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SubjectRe: [PATCH 1/4] mm: add new mmgrab() helper
On Fri 16-12-16 09:21:59, Vegard Nossum wrote:
> Apart from adding the helper function itself, the rest of the kernel is
> converted mechanically using:
>
> git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_count);/mmgrab\(\1\);/'
> git grep -l 'atomic_inc.*mm_count' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_count);/mmgrab\(\&\1\);/'
>
> This is needed for a later patch that hooks into the helper, but might be
> a worthwhile cleanup on its own.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>

Yes this make sense to me. I usually do not like wrappers around simple
atomic operations but the api will be more symmetric (and cscope will
work nicer as a bonus).

While you are there a comment explaining where mmgrab should be used
would be nice

/**
* mmgrab: pins the mm_struct
*
* Make sure that the mm struct will not get freed even after the owner
* task exits. This doesn't guarantee that the associated address space
* will still exist later on and mmget_not_zero has to be used before
* accessing it.
*
* This is a preferred way to to pin the mm struct for longer/unbound
* time.
*/

or something along those lines.

Anyway
Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> arch/alpha/kernel/smp.c | 2 +-
> arch/arc/kernel/smp.c | 2 +-
> arch/arm/kernel/smp.c | 2 +-
> arch/arm64/kernel/smp.c | 2 +-
> arch/blackfin/mach-common/smp.c | 2 +-
> arch/hexagon/kernel/smp.c | 2 +-
> arch/ia64/kernel/setup.c | 2 +-
> arch/m32r/kernel/setup.c | 2 +-
> arch/metag/kernel/smp.c | 2 +-
> arch/mips/kernel/traps.c | 2 +-
> arch/mn10300/kernel/smp.c | 2 +-
> arch/parisc/kernel/smp.c | 2 +-
> arch/powerpc/kernel/smp.c | 2 +-
> arch/s390/kernel/processor.c | 2 +-
> arch/score/kernel/traps.c | 2 +-
> arch/sh/kernel/smp.c | 2 +-
> arch/sparc/kernel/leon_smp.c | 2 +-
> arch/sparc/kernel/smp_64.c | 2 +-
> arch/sparc/kernel/sun4d_smp.c | 2 +-
> arch/sparc/kernel/sun4m_smp.c | 2 +-
> arch/sparc/kernel/traps_32.c | 2 +-
> arch/sparc/kernel/traps_64.c | 2 +-
> arch/tile/kernel/smpboot.c | 2 +-
> arch/x86/kernel/cpu/common.c | 4 ++--
> arch/xtensa/kernel/smp.c | 2 +-
> drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 +-
> drivers/gpu/drm/i915/i915_gem_userptr.c | 2 +-
> drivers/infiniband/hw/hfi1/file_ops.c | 2 +-
> fs/proc/base.c | 4 ++--
> fs/userfaultfd.c | 2 +-
> include/linux/sched.h | 5 +++++
> kernel/exit.c | 2 +-
> kernel/futex.c | 2 +-
> kernel/sched/core.c | 4 ++--
> mm/khugepaged.c | 2 +-
> mm/ksm.c | 2 +-
> mm/mmu_context.c | 2 +-
> mm/mmu_notifier.c | 2 +-
> mm/oom_kill.c | 4 ++--
> virt/kvm/kvm_main.c | 2 +-
> 40 files changed, 48 insertions(+), 43 deletions(-)
>
> diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
> index 46bf263c3153..acb4b146a607 100644
> --- a/arch/alpha/kernel/smp.c
> +++ b/arch/alpha/kernel/smp.c
> @@ -144,7 +144,7 @@ smp_callin(void)
> alpha_mv.smp_callin();
>
> /* All kernel threads share the same mm context. */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> /* inform the notifiers about the new cpu */
> diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
> index 88674d972c9d..9cbc7aba3ede 100644
> --- a/arch/arc/kernel/smp.c
> +++ b/arch/arc/kernel/smp.c
> @@ -125,7 +125,7 @@ void start_kernel_secondary(void)
> setup_processor();
>
> atomic_inc(&mm->mm_users);
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> current->active_mm = mm;
> cpumask_set_cpu(cpu, mm_cpumask(mm));
>
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 7dd14e8395e6..c6514ce0fcbc 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -371,7 +371,7 @@ asmlinkage void secondary_start_kernel(void)
> * reference and switch to it.
