From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 3A6D08D0039 for ; Tue, 8 Feb 2011 06:49:45 -0500 (EST) Message-ID: <4D512E63.1040202@oracle.com> Date: Tue, 08 Feb 2011 17:22:03 +0530 From: Gurudas Pai MIME-Version: 1.0 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 Sender: owner-linux-mm@kvack.org List-ID: 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 > 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, 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