKqxlmXHSmT8h71voJblvZ29YqR8j3r2rDGG66i+l8drORCm7sFM29zafeE3VKvBqLITurklNII8MlcJ7lcRW9IjZeB9XHqd7y5eFR0WQM/BEze3KjWZ5nvAjvudG8OOvJRBPaRtqOHy2rR7XEPlA759lmfZoR6PrGIYkI= ; Message-ID: <447DC2CC.5060900@yahoo.com.au> Date: Thu, 01 Jun 2006 02:22:36 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Linus Torvalds CC: linux-kernel@vger.kernel.org, axboe@suse.de Subject: Re: [rfc][patch] remove racy sync_page? References: <447AC011.8050708@yahoo.com.au> <20060529121556.349863b8.akpm@osdl.org> <447B8CE6.5000208@yahoo.com.au> <20060529183201.0e8173bc.akpm@osdl.org> <447BB3FD.1070707@yahoo.com.au> <447BD31E.7000503@yahoo.com.au> <447BD63D.2080900@yahoo.com.au> <447CE43A.6030700@yahoo.com.au> <447D9A41.8040601@yahoo.com.au> <447DAEDE.5070305@yahoo.com.au> <447DB765.6030702@yahoo.com.au> <447DC22C.5070503@yahoo.com.au> In-Reply-To: <447DC22C.5070503@yahoo.com.au> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1255 Lines: 34 Nick Piggin wrote: > Linus Torvalds wrote: > >> Tell me WHERE you can unplug in that sequence. I will tell you where >> you can NOT unplug: > > > ... > >> - you can NOT just unplug in the path _after_ "readpage()", because >> the IO may have been started by SOMEBODY ELSE that just did >> read-ahead, and didn't unplug (on _purpose_ - the whole point of >> doing read-ahead is to allow concurrent IO execution, so a >> read-aheader that unplugs is broken by definition) > > > Umm, this happens with the current lock_page() after readpage. And > with per-task plugs, you do not unplug anybody else. If this wasn't clear: I don't mean per-task plugs as in "the task explicitly plugs and unplugs the block device"[*]; I mean really per-task plugs. [*] That would be crazy anyway because that would imply some random task can plug an filled request queue that is going full tilt. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - 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/