Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754059AbaJCSNp (ORCPT ); Fri, 3 Oct 2014 14:13:45 -0400 Received: from mail-pd0-f170.google.com ([209.85.192.170]:46983 "EHLO mail-pd0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751573AbaJCSNn (ORCPT ); Fri, 3 Oct 2014 14:13:43 -0400 Message-ID: <542EE753.20005@kernel.dk> Date: Fri, 03 Oct 2014 12:13:39 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 MIME-Version: 1.0 To: Kent Overstreet , linux-kernel@vger.kernel.org CC: Benjamin LaHaise , Zach Brown , Jeff Moyer , Slava Pestov Subject: Re: [PATCH] aio: Fix return code of io_submit() (RFC) References: <1412359693-2535-1-git-send-email-kmo@daterainc.com> In-Reply-To: <1412359693-2535-1-git-send-email-kmo@daterainc.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014-10-03 12:08, Kent Overstreet wrote: > io_submit() could return -EAGAIN on memory allocation failure when it should > really have been returning -ENOMEM. This could confuse applications (i.e. fio) > since -EAGAIN means "too many requests outstanding, wait until completions have > been reaped" and if the application actually was tracking outstanding > completions this wouldn't make a lot of sense. > > NOTE: > > the man page seems to imply that the current behaviour (-EAGAIN on allocation > failure) has always been the case. I don't think it makes a lot of sense, but > this should probably be discussed more widely in case applications have somehow > come to rely on the current behaviour... We can't really feasibly fix this, is my worry. Fio does track the pending requests and does not get into a getevents() forever wait if it gets -EAGAIN on submission. But before the fix, it would loop forever in submission in -EAGAIN. How are applications supposed to deal with ENOMEM? I think the answer here is that they can't, it would be a fatal condition. AIO must provide isn't own guarantee of progress, with a mempool or similar. -- Jens Axboe -- 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/