> */
> cpu = smp_processor_id();
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> current->active_mm = mm;
> cpumask_set_cpu(cpu, mm_cpumask(mm));
>
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 8507703dabe4..61969ea29654 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -214,7 +214,7 @@ asmlinkage void secondary_start_kernel(void)
> * All kernel threads share the same mm context; grab a
> * reference and switch to it.
> */
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> current->active_mm = mm;
>
> set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
> diff --git a/arch/blackfin/mach-common/smp.c b/arch/blackfin/mach-common/smp.c
> index 23c4ef5f8bdc..bc5617ef7128 100644
> --- a/arch/blackfin/mach-common/smp.c
> +++ b/arch/blackfin/mach-common/smp.c
> @@ -308,7 +308,7 @@ void secondary_start_kernel(void)
>
> /* Attach the new idle task to the global mm. */
> atomic_inc(&mm->mm_users);
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> current->active_mm = mm;
>
> preempt_disable();
> diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
> index 983bae7d2665..c02a6455839e 100644
> --- a/arch/hexagon/kernel/smp.c
> +++ b/arch/hexagon/kernel/smp.c
> @@ -162,7 +162,7 @@ void start_secondary(void)
> );
>
> /* Set the memory struct */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> cpu = smp_processor_id();
> diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
> index 7ec7acc844c2..ecbff47b01f1 100644
> --- a/arch/ia64/kernel/setup.c
> +++ b/arch/ia64/kernel/setup.c
> @@ -992,7 +992,7 @@ cpu_init (void)
> */
> ia64_setreg(_IA64_REG_CR_DCR, ( IA64_DCR_DP | IA64_DCR_DK | IA64_DCR_DX | IA64_DCR_DR
> | IA64_DCR_DA | IA64_DCR_DD | IA64_DCR_LC));
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> BUG_ON(current->mm);
>
> diff --git a/arch/m32r/kernel/setup.c b/arch/m32r/kernel/setup.c
> index 136c69f1fb8a..b18bc0bd6544 100644
> --- a/arch/m32r/kernel/setup.c
> +++ b/arch/m32r/kernel/setup.c
> @@ -403,7 +403,7 @@ void __init cpu_init (void)
> printk(KERN_INFO "Initializing CPU#%d\n", cpu_id);
>
> /* Set up and load the per-CPU TSS and LDT */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> if (current->mm)
> BUG();
> diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
> index bad13232de51..af9cff547a19 100644
> --- a/arch/metag/kernel/smp.c
> +++ b/arch/metag/kernel/smp.c
> @@ -345,7 +345,7 @@ asmlinkage void secondary_start_kernel(void)
> * reference and switch to it.
> */
> atomic_inc(&mm->mm_users);
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> current->active_mm = mm;
> cpumask_set_cpu(cpu, mm_cpumask(mm));
> enter_lazy_tlb(mm, current);
> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
> index 3905003dfe2b..e50b0e0ca44c 100644
> --- a/arch/mips/kernel/traps.c
> +++ b/arch/mips/kernel/traps.c
> @@ -2177,7 +2177,7 @@ void per_cpu_trap_init(bool is_boot_cpu)
> if (!cpu_data[cpu].asid_cache)
> cpu_data[cpu].asid_cache = asid_first_version(cpu);
>
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> BUG_ON(current->mm);
> enter_lazy_tlb(&init_mm, current);
> diff --git a/arch/mn10300/kernel/smp.c b/arch/mn10300/kernel/smp.c
> index 426173c4b0b9..e65b5cc2fa67 100644
> --- a/arch/mn10300/kernel/smp.c
> +++ b/arch/mn10300/kernel/smp.c
> @@ -589,7 +589,7 @@ static void __init smp_cpu_init(void)
> }
> printk(KERN_INFO "Initializing CPU#%d\n", cpu_id);
>
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> BUG_ON(current->mm);
>
> diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
> index 75dab2871346..67b452b41ff6 100644
> --- a/arch/parisc/kernel/smp.c
> +++ b/arch/parisc/kernel/smp.c
> @@ -279,7 +279,7 @@ smp_cpu_init(int cpunum)
> set_cpu_online(cpunum, true);
>
> /* Initialise the idle task for this CPU */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> BUG_ON(current->mm);
> enter_lazy_tlb(&init_mm, current);
