Re: [PATCH 1/6] mm: change locked_vm's type from unsigned long to atomic64_t

[Christophe Leroy <christophe.leroy@xxxxxx>]

Le 02/04/2019 à 22:41, Daniel Jordan a écrit :
> 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.

Can you elaborate on the above ? Previously it was 'unsigned long', what 
were the issues ? If there was such issues, shouldn't there be a first 
patch moving it from unsigned long to u64 before this atomic64_t change 
? Or at least it should be clearly explain here what the issues are and 
how switching to a 64 bit counter fixes them.

Christophe

> Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> Cc: Alan Tull <atull@xxxxxxxxxx>
> Cc: Alexey Kardashevskiy <aik@xxxxxxxxx>
> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Moritz Fischer <mdf@xxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxxx>
> Cc: Wu Hao <hao.wu@xxxxxxxxx>
> Cc: <linux-mm@xxxxxxxxx>
> Cc: <kvm@xxxxxxxxxxxxxxx>
> Cc: <kvm-ppc@xxxxxxxxxxxxxxx>
> Cc: <linuxppc-dev@xxxxxxxxxxxxxxxx>
> Cc: <linux-fpga@xxxxxxxxxxxxxxx>
> Cc: <linux-kernel@xxxxxxxxxxxxxxx>
> ---
>   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(&current->mm->mmap_sem);
>   
> +	locked_vm = atomic64_read(&current->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, &current->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, &current->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(&current->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(&current->mm->mmap_sem);
>   
> +	locked_vm = atomic64_read(&current->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, &current->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, &current->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(&current->mm->locked_vm) << PAGE_SHIFT,
> +		rlimit(RLIMIT_MEMLOCK), ret ? "- exceeded" : "");
>   
>   	up_write(&current->mm->mmap_sem);
>   
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 8dbb270998f4..e7d787e5d839 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -36,7 +36,8 @@ static void tce_iommu_detach_group(void *iommu_data,
>   
>   static long try_increment_locked_vm(struct mm_struct *mm, long npages)
>   {
> -	long ret = 0, locked, lock_limit;
> +	long ret = 0, lock_limit;
> +	s64 locked;
>   
>   	if (WARN_ON_ONCE(!mm))
>   		return -EPERM;
> @@ -45,16 +46,16 @@ static long try_increment_locked_vm(struct mm_struct *mm, long npages)
>   		return 0;
>   
>   	down_write(&mm->mmap_sem);
> -	locked = mm->locked_vm + npages;
> +	locked = atomic64_read(&mm->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);
>   
>   	pr_debug("[%d] RLIMIT_MEMLOCK +%ld %ld/%ld%s\n", current->pid,
>   			npages << PAGE_SHIFT,
> -			mm->locked_vm << PAGE_SHIFT,
> +			atomic64_read(&mm->locked_vm) << PAGE_SHIFT,
>   			rlimit(RLIMIT_MEMLOCK),
>   			ret ? " - exceeded" : "");
>   
> @@ -69,12 +70,12 @@ static void decrement_locked_vm(struct mm_struct *mm, long npages)
>   		return;
>   
>   	down_write(&mm->mmap_sem);
> -	if (WARN_ON_ONCE(npages > mm->locked_vm))
> -		npages = mm->locked_vm;
> -	mm->locked_vm -= npages;
> +	if (WARN_ON_ONCE(npages > atomic64_read(&mm->locked_vm)))
> +		npages = atomic64_read(&mm->locked_vm);
> +	atomic64_sub(npages, &mm->locked_vm);
>   	pr_debug("[%d] RLIMIT_MEMLOCK -%ld %ld/%ld\n", current->pid,
>   			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/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 73652e21efec..5b2878697286 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -270,18 +270,19 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
>   	if (!ret) {
>   		if (npage > 0) {
>   			if (!dma->lock_cap) {
> +				s64 locked_vm = atomic64_read(&mm->locked_vm);
>   				unsigned long limit;
>   
>   				limit = task_rlimit(dma->task,
>   						RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>   
> -				if (mm->locked_vm + npage > limit)
> +				if (locked_vm + npage > limit)
>   					ret = -ENOMEM;
>   			}
>   		}
>   
>   		if (!ret)
> -			mm->locked_vm += npage;
> +			atomic64_add(npage, &mm->locked_vm);
>   
>   		up_write(&mm->mmap_sem);
>   	}
> @@ -401,6 +402,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
>   	long ret, pinned = 0, lock_acct = 0;
>   	bool rsvd;
>   	dma_addr_t iova = vaddr - dma->vaddr + dma->iova;
> +	atomic64_t *locked_vm = &current->mm->locked_vm;
>   
