From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B177D17C2 for ; Tue, 14 May 2024 03:06:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.255 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715655964; cv=none; b=VHEzUI8j0VC3XUUJ3fwxv0oj/buKrAJtNcY8rP5RCyr2ic+UpzqYu1QbZQQXf6TX288zulBCOcZcdjYz1b3WIuxfT01tjUTv/JX0fARTLFJ9JZo/UOTfyI1YRZ/JlsWn1cfBYMkd9mm5gjrABu9s2ARvxeQeIagbguJ6Yjz2JYU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715655964; c=relaxed/simple; bh=o2d1JoV821tq0V9HXFMEP8TcS85tU86xIDaBNcMvLGU=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=MizkVQc1/me+2hy+mu1BkgsOdgEuD7ZV47g+vitSslOWTJ14ZBRzOKAPA5uRpb5/4jN/950wE1G155AOE166S/HYhTHkyD9RD7ZDrngDn5i2IdZCEzfotJomxmcyVn4r5e/DYBqu2jFbU6Ie+F8uiBIcIKluIGLuLeaPM92RI+I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.255 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.252]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Vdh3p7237z1S5Vc; Tue, 14 May 2024 11:02:30 +0800 (CST) Received: from canpemm500002.china.huawei.com (unknown [7.192.104.244]) by mail.maildlp.com (Postfix) with ESMTPS id 2BE5E180080; Tue, 14 May 2024 11:05:58 +0800 (CST) Received: from [10.173.135.154] (10.173.135.154) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Tue, 14 May 2024 11:05:57 +0800 Subject: Re: [PATCH] mm/huge_memory: mark huge_zero_folio reserved To: Yang Shi CC: , , , , References: <20240511032801.1295023-1-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: <94ddebf2-8cfa-b1bb-2241-49f672186946@huawei.com> Date: Tue, 14 May 2024 11:05:57 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) On 2024/5/13 23:34, Yang Shi wrote: > On Fri, May 10, 2024 at 9:31 PM Miaohe Lin wrote: >> >> When I did memory failure tests recently, below panic occurs: >> >> kernel BUG at include/linux/mm.h:1135! >> invalid opcode: 0000 [#1] PREEMPT SMP NOPTI >> CPU: 9 PID: 137 Comm: kswapd1 Not tainted 6.9.0-rc4-00491-gd5ce28f156fe-dirty #14 >> RIP: 0010:shrink_huge_zero_page_scan+0x168/0x1a0 >> RSP: 0018:ffff9933c6c57bd0 EFLAGS: 00000246 >> RAX: 000000000000003e RBX: 0000000000000000 RCX: ffff88f61fc5c9c8 >> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff88f61fc5c9c0 >> RBP: ffffcd7c446b0000 R08: ffffffff9a9405f0 R09: 0000000000005492 >> R10: 00000000000030ea R11: ffffffff9a9405f0 R12: 0000000000000000 >> R13: 0000000000000000 R14: 0000000000000000 R15: ffff88e703c4ac00 >> FS: 0000000000000000(0000) GS:ffff88f61fc40000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 000055f4da6e9878 CR3: 0000000c71048000 CR4: 00000000000006f0 >> Call Trace: >> >> do_shrink_slab+0x14f/0x6a0 >> shrink_slab+0xca/0x8c0 >> shrink_node+0x2d0/0x7d0 >> balance_pgdat+0x33a/0x720 >> kswapd+0x1f3/0x410 >> kthread+0xd5/0x100 >> ret_from_fork+0x2f/0x50 >> ret_from_fork_asm+0x1a/0x30 >> >> Modules linked in: mce_inject hwpoison_inject >> ---[ end trace 0000000000000000 ]--- >> RIP: 0010:shrink_huge_zero_page_scan+0x168/0x1a0 >> RSP: 0018:ffff9933c6c57bd0 EFLAGS: 00000246 >> RAX: 000000000000003e RBX: 0000000000000000 RCX: ffff88f61fc5c9c8 >> RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff88f61fc5c9c0 >> RBP: ffffcd7c446b0000 R08: ffffffff9a9405f0 R09: 0000000000005492 >> R10: 00000000000030ea R11: ffffffff9a9405f0 R12: 0000000000000000 >> R13: 0000000000000000 R14: 0000000000000000 R15: ffff88e703c4ac00 >> FS: 0000000000000000(0000) GS:ffff88f61fc40000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 000055f4da6e9878 CR3: 0000000c71048000 CR4: 00000000000006f0 >> >> The root cause is that HWPoison flag will be set for huge_zero_folio >> without increasing the folio refcnt. But then unpoison_memory() will >> decrease the folio refcnt unexpectly as it appears like a successfully >> hwpoisoned folio leading to VM_BUG_ON_PAGE(page_ref_count(page) == 0) >> when releasing huge_zero_folio. >> >> Fix this issue by marking huge_zero_folio reserved. So unpoison_memory() >> will skip this page. This will make it consistent with ZERO_PAGE case too. > > If I read the code correctly, unpoison_memory() should not dec > refcount for huge zero page by calling put_page_testzero(). The huge > zero page's real refcount is actually maintained separately by > huge_zero_refcount. It is different from the regular refount in struct > folio, see get_huge_zero_page(). Sure. Huge zero folio should be skipped in unpoison_memory(). It's not supported anyway. I marked huge_zero_folio reserved in order to let unpoison_memory() skip it by folio_test_reserved(folio) check. But as David points out, the use of PG_reserve is limited, so I will find another way to fix the issue. Thanks. .