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 9c6f3fd58059..42b82364c782 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -707,7 +707,7 @@ void start_secondary(void *unused)
> unsigned int cpu = smp_processor_id();
> int i, base;
>
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> smp_store_cpu_info(cpu);
> diff --git a/arch/s390/kernel/processor.c b/arch/s390/kernel/processor.c
> index 81d0808085e6..ec9bc100895c 100644
> --- a/arch/s390/kernel/processor.c
> +++ b/arch/s390/kernel/processor.c
> @@ -73,7 +73,7 @@ void cpu_init(void)
> get_cpu_id(id);
> if (machine_has_cpu_mhz)
> update_cpu_mhz(NULL);
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> BUG_ON(current->mm);
> enter_lazy_tlb(&init_mm, current);
> diff --git a/arch/score/kernel/traps.c b/arch/score/kernel/traps.c
> index 5cea1e750cec..6f6e5a39d147 100644
> --- a/arch/score/kernel/traps.c
> +++ b/arch/score/kernel/traps.c
> @@ -336,7 +336,7 @@ void __init trap_init(void)
> set_except_vector(18, handle_dbe);
> flush_icache_range(DEBUG_VECTOR_BASE_ADDR, IRQ_VECTOR_BASE_ADDR);
>
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> cpu_cache_init();
> }
> diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
> index 38e7860845db..ee379c699c08 100644
> --- a/arch/sh/kernel/smp.c
> +++ b/arch/sh/kernel/smp.c
> @@ -178,7 +178,7 @@ asmlinkage void start_secondary(void)
> struct mm_struct *mm = &init_mm;
>
> enable_mmu();
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> atomic_inc(&mm->mm_users);
> current->active_mm = mm;
> #ifdef CONFIG_MMU
> diff --git a/arch/sparc/kernel/leon_smp.c b/arch/sparc/kernel/leon_smp.c
> index 71e16f2241c2..b99d33797e1d 100644
> --- a/arch/sparc/kernel/leon_smp.c
> +++ b/arch/sparc/kernel/leon_smp.c
> @@ -93,7 +93,7 @@ void leon_cpu_pre_online(void *arg)
> : "memory" /* paranoid */);
>
> /* Attach to the address space of init_task. */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
> diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
> index 8182f7caf5b1..c1d2bed22961 100644
> --- a/arch/sparc/kernel/smp_64.c
> +++ b/arch/sparc/kernel/smp_64.c
> @@ -122,7 +122,7 @@ void smp_callin(void)
> current_thread_info()->new_child = 0;
>
> /* Attach to the address space of init_task. */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> /* inform the notifiers about the new cpu */
> diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
> index 9d98e5002a09..7b55c50eabe5 100644
> --- a/arch/sparc/kernel/sun4d_smp.c
> +++ b/arch/sparc/kernel/sun4d_smp.c
> @@ -93,7 +93,7 @@ void sun4d_cpu_pre_online(void *arg)
> show_leds(cpuid);
>
> /* Attach to the address space of init_task. */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> local_ops->cache_all();
> diff --git a/arch/sparc/kernel/sun4m_smp.c b/arch/sparc/kernel/sun4m_smp.c
> index 278c40abce82..633c4cf6fdb0 100644
> --- a/arch/sparc/kernel/sun4m_smp.c
> +++ b/arch/sparc/kernel/sun4m_smp.c
> @@ -59,7 +59,7 @@ void sun4m_cpu_pre_online(void *arg)
> : "memory" /* paranoid */);
>
> /* Attach to the address space of init_task. */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
> diff --git a/arch/sparc/kernel/traps_32.c b/arch/sparc/kernel/traps_32.c
> index 4f21df7d4f13..ecddac5a4c96 100644
> --- a/arch/sparc/kernel/traps_32.c
> +++ b/arch/sparc/kernel/traps_32.c
> @@ -448,7 +448,7 @@ void trap_init(void)
> thread_info_offsets_are_bolixed_pete();
>
> /* Attach to the address space of init_task. */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
>
> /* NOTE: Other cpus have this done as they are started
> diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
> index 4094a51b1970..0dbbe40012ef 100644
> --- a/arch/sparc/kernel/traps_64.c
> +++ b/arch/sparc/kernel/traps_64.c
> @@ -2764,6 +2764,6 @@ void __init trap_init(void)
> /* Attach to the address space of init_task. On SMP we
> * do this in smp.c:smp_callin for other cpus.
