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 ECB74CA0EC6 for ; Mon, 11 Sep 2023 22:01:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355548AbjIKWAn (ORCPT ); Mon, 11 Sep 2023 18:00:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243276AbjIKRCl (ORCPT ); Mon, 11 Sep 2023 13:02:41 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A01AF127 for ; Mon, 11 Sep 2023 10:02:36 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AAA91C433C7; Mon, 11 Sep 2023 17:02:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1694451756; bh=SmBjocv8IcfIoepIrvAtFygjn3bdJe4VUU/7MxLBt/k=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=mquS37rcCZD8TTy2GV6rUK6VSOQfoqMmIJUDHUTpDJZ9F4/CgDOWADrA8aZPk1KDP xGv0XbLQq8f+f14VKDFshC1EXa2GkNOaqIsoON2U0aUlRNd1QXOIF3XccAB3PDWMg1 Sjp2TPBRAYbwXgM0/ysZ3xlIbgfACiJg7KBbW1neGWEA0GRv3Q/RhdVy/nw9iWuPEz jbcteseNf0P/y0zy4Rdh1L3EWLUet1hkL46+679b3l/VVdS52/P5erG8QQRvOGROQn P2a9yskTqUzZsx+9NlBqSfQ76jZAtnjWRfLNmkKugm+0fDq7pBuskrYf8sfsin2lfb XcLqINfcEw62w== Message-ID: <3d7271bdcb81239fac471bdb2c4e4ff63d3a65b3.camel@kernel.org> Subject: Re: [PATCH] netfs: Only call folio_start_fscache time for each folio From: Jeff Layton To: Dave Wysochanski , David Howells Cc: linux-cachefs@redhat.com, linux-nfs@vger.kernel.org Date: Mon, 11 Sep 2023 13:02:34 -0400 In-Reply-To: <20230608214137.856006-1-dwysocha@redhat.com> References: <20230608214137.856006-1-dwysocha@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.48.4 (3.48.4-1.module_f38+17164+63eeee4a) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Thu, 2023-06-08 at 17:41 -0400, Dave Wysochanski wrote: > If a network filesystem using netfs implements a clamp_length() > function, it can set subrequest lengths smaller than a page size. > When we loop through the folios in netfs_rreq_unlock_folios() to > set any folios to be written back, we need to make sure we only > call folio_start_fscache() once for each folio. Otherwise, > this simple testcase: > mount -o fsc,rsize=3D1024,wsize=3D1024 127.0.0.1:/export /mnt/nfs > dd if=3D/dev/zero of=3D/mnt/nfs/file.bin bs=3D4096 count=3D1 > 1+0 records in > 1+0 records out > 4096 bytes (4.1 kB, 4.0 KiB) copied, 0.0126359 s, 324 kB/s > cat /mnt/nfs/file.bin > /dev/null >=20 > will trigger an oops similar to the following: > ... > page dumped because: VM_BUG_ON_FOLIO(folio_test_private_2(folio)) > ------------[ cut here ]------------ > kernel BUG at include/linux/netfs.h:44! > ... > CPU: 5 PID: 134 Comm: kworker/u16:5 Kdump: loaded Not tainted 6.4.0-rc5 > ... > RIP: 0010:netfs_rreq_unlock_folios+0x68e/0x730 [netfs] > ... > Call Trace: > > netfs_rreq_assess+0x497/0x660 [netfs] > netfs_subreq_terminated+0x32b/0x610 [netfs] > nfs_netfs_read_completion+0x14e/0x1a0 [nfs] > nfs_read_completion+0x2f9/0x330 [nfs] > rpc_free_task+0x72/0xa0 [sunrpc] > rpc_async_release+0x46/0x70 [sunrpc] > process_one_work+0x3bd/0x710 > worker_thread+0x89/0x610 > kthread+0x181/0x1c0 > ret_from_fork+0x29/0x50 >=20 > Signed-off-by: Dave Wysochanski > --- > fs/netfs/buffered_read.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c > index 3404707ddbe7..0dafd970c1b6 100644 > --- a/fs/netfs/buffered_read.c > +++ b/fs/netfs/buffered_read.c > @@ -21,6 +21,7 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *= rreq) > pgoff_t last_page =3D ((rreq->start + rreq->len) / PAGE_SIZE) - 1; > size_t account =3D 0; > bool subreq_failed =3D false; > + bool folio_started; nit: I'd move this declaration inside the xas_for_each loop, and just initialize it to false there. > =20 > XA_STATE(xas, &rreq->mapping->i_pages, start_epage); > =20 > @@ -53,6 +54,7 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *= rreq) > =20 > pg_end =3D folio_pos(folio) + folio_size(folio) - 1; > =20 > + folio_started =3D false; > for (;;) { > loff_t sreq_end; > =20 > @@ -60,8 +62,10 @@ void netfs_rreq_unlock_folios(struct netfs_io_request = *rreq) > pg_failed =3D true; > break; > } > - if (test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags)) > + if (!folio_started && test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->fla= gs)) { > folio_start_fscache(folio); > + folio_started =3D true; > + } > pg_failed |=3D subreq_failed; > sreq_end =3D subreq->start + subreq->len - 1; > if (pg_end < sreq_end) The logic looks correct though. Reviewed-by: Jeff Layton