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Date: Sun, 18 Dec 2016 13:32:27 +0100
From: Vegard Nossum <vegard.nossum@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org
Cc: Peter Zijlstra <peterz@...radead.org>,
"Kirill A . Shutemov" <kirill@...temov.name>,
linux-kernel@...r.kernel.org,
Vegard Nossum <vegard.nossum@...cle.com>
Subject: [PATCH 2/4] mm: add new mmget() helper
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 <akpm@...ux-foundation.org>
Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: Vegard Nossum <vegard.nossum@...cle.com>
---
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
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