From patchwork Fri Nov 20 19:12:38 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 329859 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 72A5CC64E69 for ; Fri, 20 Nov 2020 19:12:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 26E0D2240A for ; Fri, 20 Nov 2020 19:12:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="rGLmJ8Ae" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731409AbgKTTMl (ORCPT ); Fri, 20 Nov 2020 14:12:41 -0500 Received: from mail.kernel.org ([198.145.29.99]:40252 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731110AbgKTTMk (ORCPT ); Fri, 20 Nov 2020 14:12:40 -0500 Received: from localhost.localdomain (c-71-198-47-131.hsd1.ca.comcast.net [71.198.47.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C941922240; Fri, 20 Nov 2020 19:12:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1605899559; bh=9uCcHEhTM74W2+kv7DPG7OQif1zF75Wc2h4i+prR13I=; h=Date:From:To:Subject:From; b=rGLmJ8Aep3WFMntf+bcghkA4ac62x8ORupIYzmQ0ivn1yBNO39IiMOG3Xr/ijfTTH qRZ+qZiGgFltF2hHJqiUnm5b2cFaaTYZ7/ZOr0nyXRXGXmCGsSmaLzAXeysdeO0Bci 5VYDZmxCW1Im3Gt3Aal7Gtgvo+AfZV6FdSnsEcUU= Date: Fri, 20 Nov 2020 11:12:38 -0800 From: akpm@linux-foundation.org To: aruna.ramakrishna@oracle.com, bert.barbe@oracle.com, davem@davemloft.net, dongli.zhang@oracle.com, edumazet@google.com, joe.jin@oracle.com, manjunath.b.patil@oracle.com, mm-commits@vger.kernel.org, rama.nichanamatlu@oracle.com, srinivas.eeda@oracle.com, stable@vger.kernel.org, vbabka@suse.cz, venkat.x.venkatsubra@oracle.com, willy@infradead.org Subject: [merged] page_frag-recover-from-memory-pressure.patch removed from -mm tree Message-ID: <20201120191238.7qAsVgioO%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm, page_frag: recover from memory pressure has been removed from the -mm tree. Its filename was page_frag-recover-from-memory-pressure.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Dongli Zhang Subject: mm, page_frag: recover from memory pressure The ethernet driver may allocate skb (and skb->data) via napi_alloc_skb(). This ends up to page_frag_alloc() to allocate skb->data from page_frag_cache->va. During the memory pressure, page_frag_cache->va may be allocated as pfmemalloc page. As a result, the skb->pfmemalloc is always true as skb->data is from page_frag_cache->va. The skb will be dropped if the sock (receiver) does not have SOCK_MEMALLOC. This is expected behaviour under memory pressure. However, once kernel is not under memory pressure any longer (suppose large amount of memory pages are just reclaimed), the page_frag_alloc() may still re-use the prior pfmemalloc page_frag_cache->va to allocate skb->data. As a result, the skb->pfmemalloc is always true unless page_frag_cache->va is re-allocated, even if the kernel is not under memory pressure any longer. Here is how kernel runs into issue. 1. The kernel is under memory pressure and allocation of PAGE_FRAG_CACHE_MAX_ORDER in __page_frag_cache_refill() will fail. Instead, the pfmemalloc page is allocated for page_frag_cache->va. 2. All skb->data from page_frag_cache->va (pfmemalloc) will have skb->pfmemalloc=true. The skb will always be dropped by sock without SOCK_MEMALLOC. This is an expected behaviour. 3. Suppose a large amount of pages are reclaimed and kernel is not under memory pressure any longer. We expect skb->pfmemalloc drop will not happen. 4. Unfortunately, page_frag_alloc() does not proactively re-allocate page_frag_alloc->va and will always re-use the prior pfmemalloc page. The skb->pfmemalloc is always true even kernel is not under memory pressure any longer. Fix this by freeing and re-allocating the page instead of recycling it. Link: https://lore.kernel.org/lkml/20201103193239.1807-1-dongli.zhang@oracle.com/ Link: https://lore.kernel.org/linux-mm/20201105042140.5253-1-willy@infradead.org/ Link: https://lkml.kernel.org/r/20201115201029.11903-1-dongli.zhang@oracle.com Fixes: 79930f5892e ("net: do not deplete pfmemalloc reserve") Signed-off-by: Dongli Zhang Suggested-by: Matthew Wilcox (Oracle) Acked-by: Vlastimil Babka Reviewed-by: Eric Dumazet Cc: Aruna Ramakrishna Cc: Bert Barbe Cc: Rama Nichanamatlu Cc: Venkat Venkatsubra Cc: Manjunath Patil Cc: Joe Jin Cc: SRINIVAS Cc: David S. Miller Cc: Signed-off-by: Andrew Morton --- mm/page_alloc.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/mm/page_alloc.c~page_frag-recover-from-memory-pressure +++ a/mm/page_alloc.c @@ -5103,6 +5103,11 @@ refill: if (!page_ref_sub_and_test(page, nc->pagecnt_bias)) goto refill; + if (unlikely(nc->pfmemalloc)) { + free_the_page(page, compound_order(page)); + goto refill; + } + #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) /* if size can vary use size else just use PAGE_SIZE */ size = nc->size;