From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hugh Dickins Subject: iput() in reclaim context Date: Wed, 21 May 2008 18:52:27 +0100 (BST) Message-ID: References: <20080515231045.GY155679365@sgi.com> <20080519054554.GY103491721@sgi.com> <20080520002503.GC173056135@sgi.com> <20080520065622.GA13968@2ka.mipt.ru> <20080520214617.GU103491721@sgi.com> <20080520222505.GA23988@2ka.mipt.ru> <20080520231942.GX103491721@sgi.com> <20080520162816.e5dfeffa.akpm@linux-foundation.org> <20080521061531.GA27362@2ka.mipt.ru> <20080520232444.8bff5ccf.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Evgeniy Polyakov , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Andrew Morton Return-path: Received: from extu-mxob-1.symantec.com ([216.10.194.28]:33156 "EHLO extu-mxob-1.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934727AbYEURxv (ORCPT ); Wed, 21 May 2008 13:53:51 -0400 In-Reply-To: <20080520232444.8bff5ccf.akpm@linux-foundation.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, 20 May 2008, Andrew Morton wrote: > On Wed, 21 May 2008 10:15:32 +0400 Evgeniy Polyakov wrote: > > On Tue, May 20, 2008 at 04:28:16PM -0700, Andrew Morton (akpm@linux-foundation.org) wrote: > > > It's more than efficiency. There are lots and lots of things we cannot > > > do in direct-reclaim context. > > > > > > ... > > > > > > c) Cannot run iput(). Or at least, we couldn't five or six years > > > ago. afaik nobody has investigated whether the situation is now > > > better or worse. I happened to notice your remark in the buffer heads defrag thread. Do you remember what that limitation was about? Because just a few months ago I discovered a shmem race which I fixed by doing igrab+iput in shmem_writepage, in the reclaim context. Feeling guilty now: I'd better investigate, but would welcome a starting pointer. (If I'm lucky, it'll be that the generic code in vmscan.c cannot use iput, but particular filesystems might themselves be safe to.) Thanks, Hugh