From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH 3/3 v2] fs: move falloc collapse range check into the filesystem methods Date: Tue, 15 Apr 2014 22:55:21 -0400 Message-ID: <20140416025521.GC21807@thunk.org> References: <1397580076-19826-1-git-send-email-lczerner@redhat.com> <1397580076-19826-3-git-send-email-lczerner@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, xfs@oss.sgi.com To: Lukas Czerner Return-path: Received: from imap.thunk.org ([74.207.234.97]:54910 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864AbaDPCzX (ORCPT ); Tue, 15 Apr 2014 22:55:23 -0400 Content-Disposition: inline In-Reply-To: <1397580076-19826-3-git-send-email-lczerner@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Apr 15, 2014 at 06:41:16PM +0200, Lukas Czerner wrote: > Currently in do_fallocate in collapse range case we're checking whether > offset + len is not bigger than i_size. However there is nothing which > would prevent i_size from changing so the check is pointless. It should > be done in the file system itself and the file system needs to make sure > that i_size is not going to change. The i_size check for the other > fallocate modes are also done in the filesystems. > > As it is now we can easily crash kernel by having two processes doing > truncate and fallocate collapse range at the same time. This can be > reproduced on ext4 and it is theoretically possible on xfs even though I > was not able to trigger it with this simple test. > > This commit removes the check from do_fallocate and adds it to the file > system. > > Signed-off-by: Lukas Czerner > Acked-by: Dave Chinner > Reviewed-by: Christoph Hellwig Thanks, updated. - Ted