From patchwork Sun Jul 26 08:02:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pengfei Li X-Patchwork-Id: 11685571 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E1F5313B6 for ; Sun, 26 Jul 2020 08:03:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D44AF2074F for ; Sun, 26 Jul 2020 08:03:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727032AbgGZIDI (ORCPT ); Sun, 26 Jul 2020 04:03:08 -0400 Received: from relay11.mail.gandi.net ([217.70.178.231]:35233 "EHLO relay11.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725848AbgGZIDI (ORCPT ); Sun, 26 Jul 2020 04:03:08 -0400 Received: from localhost.localdomain (unknown [180.110.142.179]) (Authenticated sender: fly@kernel.page) by relay11.mail.gandi.net (Postfix) with ESMTPSA id 107BC100007; Sun, 26 Jul 2020 08:02:59 +0000 (UTC) From: Pengfei Li To: akpm@linux-foundation.org Cc: bmt@zurich.ibm.com, dledford@redhat.com, willy@infradead.org, vbabka@suse.cz, kirill.shutemov@linux.intel.com, jgg@ziepe.ca, alex.williamson@redhat.com, cohuck@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Pengfei Li Subject: [PATCH 2/2] mm, util: account_locked_vm() does not hold mmap_lock Date: Sun, 26 Jul 2020 16:02:24 +0800 Message-Id: <20200726080224.205470-2-fly@kernel.page> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200726080224.205470-1-fly@kernel.page> References: <20200726080224.205470-1-fly@kernel.page> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Since mm->locked_vm is already an atomic counter, account_locked_vm() does not need to hold mmap_lock. Signed-off-by: Pengfei Li --- drivers/vfio/vfio_iommu_type1.c | 8 ++------ mm/util.c | 15 +++------------ 2 files changed, 5 insertions(+), 18 deletions(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 78013be07fe7..53818fce78a6 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -376,12 +376,8 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async) if (!mm) return -ESRCH; /* process exited */ - ret = mmap_write_lock_killable(mm); - if (!ret) { - ret = __account_locked_vm(mm, abs(npage), npage > 0, dma->task, - dma->lock_cap); - mmap_write_unlock(mm); - } + ret = __account_locked_vm(mm, abs(npage), npage > 0, + dma->task, dma->lock_cap); if (async) mmput(mm); diff --git a/mm/util.c b/mm/util.c index 473add0dc275..320fdd537aea 100644 --- a/mm/util.c +++ b/mm/util.c @@ -424,8 +424,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) * @task: task used to check RLIMIT_MEMLOCK * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped * - * Assumes @task and @mm are valid (i.e. at least one reference on each), and - * that mmap_lock is held as writer. + * Assumes @task and @mm are valid (i.e. at least one reference on each). * * Return: * * 0 on success @@ -437,8 +436,6 @@ int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, unsigned long locked_vm, limit; int ret = 0; - mmap_assert_write_locked(mm); - locked_vm = atomic64_read(&mm->locked_vm); if (inc) { if (!bypass_rlim) { @@ -476,17 +473,11 @@ EXPORT_SYMBOL_GPL(__account_locked_vm); */ int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc) { - int ret; - if (pages == 0 || !mm) return 0; - mmap_write_lock(mm); - ret = __account_locked_vm(mm, pages, inc, current, - capable(CAP_IPC_LOCK)); - mmap_write_unlock(mm); - - return ret; + return __account_locked_vm(mm, pages, inc, + current, capable(CAP_IPC_LOCK)); } EXPORT_SYMBOL_GPL(account_locked_vm);