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 D425EEE49A4 for ; Tue, 22 Aug 2023 03:32:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 564B2280005; Mon, 21 Aug 2023 23:32:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5151C94000D; Mon, 21 Aug 2023 23:32:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4036F280005; Mon, 21 Aug 2023 23:32:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 2FE4694000D for ; Mon, 21 Aug 2023 23:32:44 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id E3A321A01A2 for ; Tue, 22 Aug 2023 03:32:43 +0000 (UTC) X-FDA: 81150318606.11.8965811 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf10.hostedemail.com (Postfix) with ESMTP id D393DC0010 for ; Tue, 22 Aug 2023 03:32:41 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=emcGPZJO; dmarc=none; spf=none (imf10.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1692675162; 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=CgRqGdZVg9uPMZY4ZUetbHIkeELaVfdtXUzsN9Brwl4=; b=0VpnRZUHsG+4kiOCpKDRaRnnvqz+Tu4puGpIsskqGiePPI2U6lTRKpvluX5Ax9nCZZnawo 2Pmlwi1xIo7yfwDl05Mr4qDYL8p07tG+dMWLQo1eUYPUog8h8waaINrGZRi8Hqoo6b3PY/ UJD46giT2KBA8yAr7sAF5sUkspF5uv8= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=emcGPZJO; dmarc=none; spf=none (imf10.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1692675162; a=rsa-sha256; cv=none; b=1d2Nep0eGztYxkZ9S2GhI6XujTRM3bJ80nsfD0Ng/0diocyoTrrxsfE3GgO1rUavrf+HbL vWwGRiHSENoEjSvZQldENI4rrVhPNe0oXkja8gHqY9Vk/qiAE+G7lDDYNiQrKW8ZocX0eF MsKpGvqZJ9dABmgMDMGxLaoW0Q4osk4= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=CgRqGdZVg9uPMZY4ZUetbHIkeELaVfdtXUzsN9Brwl4=; b=emcGPZJOVPgvmumOP1Cd8faRhi /aMXlBOP6ZHbO3wYE5EwGJCHdm6Xu4wTMy1ckxPkip8b8XBjSrNNFYKAbHFOxjyddcFSRl2g+esNo GWLEf1zq4oYwNk+mpKPcZqYcaF5TRprctgfvwE8lMBxcWgwT+lAVX/K0SBKTSQP85D9PHbUL7+YOu XrD1BzNY1QBTlcpYV4QMxOeWALSpeiwgr9DcAMc8Sjp7GSsyhh6AXGUk2MtJoXBeSlbNDrGE1L+gd //Chu2bTxEKd20kWyRarn+3UImiymOpXIhlG5X95gtqcAHLU+kcfjRwxbKUUJhwO+CK2PBuiENJ79 o/kHMSzg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qYI89-00E1mP-L4; Tue, 22 Aug 2023 03:32:33 +0000 Date: Tue, 22 Aug 2023 04:32:33 +0100 From: Matthew Wilcox To: Mike Kravetz Cc: Andrew Morton , Jens Axboe , io-uring@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 07/13] mm: Remove HUGETLB_PAGE_DTOR Message-ID: References: <20230816151201.3655946-1-willy@infradead.org> <20230816151201.3655946-8-willy@infradead.org> <20230822031300.GA82632@monkey> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230822031300.GA82632@monkey> X-Rspamd-Queue-Id: D393DC0010 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 4q6j816gifish4b7fkrj54cj3j54f74m X-HE-Tag: 1692675161-404702 X-HE-Meta: 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 0cMo9psV 0/jIGQHUJ6LHpXtRhoDg2lPm6pqZjGMT1v6sjajzy4iGXO3AHBliRxhK76+rp4bxQpJqfM3e0SdY8t7dCmjnpF8eUOVFH94lgq8j21KjSuC/qczv8C/3hOMcCwBpdxrdM+gNxqmQRQz2yA3smwpxu3dzN6uBd3ObGViYbYrOCrx3HEKHKuuHScgduBA== 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 Mon, Aug 21, 2023 at 08:13:00PM -0700, Mike Kravetz wrote: > On 08/16/23 16:11, Matthew Wilcox (Oracle) wrote: > > We can use a bit in page[1].flags to indicate that this folio belongs > > to hugetlb instead of using a value in page[1].dtors. That lets > > folio_test_hugetlb() become an inline function like it should be. > > We can also get rid of NULL_COMPOUND_DTOR. > > Not 100% sure yet, but I suspect this patch/series causes the following > BUG in today's linux-next. I can do a deeper dive tomorrow. > > # echo 1 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages > # echo 0 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages > > [ 352.631099] page:ffffea0007a30000 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1e8c00 > [ 352.633674] head:ffffea0007a30000 order:8 entire_mapcount:0 nr_pages_mapped:0 pincount:0 order 8? Well, that's exciting. This is clearly x86, so it should be order 9. Did we mistakenly clear bit 0 of tail->flags? Oh. Oh yes, we do. __update_and_free_hugetlb_folio: for (i = 0; i < pages_per_huge_page(h); i++) { subpage = folio_page(folio, i); subpage->flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced | 1 << PG_dirty | 1 << PG_active | 1 << PG_private | 1 << PG_writeback); } locked PF_NO_TAIL error PF_NO_TAIL referenced PF_HEAD dirty PF_HEAD active PF_HEAD private PF_ANY writeback PF_NO_TAIL So it seems to me there's no way to set any of these bits other than PG_private. And, well, you control PG_private in hugetlbfs. Do you ever set it on tail pages? I think you can remove this entire loop and be happy?