Let's unmerge any KSM pages when setting PR_SET_MEMORY_MERGE=0, and clear the VM_MERGEABLE flag from all VMAs -- just like KSM would. Of course, only do that if we previously set PR_SET_MEMORY_MERGE=1.
Signed-off-by: David Hildenbrand david@redhat.com --- include/linux/ksm.h | 1 + kernel/sys.c | 7 +------ mm/ksm.c | 47 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 49 insertions(+), 6 deletions(-)
diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 590934bdddcf..7108bc65dc2a 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -21,6 +21,7 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
void ksm_add_vma(struct vm_area_struct *vma); int ksm_enable_merge_any(struct mm_struct *mm); +int ksm_disable_merge_any(struct mm_struct *mm);
int __ksm_enter(struct mm_struct *mm); void __ksm_exit(struct mm_struct *mm); diff --git a/kernel/sys.c b/kernel/sys.c index 72cdb16e2636..3436376667d7 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2698,12 +2698,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, if (arg2) { error = ksm_enable_merge_any(me->mm); } else { - /* - * TODO: we might want disable KSM on all VMAs and - * trigger unsharing to completely disable KSM. - */ - clear_bit(MMF_VM_MERGE_ANY, &me->mm->flags); - error = 0; + error = ksm_disable_merge_any(me->mm); } mmap_write_unlock(me->mm); break; diff --git a/mm/ksm.c b/mm/ksm.c index a959e8925413..813f7fbc1832 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2520,6 +2520,22 @@ static void __ksm_add_vma(struct vm_area_struct *vma) vm_flags_set(vma, VM_MERGEABLE); }
+static int __ksm_del_vma(struct vm_area_struct *vma) +{ + int err; + + if (!(vma->vm_flags & VM_MERGEABLE)) + return 0; + + if (vma->anon_vma) { + err = unmerge_ksm_pages(vma, vma->vm_start, vma->vm_end); + if (err) + return err; + } + + vm_flags_clear(vma, VM_MERGEABLE); + return 0; +} /** * ksm_add_vma - Mark vma as mergeable if compatible * @@ -2542,6 +2558,20 @@ static void ksm_add_vmas(struct mm_struct *mm) __ksm_add_vma(vma); }
+static int ksm_del_vmas(struct mm_struct *mm) +{ + struct vm_area_struct *vma; + int err; + + VMA_ITERATOR(vmi, mm, 0); + for_each_vma(vmi, vma) { + err = __ksm_del_vma(vma); + if (err) + return err; + } + return 0; +} + /** * ksm_enable_merge_any - Add mm to mm ksm list and enable merging on all * compatible VMA's @@ -2569,6 +2599,23 @@ int ksm_enable_merge_any(struct mm_struct *mm) return 0; }
+int ksm_disable_merge_any(struct mm_struct *mm) +{ + int err; + + if (!test_bit(MMF_VM_MERGE_ANY, &mm->flags)) + return 0; + + err = ksm_del_vmas(mm); + if (err) { + ksm_add_vmas(mm); + return err; + } + + clear_bit(MMF_VM_MERGE_ANY, &mm->flags); + return 0; +} + int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags) {