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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1061C433F5 for ; Sat, 14 May 2022 02:46:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229481AbiENCqA (ORCPT ); Fri, 13 May 2022 22:46:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229781AbiENCp7 (ORCPT ); Fri, 13 May 2022 22:45:59 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1651233457D for ; Fri, 13 May 2022 17:47:19 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A254461B8E for ; Sat, 14 May 2022 00:18:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0772EC385AA; Sat, 14 May 2022 00:18:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1652487520; bh=DJgnkxJrfZ8R1WC8NtnRuD0n2cPwMF1E0o/YZ6Madk0=; h=Date:To:From:Subject:From; b=DbrT+xC2yKYXaJd8Y0ql05CKbiO12853sS82cMeFgHpEaHArq864Gz6Z2NOdXUWcX 76BX7Q81N8qtyvXHTlq4kA9vs/SZV1EkH4mA48vt/9Slb88YtXtlLqOwpwX6NdBPm4 UfkwgsSlI7BKKvy9+OtAXRVe+dUSEg+E9tuwZjcE= Date: Fri, 13 May 2022 17:18:39 -0700 To: mm-commits@vger.kernel.org, sfr@canb.auug.org.au, paulmck@kernel.org, joaodias@google.com, jhubbard@nvidia.com, david@redhat.com, minchan@kernel.org, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-fix-is_pinnable_page-against-on-cma-page.patch added to mm-unstable branch Message-Id: <20220514001840.0772EC385AA@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm: fix is_pinnable_page against on cma page has been added to the -mm mm-unstable branch. Its filename is mm-fix-is_pinnable_page-against-on-cma-page.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-is_pinnable_page-against-on-cma-page.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Minchan Kim Subject: mm: fix is_pinnable_page against on cma page 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. [minchan@kernel.org: restore __mt definition] [minchan@kernel.org: changes per Paul and John] Link: https://lkml.kernel.org/r/20220512204143.3961150-1-minchan@kernel.org Link: https://lkml.kernel.org/r/20220510211743.95831-1-minchan@kernel.org Signed-off-by: Minchan Kim Cc: David Hildenbrand Cc: "Paul E . McKenney" Cc: John Hubbard Cc: John Dias Cc: Stephen Rothwell Signed-off-by: Andrew Morton --- include/linux/mm.h | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) --- a/include/linux/mm.h~mm-fix-is_pinnable_page-against-on-cma-page +++ a/include/linux/mm.h @@ -1625,8 +1625,21 @@ static inline bool page_needs_cow_for_dm #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 + /* + * Defend against future compiler LTO features, or code refactoring + * that inlines the above function, by forcing a single read. Because, + * this routine races with set_pageblock_migratetype(), and we want to + * avoid reading zero, when actually one or the other flags was set. + */ + int __mt = get_pageblock_migratetype(page); + int mt = __READ_ONCE(__mt); + + if (mt & (MIGRATE_CMA | 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) _ Patches currently in -mm which might be from minchan@kernel.org are mm-dont-be-stuck-to-rmap-lock-on-reclaim-path.patch mm-fix-is_pinnable_page-against-on-cma-page.patch