From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D04DC7EE29 for ; Fri, 9 Jun 2023 00:50:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232788AbjFIAug (ORCPT ); Thu, 8 Jun 2023 20:50:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229477AbjFIAue (ORCPT ); Thu, 8 Jun 2023 20:50:34 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63AD130DD for ; Thu, 8 Jun 2023 17:50:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EA6C26519C for ; Fri, 9 Jun 2023 00:50:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27CC3C433EF; Fri, 9 Jun 2023 00:50:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1686271832; bh=87EB8I2ht9Y+kEq5/TYmOKwCXNNl7S/E+DgNT6aNAw0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=EcmJE2zUJx0QdT/MAxGJmLaUKyEQ1DhulADibs1DCIKVZM6KSqe0VbHT7feN3MS0L 21/6V3scYHcyJyuojPUmrLgx4XJ4cX6TyyDrmkm9X3kFw9fjLTKvAuDSmTYRQDKRmH XZkddce8Cnk8QFk+0AdMngWI2h/80Rc928HUXZGQ= Date: Thu, 8 Jun 2023 17:50:31 -0700 From: Andrew Morton To: "Vishal Moola (Oracle)" Cc: linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org, dhowells@redhat.com Subject: Re: [PATCH] afs: Fix waiting for writeback then skipping folio Message-Id: <20230608175031.9c534e7f554de89e3d972ab2@linux-foundation.org> In-Reply-To: <20230607204120.89416-2-vishal.moola@gmail.com> References: <20230607204120.89416-1-vishal.moola@gmail.com> <20230607204120.89416-2-vishal.moola@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 7 Jun 2023 13:41:20 -0700 "Vishal Moola (Oracle)" wrote: > Commit acc8d8588cb7 converted afs_writepages_region() to write back a > folio batch. The function waits for writeback to a folio, but then > proceeds to the rest of the batch without trying to write that folio > again. This patch fixes has it attempt to write the folio again. > > This has only been compile tested. This seems fairly serious? > --- a/fs/afs/write.c > +++ b/fs/afs/write.c > @@ -731,6 +731,7 @@ static int afs_writepages_region(struct address_space *mapping, > * (changing page->mapping to NULL), or even swizzled > * back from swapper_space to tmpfs file mapping > */ > +try_again: > if (wbc->sync_mode != WB_SYNC_NONE) { > ret = folio_lock_killable(folio); > if (ret < 0) { > @@ -757,6 +758,7 @@ static int afs_writepages_region(struct address_space *mapping, > #ifdef CONFIG_AFS_FSCACHE > folio_wait_fscache(folio); > #endif > + goto try_again; > } else { > start += folio_size(folio); > } >From my reading, we'll fail to write out the dirty data. Presumably not easily observable, as it will get written out again later on. But we're also calling afs_write_back_from_locked_folio() with an unlocked folio, which might cause mayhem. So I'm suspecting that a cc:stable is needed. David, could you please take a look and perhaps retest? Thanks.