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from [10.61.2.175] ([122.99.82.10]) by smtp.gmail.com with ESMTPSA id n27sm2608734pfb.129.2019.05.23.23.43.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 May 2019 23:43:19 -0700 (PDT) Subject: Re: [PATCH] mm: add account_locked_vm utility function To: Daniel Jordan Cc: akpm@linux-foundation.org, Alan Tull , Alex Williamson , Benjamin Herrenschmidt , Christoph Lameter , Christophe Leroy , Davidlohr Bueso , Jason Gunthorpe , Mark Rutland , Michael Ellerman , Moritz Fischer , Paul Mackerras , Steve Sistare , Wu Hao , 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 References: <20190503201629.20512-1-daniel.m.jordan@oracle.com> <4b42057f-b998-f87c-4e0f-a91abcb366f9@ozlabs.ru> <20190520153020.mzvjsjwefwxz6cau@ca-dmjordan1.us.oracle.com> From: Alexey Kardashevskiy Openpgp: preference=signencrypt Autocrypt: addr=aik@ozlabs.ru; keydata= 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X2tXyeBixa3i/6dWJ4nIp3vGQicQkut1YBwR7dJq67/FCV3Mlj94jI0myHT5PIrCS2S8LtWX ikTJSxWUKmh7OP5mrqhwNe0ezgGiWxxvyNwThOHc5JvpzJLd32VDFilbxgu4Hhnf6LcgZJ2c Zd44XWqUu7FzVOYaSgIvTP0hNrBYm/E6M7yrLbs3JY74fGzPWGRbBUHTZXQEqQnZglXaVB5V ZhSFtHopZnBSCUSNDbB+QGy4B/E++Bb02IBTGl/JxmOwG+kZUnymsPvTtnNIeTLHxN/H/ae0 c7E5M+/NpslPCmYnDjs5qg0/3ihh6XuOGggZQOqrYPC3PnsNs3NxirwOkVPQgO6mXxpuifvJ DG9EMkK8IBXnLulqVk54kf7fE0jT/d8RTtJIA92GzsgdK2rpT1MBKKVffjRFGwN7nQVOzi4T XrB5p+6ML7Bd84xOEGsj/vdaXmz1esuH7BOZAGEZfLRCHJ0GVCSssg== Message-ID: Date: Fri, 24 May 2019 16:43:10 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190520153020.mzvjsjwefwxz6cau@ca-dmjordan1.us.oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/05/2019 01:30, Daniel Jordan wrote: > On Mon, May 20, 2019 at 04:19:34PM +1000, Alexey Kardashevskiy wrote: >> On 04/05/2019 06:16, Daniel Jordan wrote: >>> locked_vm accounting is done roughly the same way in five places, so >>> unify them in a helper. Standardize the debug prints, which vary >>> slightly. >> >> And I rather liked that prints were different and tell precisely which >> one of three each printk is. > > I'm not following. One of three...callsites? But there were five callsites. Well, 3 of them are mine, I was referring to them :) > Anyway, I added a _RET_IP_ to the debug print so you can differentiate. I did not know that existed, cool! > >> I commented below but in general this seems working. >> >> Tested-by: Alexey Kardashevskiy > > Thanks! And for the review as well. > >>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c >>> index 6b64e45a5269..d39a1b830d82 100644 >>> --- a/drivers/vfio/vfio_iommu_spapr_tce.c >>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c >>> @@ -34,49 +35,13 @@ >>> static void tce_iommu_detach_group(void *iommu_data, >>> struct iommu_group *iommu_group); >>> >>> -static long try_increment_locked_vm(struct mm_struct *mm, long npages) >>> +static int tce_account_locked_vm(struct mm_struct *mm, unsigned long npages, >>> + bool inc) >>> { >>> - long ret = 0, locked, lock_limit; >>> - >>> if (WARN_ON_ONCE(!mm)) >>> return -EPERM; >> >> >> If this WARN_ON is the only reason for having tce_account_locked_vm() >> instead of calling account_locked_vm() directly, you can then ditch the >> check as I have never ever seen this triggered. > > Great, will do. > >>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c >>> index d0f731c9920a..15ac76171ccd 100644 >>> --- a/drivers/vfio/vfio_iommu_type1.c >>> +++ b/drivers/vfio/vfio_iommu_type1.c >>> @@ -273,25 +273,14 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async) >>> 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; >>> - >>> - if (mm->locked_vm + npage > limit) >>> - ret = -ENOMEM; >>> - } >>> - } >>> + if (ret) >>> + goto out; >> >> >> A single "goto" to jump just 3 lines below seems unnecessary. > > No strong preference here, I'll take out the goto. > >>> +int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, >>> + struct task_struct *task, bool bypass_rlim) >>> +{ >>> + unsigned long locked_vm, limit; >>> + int ret = 0; >>> + >>> + locked_vm = mm->locked_vm; >>> + if (inc) { >>> + if (!bypass_rlim) { >>> + limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT; >>> + if (locked_vm + pages > limit) { >>> + ret = -ENOMEM; >>> + goto out; >>> + } >>> + } >> >> Nit: >> >> if (!ret) >> >> and then you don't need "goto out". > > Ok, sure. > >>> + mm->locked_vm = locked_vm + pages; >>> + } else { >>> + WARN_ON_ONCE(pages > locked_vm); >>> + mm->locked_vm = locked_vm - pages; >> >> >> Can go negative here. Not a huge deal but inaccurate imo. > > I hear you, but setting a negative value to zero, as we had done previously, > doesn't make much sense to me. Ok then. I have not seen these WARN_ON for a very long time anyway. -- Alexey 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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE709C072B5 for ; Fri, 24 May 2019 06:44:45 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 30B3E20868 for ; Fri, 24 May 2019 06:44:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" 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kvm@vger.kernel.org, Alan Tull , linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-mm@kvack.org, Alex Williamson , Jason Gunthorpe , Moritz Fischer , Steve Sistare , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Christoph Lameter , Wu Hao Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 21/05/2019 01:30, Daniel Jordan wrote: > On Mon, May 20, 2019 at 04:19:34PM +1000, Alexey Kardashevskiy wrote: >> On 04/05/2019 06:16, Daniel Jordan wrote: >>> locked_vm accounting is done roughly the same way in five places, so >>> unify them in a helper. Standardize the debug prints, which vary >>> slightly. >> >> And I rather liked that prints were different and tell precisely which >> one of three each printk is. > > I'm not following. One of three...callsites? But there were five callsites. Well, 3 of them are mine, I was referring to them :) > Anyway, I added a _RET_IP_ to the debug print so you can differentiate. I did not know that existed, cool! > >> I commented below but in general this seems working. >> >> Tested-by: Alexey Kardashevskiy > > Thanks! And for the review as well. > >>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c >>> index 6b64e45a5269..d39a1b830d82 100644 >>> --- a/drivers/vfio/vfio_iommu_spapr_tce.c >>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c >>> @@ -34,49 +35,13 @@ >>> static void tce_iommu_detach_group(void *iommu_data, >>> struct iommu_group *iommu_group); >>> >>> -static long try_increment_locked_vm(struct mm_struct *mm, long npages) >>> +static int tce_account_locked_vm(struct mm_struct *mm, unsigned long npages, >>> + bool inc) >>> { >>> - long ret = 0, locked, lock_limit; >>> - >>> if (WARN_ON_ONCE(!mm)) >>> return -EPERM; >> >> >> If this WARN_ON is the only reason for having tce_account_locked_vm() >> instead of calling account_locked_vm() directly, you can then ditch the >> check as I have never ever seen this triggered. > > Great, will do. > >>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c >>> index d0f731c9920a..15ac76171ccd 100644 >>> --- a/drivers/vfio/vfio_iommu_type1.c >>> +++ b/drivers/vfio/vfio_iommu_type1.c >>> @@ -273,25 +273,14 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async) >>> 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; >>> - >>> - if (mm->locked_vm + npage > limit) >>> - ret = -ENOMEM; >>> - } >>> - } >>> + if (ret) >>> + goto out; >> >> >> A single "goto" to jump just 3 lines below seems unnecessary. > > No strong preference here, I'll take out the goto. > >>> +int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, >>> + struct task_struct *task, bool bypass_rlim) >>> +{ >>> + unsigned long locked_vm, limit; >>> + int ret = 0; >>> + >>> + locked_vm = mm->locked_vm; >>> + if (inc) { >>> + if (!bypass_rlim) { >>> + limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT; >>> + if (locked_vm + pages > limit) { >>> + ret = -ENOMEM; >>> + goto out; >>> + } >>> + } >> >> Nit: >> >> if (!ret) >> >> and then you don't need "goto out". > > Ok, sure. > >>> + mm->locked_vm = locked_vm + pages; >>> + } else { >>> + WARN_ON_ONCE(pages > locked_vm); >>> + mm->locked_vm = locked_vm - pages; >> >> >> Can go negative