From nobody Sun May 10 09:53:42 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C704C433EF for ; Tue, 10 May 2022 21:17:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234364AbiEJVRu (ORCPT ); Tue, 10 May 2022 17:17:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231347AbiEJVRs (ORCPT ); Tue, 10 May 2022 17:17:48 -0400 Received: from mail-pf1-x432.google.com (mail-pf1-x432.google.com [IPv6:2607:f8b0:4864:20::432]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C34850B32 for ; Tue, 10 May 2022 14:17:47 -0700 (PDT) Received: by mail-pf1-x432.google.com with SMTP id 204so247723pfx.3 for ; Tue, 10 May 2022 14:17:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=M3iS8vaaqUD8jfRE0NHdoQBHIwBnV2ugHoNQ4Z+Efx8=; b=cocBJOXiSqOkGGCNk9vDNCQQromh/mWnuC+KMasoT9HGNJtSh3PKZH/eXlf1MGxv2F Is1s24zAzJD01Gp0dG8sxbzC7wMFtiuh42LCRFmPe5+0Ti2p7CU9Ux0izG8VSpZcCnWd cDB3vIOlJt1xhiDB+uVmPm6ElIEsY52Dr6/90nJw4pQ1eWOHdwOfT3p6GTeAO/x7u14w pp2P2w5PBZkcACDjHKzqwSP0qTlEoqLRQVEXEgXrBH5oAg/0YN+IWl+QyV4hioH683zx gwliS5xHmZ0wysoH5R9CipYm1N3AhJRRYkLhKo24V4SGi7OlTjnCKQ2BToBM0uJQ7V83 g2jw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :mime-version:content-transfer-encoding; bh=M3iS8vaaqUD8jfRE0NHdoQBHIwBnV2ugHoNQ4Z+Efx8=; b=zLQASLzyEtg1XQchQHaakQ9+NVUCUJPJY0UtTG1NUne+XHP4FJYhP60rE5ZcQy2oBT Z263ZJb05Fd57Y1tVwB2+Ak3jZj47AwxHkk4jEgpqkSBSaQR6ZEowtxkcw1ksrf+T9P6 3ANUVt/Yk6kDlZHk7387c2OCvvseOOLhHtx0atZZ/RNCFix5KKkMxPfIurLCAfPe7yNE GUQ49bIOn73dTl9tDvA2Eane6ZMMhkmp+vtiFJqnTV5he0BR0qzA6hsL4YU9ixu2Au7N AH73pLS6JsdIMLq0HiZiqIQ2otHWZartyrGxMMJxfRHexh3sy0VFmZp/kouoHIvdu9RA DafQ== X-Gm-Message-State: AOAM53165w8+gBtfw2P372FM1IZqh2g58/zAFXlJK3idSbq/NJGR2l3Z mt6t+YqNutEA9qXBzrHKozAvKVC2lpU= X-Google-Smtp-Source: ABdhPJx2Y9Xq+3njREh94u64LTI6mtZXpzrndPub0LLJisx1paZBupZB0tvPmrQAG6GfjBG0L8/Qvg== X-Received: by 2002:a63:1202:0:b0:3da:ec25:b232 with SMTP id h2-20020a631202000000b003daec25b232mr3876532pgl.163.1652217467051; Tue, 10 May 2022 14:17:47 -0700 (PDT) Received: from bbox-1.mtv.corp.google.com ([2620:15c:211:201:c98a:65b0:edca:b69a]) by smtp.gmail.com with ESMTPSA id q1-20020a170902bd8100b0015e8d4eb28esm67639pls.216.2022.05.10.14.17.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 May 2022 14:17:46 -0700 (PDT) Sender: Minchan Kim From: Minchan Kim To: Andrew Morton Cc: linux-mm , LKML , "Paul E . McKenney" , John Hubbard , John Dias , Minchan Kim , David Hildenbrand Subject: [PATCH v4] mm: fix is_pinnable_page against on cma page Date: Tue, 10 May 2022 14:17:43 -0700 Message-Id: <20220510211743.95831-1-minchan@kernel.org> X-Mailer: git-send-email 2.36.0.512.ge40c2bad7a-goog MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Pages on CMA area could have MIGRATE_ISOLATE as well as MIGRATE_CMA so current is_pinnable_page could miss CMA pages which has MIGRATE_ ISOLATE. It ends up pinning CMA pages as longterm at pin_user_pages APIs so CMA allocation keep failed until the pin is released. CPU 0 CPU 1 - Task B cma_alloc alloc_contig_range pin_user_pages_fast(FOLL_LONGTERM) change pageblock as MIGRATE_ISOLATE internal_get_user_pages_fast lockless_pages_from_mm gup_pte_range try_grab_folio is_pinnable_page return true; So, pinned the page successfully. page migration failure with pinned page .. .. After 30 sec unpin_user_page(page) CMA allocation succeeded after 30 sec. The CMA allocation path protects the migration type change race using zone->lock but what GUP path need to know is just whether the page is on CMA area or not rather than exact migration type. Thus, we don't need zone->lock but just checks migration type in either of (MIGRATE_ISOLATE and MIGRATE_CMA). Adding the MIGRATE_ISOLATE check in is_pinnable_page could cause rejecting of pinning pages on MIGRATE_ISOLATE pageblocks even though it's neither CMA nor movable zone if the page is temporarily unmovable. However, such a migration failure by unexpected temporal refcount holding is general issue, not only come from MIGRATE_ISOLATE and the MIGRATE_ISOLATE is also transient state like other temporal elevated refcount problem. Cc: David Hildenbrand Signed-off-by: Minchan Kim Acked-by: Paul E. McKenney Reviewed-by: John Hubbard --- * from v3 - https://lore.kernel.org/all/20220509153430.4125710-1-minchan@ke= rnel.org/ * Fix typo and adding more description - akpm * from v2 - https://lore.kernel.org/all/20220505064429.2818496-1-minchan@ke= rnel.org/ * Use __READ_ONCE instead of volatile - akpm * from v1 - https://lore.kernel.org/all/20220502173558.2510641-1-minchan@ke= rnel.org/ * fix build warning - lkp * fix refetching issue of migration type * add side effect on !ZONE_MOVABLE and !MIGRATE_CMA in description - david include/linux/mm.h | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6acca5cecbc5..cbf79eb790e0 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1625,8 +1625,19 @@ static inline bool page_needs_cow_for_dma(struct vm_= area_struct *vma, #ifdef CONFIG_MIGRATION static inline bool is_pinnable_page(struct page *page) { - return !(is_zone_movable_page(page) || is_migrate_cma_page(page)) || - is_zero_pfn(page_to_pfn(page)); +#ifdef CONFIG_CMA + /* + * use volatile to use local variable mt instead of + * refetching mt value. + */ + int __mt =3D get_pageblock_migratetype(page); + int mt =3D __READ_ONCE(__mt); + + if (mt =3D=3D MIGRATE_CMA || mt =3D=3D MIGRATE_ISOLATE) + return false; +#endif + + return !(is_zone_movable_page(page) || is_zero_pfn(page_to_pfn(page))); } #else static inline bool is_pinnable_page(struct page *page) --=20 2.36.0.512.ge40c2bad7a-goog