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 @@ -139,7 +139,7 @@ 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 @@ -2948,6 +2948,27 @@ 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 @@ -1000,7 +1000,7 @@ 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; @@ -1188,7 +1188,7 @@ 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 @@ -1671,7 +1671,7 @@ 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, @@ -1720,7 +1720,7 @@ 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); } /* @@ -1757,8 +1757,8 @@ 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) { @@ -1781,7 +1781,7 @@ 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 _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
