From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753640Ab3IKKMh (ORCPT ); Wed, 11 Sep 2013 06:12:37 -0400 Received: from mail-lb0-f169.google.com ([209.85.217.169]:62326 "EHLO mail-lb0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753371Ab3IKKMd convert rfc822-to-8bit (ORCPT ); Wed, 11 Sep 2013 06:12:33 -0400 MIME-Version: 1.0 X-Originating-IP: [86.59.245.170] In-Reply-To: <52208313.6000700@parallels.com> References: <20130812163935.10366.88320.stgit@maximpc.sw.ru> <20130816112854.5630.1907.stgit@maximpc.sw.ru> <20130829154110.GB19636@tucsk.piliscsaba.szeredi.hu> <521F7672.7050407@parallels.com> <20130829163744.GC19636@tucsk.piliscsaba.szeredi.hu> <52208313.6000700@parallels.com> Date: Wed, 11 Sep 2013 12:12:31 +0200 Message-ID: Subject: Re: [PATCH 2/2] fuse: wait for writeback in fuse_file_fallocate() -v2 From: Miklos Szeredi To: Maxim Patlasov Cc: fuse-devel , Brian Foster , Pavel Emelianov , Kernel Mailing List , devel@openvz.org 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 Fri, Aug 30, 2013 at 1:33 PM, Maxim Patlasov wrote: > 08/30/2013 01:13 PM, Miklos Szeredi пишет: > >> On Thu, Aug 29, 2013 at 6:41 PM, Miklos Szeredi wrote: >>> >>> BTW, isn't it enough to do the filemap_write_and_wait() *plus* the >>> fuse_set_nowrite()? >> >> Thought about it a bit and I think this should do fine. >> >> Any writes before the fallocate will go trough before the fallocate. >> i_mutex guarantees that only one instance of fuse_set_nowrite() is >> running. Any mmaped writes during the fallocate() will go after the >> fallocate request and the page cache truncation and that's fine too. >> Page cache is consistent since it doens't contain pages for those >> writes to the hole. Subsequent reads to that area will fill them in. >> >> Any other concerns? > > > No. What you suggest looks as a neat and correct solution. I'll resend the > updated patch after some testing (since now till Monday). > > As for proof-of-correctness, all you wrote above is correct, but the first > point had been boiling my mind for a while. I came to the following > reasoning (hopefully it is what you meant): > > The fact that filemap_write_and_wait() returned infers that > end_page_writeback() was called for all relevant pages. And fuse doesn't > call it before adding request to fi->queued_writes and calling > fuse_flush_writepages(). And the latter, in turn, guarantees proper > accounting of request in fi->writectr. Here, of course, it's crucial that we > can't have concurrent fuse_set_nowrite(), as you explained. Hence, so far as > fi->writectr was bumped, fuse_set_nowrite() we call after > filemap_write_and_wait() would wait until all changes have gone to the > server. Any news about this? Thanks, Miklos