Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755541Ab3FMLtM (ORCPT ); Thu, 13 Jun 2013 07:49:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:28118 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751453Ab3FMLtK (ORCPT ); Thu, 13 Jun 2013 07:49:10 -0400 Message-ID: <51B9B0F8.3070301@redhat.com> Date: Thu, 13 Jun 2013 07:46:00 -0400 From: Brian Foster User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Maxim Patlasov CC: miklos@szeredi.hu, fuse-devel@lists.sourceforge.net, avati@redhat.com, linux-kernel@vger.kernel.org, devel@openvz.org Subject: Re: [PATCH] fuse: hold i_mutex in fuse_file_fallocate() - v2 References: <20130613081551.11870.77028.stgit@maximpc.sw.ru> In-Reply-To: <20130613081551.11870.77028.stgit@maximpc.sw.ru> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2499 Lines: 71 On 06/13/2013 04:16 AM, Maxim Patlasov wrote: > Changing size of a file on server and local update (fuse_write_update_size) > should be always protected by inode->i_mutex. Otherwise a race like this is > possible: > > 1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE). > fuse_file_fallocate() sends FUSE_FALLOCATE request to the server. > 2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr() > sends shrinking FUSE_SETATTR request to the server and updates local i_size > by i_size_write(inode, outarg.attr.size). > 3. Process 'A' resumes execution of fuse_file_fallocate() and calls > fuse_write_update_size(inode, offset + length). But 'offset + length' was > obsoleted by ftruncate from previous step. > > Changed in v2 (thanks Brian and Anand for suggestions): > - made relation between mutex_lock() and fuse_set_nowrite(inode) more > explicit and clear. > - updated patch description to use ftruncate(2) in example > > Signed-off-by: Maxim V. Patlasov > --- Makes more sense and I like the cleanup... thanks. Reviewed-by: Brian Foster > fs/fuse/file.c | 12 ++++++++---- > 1 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > index e570081..35f2810 100644 > --- a/fs/fuse/file.c > +++ b/fs/fuse/file.c > @@ -2470,13 +2470,16 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, > .mode = mode > }; > int err; > + bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) || > + (mode & FALLOC_FL_PUNCH_HOLE); > > if (fc->no_fallocate) > return -EOPNOTSUPP; > > - if (mode & FALLOC_FL_PUNCH_HOLE) { > + if (lock_inode) { > mutex_lock(&inode->i_mutex); > - fuse_set_nowrite(inode); > + if (mode & FALLOC_FL_PUNCH_HOLE) > + fuse_set_nowrite(inode); > } > > req = fuse_get_req_nopages(fc); > @@ -2511,8 +2514,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, > fuse_invalidate_attr(inode); > > out: > - if (mode & FALLOC_FL_PUNCH_HOLE) { > - fuse_release_nowrite(inode); > + if (lock_inode) { > + if (mode & FALLOC_FL_PUNCH_HOLE) > + fuse_release_nowrite(inode); > mutex_unlock(&inode->i_mutex); > } > > -- 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/