>   	/* This code path is only user initiated */
>   	if (!current->mm)
> @@ -418,7 +420,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
>   	 * pages are already counted against the user.
>   	 */
>   	if (!rsvd && !vfio_find_vpfn(dma, iova)) {
> -		if (!dma->lock_cap && current->mm->locked_vm + 1 > limit) {
> +		if (!dma->lock_cap && atomic64_read(locked_vm) + 1 > limit) {
>   			put_pfn(*pfn_base, dma->prot);
>   			pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
>   					limit << PAGE_SHIFT);
> @@ -445,7 +447,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
>   
>   		if (!rsvd && !vfio_find_vpfn(dma, iova)) {
>   			if (!dma->lock_cap &&
> -			    current->mm->locked_vm + lock_acct + 1 > limit) {
> +			    atomic64_read(locked_vm) + lock_acct + 1 > limit) {
>   				put_pfn(pfn, dma->prot);
>   				pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
>   					__func__, limit << PAGE_SHIFT);
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 92a91e7816d8..61da4b24d0e0 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -58,7 +58,7 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
>   	swap = get_mm_counter(mm, MM_SWAPENTS);
>   	SEQ_PUT_DEC("VmPeak:\t", hiwater_vm);
>   	SEQ_PUT_DEC(" kB\nVmSize:\t", total_vm);
> -	SEQ_PUT_DEC(" kB\nVmLck:\t", mm->locked_vm);
> +	SEQ_PUT_DEC(" kB\nVmLck:\t", atomic64_read(&mm->locked_vm));
>   	SEQ_PUT_DEC(" kB\nVmPin:\t", atomic64_read(&mm->pinned_vm));
>   	SEQ_PUT_DEC(" kB\nVmHWM:\t", hiwater_rss);
>   	SEQ_PUT_DEC(" kB\nVmRSS:\t", total_rss);
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 7eade9132f02..5059b99a0827 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -410,7 +410,7 @@ struct mm_struct {
>   		unsigned long hiwater_vm;  /* High-water virtual memory usage */
>   
>   		unsigned long total_vm;	   /* Total pages mapped */
> -		unsigned long locked_vm;   /* Pages that have PG_mlocked set */
> +		atomic64_t    locked_vm;   /* Pages that have PG_mlocked set */
>   		atomic64_t    pinned_vm;   /* Refcount permanently increased */
>   		unsigned long data_vm;	   /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
>   		unsigned long exec_vm;	   /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 9dcd18aa210b..56be8cdc7b4a 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -979,7 +979,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
>   	mm->core_state = NULL;
>   	mm_pgtables_bytes_init(mm);
>   	mm->map_count = 0;
> -	mm->locked_vm = 0;
> +	atomic64_set(&mm->locked_vm, 0);
>   	atomic64_set(&mm->pinned_vm, 0);
>   	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
>   	spin_lock_init(&mm->page_table_lock);
> diff --git a/mm/debug.c b/mm/debug.c
> index eee9c221280c..b9cd71927d3c 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -136,7 +136,7 @@ void dump_mm(const struct mm_struct *mm)
>   #endif
>   		"mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
>   		"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
> -		"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
> +		"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %llx\n"
>   		"pinned_vm %llx data_vm %lx exec_vm %lx stack_vm %lx\n"
>   		"start_code %lx end_code %lx start_data %lx end_data %lx\n"
>   		"start_brk %lx brk %lx start_stack %lx\n"
> @@ -167,7 +167,8 @@ void dump_mm(const struct mm_struct *mm)
>   		atomic_read(&mm->mm_count),
>   		mm_pgtables_bytes(mm),
>   		mm->map_count,
> -		mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
> +		mm->hiwater_rss, mm->hiwater_vm, mm->total_vm,
> +		(u64)atomic64_read(&mm->locked_vm),
>   		(u64)atomic64_read(&mm->pinned_vm),
>   		mm->data_vm, mm->exec_vm, mm->stack_vm,
>   		mm->start_code, mm->end_code, mm->start_data, mm->end_data,
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 080f3b36415b..e492a155c51a 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -562,7 +562,7 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
>   		nr_pages = -nr_pages;
>   	else if (old_flags & VM_LOCKED)
>   		nr_pages = 0;
> -	mm->locked_vm += nr_pages;
> +	atomic64_add(nr_pages, &mm->locked_vm);
>   
>   	/*
>   	 * vm_flags is protected by the mmap_sem held in write mode.
> @@ -687,7 +687,7 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
>   	if (down_write_killable(&current->mm->mmap_sem))
>   		return -EINTR;
>   
