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 X-Spam-Level: X-Spam-Status: No, score=-18.8 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, USER_AGENT_GIT autolearn=ham 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 ACCC3C64E7B for ; Mon, 23 Nov 2020 12:30:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 553E220728 for ; Mon, 23 Nov 2020 12:30:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Jx6IcAQ0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730706AbgKWMaM (ORCPT ); Mon, 23 Nov 2020 07:30:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:40830 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729463AbgKWMaF (ORCPT ); Mon, 23 Nov 2020 07:30:05 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 819C320728; Mon, 23 Nov 2020 12:30:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1606134603; bh=ckLGTPmLdHant24hqWtEtHi0/xl8Z9Q9NFtgMa600mE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Jx6IcAQ0imoUyTWroKL32H/4+rZEbXDVt2Ls7y/qWNndAXPWSttMF9rnfI7o+cxH/ vwo0gJhR7Rj9zQkOrrjD4RGNlOCdDVottrMUM6892ThrxHbwV/UKMidQ8vNK9TQnGJ n/sk2NpM+sxrg1nepmNfq4ty51z59xsDQ3g1du6c= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Matthew Wilcox (Oracle)" , Aruna Ramakrishna , Bert Barbe , Rama Nichanamatlu , Venkat Venkatsubra , Manjunath Patil , Joe Jin , SRINIVAS , Dongli Zhang , Vlastimil Babka , Eric Dumazet , Jakub Kicinski Subject: [PATCH 4.19 18/91] page_frag: Recover from memory pressure Date: Mon, 23 Nov 2020 13:21:38 +0100 Message-Id: <20201123121810.192035859@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201123121809.285416732@linuxfoundation.org> References: <20201123121809.285416732@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dongli Zhang [ Upstream commit d8c19014bba8f565d8a2f1f46b4e38d1d97bf1a7 ] 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. Suggested-by: Matthew Wilcox (Oracle) Cc: Aruna Ramakrishna Cc: Bert Barbe Cc: Rama Nichanamatlu Cc: Venkat Venkatsubra Cc: Manjunath Patil Cc: Joe Jin Cc: SRINIVAS Fixes: 79930f5892e1 ("net: do not deplete pfmemalloc reserve") Signed-off-by: Dongli Zhang Acked-by: Vlastimil Babka Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/20201115201029.11903-1-dongli.zhang@oracle.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- mm/page_alloc.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4554,6 +4554,11 @@ 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;