Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752866Ab2ECGa6 (ORCPT ); Thu, 3 May 2012 02:30:58 -0400 Received: from mail-ob0-f174.google.com ([209.85.214.174]:61245 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751118Ab2ECGa5 convert rfc822-to-8bit (ORCPT ); Thu, 3 May 2012 02:30:57 -0400 MIME-Version: 1.0 In-Reply-To: References: <1335932890-25294-1-git-send-email-minchan@kernel.org> <20120502124610.175e099c.akpm@linux-foundation.org> <4FA1D93C.9000306@kernel.org> Date: Thu, 3 May 2012 16:30:56 +1000 Message-ID: Subject: Re: [PATCH] vmalloc: add warning in __vmalloc From: Nick Piggin To: Sage Weil Cc: Minchan Kim , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kosaki.motohiro@gmail.com, rientjes@google.com, Neil Brown , Artem Bityutskiy , David Woodhouse , "Theodore Ts'o" , Adrian Hunter , Steven Whitehouse , "David S. Miller" , James Morris , Alexander Viro , linux-fsdevel Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1730 Lines: 38 On 3 May 2012 15:46, Sage Weil wrote: > On Thu, 3 May 2012, Minchan Kim wrote: >> On 05/03/2012 04:46 AM, Andrew Morton wrote: >> > Well.  What are we actually doing here?  Causing the kernel to spew a >> > warning due to known-buggy callsites, so that users will report the >> > warnings, eventually goading maintainers into fixing their stuff. >> > >> > This isn't very efficient :( >> >> >> Yes. I hope maintainers fix it before merging this. >> >> > >> > It would be better to fix that stuff first, then add the warning to >> > prevent reoccurrences.  Yes, maintainers are very naughty and probably >> > do need cattle prods^W^W warnings to motivate them to fix stuff, but we >> > should first make an effort to get these things fixed without >> > irritating and alarming our users. >> > >> > Where are these offending callsites? > > Okay, maybe this is a stupid question, but: if an fs can't call vmalloc > with GFP_NOFS without risking deadlock, calling with GFP_KERNEL instead > doesn't fix anything (besides being more honest).  This really means that > vmalloc is effectively off-limits for file systems in any > writeback-related path, right? Anywhere it cannot reenter the filesystem, yes. GFP_NOFS is effectively GFP_KERNEL when calling vmalloc. Note that in writeback paths, a "good citizen" filesystem should not require any allocations, or at least it should be able to tolerate allocation failures. So fixing that would be a good idea anyway. -- 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/