here. Not a huge deal but inaccurate imo. > > I hear you, but setting a negative value to zero, as we had done previously, > doesn't make much sense to me. Ok then. I have not seen these WARN_ON for a very long time anyway. -- Alexey From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Kardashevskiy Date: Fri, 24 May 2019 06:43:10 +0000 Subject: Re: [PATCH] mm: add account_locked_vm utility function Message-Id: List-Id: References: <20190503201629.20512-1-daniel.m.jordan@oracle.com> <4b42057f-b998-f87c-4e0f-a91abcb366f9@ozlabs.ru> <20190520153020.mzvjsjwefwxz6cau@ca-dmjordan1.us.oracle.com> In-Reply-To: <20190520153020.mzvjsjwefwxz6cau@ca-dmjordan1.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Daniel Jordan Cc: akpm@linux-foundation.org, Alan Tull , Alex Williamson , Benjamin Herrenschmidt , Christoph Lameter , Christophe Leroy , Davidlohr Bueso , Jason Gunthorpe , Mark Rutland , Michael Ellerman , Moritz Fischer , Paul Mackerras , Steve Sistare , Wu Hao , 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 On 21/05/2019 01:30, Daniel Jordan wrote: > On Mon, May 20, 2019 at 04:19:34PM +1000, Alexey Kardashevskiy wrote: >> On 04/05/2019 06:16, Daniel Jordan wrote: >>> locked_vm accounting is done roughly the same way in five places, so >>> unify them in a helper. Standardize the debug prints, which vary >>> slightly. >> >> And I rather liked that prints were different and tell precisely which >> one of three each printk is. > > I'm not following. One of three...callsites? But there were five callsites. Well, 3 of them are mine, I was referring to them :) > Anyway, I added a _RET_IP_ to the debug print so you can differentiate. I did not know that existed, cool! > >> I commented below but in general this seems working. >> >> Tested-by: Alexey Kardashevskiy > > Thanks! And for the review as well. > >>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c >>> index 6b64e45a5269..d39a1b830d82 100644 >>> --- a/drivers/vfio/vfio_iommu_spapr_tce.c >>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c >>> @@ -34,49 +35,13 @@ >>> static void tce_iommu_detach_group(void *iommu_data, >>> struct iommu_group *iommu_group); >>> >>> -static long try_increment_locked_vm(struct mm_struct *mm, long npages) >>> +static int tce_account_locked_vm(struct mm_struct *mm, unsigned long npages, >>> + bool inc) >>> { >>> - long ret = 0, locked, lock_limit; >>> - >>> if (WARN_ON_ONCE(!mm)) >>> return -EPERM; >> >> >> If this WARN_ON is the only reason for having tce_account_locked_vm() >> instead of calling account_locked_vm() directly, you can then ditch the >> check as I have never ever seen this triggered. > > Great, will do. > >>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c >>> index d0f731c9920a..15ac76171ccd 100644 >>> --- a/drivers/vfio/vfio_iommu_type1.c >>> +++ b/drivers/vfio/vfio_iommu_type1.c >>> @@ -273,25 +273,14 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async) >>> 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; >>> - >>> - if (mm->locked_vm + npage > limit) >>> - ret = -ENOMEM; >>> - } >>> - } >>> + if (ret) >>> + goto out; >> >> >> A single "goto" to jump just 3 lines below seems unnecessary. > > No strong preference here, I'll take out the goto. > >>> +int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, >>> + struct task_struct *task, bool bypass_rlim) >>> +{ >>> + unsigned long locked_vm, limit; >>> + int ret = 0; >>> + >>> + locked_vm = mm->locked_vm; >>> + if (inc) { >>> + if (!bypass_rlim) { >>> + limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT; >>> + if (locked_vm + pages > limit) { >>> + ret = -ENOMEM; >>> + goto out; >>> + } >>> + } >> >> Nit: >> >> if (!ret) >> >> and then you don't need "goto out". > > Ok, sure. > >>> + mm->locked_vm = locked_vm + pages; >>> + } else { >>> + WARN_ON_ONCE(pages > locked_vm); >>> + mm->locked_vm = locked_vm - pages; >> >> >> Can go negative here. Not a huge deal but inaccurate imo. > > I hear you, but setting a negative value to zero, as we had done previously, > doesn't make much sense to me. Ok then. I have not seen these WARN_ON for a very long time anyway. -- Alexey