Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753590Ab1BHLuA (ORCPT ); Tue, 8 Feb 2011 06:50:00 -0500 Received: from rcsinet10.oracle.com ([148.87.113.121]:53617 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753516Ab1BHLt7 (ORCPT ); Tue, 8 Feb 2011 06:49:59 -0500 Message-ID: <4D512E63.1040202@oracle.com> Date: Tue, 08 Feb 2011 17:22:03 +0530 From: Gurudas Pai User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Miklos Szeredi CC: Hugh Dickins , hch@infradead.org, akpm@linux-foundation.org, lkml20101129@newton.leun.net, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm: prevent concurrent unmap_mapping_range() on the same inode References: <20110120124043.GA4347@infradead.org> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: acsmt354.oracle.com [141.146.40.154] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090202.4D512DB8.00E7:SCFMA4539814,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1981 Lines: 48 > On Wed, 26 Jan 2011, Hugh Dickins wrote: >> I had wanted to propose that for now you modify just fuse to use >> i_alloc_sem for serialization there, and I provide a patch to >> unmap_mapping_range() to give safety to whatever other cases there are >> (I'm now sure there are other cases, but also sure that I cannot >> safely identify them all and fix them correctly at source myself - >> even if I found time to do the patches, they'd need at least a release >> cycle to bed in with BUG_ONs). > > Since fuse is the only one where the BUG has actually been triggered, > and since there are problems with all the proposed generic approaches, > I concur. I didn't want to use i_alloc_sem here as it's more > confusing than a new mutex. > > Gurudas, could you please give this patch a go in your testcase? I found this BUG with nfs, so trying with current patch may not help. https://lkml.org/lkml/2010/12/29/9 Let me know if I have to run this > > From: Miklos Szeredi > Subject: fuse: prevent concurrent unmap on the same inode > > Running a fuse filesystem with multiple open()'s in parallel can > trigger a "kernel BUG at mm/truncate.c:475" > > The reason is, unmap_mapping_range() is not prepared for more than > one concurrent invocation per inode. > > Truncate and hole punching already serialize with i_mutex. Other > callers of unmap_mapping_range() do not, and it's difficult to get > i_mutex protection for all callers. In particular ->d_revalidate(), > which calls invalidate_inode_pages2_range() in fuse, may be called > with or without i_mutex. > > This patch adds a new mutex to fuse_inode to prevent running multiple > concurrent unmap_mapping_range() on the same mapping. Thanks, -Guru -- 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/