From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932448AbcJZJZ6 (ORCPT ); Wed, 26 Oct 2016 05:25:58 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:35860 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932207AbcJZJZw (ORCPT ); Wed, 26 Oct 2016 05:25:52 -0400 From: Lorenzo Stoakes To: linux-mm@kvack.org Cc: Linus Torvalds , Michal Hocko , Jan Kara , Hugh Dickins , Dave Hansen , Rik van Riel , Mel Gorman , Andrew Morton , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Lorenzo Stoakes Subject: [PATCH v2] mm: remove unnecessary __get_user_pages_unlocked() calls Date: Wed, 26 Oct 2016 10:25:48 +0100 Message-Id: <20161026092548.12712-1-lstoakes@gmail.com> X-Mailer: git-send-email 2.10.1 In-Reply-To: <20161025233609.5601-1-lstoakes@gmail.com> References: <20161025233609.5601-1-lstoakes@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In hva_to_pfn_slow() we are able to replace __get_user_pages_unlocked() with get_user_pages_unlocked() since we can now pass gup_flags. In async_pf_execute() we need to pass different tsk, mm arguments so get_user_pages_remote() is the sane replacement here (having added manual acquisition and release of mmap_sem.) Since we pass a NULL pages parameter the subsequent call to __get_user_pages_locked() will have previously bailed any attempt at VM_FAULT_RETRY, so we do not change this behaviour by using get_user_pages_remote() which does not invoke VM_FAULT_RETRY logic at all. Additionally get_user_pages_remote() reintroduces use of the FOLL_TOUCH flag. However, this flag was originally silently dropped by 1e9877902dc7e ("mm/gup: Introduce get_user_pages_remote()"), so this appears to have been unintentional and reintroducing it is therefore not an issue. Signed-off-by: Lorenzo Stoakes --- v2: update description to reference dropped FOLL_TOUCH flag virt/kvm/async_pf.c | 7 ++++--- virt/kvm/kvm_main.c | 5 ++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c index 8035cc1..e8c832c 100644 --- a/virt/kvm/async_pf.c +++ b/virt/kvm/async_pf.c @@ -82,10 +82,11 @@ static void async_pf_execute(struct work_struct *work) /* * This work is run asynchromously to the task which owns * mm and might be done in another context, so we must - * use FOLL_REMOTE. + * access remotely. */ - __get_user_pages_unlocked(NULL, mm, addr, 1, NULL, - FOLL_WRITE | FOLL_REMOTE); + down_read(&mm->mmap_sem); + get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL); + up_read(&mm->mmap_sem); kvm_async_page_present_sync(vcpu, apf); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 2907b7b..c45d951 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1415,13 +1415,12 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault, npages = get_user_page_nowait(addr, write_fault, page); up_read(¤t->mm->mmap_sem); } else { - unsigned int flags = FOLL_TOUCH | FOLL_HWPOISON; + unsigned int flags = FOLL_HWPOISON; if (write_fault) flags |= FOLL_WRITE; - npages = __get_user_pages_unlocked(current, current->mm, addr, 1, - page, flags); + npages = get_user_pages_unlocked(addr, 1, page, flags); } if (npages != 1) return npages; -- 2.10.1