With the oom-killer being able to operate on locked pages, exit_mmap does not need to ensure that oom_reap_task_mm is done before it can proceed. Instead it can rely on mmap_lock write lock to prevent oom-killer from operating on the vma tree while it's freeing page tables. exit_mmap can hold mmap_lock read lock when unmapping vmas and then take mmap_lock write lock before freeing page tables.
Signed-off-by: Suren Baghdasaryan surenb@google.com --- include/linux/oom.h | 2 -- mm/mmap.c | 25 ++++++------------------- mm/oom_kill.c | 2 +- 3 files changed, 7 insertions(+), 22 deletions(-)
diff --git a/include/linux/oom.h b/include/linux/oom.h index 2db9a1432511..6cdf0772dbae 100644 --- a/include/linux/oom.h +++ b/include/linux/oom.h @@ -106,8 +106,6 @@ static inline vm_fault_t check_stable_address_space(struct mm_struct *mm) return 0; }
-bool __oom_reap_task_mm(struct mm_struct *mm); - long oom_badness(struct task_struct *p, unsigned long totalpages);
diff --git a/mm/mmap.c b/mm/mmap.c index 313b57d55a63..feaa840fb95d 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3105,30 +3105,13 @@ void exit_mmap(struct mm_struct *mm) /* mm's last user has gone, and its about to be pulled down */ mmu_notifier_release(mm);
- if (unlikely(mm_is_oom_victim(mm))) { - /* - * Manually reap the mm to free as much memory as possible. - * Then, as the oom reaper does, set MMF_OOM_SKIP to disregard - * this mm from further consideration. Taking mm->mmap_lock for - * write after setting MMF_OOM_SKIP will guarantee that the oom - * reaper will not run on this mm again after mmap_lock is - * dropped. - * - * Nothing can be holding mm->mmap_lock here and the above call - * to mmu_notifier_release(mm) ensures mmu notifier callbacks in - * __oom_reap_task_mm() will not block. - */ - (void)__oom_reap_task_mm(mm); - set_bit(MMF_OOM_SKIP, &mm->flags); - } - - mmap_write_lock(mm); + mmap_read_lock(mm); arch_exit_mmap(mm);
vma = mm->mmap; if (!vma) { /* Can happen if dup_mmap() received an OOM */ - mmap_write_unlock(mm); + mmap_read_unlock(mm); return; }
@@ -3138,6 +3121,10 @@ void exit_mmap(struct mm_struct *mm) /* update_hiwater_rss(mm) here? but nobody should be looking */ /* Use -1 here to ensure all VMAs in the mm are unmapped */ unmap_vmas(&tlb, vma, 0, -1); + mmap_read_unlock(mm); + /* Set MMF_OOM_SKIP to disregard this mm from further consideration.*/ + set_bit(MMF_OOM_SKIP, &mm->flags); + mmap_write_lock(mm); free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING); tlb_finish_mmu(&tlb);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 49d7df39b02d..36355b162727 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -509,7 +509,7 @@ static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait); static struct task_struct *oom_reaper_list; static DEFINE_SPINLOCK(oom_reaper_lock);
-bool __oom_reap_task_mm(struct mm_struct *mm) +static bool __oom_reap_task_mm(struct mm_struct *mm) { struct vm_area_struct *vma; bool ret = true;