From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx118.postini.com [74.125.245.118]) by kanga.kvack.org (Postfix) with SMTP id 7ED846B004D for ; Thu, 3 May 2012 02:30:57 -0400 (EDT) Received: by obbwd18 with SMTP id wd18so2721882obb.14 for ; Wed, 02 May 2012 23:30:56 -0700 (PDT) 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: 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 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. =C2=A0What are we actually doing here? =C2=A0Causing 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. =C2=A0Yes, maintainers are very naughty and pro= bably >> > do need cattle prods^W^W warnings to motivate them to fix stuff, but w= e >> > 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). =C2=A0This 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 requir= e any allocations, or at least it should be able to tolerate allocation failu= res. So fixing that would be a good idea anyway. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org