> -	locked += current->mm->locked_vm;
> +	locked += atomic64_read(&current->mm->locked_vm);
>   	if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
>   		/*
>   		 * It is possible that the regions requested intersect with
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 41eb48d9b527..03576c1d530c 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1339,7 +1339,7 @@ static inline int mlock_future_check(struct mm_struct *mm,
>   	/*  mlock MCL_FUTURE? */
>   	if (flags & VM_LOCKED) {
>   		locked = len >> PAGE_SHIFT;
> -		locked += mm->locked_vm;
> +		locked += atomic64_read(&mm->locked_vm);
>   		lock_limit = rlimit(RLIMIT_MEMLOCK);
>   		lock_limit >>= PAGE_SHIFT;
>   		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
> @@ -1825,7 +1825,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>   					vma == get_gate_vma(current->mm))
>   			vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
>   		else
> -			mm->locked_vm += (len >> PAGE_SHIFT);
> +			atomic64_add(len >> PAGE_SHIFT, &mm->locked_vm);
>   	}
>   
>   	if (file)
> @@ -2301,7 +2301,7 @@ static int acct_stack_growth(struct vm_area_struct *vma,
>   	if (vma->vm_flags & VM_LOCKED) {
>   		unsigned long locked;
>   		unsigned long limit;
> -		locked = mm->locked_vm + grow;
> +		locked = atomic64_read(&mm->locked_vm) + grow;
>   		limit = rlimit(RLIMIT_MEMLOCK);
>   		limit >>= PAGE_SHIFT;
>   		if (locked > limit && !capable(CAP_IPC_LOCK))
> @@ -2395,7 +2395,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
>   				 */
>   				spin_lock(&mm->page_table_lock);
>   				if (vma->vm_flags & VM_LOCKED)
> -					mm->locked_vm += grow;
> +					atomic64_add(grow, &mm->locked_vm);
>   				vm_stat_account(mm, vma->vm_flags, grow);
>   				anon_vma_interval_tree_pre_update_vma(vma);
>   				vma->vm_end = address;
> @@ -2475,7 +2475,7 @@ int expand_downwards(struct vm_area_struct *vma,
>   				 */
>   				spin_lock(&mm->page_table_lock);
>   				if (vma->vm_flags & VM_LOCKED)
> -					mm->locked_vm += grow;
> +					atomic64_add(grow, &mm->locked_vm);
>   				vm_stat_account(mm, vma->vm_flags, grow);
>   				anon_vma_interval_tree_pre_update_vma(vma);
>   				vma->vm_start = address;
> @@ -2796,11 +2796,11 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
>   	/*
>   	 * unlock any mlock()ed ranges before detaching vmas
>   	 */
> -	if (mm->locked_vm) {
> +	if (atomic64_read(&mm->locked_vm)) {
>   		struct vm_area_struct *tmp = vma;
>   		while (tmp && tmp->vm_start < end) {
>   			if (tmp->vm_flags & VM_LOCKED) {
> -				mm->locked_vm -= vma_pages(tmp);
> +				atomic64_sub(vma_pages(tmp), &mm->locked_vm);
>   				munlock_vma_pages_all(tmp);
>   			}
>   
> @@ -3043,7 +3043,7 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla
>   	mm->total_vm += len >> PAGE_SHIFT;
>   	mm->data_vm += len >> PAGE_SHIFT;
>   	if (flags & VM_LOCKED)
> -		mm->locked_vm += (len >> PAGE_SHIFT);
> +		atomic64_add(len >> PAGE_SHIFT, &mm->locked_vm);
>   	vma->vm_flags |= VM_SOFTDIRTY;
>   	return 0;
>   }
> @@ -3115,7 +3115,7 @@ void exit_mmap(struct mm_struct *mm)
>   		up_write(&mm->mmap_sem);
>   	}
>   
> -	if (mm->locked_vm) {
> +	if (atomic64_read(&mm->locked_vm)) {
>   		vma = mm->mmap;
>   		while (vma) {
>   			if (vma->vm_flags & VM_LOCKED)
> diff --git a/mm/mremap.c b/mm/mremap.c
> index e3edef6b7a12..9a4046bb2875 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -422,7 +422,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
>   	}
>   
>   	if (vm_flags & VM_LOCKED) {
> -		mm->locked_vm += new_len >> PAGE_SHIFT;
> +		atomic64_add(new_len >> PAGE_SHIFT, &mm->locked_vm);
>   		*locked = true;
>   	}
>   
> @@ -473,7 +473,7 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
>   
>   	if (vma->vm_flags & VM_LOCKED) {
>   		unsigned long locked, lock_limit;
> -		locked = mm->locked_vm << PAGE_SHIFT;
> +		locked = atomic64_read(&mm->locked_vm) << PAGE_SHIFT;
>   		lock_limit = rlimit(RLIMIT_MEMLOCK);
>   		locked += new_len - old_len;
>   		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
> @@ -679,7 +679,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
>   
>   			vm_stat_account(mm, vma->vm_flags, pages);
>   			if (vma->vm_flags & VM_LOCKED) {
> -				mm->locked_vm += pages;
> +				atomic64_add(pages, &mm->locked_vm);
>   				locked = true;
>   				new_addr = addr;
>   			}