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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A07ADC32793 for ; Wed, 18 Jan 2023 16:24:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C16716B0072; Wed, 18 Jan 2023 11:24:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BC66C6B0073; Wed, 18 Jan 2023 11:24:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A8E736B0074; Wed, 18 Jan 2023 11:24:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 9937C6B0072 for ; Wed, 18 Jan 2023 11:24:50 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 6E95C140772 for ; Wed, 18 Jan 2023 16:24:50 +0000 (UTC) X-FDA: 80368443540.09.DE7A295 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf13.hostedemail.com (Postfix) with ESMTP id 97AD220004 for ; Wed, 18 Jan 2023 16:24:47 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=RFkJUvHM; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of agruenba@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=agruenba@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1674059087; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=H4gPDbXgRwcEu9eRFB58g+gXi6AVjus+QHhs3v57+Uw=; b=Az4+FMMiRu8iaAkDs5VhfZ17ORY+vGpMksT1trMHFoOP2yoQ3yGH5p9CF9bBYQgYkw4sil EtXmmpLZ6+kb60SX1emufJ6oFPElW7q8QzoDFM9XvJt2yabcDVIY6cOCWs13Vv/2k2DYgP BcjINxeROi+QGBmmiVy2IkkoYtdYDUI= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=RFkJUvHM; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf13.hostedemail.com: domain of agruenba@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=agruenba@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1674059087; a=rsa-sha256; cv=none; b=8LjoIELF22XwgOFfsBIKAStwQ7SSFopvWVwbYkE+dCNz6Tt83Esx+njdmM/0xGfyb9G8PQ 6EpkLkxhF/Po67ySGZ/ti8ybxLgHhKKIoJ4DD3N7LZqg0kIBW6oNcko3gpS9kkkij0Ou/0 7oYmAeY2HjMpzZYNgtjqyKRLVhjPbJ8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674059087; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=H4gPDbXgRwcEu9eRFB58g+gXi6AVjus+QHhs3v57+Uw=; b=RFkJUvHMDuQchLyf9vNPTzTv5UVaDoKxoCJTZppqYkj2s0qUgfuEbJgv/ZmdNdzwzNxnjq 50CrQEY3XS1c8udSuRqqwLtRa32gFxHXyTokNsJvGaBpJQz/OVV8QgGk6gmZ2SVpbtCg9q ZPTWjWKOkbiYib+xcsWK7fLLSQIxJRQ= Received: from mail-pj1-f71.google.com (mail-pj1-f71.google.com [209.85.216.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-192--zXwQENJN6aNYyssqP8x_A-1; Wed, 18 Jan 2023 11:24:45 -0500 X-MC-Unique: -zXwQENJN6aNYyssqP8x_A-1 Received: by mail-pj1-f71.google.com with SMTP id oo13-20020a17090b1c8d00b0022936a63a22so1714366pjb.8 for ; Wed, 18 Jan 2023 08:24:45 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=H4gPDbXgRwcEu9eRFB58g+gXi6AVjus+QHhs3v57+Uw=; b=KDJdXa5SjAtrJbk5DmrO9fwKbQGRcwnHyeugGPvUCEgtj4SYR384n47ThcY82FzRi2 pWqOHkemIF1KhcND7jDTg0SnemArZRyXGWpxKNMrozKRAtjATEVQogQIitWdcD8lqrSQ 4/ixAyNIrnO4slAiLG+gqVzJoLinTWJwIqWFy6QbZ4Ogx9bclbRzqdnsbLL30eMnlvLm 3gqePRgT5Xa/RkrFBPnXtiqa5heJbptTdFKrjFFi7ccPWv/N0dE8ECi8+U/3Ke2LBXz8 zPYuP15bh6VSeqC7slMG58Oe+sBDs8Vfmx4dmunMTy54jQgh1Y5D6uCwByOgVSi66h6Q ZRog== X-Gm-Message-State: AFqh2kqQbLDG0oImsrPWlxUSKcDmrmqc8gogAjkBj2X51nRvyXQ905j1 