From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44352 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755126AbeDWNxK (ORCPT ); Mon, 23 Apr 2018 09:53:10 -0400 Date: Mon, 23 Apr 2018 09:53:09 -0400 From: Vivek Goyal To: Miklos Szeredi Cc: Miklos Szeredi , overlayfs , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 13/35] ovl: readd fsync Message-ID: <20180423135309.GC2794@redhat.com> References: <20180412150826.20988-1-mszeredi@redhat.com> <20180412150826.20988-14-mszeredi@redhat.com> <20180423133617.GB2794@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Apr 23, 2018 at 03:39:45PM +0200, Miklos Szeredi wrote: > On Mon, Apr 23, 2018 at 3:36 PM, Vivek Goyal wrote: > > On Thu, Apr 12, 2018 at 05:08:04PM +0200, Miklos Szeredi wrote: > >> Implement stacked fsync(). > >> > >> Signed-off-by: Miklos Szeredi > >> --- > >> fs/overlayfs/file.c | 20 ++++++++++++++++++++ > >> 1 file changed, 20 insertions(+) > >> > >> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c > >> index b98204c1c19c..4417527667ff 100644 > >> --- a/fs/overlayfs/file.c > >> +++ b/fs/overlayfs/file.c > >> @@ -222,10 +222,30 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) > >> return ret; > >> } > >> > >> +static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync) > >> +{ > >> + struct fd real; > >> + const struct cred *old_cred; > >> + int ret; > >> + > >> + ret = ovl_real_file(file, &real); > >> + if (ret) > >> + return ret; > >> + > >> + old_cred = ovl_override_creds(file_inode(file)->i_sb); > >> + ret = vfs_fsync_range(real.file, start, end, datasync); > >> + revert_creds(old_cred); > > > > Can we avoid calling fsync() on real file if it is not upper. Is it worth > > optimizing. > > Not sure it's worth bothering with. If caller of fsync(2) didn't > worry about cost, then why should we? I was thinking more from the point of view of metadata copy up patches. For a metacopy file, I was thinking if I can just issue fsync() on upper file and skip it on lower file. Anyway, I don't have any strong opinion here. Vivek