> */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> }
> diff --git a/arch/tile/kernel/smpboot.c b/arch/tile/kernel/smpboot.c
> index 6c0abaacec33..53ce940a5016 100644
> --- a/arch/tile/kernel/smpboot.c
> +++ b/arch/tile/kernel/smpboot.c
> @@ -160,7 +160,7 @@ static void start_secondary(void)
> __this_cpu_write(current_asid, min_asid);
>
> /* Set up this thread as another owner of the init_mm */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> current->active_mm = &init_mm;
> if (current->mm)
> BUG();
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index cc9e980c68ec..b580da4582e1 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1555,7 +1555,7 @@ void cpu_init(void)
> for (i = 0; i <= IO_BITMAP_LONGS; i++)
> t->io_bitmap[i] = ~0UL;
>
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> me->active_mm = &init_mm;
> BUG_ON(me->mm);
> enter_lazy_tlb(&init_mm, me);
> @@ -1606,7 +1606,7 @@ void cpu_init(void)
> /*
> * Set up and load the per-CPU TSS and LDT
> */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> curr->active_mm = &init_mm;
> BUG_ON(curr->mm);
> enter_lazy_tlb(&init_mm, curr);
> diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c
> index fc4ad21a5ed4..9bf5cea3bae4 100644
> --- a/arch/xtensa/kernel/smp.c
> +++ b/arch/xtensa/kernel/smp.c
> @@ -136,7 +136,7 @@ void secondary_start_kernel(void)
> /* All kernel threads share the same mm context. */
>
> atomic_inc(&mm->mm_users);
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> current->active_mm = mm;
> cpumask_set_cpu(cpu, mm_cpumask(mm));
> enter_lazy_tlb(mm, current);
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> index ef7c8de7060e..ca5f2aa7232d 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> @@ -262,7 +262,7 @@ static void kfd_process_notifier_release(struct mmu_notifier *mn,
> * and because the mmu_notifier_unregister function also drop
> * mm_count we need to take an extra count here.
> */
> - atomic_inc(&p->mm->mm_count);
> + mmgrab(p->mm);
> mmu_notifier_unregister_no_release(&p->mmu_notifier, p->mm);
> mmu_notifier_call_srcu(&p->rcu, &kfd_process_destroy_delayed);
> }
> diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
> index c6f780f5abc9..f21ca404af79 100644
> --- a/drivers/gpu/drm/i915/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
> @@ -341,7 +341,7 @@ i915_gem_userptr_init__mm_struct(struct drm_i915_gem_object *obj)
> mm->i915 = to_i915(obj->base.dev);
>
> mm->mm = current->mm;
> - atomic_inc(&current->mm->mm_count);
> + mmgrab(current->mm);
>
> mm->mn = NULL;
>
> diff --git a/drivers/infiniband/hw/hfi1/file_ops.c b/drivers/infiniband/hw/hfi1/file_ops.c
> index bd786b7bd30b..2e1a6643a910 100644
> --- a/drivers/infiniband/hw/hfi1/file_ops.c
> +++ b/drivers/infiniband/hw/hfi1/file_ops.c
> @@ -185,7 +185,7 @@ static int hfi1_file_open(struct inode *inode, struct file *fp)
> if (fd) {
> fd->rec_cpu_num = -1; /* no cpu affinity by default */
> fd->mm = current->mm;
> - atomic_inc(&fd->mm->mm_count);
> + mmgrab(fd->mm);
> fp->private_data = fd;
> } else {
> fp->private_data = NULL;
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index ca651ac00660..0b8ccacae8b3 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -795,7 +795,7 @@ struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode)
>
> if (!IS_ERR_OR_NULL(mm)) {
> /* ensure this mm_struct can't be freed */
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> /* but do not pin its memory */
> mmput(mm);
> }
> @@ -1093,7 +1093,7 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
> if (p) {
> if (atomic_read(&p->mm->mm_users) > 1) {
> mm = p->mm;
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> }
> task_unlock(p);
> }
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index 85959d8324df..ffa9c7cbc5fa 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -1304,7 +1304,7 @@ static struct file *userfaultfd_file_create(int flags)
> ctx->released = false;
> ctx->mm = current->mm;
> /* prevent the mm struct to be freed */
> - atomic_inc(&ctx->mm->mm_count);
> + mmgrab(ctx->mm);
>
> file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
> O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e9c009dc3a4a..31ae1f49eebb 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2872,6 +2872,11 @@ static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)
> */
> extern struct mm_struct * mm_alloc(void);
>
> +static inline void mmgrab(struct mm_struct *mm)
> +{
> + atomic_inc(&mm->mm_count);
> +}
> +
> /* mmdrop drops the mm and the page tables */
