From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756506AbZENRzC (ORCPT ); Thu, 14 May 2009 13:55:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752559AbZENRyu (ORCPT ); Thu, 14 May 2009 13:54:50 -0400 Received: from fxip-0047f.externet.hu ([88.209.222.127]:34984 "EHLO pomaz-ex.szeredi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751159AbZENRyt (ORCPT ); Thu, 14 May 2009 13:54:49 -0400 To: jens.axboe@oracle.com CC: miklos@szeredi.hu, akpm@linux-foundation.org, max@duempel.org, torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org In-reply-to: <20090514172935.GR4140@kernel.dk> (message from Jens Axboe on Thu, 14 May 2009 19:29:35 +0200) Subject: Re: [patch 2/3] splice: implement default splice_read method References: <20090507133734.450612199@szeredi.hu> <20090507133748.161689790@szeredi.hu> <20090512223500.d7ef4648.akpm@linux-foundation.org> <20090513063707.GC4140@kernel.dk> <20090514172935.GR4140@kernel.dk> Message-Id: From: Miklos Szeredi Date: Thu, 14 May 2009 19:54:33 +0200 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 14 May 2009, Jens Axboe wrote: > > The bigger problem is that the default_file_splice_write() > > implementation in the other patch does the same (it calls > > buf->ops->map() on all buffers). > > Yep that's even worse, as that should go BUG() pretty much immediately > when the KM_USER0 slot is reused! No, ->map() calls plain kmap() if "atomic" argument is zero. Nevertheless the deadlock due to multiple kmaps is still possible. > > Hmm. Simple solution would be to do a write() for each buffer. But > > this only affects HIGHMEM kernels, so it's a bit pointless to do that > > on all archs. Sigh... > > It is unfortunate, we are going to be stuck with that for some time > still... I'm going to be offline till next monday, I'll post a fix after that. Thanks, Miklos