From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932944AbeDXMYT (ORCPT ); Tue, 24 Apr 2018 08:24:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:37830 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757691AbeDXMYQ (ORCPT ); Tue, 24 Apr 2018 08:24:16 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F12FE21774 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jlayton@kernel.org Message-ID: <1524572654.5929.3.camel@kernel.org> Subject: Re: [PATCH] Always report a writeback error once From: Jeff Layton To: Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andres Freund Date: Tue, 24 Apr 2018 08:24:14 -0400 In-Reply-To: <20180423204208.GG13383@bombadil.infradead.org> References: <20180423204208.GG13383@bombadil.infradead.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 (3.26.6-1.fc27) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2018-04-23 at 13:42 -0700, Matthew Wilcox wrote: > The errseq_t infrastructure assumes that errors which occurred before > the file descriptor was opened are of no interest to the application. > This turns out to be a regression for some applications, notably Postgres. > > Before errseq_t, a writeback error would be reported exactly once (as > long as the inode remained in memory), so Postgres could open a file, > call fsync() and find out whether there had been a writeback error on > that file from another process. > > This patch restores that behaviour by reporting errors to file descriptors > which are opened after the error occurred, but before it was reported > to any file descriptor. > > Cc: stable@vger.kernel.org > Fixes: 5660e13d2fd6 ("fs: new infrastructure for writeback error handling and reporting") > Signed-off-by: Matthew Wilcox > > diff --git a/lib/errseq.c b/lib/errseq.c > index df782418b333..093f1fba4ee0 100644 > --- a/lib/errseq.c > +++ b/lib/errseq.c > @@ -119,19 +119,11 @@ EXPORT_SYMBOL(errseq_set); > errseq_t errseq_sample(errseq_t *eseq) > { > errseq_t old = READ_ONCE(*eseq); > - errseq_t new = old; > > - /* > - * For the common case of no errors ever having been set, we can skip > - * marking the SEEN bit. Once an error has been set, the value will > - * never go back to zero. > - */ > - if (old != 0) { > - new |= ERRSEQ_SEEN; > - if (old != new) > - cmpxchg(eseq, old, new); > - } > - return new; > + /* If nobody has seen this error yet, then we can be the first. */ > + if (!(old & ERRSEQ_SEEN)) > + old = 0; > + return old; > } > EXPORT_SYMBOL(errseq_sample); > Patch looks good to me, modulo the comment fix that Andres pointed out. Reviewed-by: Jeff Layton