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 54990C433F5 for ; Thu, 31 Mar 2022 04:32:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229484AbiCaEef (ORCPT ); Thu, 31 Mar 2022 00:34:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229480AbiCaEea (ORCPT ); Thu, 31 Mar 2022 00:34:30 -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 594355A15C for ; Wed, 30 Mar 2022 21:32:40 -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 DC0AA6146B for ; Thu, 31 Mar 2022 04:32:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 388C2C340ED; Thu, 31 Mar 2022 04:32:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648701159; bh=kw4JjFQevLMXzKDN3tyQrxRr/swySxc1032VUjdlgUI=; h=Date:To:From:Subject:From; b=RnQPMtrB+KWGTbzt+w0StSafs3yIIvwoYz8J1ww7CQuBCrNGcNND7O7hfL0sgyhxk VyXUiJ2xckehj0Ai63ihPgzMGQscZm7dpIljwuWFUE37OPXfOAkyajSjEmfHc9fVKe esxD+Pe8Fq6onMv3P/n0KcjjSK9bQuGsqJNyeED0= Date: Wed, 30 Mar 2022 21:32:38 -0700 To: mm-commits@vger.kernel.org, zhangliang5@huawei.com, willy@infradead.org, vbabka@suse.cz, shy828301@gmail.com, shakeelb@google.com, rppt@linux.ibm.com, rientjes@google.com, riel@surriel.com, peterx@redhat.com, pedrodemargomes@gmail.com, oleg@redhat.com, oded.gabbay@gmail.com, namit@vmware.com, mike.kravetz@oracle.com, mhocko@kernel.org, kirill.shutemov@linux.intel.com, khalid.aziz@oracle.com, jhubbard@nvidia.com, jgg@nvidia.com, jannh@google.com, jack@suse.cz, hughd@google.com, hch@lst.de, guro@fb.com, ddutile@redhat.com, aarcange@redhat.com, david@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-memory-slightly-simplify-copy_present_pte.patch added to -mm tree Message-Id: <20220331043239.388C2C340ED@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/memory: slightly simplify copy_present_pte() has been added to the -mm tree. Its filename is mm-memory-slightly-simplify-copy_present_pte.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-memory-slightly-simplify-copy_present_pte.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-memory-slightly-simplify-copy_present_pte.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: David Hildenbrand Subject: mm/memory: slightly simplify copy_present_pte() Let's move the pinning check into the caller, to simplify return code logic and prepare for further changes: relocating the page_needs_cow_for_dma() into rmap handling code. While at it, remove the unused pte parameter and simplify the comments a bit. No functional change intended. Link: https://lkml.kernel.org/r/20220329160440.193848-4-david@redhat.com Signed-off-by: David Hildenbrand Cc: Andrea Arcangeli Cc: Christoph Hellwig Cc: David Rientjes Cc: Don Dutile Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Jason Gunthorpe Cc: John Hubbard Cc: Khalid Aziz Cc: "Kirill A. Shutemov" Cc: Liang Zhang Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Kravetz Cc: Mike Rapoport Cc: Nadav Amit Cc: Oded Gabbay Cc: Oleg Nesterov Cc: Pedro Demarchi Gomes Cc: Peter Xu Cc: Rik van Riel Cc: Roman Gushchin Cc: Shakeel Butt Cc: Vlastimil Babka Cc: Yang Shi Signed-off-by: Andrew Morton --- mm/memory.c | 53 +++++++++++++++----------------------------------- 1 file changed, 16 insertions(+), 37 deletions(-) --- a/mm/memory.c~mm-memory-slightly-simplify-copy_present_pte +++ a/mm/memory.c @@ -862,19 +862,11 @@ copy_nonpresent_pte(struct mm_struct *ds } /* - * Copy a present and normal page if necessary. + * Copy a present and normal page. * - * NOTE! The usual case is that this doesn't need to do - * anything, and can just return a positive value. That - * will let the caller know that it can just increase - * the page refcount and re-use the pte the traditional - * way. - * - * But _if_ we need to copy it because it needs to be - * pinned in the parent (and the child