From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw1-f69.google.com (mail-yw1-f69.google.com [209.85.161.69]) by kanga.kvack.org (Postfix) with ESMTP id 4C7186B0277 for ; Mon, 5 Nov 2018 11:56:44 -0500 (EST) Received: by mail-yw1-f69.google.com with SMTP id a62-v6so7834645ywf.16 for ; Mon, 05 Nov 2018 08:56:44 -0800 (PST) Received: from userp2120.oracle.com (userp2120.oracle.com. [156.151.31.85]) by mx.google.com with ESMTPS id r4-v6si23252143yba.429.2018.11.05.08.56.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 05 Nov 2018 08:56:43 -0800 (PST) From: Daniel Jordan Subject: [RFC PATCH v4 08/13] vfio: remove unnecessary mmap_sem writer acquisition around locked_vm Date: Mon, 5 Nov 2018 11:55:53 -0500 Message-Id: <20181105165558.11698-9-daniel.m.jordan@oracle.com> In-Reply-To: <20181105165558.11698-1-daniel.m.jordan@oracle.com> References: <20181105165558.11698-1-daniel.m.jordan@oracle.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: aarcange@redhat.com, aaron.lu@intel.com, akpm@linux-foundation.org, alex.williamson@redhat.com, bsd@redhat.com, daniel.m.jordan@oracle.com, darrick.wong@oracle.com, dave.hansen@linux.intel.com, jgg@mellanox.com, jwadams@google.com, jiangshanlai@gmail.com, mhocko@kernel.org, mike.kravetz@oracle.com, Pavel.Tatashin@microsoft.com, prasad.singamsetty@oracle.com, rdunlap@infradead.org, steven.sistare@oracle.com, tim.c.chen@intel.com, tj@kernel.org, vbabka@suse.cz Now that mmap_sem is no longer required for modifying locked_vm, remove it in the VFIO code. [XXX Can be sent separately, along with similar conversions in the other places mmap_sem was taken for locked_vm. While at it, could make similar changes to pinned_vm.] Signed-off-by: Daniel Jordan --- drivers/vfio/vfio_iommu_type1.c | 26 +++++++++----------------- 1 file changed, 9 insertions(+), 17 deletions(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index f307dc9d5e19..9e52a24eb45b 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -258,7 +258,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn) static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async) { struct mm_struct *mm; - int ret; + long locked_vm; + int ret = 0; if (!npage) return 0; @@ -267,24 +268,15 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async) if (!mm) return -ESRCH; /* process exited */ - ret = down_write_killable(&mm->mmap_sem); - if (!ret) { - if (npage > 0) { - if (!dma->lock_cap) { - unsigned long limit; - - limit = task_rlimit(dma->task, - RLIMIT_MEMLOCK) >> PAGE_SHIFT; + locked_vm = atomic_long_add_return(npage, &mm->locked_vm); - if (atomic_long_read(&mm->locked_vm) + npage > limit) - ret = -ENOMEM; - } + if (npage > 0 && !dma->lock_cap) { + unsigned long limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >> + PAGE_SHIFT; + if (locked_vm > limit) { + atomic_long_sub(npage, &mm->locked_vm); + ret = -ENOMEM; } - - if (!ret) - atomic_long_add(npage, &mm->locked_vm); - - up_write(&mm->mmap_sem); } if (async) -- 2.19.1