The patch titled
Subject: mm: add new mmget() helper
has been added to the -mm tree. Its filename is
mm-add-new-mmget-helper.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-add-new-mmget-helper.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-add-new-mmget-helper.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Subject: 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.)
Link: http://lkml.kernel.org/r/20161218123229.22952-2-vegard.nossum@xxxxxxxxxx
Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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 -puN arch/arc/kernel/smp.c~mm-add-new-mmget-helper arch/arc/kernel/smp.c
--- a/arch/arc/kernel/smp.c~mm-add-new-mmget-helper
+++ a/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 -puN arch/blackfin/mach-common/smp.c~mm-add-new-mmget-helper arch/blackfin/mach-common/smp.c
--- a/arch/blackfin/mach-common/smp.c~mm-add-new-mmget-helper
+++ a/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 -puN arch/frv/mm/mmu-context.c~mm-add-new-mmget-helper arch/frv/mm/mmu-context.c
--- a/arch/frv/mm/mmu-context.c~mm-add-new-mmget-helper
+++ a/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 -puN arch/metag/kernel/smp.c~mm-add-new-mmget-helper arch/metag/kernel/smp.c
--- a/arch/metag/kernel/smp.c~mm-add-new-mmget-helper
+++ a/arch/metag/kernel/smp.c
@@ -344,7 +344,7 @@ asmlinkage void secondary_start_kernel(v
* 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 -puN arch/sh/kernel/smp.c~mm-add-new-mmget-helper arch/sh/kernel/smp.c
--- a/arch/sh/kernel/smp.c~mm-add-new-mmget-helper
+++ a/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 -puN arch/xtensa/kernel/smp.c~mm-add-new-mmget-helper arch/xtensa/kernel/smp.c
--- a/arch/xtensa/kernel/smp.c~mm-add-new-mmget-helper
+++ a/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 -puN include/linux/sched.h~mm-add-new-mmget-helper include/linux/sched.h
--- a/include/linux/sched.h~mm-add-new-mmget-helper
+++ a/include/linux/sched.h
@@ -2943,6 +2943,27 @@ static inline void mmdrop_async(struct m
}
}
+/**
+ * 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 -puN kernel/fork.c~mm-add-new-mmget-helper kernel/fork.c
--- a/kernel/fork.c~mm-add-new-mmget-helper
+++ a/kernel/fork.c
@@ -998,7 +998,7 @@ struct mm_struct *get_task_mm(struct tas
if (task->flags & PF_KTHREAD)
mm = NULL;
else
- atomic_inc(&mm->mm_users);
+ mmget(mm);
}
task_unlock(task);
return mm;
@@ -1186,7 +1186,7 @@ static int copy_mm(unsigned long clone_f
vmacache_flush(tsk);
if (clone_flags & CLONE_VM) {
- atomic_inc(&oldmm->mm_users);
+ mmget(oldmm);
mm = oldmm;
goto good_mm;
}
diff -puN mm/swapfile.c~mm-add-new-mmget-helper mm/swapfile.c
--- a/mm/swapfile.c~mm-add-new-mmget-helper
+++ a/mm/swapfile.c
@@ -1415,7 +1415,7 @@ int try_to_unuse(unsigned int type, bool
* that.
*/
start_mm = &init_mm;
- atomic_inc(&init_mm.mm_users);
+ mmget(&init_mm);
/*
* Keep on scanning until all entries have gone. Usually,
@@ -1464,7 +1464,7 @@ int try_to_unuse(unsigned int type, bool
if (atomic_read(&start_mm->mm_users) == 1) {
mmput(start_mm);
start_mm = &init_mm;
- atomic_inc(&init_mm.mm_users);
+ mmget(&init_mm);
}
/*
@@ -1501,8 +1501,8 @@ int try_to_unuse(unsigned int type, bool
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) {
@@ -1525,7 +1525,7 @@ int try_to_unuse(unsigned int type, bool
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 -puN virt/kvm/async_pf.c~mm-add-new-mmget-helper virt/kvm/async_pf.c
--- a/virt/kvm/async_pf.c~mm-add-new-mmget-helper
+++ a/virt/kvm/async_pf.c
@@ -204,7 +204,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *
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
_
Patches currently in -mm which might be from vegard.nossum@xxxxxxxxxx are
mm-add-new-mmgrab-helper.patch
mm-add-new-mmget-helper.patch
mm-use-mmget_not_zero-helper.patch
mm-clarify-mm_structmm_userscount-documentation.patch
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