Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932634Ab3FMIR1 (ORCPT ); Thu, 13 Jun 2013 04:17:27 -0400 Received: from relay.parallels.com ([195.214.232.42]:60275 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755531Ab3FMIRZ (ORCPT ); Thu, 13 Jun 2013 04:17:25 -0400 Subject: [PATCH] fuse: hold i_mutex in fuse_file_fallocate() - v2 To: miklos@szeredi.hu From: Maxim Patlasov Cc: fuse-devel@lists.sourceforge.net, bfoster@redhat.com, avati@redhat.com, linux-kernel@vger.kernel.org, devel@openvz.org Date: Thu, 13 Jun 2013 12:16:39 +0400 Message-ID: <20130613081551.11870.77028.stgit@maximpc.sw.ru> User-Agent: StGit/0.15 MIME-Version: 1.0 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: 2233 Lines: 64 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 --- 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/