From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758032Ab3HMN1J (ORCPT ); Tue, 13 Aug 2013 09:27:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18780 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757828Ab3HMN1I (ORCPT ); Tue, 13 Aug 2013 09:27:08 -0400 Message-ID: <520A3352.5070709@redhat.com> Date: Tue, 13 Aug 2013 09:23:30 -0400 From: Brian Foster User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Maxim Patlasov CC: miklos@szeredi.hu, fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, devel@openvz.org, xemul@parallels.com Subject: Re: [PATCH 2/2] fuse: wait for writeback in fuse_file_fallocate() References: <20130812163739.10366.64896.stgit@maximpc.sw.ru> <20130812163935.10366.88320.stgit@maximpc.sw.ru> <520A2114.1040203@redhat.com> <520A2D0E.5050103@parallels.com> In-Reply-To: <520A2D0E.5050103@parallels.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/13/2013 08:56 AM, Maxim Patlasov wrote: > Hi, > > 08/13/2013 04:05 PM, Brian Foster пишет: >> ... >> @@ -2478,8 +2516,11 @@ static long fuse_file_fallocate(struct file >> *file, int mode, loff_t offset, >> if (lock_inode) { >> mutex_lock(&inode->i_mutex); >> - if (mode & FALLOC_FL_PUNCH_HOLE) >> - fuse_set_nowrite(inode); >> + if (mode & FALLOC_FL_PUNCH_HOLE) { >> + truncate_pagecache_range(inode, offset, >> + offset + length - 1); >> + fuse_wait_on_writeback(inode, offset, length); >> + } >> If this happens to be the first attempt on an fs that doesn't support >> fallocate, we'll return -EOPNOTSUPP after having already punched out the >> data in the pagecache. > > Yes, this is unpleasant, but it's not critical, imo. We're returning an > error code (even though equal to -EOPNOTSUPP) and a sane application > should not make any assumption about current state of the punched > region. Also, the application intended to discard given region of the > file, so why should it pay care for its content afterwards? > I agree, though most users probably wouldn't expect that a blatant error like EOPNOTSUPP leave the range in a weird state. What's more, it only does so if it's the first attempt and behaves more appropriately after that. >> What about replacing the nowrite logic with a >> flush (and still followed by your new writeback wait logic) rather than >> moving the pagecache truncate? > > The "flush" you mentioned should firstly flush page cache. > invalidate_inode_pages2_range() seems to be a candidate. We definitely > cannot ignore error code from it because it can be fuse_launder_page() > who got -ENOMEM from fuse_writepage_locked(). In case of err == -ENOMEM, > we could safely fail fallocate, but what should we do if it's -EBUSY? > Any ideas? > I was referring to something like filemap_write_and_wait_range(), for example. Then continue to use truncate_pagecache_range() as we do today. Thoughts? Brian > Thanks, > Maxim