From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga07-in.huawei.com (szxga07-in.huawei.com [45.249.212.35]) (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 5F65CAD55 for ; Tue, 14 May 2024 03:07:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.35 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715656046; cv=none; b=NJYA154MgjMVjAFkSLNKTN0dxNQKlMk7EWhiiWoPTLeGYoR5ZbFTS70vuH6BzT5h+ezwo3Szv/h8cvz1NIVHsmNY6qhf2BP6tL0I1+UT/0mTVUWJi6ECeWnAEB+KImQG3GuQ4fDoCMj9rJI+sX8i4Mg37psiq1pCO2pd3O9h8Z0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715656046; c=relaxed/simple; bh=F2njWTEw3+KoYOErxyCM/MJ9L27NSzGQk1yLIS0vnZ0=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=QxHSu09YsM60EObkUcLX+n8/OUwfu8NeTdv7ztvhVdIy3x5TKcUz/v8AZcZG4OlEQJjr/vcJQsuF5J1JQ3IkS3kx9y3+YVARPf1Cl+jDCSO0F2W7yggoic7n4lOLHIl+twFLPXLOzzCydt8rBR6UmC4/k1QT3Dr80SOFC1hVjBY= 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=45.249.212.35 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 [172.19.162.112]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4Vdh5T5p1Zz1RJPr; Tue, 14 May 2024 11:03:57 +0800 (CST) Received: from canpemm500002.china.huawei.com (unknown [7.192.104.244]) by mail.maildlp.com (Postfix) with ESMTPS id BB218140360; Tue, 14 May 2024 11:07:19 +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 11:07:19 +0800 Subject: Re: [PATCH] mm/huge_memory: mark huge_zero_folio reserved To: David Hildenbrand , CC: , , , , References: <20240511032801.1295023-1-linmiaohe@huawei.com> <1ca64fc3-1b96-466e-aa25-a8f9f6805edc@redhat.com> From: Miaohe Lin Message-ID: <2b5e2b42-7fa6-ab51-494a-0414d1c75290@huawei.com> Date: Tue, 14 May 2024 11:07:18 +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: <1ca64fc3-1b96-466e-aa25-a8f9f6805edc@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) On 2024/5/13 23:40, David Hildenbrand wrote: > On 11.05.24 05:28, 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. >> >> Fixes: 478d134e9506 ("mm/huge_memory: do not overkill when splitting huge_zero_page") >> Signed-off-by: Miaohe Lin >> Cc: >> --- >>   mm/huge_memory.c | 2 ++ >>   1 file changed, 2 insertions(+) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 317de2afd371..d508ff793145 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -212,6 +212,7 @@ static bool get_huge_zero_page(void) >>           folio_put(zero_folio); >>           goto retry; >>       } >> +    __folio_set_reserved(zero_folio); > > We want to limit/remove the use of PG_reserve. Please find a different way (e.g., simply checking for the huge zero page directly). I see. Will drop this patch and find another one. Thanks. .