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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id e65sm16713492pfc.184.2019.02.11.14.56.20 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Feb 2019 14:56:20 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1gtKUu-0003Rw-6N; Mon, 11 Feb 2019 15:56:20 -0700 Date: Mon, 11 Feb 2019 15:56:20 -0700 From: Jason Gunthorpe To: Daniel Jordan Cc: akpm@linux-foundation.org, dave@stgolabs.net, jack@suse.cz, cl@linux.com, linux-mm@kvack.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org, alex.williamson@redhat.com, paulus@ozlabs.org, benh@kernel.crashing.org, mpe@ellerman.id.au, hao.wu@intel.com, atull@kernel.org, mdf@kernel.org, aik@ozlabs.ru Subject: Re: [PATCH 1/5] vfio/type1: use pinned_vm instead of locked_vm to account pinned pages Message-ID: <20190211225620.GO24692@ziepe.ca> References: <20190211224437.25267-1-daniel.m.jordan@oracle.com> <20190211224437.25267-2-daniel.m.jordan@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190211224437.25267-2-daniel.m.jordan@oracle.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 11, 2019 at 05:44:33PM -0500, Daniel Jordan wrote: > Beginning with bc3e53f682d9 ("mm: distinguish between mlocked and pinned > pages"), locked and pinned pages are accounted separately. Type1 > accounts pinned pages to locked_vm; use pinned_vm instead. > > pinned_vm recently became atomic and so no longer relies on mmap_sem > held as writer: delete. > > Signed-off-by: Daniel Jordan > drivers/vfio/vfio_iommu_type1.c | 31 ++++++++++++------------------- > 1 file changed, 12 insertions(+), 19 deletions(-) > > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 73652e21efec..a56cc341813f 100644 > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -257,7 +257,8 @@ 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; > + s64 pinned_vm; > + int ret = 0; > > if (!npage) > return 0; > @@ -266,24 +267,15 @@ 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; > + pinned_vm = atomic64_add_return(npage, &mm->pinned_vm); > > - if (mm->locked_vm + npage > limit) > - ret = -ENOMEM; > - } > + if (npage > 0 && !dma->lock_cap) { > + unsigned long limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >> > + > - PAGE_SHIFT; I haven't looked at this super closely, but how does this stuff work? do_mlock doesn't touch pinned_vm, and this doesn't touch locked_vm... Shouldn't all this be 'if (locked_vm + pinned_vm < RLIMIT_MEMLOCK)' ? Otherwise MEMLOCK is really doubled.. Jason