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 4B29BC433F5 for ; Mon, 7 Mar 2022 00:24:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232484AbiCGAZl (ORCPT ); Sun, 6 Mar 2022 19:25:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231548AbiCGAZl (ORCPT ); Sun, 6 Mar 2022 19:25:41 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8F9D13D19 for ; Sun, 6 Mar 2022 16:24:47 -0800 (PST) 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 82B5F60FF1 for ; Mon, 7 Mar 2022 00:24:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DBA9AC340EC; Mon, 7 Mar 2022 00:24:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1646612686; bh=9AXQgEjbfkuO7m8C/NzF3aQQSHt8Mko4z7H5lpraasM=; h=Date:To:From:Subject:From; b=Lz0hC4bDPZ5VfU3y58DyRMHcBalVrtpU3zGZG6XWLN6HoSv/YxZ72yb7RXPT47eEo qe3gv0ryTl9TSnXNtMoLzzK1nd/aV8c44pkE4eZ2CY526OgtbkhgPPnUNkVcvghTOG 7vNaa6CglpAX4xnWCv7I2gqXHTu3CwLvYpjJ9774= Date: Sun, 06 Mar 2022 16:24:46 -0800 To: mm-commits@vger.kernel.org, sashal@kernel.org, mike.kravetz@oracle.com, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, dave@stgolabs.net, hughd@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-unmap_mapping_range_tree-with-i_mmap_rwsem-shared.patch added to -mm tree Message-Id: <20220307002446.DBA9AC340EC@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: unmap_mapping_range_tree() with i_mmap_rwsem shared has been added to the -mm tree. Its filename is mm-unmap_mapping_range_tree-with-i_mmap_rwsem-shared.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-unmap_mapping_range_tree-with-i_mmap_rwsem-shared.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-unmap_mapping_range_tree-with-i_mmap_rwsem-shared.patch 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 and is updated there every 3-4 working days ------------------------------------------------------ From: Hugh Dickins Subject: mm: unmap_mapping_range_tree() with i_mmap_rwsem shared Revert 48ec833b7851 ("Revert "mm/memory.c: share the i_mmap_rwsem"") to reinstate c8475d144abb ("mm/memory.c: share the i_mmap_rwsem"): the unmap_mapping_range family of functions do the unmapping of user pages (ultimately via zap_page_range_single) without modifying the interval tree itself, and unmapping races are necessarily guarded by page table lock, thus the i_mmap_rwsem should be shared in unmap_mapping_pages() and unmap_mapping_folio(). Commit 48ec833b7851 was intended as a short-term measure, allowing the other shared lock changes into 3.19 final, before investigating three trinity crashes, one of which had been bisected to commit c8475d144ab: [1] https://lkml.org/lkml/2014/11/14/342 https://lore.kernel.org/lkml/5466142C.60100@oracle.com/ [2] https://lkml.org/lkml/2014/12/22/213 https://lore.kernel.org/lkml/549832E2.8060609@oracle.com/ [3] https://lkml.org/lkml/2014/12/9/741 https://lore.kernel.org/lkml/5487ACC5.1010002@oracle.com/ Two of those were Bad page states: free_pages_prepare() found PG_mlocked still set - almost certain to have been fixed by 4.4 commit b87537d9e2fe ("mm: rmap use pte lock not mmap_sem to set PageMlocked"). The NULL deref on rwsem in [2]: unclear, only happened once, not bisected to c8475d144ab. No change to the i_mmap_lock_write() around __unmap_hugepage_range_final() in unmap_single_vma(): IIRC that's a special usage, helping to serialize hugetlbfs page table sharing, not to be dabbled with lightly. No change to other uses of i_mmap_lock_write() by hugetlbfs. I am not aware of any significant gains from the concurrency allowed by this commit: it is submitted more to resolve an ancient misunderstanding. Link: https://lkml.kernel.org/r/e4a5e356-6c87-47b2-3ce8-c2a95ae84e20@google.com Signed-off-by: Hugh Dickins Cc: "Kirill A. Shutemov" Cc: Davidlohr Bueso Cc: Sasha Levin Cc: Mel Gorman Cc: Mike Kravetz Signed-off-by: Andrew Morton --- mm/memory.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/mm/memory.c~mm-unmap_mapping_range_tree-with-i_mmap_rwsem-shared +++ a/mm/memory.c @@ -3388,11 +3388,11 @@ void unmap_mapping_folio(struct folio *f details.even_cows = false; details.single_folio = folio; - i_mmap_lock_write(mapping); + i_mmap_lock_read(mapping); if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))) unmap_mapping_range_tree(&mapping->i_mmap, first_index, last_index, &details); - i_mmap_unlock_write(mapping); + i_mmap_unlock_read(mapping); } /** @@ -3418,11 +3418,11 @@ void unmap_mapping_pages(struct address_ if (last_index < first_index) last_index = ULONG_MAX; - i_mmap_lock_write(mapping); + i_mmap_lock_read(mapping); if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))) unmap_mapping_range_tree(&mapping->i_mmap, first_index, last_index, &details); - i_mmap_unlock_write(mapping); + i_mmap_unlock_read(mapping); } EXPORT_SYMBOL_GPL(unmap_mapping_pages); _ Patches currently in -mm which might be from hughd@google.com are mm-fs-delete-pf_swapwrite.patch tmpfs-support-for-file-creation-time-fix.patch shmem-mapping_set_exiting-to-help-mapped-resilience.patch mm-_install_special_mapping-apply-vm_locked_clear_mask.patch mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch mm-thp-clearpagedoublemap-in-first-page_add_file_rmap.patch mm-delete-__clearpagewaiters.patch mm-filemap_unaccount_folio-large-skip-mapcount-fixup.patch mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch mm-warn-on-deleting-redirtied-only-if-accounted.patch mm-unmap_mapping_range_tree-with-i_mmap_rwsem-shared.patch