> extern void __mmdrop(struct mm_struct *);
> static inline void mmdrop(struct mm_struct *mm)
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 3076f3089919..b12753840050 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -500,7 +500,7 @@ static void exit_mm(struct task_struct *tsk)
> __set_task_state(tsk, TASK_RUNNING);
> down_read(&mm->mmap_sem);
> }
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> BUG_ON(mm != tsk->active_mm);
> /* more a memory barrier than a real lock */
> task_lock(tsk);
> diff --git a/kernel/futex.c b/kernel/futex.c
> index 2c4be467fecd..cbe6056c17c1 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -338,7 +338,7 @@ static inline bool should_fail_futex(bool fshared)
>
> static inline void futex_get_mm(union futex_key *key)
> {
> - atomic_inc(&key->private.mm->mm_count);
> + mmgrab(key->private.mm);
> /*
> * Ensure futex_get_mm() implies a full barrier such that
> * get_futex_key() implies a full barrier. This is relied upon
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 154fd689fe02..ee1fb0070544 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2877,7 +2877,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
>
> if (!mm) {
> next->active_mm = oldmm;
> - atomic_inc(&oldmm->mm_count);
> + mmgrab(oldmm);
> enter_lazy_tlb(oldmm, next);
> } else
> switch_mm_irqs_off(oldmm, mm, next);
> @@ -7667,7 +7667,7 @@ void __init sched_init(void)
> /*
> * The boot idle thread does lazy MMU switching as well:
> */
> - atomic_inc(&init_mm.mm_count);
> + mmgrab(&init_mm);
> enter_lazy_tlb(&init_mm, current);
>
> /*
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 87e1a7ca3846..1343271a18f1 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -420,7 +420,7 @@ int __khugepaged_enter(struct mm_struct *mm)
> list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
> spin_unlock(&khugepaged_mm_lock);
>
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> if (wakeup)
> wake_up_interruptible(&khugepaged_wait);
>
> diff --git a/mm/ksm.c b/mm/ksm.c
> index 9ae6011a41f8..5a49aad9d87b 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -1813,7 +1813,7 @@ int __ksm_enter(struct mm_struct *mm)
> spin_unlock(&ksm_mmlist_lock);
>
> set_bit(MMF_VM_MERGEABLE, &mm->flags);
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
>
> if (needs_wakeup)
> wake_up_interruptible(&ksm_thread_wait);
> diff --git a/mm/mmu_context.c b/mm/mmu_context.c
> index 6f4d27c5bb32..daf67bb02b4a 100644
> --- a/mm/mmu_context.c
> +++ b/mm/mmu_context.c
> @@ -25,7 +25,7 @@ void use_mm(struct mm_struct *mm)
> task_lock(tsk);
> active_mm = tsk->active_mm;
> if (active_mm != mm) {
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> tsk->active_mm = mm;
> }
> tsk->mm = mm;
> diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
> index f4259e496f83..32bc9f2ff7eb 100644
> --- a/mm/mmu_notifier.c
> +++ b/mm/mmu_notifier.c
> @@ -275,7 +275,7 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn,
> mm->mmu_notifier_mm = mmu_notifier_mm;
> mmu_notifier_mm = NULL;
> }
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
>
> /*
> * Serialize the update against mmu_notifier_unregister. A
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index ec9f11d4f094..ead093c6f2a6 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -660,7 +660,7 @@ static void mark_oom_victim(struct task_struct *tsk)
>
> /* oom_mm is bound to the signal struct life time. */
> if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
> - atomic_inc(&tsk->signal->oom_mm->mm_count);
> + mmgrab(tsk->signal->oom_mm);
>
> /*
> * Make sure that the task is woken up from uninterruptible sleep
> @@ -877,7 +877,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
>
> /* Get a reference to safely compare mm after task_unlock(victim) */
> mm = victim->mm;
> - atomic_inc(&mm->mm_count);
> + mmgrab(mm);
> /*
> * We should send SIGKILL before setting TIF_MEMDIE in order to prevent
> * the OOM victim from depleting the memory reserves from the user
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 7f9ee2929cfe..43914b981691 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -613,7 +613,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
> return ERR_PTR(-ENOMEM);
>
> spin_lock_init(&kvm->mmu_lock);
> - atomic_inc(&current->mm->mm_count);
> + mmgrab(current->mm);
> kvm->mm = current->mm;
> kvm_eventfd_init(kvm);
> mutex_init(&kvm->lock);
> --
> 2.11.0.1.gaa10c3f
>

--
Michal Hocko
SUSE Labs

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