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.
(Michal Hocko provided most of the kerneldoc comment.)
Cc: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Signed-off-by: Vegard Nossum <[email protected]>
---
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 | 22 ++++++++++++++++++++++
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, 65 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 cb87234cfcf2..959e41196cba 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -222,7 +222,7 @@ 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;
/*
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 9e60ef144d03..b8fc689c9e2a 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 496fa926e1e0..83dd1331a30e 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 729f92ba8224..5b88f78c40f5 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1498,7 +1498,7 @@ 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);
@@ -1549,7 +1549,7 @@ 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 d068af2ec3a3..1f27529cb48e 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -334,7 +334,7 @@ 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(¤t->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 5ea836362870..32f04999d930 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -798,7 +798,7 @@ 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);
}
@@ -1096,7 +1096,7 @@ 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 d96e2f30084b..a02bbf5897e6 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1306,7 +1306,7 @@ 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 a440cf178191..6ce46220bda2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2911,6 +2911,28 @@ static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)
*/
extern struct mm_struct * mm_alloc(void);
+/**
+ * mmgrab() - Pin a &struct mm_struct.
+ * @mm: The &struct mm_struct to pin.
+ *
+ * Make sure that @mm will not get freed even after the owning 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 @mm for a longer/unbounded amount
+ * of time.
+ *
+ * Use mmdrop() to release the reference acquired by mmgrab().
+ *
+ * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
+ * of &mm_struct.mm_count vs &mm_struct.mm_users.
+ */
+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 aacff8e2aec0..a0bfdace6a07 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -509,7 +509,7 @@ 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 9246d9f593d1..cc84e6bd6a4d 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 966556ebdbb3..49d7076d93c3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2878,7 +2878,7 @@ 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);
@@ -7686,7 +7686,7 @@ 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 e32389a97030..4cf3b3af6313 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 de102cae7125..3a61b572fa2c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -616,7 +616,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
return ERR_PTR(-ENOMEM);
spin_lock_init(&kvm->mmu_lock);
- atomic_inc(¤t->mm->mm_count);
+ mmgrab(current->mm);
kvm->mm = current->mm;
kvm_eventfd_init(kvm);
mutex_init(&kvm->lock);
--
2.11.0.1.gaa10c3f
Apart from adding the helper function itself, the rest of the kernel is
converted mechanically using:
git grep -l 'atomic_inc.*mm_users' | xargs sed -i 's/atomic_inc(&\(.*\)->mm_users);/mmget\(\1\);/'
git grep -l 'atomic_inc.*mm_users' | xargs sed -i 's/atomic_inc(&\(.*\)\.mm_users);/mmget\(\&\1\);/'
This is needed for a later patch that hooks into the helper, but might be
a worthwhile cleanup on its own.
(Michal Hocko provided most of the kerneldoc comment.)
Cc: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Signed-off-by: Vegard Nossum <[email protected]>
---
arch/arc/kernel/smp.c | 2 +-
arch/blackfin/mach-common/smp.c | 2 +-
arch/frv/mm/mmu-context.c | 2 +-
arch/metag/kernel/smp.c | 2 +-
arch/sh/kernel/smp.c | 2 +-
arch/xtensa/kernel/smp.c | 2 +-
include/linux/sched.h | 21 +++++++++++++++++++++
kernel/fork.c | 4 ++--
