Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755007Ab3H3Ldn (ORCPT ); Fri, 30 Aug 2013 07:33:43 -0400 Received: from relay.parallels.com ([195.214.232.42]:43767 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754264Ab3H3Ldm (ORCPT ); Fri, 30 Aug 2013 07:33:42 -0400 Message-ID: <52208313.6000700@parallels.com> Date: Fri, 30 Aug 2013 15:33:39 +0400 From: Maxim Patlasov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Miklos Szeredi CC: fuse-devel , Brian Foster , Pavel Emelianov , Kernel Mailing List , Subject: Re: [PATCH 2/2] fuse: wait for writeback in fuse_file_fallocate() -v2 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> In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.30.17.2] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1873 Lines: 39 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. Thanks, Maxim -- 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/