From patchwork Wed May 5 01:38:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12238963 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=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 3FEC2C433ED for ; Wed, 5 May 2021 01:38:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E483461182 for ; Wed, 5 May 2021 01:38:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E483461182 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5DD6D6B00CB; Tue, 4 May 2021 21:38:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 51E9C6B00CD; Tue, 4 May 2021 21:38:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 08F1B6B00CE; Tue, 4 May 2021 21:38:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0032.hostedemail.com [216.40.44.32]) by kanga.kvack.org (Postfix) with ESMTP id CB1376B00CB for ; Tue, 4 May 2021 21:38:44 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 8E0DB181AF5C3 for ; Wed, 5 May 2021 01:38:44 +0000 (UTC) X-FDA: 78105468168.08.60F062B Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf22.hostedemail.com (Postfix) with ESMTP id D159EC0007E4 for ; Wed, 5 May 2021 01:38:36 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id B19F1610A1; Wed, 5 May 2021 01:38:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620178723; bh=49hbTOzL9Hd6mB4cRIxZJM2ydCd9FAJqMdKKM6aYOH8=; h=Date:From:To:Subject:In-Reply-To:From; b=bfhMYd4YAEI4YvYYj8JakuOrglS2aNfIPQzMP+henhrQ/tmR83oLIwt8dssQIvjUp /Ueh9zsWKSihPKS2Jqpbe8WjMXnxJJX6Dc2RBCHJeZEZ/1PsWysG02RozskUEGIKfm 4A9mWhbzZW9j3mzr7NBCZL/BYmRpv2kNNHUuEBm8= Date: Tue, 04 May 2021 18:38:42 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dan.j.williams@intel.com, david@redhat.com, iamjoonsoo.kim@lge.com, ira.weiny@intel.com, jgg@nvidia.com, jgg@ziepe.ca, jhubbard@nvidia.com, jmorris@namei.org, linux-mm@kvack.org, mgorman@suse.de, mhocko@kernel.org, mhocko@suse.com, mike.kravetz@oracle.com, mingo@redhat.com, mm-commits@vger.kernel.org, osalvador@suse.de, pasha.tatashin@soleen.com, peterz@infradead.org, rientjes@google.com, rostedt@goodmis.org, sashal@kernel.org, torvalds@linux-foundation.org, tyhicks@linux.microsoft.com, vbabka@suse.cz, willy@infradead.org Subject: [patch 111/143] mm/gup: check every subpage of a compound page during isolation Message-ID: <20210505013842.bA5AgeZ-Y%akpm@linux-foundation.org> In-Reply-To: <20210504183219.a3cc46aee4013d77402276c5@linux-foundation.org> User-Agent: s-nail v14.8.16 Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=bfhMYd4Y; dmarc=none; spf=pass (imf22.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Stat-Signature: x5wim8hgndg7317acjmx3fqffyxca5to X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: D159EC0007E4 Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf22; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620178716-223106 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Pavel Tatashin Subject: mm/gup: check every subpage of a compound page during isolation When pages are isolated in check_and_migrate_movable_pages() we skip compound number of pages at a time. However, as Jason noted, it is not necessary correct that pages[i] corresponds to the pages that we skipped. This is because it is possible that the addresses in this range had split_huge_pmd()/split_huge_pud(), and these functions do not update the compound page metadata. The problem can be reproduced if something like this occurs: 1. User faulted huge pages. 2. split_huge_pmd() was called for some reason 3. User has unmapped some sub-pages in the range 4. User tries to longterm pin the addresses. The resulting pages[i] might end-up having pages which are not compound size page aligned. Link: https://lkml.kernel.org/r/20210215161349.246722-3-pasha.tatashin@soleen.com Fixes: aa712399c1e8 ("mm/gup: speed up check_and_migrate_cma_pages() on huge page") Signed-off-by: Pavel Tatashin Reported-by: Jason Gunthorpe Reviewed-by: Jason Gunthorpe Cc: Dan Williams Cc: David Hildenbrand Cc: David Rientjes Cc: Ingo Molnar Cc: Ira Weiny Cc: James Morris Cc: Jason Gunthorpe Cc: John Hubbard Cc: Joonsoo Kim Cc: Matthew Wilcox Cc: Mel Gorman Cc: Michal Hocko Cc: Michal Hocko Cc: Mike Kravetz Cc: Oscar Salvador Cc: Peter Zijlstra Cc: Sasha Levin Cc: Steven Rostedt (VMware) Cc: Tyler Hicks Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/gup.c | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-) --- a/mm/gup.c~mm-gup-check-every-subpage-of-a-compound-page-during-isolation +++ a/mm/gup.c @@ -1609,26 +1609,23 @@ static long check_and_migrate_cma_pages( unsigned int gup_flags) { unsigned long i; - unsigned long step; bool drain_allow = true; bool migrate_allow = true; LIST_HEAD(cma_page_list); long ret = nr_pages; + struct page *prev_head, *head; struct migration_target_control mtc = { .nid = NUMA_NO_NODE, .gfp_mask = GFP_USER | __GFP_NOWARN, }; check_again: - for (i = 0; i < nr_pages;) { - - struct page *head = compound_head(pages[i]); - - /* - * gup may start from a tail page. Advance step by the left - * part. - */ - step = compound_nr(head) - (pages[i] - head); + prev_head = NULL; + for (i = 0; i < nr_pages; i++) { + head = compound_head(pages[i]); + if (head == prev_head) + continue; + prev_head = head; /* * If we get a page from the CMA zone, since we are going to * be pinning these entries, we might as well move them out @@ -1652,8 +1649,6 @@ check_again: } } } - - i += step; } if (!list_empty(&cma_page_list)) {