mm/swapfile.c | 10 +++++-----
virt/kvm/async_pf.c | 2 +-
10 files changed, 35 insertions(+), 14 deletions(-)
diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
index 9cbc7aba3ede..eec70cb71db1 100644
--- a/arch/arc/kernel/smp.c
+++ b/arch/arc/kernel/smp.c
@@ -124,7 +124,7 @@ void start_kernel_secondary(void)
/* MMU, Caches, Vector Table, Interrupts etc */
setup_processor();
- atomic_inc(&mm->mm_users);
+ mmget(mm);
mmgrab(mm);
current->active_mm = mm;
cpumask_set_cpu(cpu, mm_cpumask(mm));
diff --git a/arch/blackfin/mach-common/smp.c b/arch/blackfin/mach-common/smp.c
index bc5617ef7128..a2e6db2ce811 100644
--- a/arch/blackfin/mach-common/smp.c
+++ b/arch/blackfin/mach-common/smp.c
@@ -307,7 +307,7 @@ void secondary_start_kernel(void)
local_irq_disable();
/* Attach the new idle task to the global mm. */
- atomic_inc(&mm->mm_users);
+ mmget(mm);
mmgrab(mm);
current->active_mm = mm;
diff --git a/arch/frv/mm/mmu-context.c b/arch/frv/mm/mmu-context.c
index 81757d55a5b5..3473bde77f56 100644
--- a/arch/frv/mm/mmu-context.c
+++ b/arch/frv/mm/mmu-context.c
@@ -188,7 +188,7 @@ int cxn_pin_by_pid(pid_t pid)
task_lock(tsk);
if (tsk->mm) {
mm = tsk->mm;
- atomic_inc(&mm->mm_users);
+ mmget(mm);
ret = 0;
}
task_unlock(tsk);
diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
index af9cff547a19..c622293254e4 100644
--- a/arch/metag/kernel/smp.c
+++ b/arch/metag/kernel/smp.c
@@ -344,7 +344,7 @@ 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_users);
+ mmget(mm);
mmgrab(mm);
current->active_mm = mm;
cpumask_set_cpu(cpu, mm_cpumask(mm));
diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
index ee379c699c08..edc4769b047e 100644
--- a/arch/sh/kernel/smp.c
+++ b/arch/sh/kernel/smp.c
@@ -179,7 +179,7 @@ asmlinkage void start_secondary(void)
enable_mmu();
mmgrab(mm);
- atomic_inc(&mm->mm_users);
+ mmget(mm);
current->active_mm = mm;
#ifdef CONFIG_MMU
enter_lazy_tlb(mm, current);
diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c
index 9bf5cea3bae4..fcea72019df7 100644
--- a/arch/xtensa/kernel/smp.c
+++ b/arch/xtensa/kernel/smp.c
@@ -135,7 +135,7 @@ void secondary_start_kernel(void)
/* All kernel threads share the same mm context. */
- atomic_inc(&mm->mm_users);
+ mmget(mm);
mmgrab(mm);
current->active_mm = mm;
cpumask_set_cpu(cpu, mm_cpumask(mm));
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6ce46220bda2..9fc07aaf5c97 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2955,6 +2955,27 @@ static inline void mmdrop_async(struct mm_struct *mm)
}
}
+/**
+ * mmget() - Pin the address space associated with a &struct mm_struct.
+ * @mm: The address space to pin.
+ *
+ * Make sure that the address space of the given &struct mm_struct doesn't
+ * go away. This does not protect against parts of the address space being
+ * modified or freed, however.
+ *
+ * Never use this function to pin this address space for an
+ * unbounded/indefinite amount of time.
+ *
+ * Use mmput() to release the reference acquired by mmget().
+ *
+ * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
+ * of &mm_struct.mm_count vs &mm_struct.mm_users.
+ */
+static inline void mmget(struct mm_struct *mm)
+{
+ atomic_inc(&mm->mm_users);
+}
+
static inline bool mmget_not_zero(struct mm_struct *mm)
{
return atomic_inc_not_zero(&mm->mm_users);
diff --git a/kernel/fork.c b/kernel/fork.c
index 869b8ccc00bf..0e2aaa1837b3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -994,7 +994,7 @@ struct mm_struct *get_task_mm(struct task_struct *task)
if (task->flags & PF_KTHREAD)
mm = NULL;
else
- atomic_inc(&mm->mm_users);
+ mmget(mm);
}
task_unlock(task);
return mm;
@@ -1182,7 +1182,7 @@ static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
vmacache_flush(tsk);
if (clone_flags & CLONE_VM) {
- atomic_inc(&oldmm->mm_users);
+ mmget(oldmm);
mm = oldmm;
goto good_mm;
}
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 1c6e0321205d..914c31cc143c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1401,7 +1401,7 @@ int try_to_unuse(unsigned int type, bool frontswap,
* that.
