From patchwork Fri Jun 25 01:39:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 467398 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 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 12977C49EA7 for ; Fri, 25 Jun 2021 01:39:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3E60613BD for ; Fri, 25 Jun 2021 01:39:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233034AbhFYBmN (ORCPT ); Thu, 24 Jun 2021 21:42:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:32894 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232942AbhFYBmN (ORCPT ); Thu, 24 Jun 2021 21:42:13 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7FF3E61220; Fri, 25 Jun 2021 01:39:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1624585193; bh=A96yUig542IiOvcZ5BLFFXMBRZa0lxHhyMc7JoIOviI=; h=Date:From:To:Subject:In-Reply-To:From; b=w4nXOIyrxzMhoFwnOiwXYqbRRNMYzLEAnzq64m8uqXdc9IQa7EoalsVEuJsOwD881 Dp6AuaSpOdKQKV2hdZ8sMuBtklSclND1fDyx9WeWczMphcrxsq1uzq/5sjxLSwznrA ALC3ohaS5fm6I4JR6STBpC4e4V9tDWrfjX3XXooo= Date: Thu, 24 Jun 2021 18:39:52 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dave@stgolabs.net, dvhart@infradead.org, hughd@google.com, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, mgorman@techsingularity.net, mike.kravetz@oracle.com, mingo@redhat.com, mm-commits@vger.kernel.org, neelnatu@google.com, peterz@infradead.org, stable@vger.kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org, wetpzy@gmail.com, willy@infradead.org Subject: [patch 17/24] mm, futex: fix shared futex pgoff on shmem huge page Message-ID: <20210625013952.eaD8IsXDa%akpm@linux-foundation.org> In-Reply-To: <20210624183838.ac3161ca4a43989665ac8b2f@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Hugh Dickins Subject: mm, futex: fix shared futex pgoff on shmem huge page If more than one futex is placed on a shmem huge page, it can happen that waking the second wakes the first instead, and leaves the second waiting: the key's shared.pgoff is wrong. When 3.11 commit 13d60f4b6ab5 ("futex: Take hugepages into account when generating futex_key"), the only shared huge pages came from hugetlbfs, and the code added to deal with its exceptional page->index was put into hugetlb source. Then that was missed when 4.8 added shmem huge pages. page_to_pgoff() is what others use for this nowadays: except that, as currently written, it gives the right answer on hugetlbfs head, but nonsense on hugetlbfs tails. Fix that by calling hugetlbfs-specific hugetlb_basepage_index() on PageHuge tails as well as on head. Yes, it's unconventional to declare hugetlb_basepage_index() there in pagemap.h, rather than in hugetlb.h; but I do not expect anything but page_to_pgoff() ever to need it. [akpm@linux-foundation.org: give hugetlb_basepage_index() prototype the correct scope] Link: https://lkml.kernel.org/r/b17d946b-d09-326e-b42a-52884c36df32@google.com Fixes: 800d8c63b2e9 ("shmem: add huge pages support") Reported-by: Neel Natu Signed-off-by: Hugh Dickins Reviewed-by: Matthew Wilcox (Oracle) Acked-by: Thomas Gleixner Cc: "Kirill A. Shutemov" Cc: Zhang Yi Cc: Mel Gorman Cc: Mike Kravetz Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Darren Hart Cc: Davidlohr Bueso Cc: Signed-off-by: Andrew Morton --- include/linux/hugetlb.h | 16 ---------------- include/linux/pagemap.h | 13 +++++++------ kernel/futex.c | 3 +-- mm/hugetlb.c | 5 +---- 4 files changed, 9 insertions(+), 28 deletions(-) --- a/include/linux/hugetlb.h~mm-futex-fix-shared-futex-pgoff-on-shmem-huge-page +++ a/include/linux/hugetlb.h @@ -741,17 +741,6 @@ static inline int hstate_index(struct hs return h - hstates; } -pgoff_t __basepage_index(struct page *page); - -/* Return page->index in PAGE_SIZE units */ -static inline pgoff_t basepage_index(struct page *page) -{ - if (!PageCompound(page)) - return page->index; - - return __basepage_index(page); -} - extern int dissolve_free_huge_page(struct page *page); extern int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn); @@ -988,11 +977,6 @@ static inline int hstate_index(struct hs return 0; } -static inline pgoff_t basepage_index(struct page *page) -{ - return page->index; -} - static inline int dissolve_free_huge_page(struct page *page) { return 0; --- a/include/linux/pagemap.h~mm-futex-fix-shared-futex-pgoff-on-shmem-huge-page +++ a/include/linux/pagemap.h @@ -516,7 +516,7 @@ static inline struct page *read_mapping_ } /* - * Get index of the page with in radix-tree + * Get index of the page within radix-tree (but not for hugetlb pages). * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE) */ static inline pgoff_t page_to_index(struct page *page) @@ -535,15 +535,16 @@ static inline pgoff_t page_to_index(stru return pgoff; } +extern pgoff_t hugetlb_basepage_index(struct page *page); + /* - * Get the offset in PAGE_SIZE. - * (TODO: hugepage should have ->index in PAGE_SIZE) + * Get the offset in PAGE_SIZE (even for hugetlb pages). + * (TODO: hugetlb pages should have ->index in PAGE_SIZE) */ static inline pgoff_t page_to_pgoff(struct page *page) { - if (unlikely(PageHeadHuge(page))) - return page->index << compound_order(page); - + if (unlikely(PageHuge(page))) + return hugetlb_basepage_index(page); return page_to_index(page); } --- a/kernel/futex.c~mm-futex-fix-shared-futex-pgoff-on-shmem-huge-page +++ a/kernel/futex.c @@ -35,7 +35,6 @@ #include #include #include -#include #include #include #include @@ -650,7 +649,7 @@ again: key->both.offset |= FUT_OFF_INODE; /* inode-based key */ key->shared.i_seq = get_inode_sequence_number(inode); - key->shared.pgoff = basepage_index(tail); + key->shared.pgoff = page_to_pgoff(tail); rcu_read_unlock(); } --- a/mm/hugetlb.c~mm-futex-fix-shared-futex-pgoff-on-shmem-huge-page +++ a/mm/hugetlb.c @@ -1588,15 +1588,12 @@ struct address_space *hugetlb_page_mappi return NULL; } -pgoff_t __basepage_index(struct page *page) +pgoff_t hugetlb_basepage_index(struct page *page) { struct page *page_head = compound_head(page); pgoff_t index = page_index(page_head); unsigned long compound_idx; - if (!PageHuge(page_head)) - return page_index(page); - if (compound_order(page_head) >= MAX_ORDER) compound_idx = page_to_pfn(page) - page_to_pfn(page_head); else