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[195.135.220.15]) by mx.google.com with ESMTPS id w16si465364eje.64.2019.03.16.01.23.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Mar 2019 01:23:56 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A4B91AD3B; Sat, 16 Mar 2019 08:23:55 +0000 (UTC) Date: Sat, 16 Mar 2019 09:23:54 +0100 From: Michal Hocko To: Oscar Salvador Cc: akpm@linux-foundation.org, anshuman.khandual@arm.com, william.kucharski@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jan Kara , Hugh Dickins Subject: Re: [PATCH] mm: Fix __dump_page when mapping->host is not set Message-ID: <20190316082354.GF15672@dhcp22.suse.cz> References: <20190315121826.23609-1-osalvador@suse.de> <20190315124733.GE15672@dhcp22.suse.cz> <20190315143304.pkuvj4qwtlzgm7iq@d104.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190315143304.pkuvj4qwtlzgm7iq@d104.suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) 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: On Fri 15-03-19 15:33:07, Oscar Salvador wrote: > On Fri, Mar 15, 2019 at 01:47:33PM +0100, Michal Hocko wrote: > > diff --git a/mm/debug.c b/mm/debug.c > > index 1611cf00a137..499c26d5ebe5 100644 > > --- a/mm/debug.c > > +++ b/mm/debug.c > > @@ -78,6 +78,9 @@ void __dump_page(struct page *page, const char *reason) > > else if (PageKsm(page)) > > pr_warn("ksm "); > > else if (mapping) { > > + if (PageSwapCache(page)) > > + mapping = page_swap_info(page)->swap_file->f_mapping; > > + > > pr_warn("%ps ", mapping->a_ops); > > if (mapping->host->i_dentry.first) { > > struct dentry *dentry; > > This looks like a much nicer fix, indeed. If we go this way then we should swap the order and print the mapping before we alter it. > I gave it a spin and it works. Thanks for testing! > Since the mapping is set during the swapon, I would assume that this should > always work for swap. > Although I am not sure if once you start playing with e.g zswap the picture can > change. > > Let us wait for Hugh and Jan. Yes, I really cannot tell this is really safe. Maybe we want to do the check for host anyway. Just to be sure. -- Michal Hocko SUSE Labs