*/
start_mm = &init_mm;
- atomic_inc(&init_mm.mm_users);
+ mmget(&init_mm);
/*
* Keep on scanning until all entries have gone. Usually,
@@ -1450,7 +1450,7 @@ int try_to_unuse(unsigned int type, bool frontswap,
if (atomic_read(&start_mm->mm_users) == 1) {
mmput(start_mm);
start_mm = &init_mm;
- atomic_inc(&init_mm.mm_users);
+ mmget(&init_mm);
}
/*
@@ -1487,8 +1487,8 @@ int try_to_unuse(unsigned int type, bool frontswap,
struct mm_struct *prev_mm = start_mm;
struct mm_struct *mm;
- atomic_inc(&new_start_mm->mm_users);
- atomic_inc(&prev_mm->mm_users);
+ mmget(new_start_mm);
+ mmget(prev_mm);
spin_lock(&mmlist_lock);
while (swap_count(*swap_map) && !retval &&
(p = p->next) != &start_mm->mmlist) {
@@ -1511,7 +1511,7 @@ int try_to_unuse(unsigned int type, bool frontswap,
if (set_start_mm && *swap_map < swcount) {
mmput(new_start_mm);
- atomic_inc(&mm->mm_users);
+ mmget(mm);
new_start_mm = mm;
set_start_mm = 0;
}
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 3815e940fbea..2366177172f6 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -204,7 +204,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
work->addr = hva;
work->arch = *arch;
work->mm = current->mm;
- atomic_inc(&work->mm->mm_users);
+ mmget(work->mm);
kvm_get_kvm(work->vcpu->kvm);
/* this can't really happen otherwise gfn_to_pfn_async
--
2.11.0.1.gaa10c3f
Clarify documentation relating to mm_users and mm_count, and switch to
kernel-doc syntax.
Signed-off-by: Vegard Nossum <[email protected]>
---
include/linux/mm_types.h | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 08d947fc4c59..316c3e1fc226 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -407,8 +407,27 @@ struct mm_struct {
unsigned long task_size; /* size of task vm space */
unsigned long highest_vm_end; /* highest vma end address */
pgd_t * pgd;
- atomic_t mm_users; /* How many users with user space? */
- atomic_t mm_count; /* How many references to "struct mm_struct" (users count as 1) */
+
+ /**
+ * @mm_users: The number of users including userspace.
+ *
+ * Use mmget()/mmget_not_zero()/mmput() to modify. When this drops
+ * to 0 (i.e. when the task exits and there are no other temporary
+ * reference holders), we also release a reference on @mm_count
+ * (which may then free the &struct mm_struct if @mm_count also
+ * drops to 0).
+ */
+ atomic_t mm_users;
+
+ /**
+ * @mm_count: The number of references to &struct mm_struct
+ * (@mm_users count as 1).
+ *
+ * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
+ * &struct mm_struct is freed.
+ */
+ atomic_t mm_count;
+
atomic_long_t nr_ptes; /* PTE page table pages */
#if CONFIG_PGTABLE_LEVELS > 2
atomic_long_t nr_pmds; /* PMD page table pages */
--
2.11.0.1.gaa10c3f
We already have the helper, we can convert the rest of the kernel
mechanically using:
git grep -l 'atomic_inc_not_zero.*mm_users' | xargs sed -i 's/atomic_inc_not_zero(&\(.*\)->mm_users)/mmget_not_zero\(\1\)/'
This is needed for a later patch that hooks into the helper, but might be
a worthwhile cleanup on its own.
Cc: Andrew Morton <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Signed-off-by: Vegard Nossum <[email protected]>
---
drivers/gpu/drm/i915/i915_gem_userptr.c | 2 +-
drivers/iommu/intel-svm.c | 2 +-
fs/proc/base.c | 4 ++--
fs/proc/task_mmu.c | 4 ++--
fs/proc/task_nommu.c | 2 +-
kernel/events/uprobes.c | 2 +-
mm/swapfile.c | 2 +-
7 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 1f27529cb48e..89be48ed7c77 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -507,7 +507,7 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
flags |= FOLL_WRITE;
ret = -EFAULT;
- if (atomic_inc_not_zero(&mm->mm_users)) {
+ if (mmget_not_zero(mm)) {
down_read(&mm->mmap_sem);
while (pinned < npages) {
ret = get_user_pages_remote
diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index cb72e0011310..51f2b228723f 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -579,7 +579,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
if (!svm->mm)
goto bad_req;
/* If the mm is already defunct, don't handle faults. */
- if (!atomic_inc_not_zero(&svm->mm->mm_users))
+ if (!mmget_not_zero(svm->mm))
goto bad_req;
down_read(&svm->mm->mmap_sem);