KWGiExSltA+ZxEhXHwGN6Uv9EYWy8JwbOyk9qHjTfbqVFBlPAzXdtGocDh2AOa+Z0yzoxZquReK 4I53PezGGHaLHCGlUnAKeSF6GSbw= X-Received: by 2002:a63:5849:0:b0:478:eb77:b104 with SMTP id i9-20020a635849000000b00478eb77b104mr618321pgm.236.1674059084730; Wed, 18 Jan 2023 08:24:44 -0800 (PST) X-Google-Smtp-Source: AMrXdXtvkaGNY8lVgDyNm0tuarLhfWyFgPfPp/0vXS/hCHoGVIWXwNRYT3XKDintDuiBfiXwyin720mSswN72fFwbPw= X-Received: by 2002:a63:5849:0:b0:478:eb77:b104 with SMTP id i9-20020a635849000000b00478eb77b104mr618307pgm.236.1674059084379; Wed, 18 Jan 2023 08:24:44 -0800 (PST) MIME-Version: 1.0 References: <20230118094329.9553-1-hch@lst.de> <20230118094329.9553-8-hch@lst.de> In-Reply-To: From: Andreas Gruenbacher Date: Wed, 18 Jan 2023 17:24:32 +0100 Message-ID: Subject: Re: [Cluster-devel] [PATCH 7/9] gfs2: handle a NULL folio in gfs2_jhead_process_page To: Matthew Wilcox Cc: Christoph Hellwig , linux-xfs@vger.kernel.org, linux-nilfs@vger.kernel.org, Hugh Dickins , cluster-devel@redhat.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Andrew Morton , linux-ext4@vger.kernel.org, linux-afs@lists.infradead.org, linux-btrfs@vger.kernel.org X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 97AD220004 X-Stat-Signature: d4rywgrqr7b8ejzdwhpdheia9amx9rdx X-HE-Tag: 1674059087-992441 X-HE-Meta: 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 or21hGRL /0b4Ze7eZZZMkJznzO2978F2jalY/0XbZKIJ51NC3/En0np5nna2M4dar5WVXfmRphIJIdk9gMv+JPcc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: [Christoph's email ended up in my spam folder; I hope that was a one-time-only occurrence.] On Wed, Jan 18, 2023 at 5:00 PM Matthew Wilcox wrote: > On Wed, Jan 18, 2023 at 10:43:27AM +0100, Christoph Hellwig wrote: > > filemap_get_folio can return NULL, so exit early for that case. > > I'm not sure it can return NULL in this specific case. As I understand > this code, we're scanning the journal looking for the log head. We've > just submitted the bio to read this page. I suppose memory pressure > could theoretically push the page out, but if it does, we're doing the > wrong thing by just returning here; we need to retry reading the page. > > Assuming we're not willing to do the work to add that case, I think I'd > rather see the crash in folio_wait_locked() than get data corruption > from failing to find the head of the log. > > > Signed-off-by: Christoph Hellwig > > --- > > fs/gfs2/lops.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c > > index 1902413d5d123e..51d4b610127cdb 100644 > > --- a/fs/gfs2/lops.c > > +++ b/fs/gfs2/lops.c > > @@ -472,6 +472,8 @@ static void gfs2_jhead_process_page(struct gfs2_jdesc *jd, unsigned long index, > > struct folio *folio; > > > > folio = filemap_get_folio(jd->jd_inode->i_mapping, index); > > + if (!folio) > > + return; We're actually still holding a reference to the folio from the find_or_create_page() in gfs2_find_jhead() here, so we know that memory pressure can't push the page out and filemap_get_folio() won't return NULL. > > > > folio_wait_locked(folio); > > if (folio_test_error(folio)) > > -- > > 2.39.0 > > > Thanks, Andreas