should get its own - * copy rather than just a reference to the same page), - * we'll do that here and return zero to let the caller - * know we're done. + * NOTE! The usual case is that this isn't required; + * instead, the caller can just increase the page refcount + * and re-use the pte the traditional way. * * And if we need a pre-allocated page but don't yet have * one, return a negative error to let the preallocation @@ -884,25 +876,10 @@ copy_nonpresent_pte(struct mm_struct *ds static inline int copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, - struct page **prealloc, pte_t pte, struct page *page) + struct page **prealloc, struct page *page) { struct page *new_page; - - /* - * What we want to do is to check whether this page may - * have been pinned by the parent process. If so, - * instead of wrprotect the pte on both sides, we copy - * the page immediately so that we'll always guarantee - * the pinned page won't be randomly replaced in the - * future. - * - * The page pinning checks are just "has this mm ever - * seen pinning", along with the (inexact) check of - * the page count. That might give false positives for - * for pinning, but it will work correctly. - */ - if (likely(!page_needs_cow_for_dma(src_vma, page))) - return 1; + pte_t pte; new_page = *prealloc; if (!new_page) @@ -944,14 +921,16 @@ copy_present_pte(struct vm_area_struct * struct page *page; page = vm_normal_page(src_vma, addr, pte); - if (page) { - int retval; - - retval = copy_present_page(dst_vma, src_vma, dst_pte, src_pte, - addr, rss, prealloc, pte, page); - if (retval <= 0) - return retval; - + if (page && unlikely(page_needs_cow_for_dma(src_vma, page))) { + /* + * If this page may have been pinned by the parent process, + * copy the page immediately for the child so that we'll always + * guarantee the pinned page won't be randomly replaced in the + * future. + */ + return copy_present_page(dst_vma, src_vma, dst_pte, src_pte, + addr, rss, prealloc, page); + } else if (page) { get_page(page); page_dup_rmap(page, false); rss[mm_counter(page)]++; _ Patches currently in -mm which might be from david@redhat.com are mm-rmap-fix-missing-swap_free-in-try_to_unmap-after-arch_unmap_one-failed.patch mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range.patch mm-memory-slightly-simplify-copy_present_pte.patch mm-rmap-split-page_dup_rmap-into-page_dup_file_rmap-and-page_try_dup_anon_rmap.patch mm-rmap-convert-rmap-flags-to-a-proper-distinct-rmap_t-type.patch mm-rmap-remove-do_page_add_anon_rmap.patch mm-rmap-pass-rmap-flags-to-hugepage_add_anon_rmap.patch mm-rmap-drop-compound-parameter-from-page_add_new_anon_rmap.patch mm-rmap-use-page_move_anon_rmap-when-reusing-a-mapped-pageanon-page-exclusively.patch mm-huge_memory-remove-outdated-vm_warn_on_once_page-from-unmap_page.patch mm-page-flags-reuse-pg_mappedtodisk-as-pg_anon_exclusive-for-pageanon-pages.patch mm-remember-exclusively-mapped-anonymous-pages-with-pg_anon_exclusive.patch mm-gup-disallow-follow_pagefoll_pin.patch mm-support-gup-triggered-unsharing-of-anonymous-pages.patch mm-gup-trigger-fault_flag_unshare-when-r-o-pinning-a-possibly-shared-anonymous-page.patch mm-gup-sanity-check-with-config_debug_vm-that-anonymous-pages-are-exclusive-when-unpinning.patch mm-swap-remember-pg_anon_exclusive-via-a-swp-pte-bit.patch mm-debug_vm_pgtable-add-tests-for-__have_arch_pte_swp_exclusive.patch x86-pgtable-support-__have_arch_pte_swp_exclusive.patch arm64-pgtable-support-__have_arch_pte_swp_exclusive.patch s390-pgtable-cleanup-description-of-swp-pte-layout.patch s390-pgtable-support-__have_arch_pte_swp_exclusive.patch powerpc-pgtable-remove-_page_bit_swap_type-for-book3s.patch powerpc-pgtable-support-__have_arch_pte_swp_exclusive-for-book3s.patch