vma = find_extend_vma(svm->mm, address);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 32f04999d930..ec7304f5117a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -845,7 +845,7 @@ static ssize_t mem_rw(struct file *file, char __user *buf,
return -ENOMEM;
copied = 0;
- if (!atomic_inc_not_zero(&mm->mm_users))
+ if (!mmget_not_zero(mm))
goto free;
/* Maybe we should limit FOLL_FORCE to actual ptrace users? */
@@ -953,7 +953,7 @@ static ssize_t environ_read(struct file *file, char __user *buf,
return -ENOMEM;
ret = 0;
- if (!atomic_inc_not_zero(&mm->mm_users))
+ if (!mmget_not_zero(mm))
goto free;
down_read(&mm->mmap_sem);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 958f32545064..6c07c7813b26 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -167,7 +167,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
return ERR_PTR(-ESRCH);
mm = priv->mm;
- if (!mm || !atomic_inc_not_zero(&mm->mm_users))
+ if (!mm || !mmget_not_zero(mm))
return NULL;
down_read(&mm->mmap_sem);
@@ -1352,7 +1352,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
unsigned long end_vaddr;
int ret = 0, copied = 0;
- if (!mm || !atomic_inc_not_zero(&mm->mm_users))
+ if (!mm || !mmget_not_zero(mm))
goto out;
ret = -EINVAL;
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 37175621e890..1ef97cfcf422 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -219,7 +219,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
return ERR_PTR(-ESRCH);
mm = priv->mm;
- if (!mm || !atomic_inc_not_zero(&mm->mm_users))
+ if (!mm || !mmget_not_zero(mm))
return NULL;
down_read(&mm->mmap_sem);
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 215871bda3a2..f164fe8ca5ff 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -741,7 +741,7 @@ build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
continue;
}
- if (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
+ if (!mmget_not_zero(vma->vm_mm))
continue;
info = prev;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 914c31cc143c..5502feef0a4a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1493,7 +1493,7 @@ int try_to_unuse(unsigned int type, bool frontswap,
while (swap_count(*swap_map) && !retval &&
(p = p->next) != &start_mm->mmlist) {
mm = list_entry(p, struct mm_struct, mmlist);
- if (!atomic_inc_not_zero(&mm->mm_users))
+ if (!mmget_not_zero(mm))
continue;
spin_unlock(&mmlist_lock);
mmput(prev_mm);
--
2.11.0.1.gaa10c3f
For all 4,
Acked-by: Peter Zijlstra (Intel) <[email protected]>
On Sun 18-12-16 13:32:29, Vegard Nossum wrote:
> Clarify documentation relating to mm_users and mm_count, and switch to
> kernel-doc syntax.
Looks good to me.
> Signed-off-by: Vegard Nossum <[email protected]>
Acked-by: Michal Hocko <[email protected]>
> ---
> include/linux/mm_types.h | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 08d947fc4c59..316c3e1fc226 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -407,8 +407,27 @@ struct mm_struct {
> unsigned long task_size; /* size of task vm space */
> unsigned long highest_vm_end; /* highest vma end address */
> pgd_t * pgd;
> - atomic_t mm_users; /* How many users with user space? */
> - atomic_t mm_count; /* How many references to "struct mm_struct" (users count as 1) */
> +
> + /**
> + * @mm_users: The number of users including userspace.
> + *
> + * Use mmget()/mmget_not_zero()/mmput() to modify. When this drops
> + * to 0 (i.e. when the task exits and there are no other temporary
> + * reference holders), we also release a reference on @mm_count
> + * (which may then free the &struct mm_struct if @mm_count also
> + * drops to 0).
> + */
> + atomic_t mm_users;
> +
> + /**
> + * @mm_count: The number of references to &struct mm_struct
> + * (@mm_users count as 1).
> + *
> + * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
> + * &struct mm_struct is freed.
> + */
> + atomic_t mm_count;
> +
> atomic_long_t nr_ptes; /* PTE page table pages */
> #if CONFIG_PGTABLE_LEVELS > 2
> atomic_long_t nr_pmds; /* PMD page table pages */
> --
> 2.11.0.1.gaa10c3f
>
--
Michal Hocko
SUSE Labs
On Sun, 18 Dec 2016, 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.
>
> (Michal Hocko provided most of the kerneldoc comment.)
>
> Cc: Andrew Morton <[email protected]>
> Acked-by: Michal Hocko <[email protected]>
> Signed-off-by: Vegard Nossum <[email protected]>
Acked-by: David Rientjes <[email protected]>
for the series