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v3mr23558373plp.27.1554956551126; Wed, 10 Apr 2019 21:22:31 -0700 (PDT) Received: from [10.61.2.175] ([122.99.82.10]) by smtp.gmail.com with ESMTPSA id n3sm64976997pfa.99.2019.04.10.21.22.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Apr 2019 21:22:30 -0700 (PDT) Subject: Re: [PATCH 1/6] mm: change locked_vm's type from unsigned long to atomic64_t To: Daniel Jordan , akpm@linux-foundation.org Cc: Alan Tull , Alex Williamson , Benjamin Herrenschmidt , Christoph Lameter , Davidlohr Bueso , Michael Ellerman , Moritz Fischer , Paul Mackerras , 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: <20190402204158.27582-1-daniel.m.jordan@oracle.com> <20190402204158.27582-2-daniel.m.jordan@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: <614ea07a-dd1e-2561-b6f4-2d698bf55f5b@ozlabs.ru> Date: Thu, 11 Apr 2019 14:22:23 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190402204158.27582-2-daniel.m.jordan@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 03/04/2019 07:41, Daniel Jordan wrote: > Taking and dropping mmap_sem to modify a single counter, locked_vm, is > overkill when the counter could be synchronized separately. > > Make mmap_sem a little less coarse by changing locked_vm to an atomic, > the 64-bit variety to avoid issues with overflow on 32-bit systems. > > Signed-off-by: Daniel Jordan > Cc: Alan Tull > Cc: Alexey Kardashevskiy > Cc: Alex Williamson > Cc: Andrew Morton > Cc: Benjamin Herrenschmidt > Cc: Christoph Lameter > Cc: Davidlohr Bueso > Cc: Michael Ellerman > Cc: Moritz Fischer > Cc: Paul Mackerras > Cc: Wu Hao > Cc: > Cc: > Cc: > Cc: > Cc: > Cc: > --- > arch/powerpc/kvm/book3s_64_vio.c | 14 ++++++++------ > arch/powerpc/mm/mmu_context_iommu.c | 15 ++++++++------- > drivers/fpga/dfl-afu-dma-region.c | 18 ++++++++++-------- > drivers/vfio/vfio_iommu_spapr_tce.c | 17 +++++++++-------- > drivers/vfio/vfio_iommu_type1.c | 10 ++++++---- > fs/proc/task_mmu.c | 2 +- > include/linux/mm_types.h | 2 +- > kernel/fork.c | 2 +- > mm/debug.c | 5 +++-- > mm/mlock.c | 4 ++-- > mm/mmap.c | 18 +++++++++--------- > mm/mremap.c | 6 +++--- > 12 files changed, 61 insertions(+), 52 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c > index f02b04973710..e7fdb6d10eeb 100644 > --- a/arch/powerpc/kvm/book3s_64_vio.c > +++ b/arch/powerpc/kvm/book3s_64_vio.c > @@ -59,32 +59,34 @@ static unsigned long kvmppc_stt_pages(unsigned long tce_pages) > static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc) > { > long ret = 0; > + s64 locked_vm; > > if (!current || !current->mm) > return ret; /* process exited */ > > down_write(¤t->mm->mmap_sem); > > + locked_vm = atomic64_read(¤t->mm->locked_vm); > if (inc) { > unsigned long locked, lock_limit; > > - locked = current->mm->locked_vm + stt_pages; > + locked = locked_vm + stt_pages; > lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; > if (locked > lock_limit && !capable(CAP_IPC_LOCK)) > ret = -ENOMEM; > else > - current->mm->locked_vm += stt_pages; > + atomic64_add(stt_pages, ¤t->mm->locked_vm); > } else { > - if (WARN_ON_ONCE(stt_pages > current->mm->locked_vm)) > - stt_pages = current->mm->locked_vm; > + if (WARN_ON_ONCE(stt_pages > locked_vm)) > + stt_pages = locked_vm; > > - current->mm->locked_vm -= stt_pages; > + atomic64_sub(stt_pages, ¤t->mm->locked_vm); > } > > pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%ld %ld/%ld%s\n", current->pid, > inc ? '+' : '-', > stt_pages << PAGE_SHIFT, > - current->mm->locked_vm << PAGE_SHIFT, > + atomic64_read(¤t->mm->locked_vm) << PAGE_SHIFT, > rlimit(RLIMIT_MEMLOCK), > ret ? " - exceeded" : ""); > > diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c > index e7a9c4f6bfca..8038ac24a312 100644 > --- a/arch/powerpc/mm/mmu_context_iommu.c > +++ b/arch/powerpc/mm/mmu_context_iommu.c > @@ -55,30 +55,31 @@ static long mm_iommu_adjust_locked_vm(struct mm_struct *mm, > unsigned long npages, bool incr) > { > long ret = 0, locked, lock_limit; > + s64 locked_vm; > > if (!npages) > return 0; > > down_write(&mm->mmap_sem); > - > + locked_vm = atomic64_read(&mm->locked_vm); > if (incr) { > - locked = mm->locked_vm + npages; > + locked = locked_vm + npages; > lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; > if (locked > lock_limit && !capable(CAP_IPC_LOCK)) > ret = -ENOMEM; > else > - mm->locked_vm += npages; > + atomic64_add(npages, &mm->locked_vm); > } else { > - if (WARN_ON_ONCE(npages > mm->locked_vm)) > - npages = mm->locked_vm; > - mm->locked_vm -= npages; > + if (WARN_ON_ONCE(npages > locked_vm)) > + npages = locked_vm; > + atomic64_sub(npages, &mm->locked_vm); > } > > pr_debug("[%d] RLIMIT_MEMLOCK HASH64 %c%ld %ld/%ld\n", > current ? current->pid : 0, > incr ? '+' : '-', > npages << PAGE_SHIFT, > - mm->locked_vm << PAGE_SHIFT, > + atomic64_read(&mm->locked_vm) << PAGE_SHIFT, > rlimit(RLIMIT_MEMLOCK)); > up_write(&mm->mmap_sem); > > diff --git a/drivers/fpga/dfl-afu-dma-region.c b/drivers/fpga/dfl-afu-dma-region.c > index e18a786fc943..08132fd9b6b7 100644 > --- a/drivers/fpga/dfl-afu-dma-region.c > +++ b/drivers/fpga/dfl-afu-dma-region.c > @@ -45,6 +45,7 @@ void afu_dma_region_init(struct dfl_feature_platform_data *pdata) > static int afu_dma_adjust_locked_vm(struct device *dev, long npages, bool incr) > { > unsigned long locked, lock_limit; > + s64 locked_vm; > int ret = 0; > > /* the task is exiting. */ > @@ -53,24 +54,25 @@ static int afu_dma_adjust_locked_vm(struct device *dev, long npages, bool incr) > > down_write(¤t->mm->mmap_sem); > > + locked_vm = atomic64_read(¤t->mm->locked_vm); > if (incr) { > - locked = current->mm->locked_vm + npages; > + locked = locked_vm + npages; > lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; > > if (locked > lock_limit && !capable(CAP_IPC_LOCK)) > ret = -ENOMEM; > else > - current->mm->locked_vm += npages; > + atomic64_add(npages, ¤t->mm->locked_vm); > } else { > - if (WARN_ON_ONCE(npages > current->mm->locked_vm)) > - npages = current->mm->locked_vm; > - current->mm->locked_vm -= npages; > + if (WARN_ON_ONCE(npages > locked_vm)) > + npages = locked_vm; > + atomic64_sub(npages, ¤t->mm->locked_vm); > } > > - dev_dbg(dev, "[%d] RLIMIT_MEMLOCK %c%ld %ld/%ld%s\n", current->pid, > + dev_dbg(dev, "[%d] RLIMIT_MEMLOCK %c%ld %lld/%lu%s\n", current->pid, > incr ? '+' : '-', npages << PAGE_SHIFT, > - current->mm->locked_vm << PAGE_SHIFT, rlimit(RLIMIT_MEMLOCK), > - ret ? "- exceeded" : ""); > + (s64)atomic64_read(¤t->mm->locked_vm) << PAGE_SHIFT, > + rlimit(RLIMIT_MEMLOCK), ret ? "- exceeded" : ""); atomic64_read() returns "long" which matches "%ld", why this change (and similar below)? You did not do this in the two pr_debug()s above anyway. -- Alexey