From: David Hildenbrand <david@redhat.com> mainline inclusion from mainline-v6.4-rc1 commit 24139c07f413ef4b555482c758343d71392a19bc category: feature bugzilla: https://atomgit.com/openeuler/kernel/issues/10169 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Patch series "mm/ksm: improve PR_SET_MEMORY_MERGE=0 handling and cleanup disabling KSM", v2. (1) Make PR_SET_MEMORY_MERGE=0 unmerge pages like setting MADV_UNMERGEABLE does, (2) add a selftest for it and (3) factor out disabling of KSM from s390/gmap code. This patch (of 3): 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. Link: https://lkml.kernel.org/r/20230422205420.30372-1-david@redhat.com Link: https://lkml.kernel.org/r/20230422205420.30372-2-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Stefan Roesch <shr@devkernel.io> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Janosch Frank <frankja@linux.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Rik van Riel <riel@surriel.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: kernel/sys.c mm/ksm.c Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- include/linux/ksm.h | 1 + kernel/sys.c | 12 +++------ mm/ksm.c | 59 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 63 insertions(+), 9 deletions(-) diff --git a/include/linux/ksm.h b/include/linux/ksm.h index a7cfcab99b0d..99a4484ac37c 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -24,6 +24,7 @@ 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 6b1958150a49..06755cdb45f9 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2488,16 +2488,10 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, if (down_write_killable(&me->mm->mmap_sem)) return -EINTR; - if (arg2) { + 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; - } + else + error = ksm_disable_merge_any(me->mm); up_write(&me->mm->mmap_sem); break; case PR_GET_MEMORY_MERGE: diff --git a/mm/ksm.c b/mm/ksm.c index d0624f645ca3..ac1ecc5d85ed 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2499,6 +2499,23 @@ static void __ksm_add_vma(struct vm_area_struct *vma) vma->vm_flags |= 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; + } + + vma->vm_flags &= ~VM_MERGEABLE; + return 0; +} + /** * ksm_add_vma - Mark vma as mergeable if compatible * @@ -2520,6 +2537,19 @@ 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; + + for (vma = mm->mmap; vma; vma = vma->vm_next) { + 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 @@ -2547,6 +2577,35 @@ int ksm_enable_merge_any(struct mm_struct *mm) return 0; } +/** + * ksm_disable_merge_any - Disable merging on all compatible VMA's of the mm, + * previously enabled via ksm_enable_merge_any(). + * + * Disabling merging implies unmerging any merged pages, like setting + * MADV_UNMERGEABLE would. If unmerging fails, the whole operation fails and + * merging on all compatible VMA's remains enabled. + * + * @mm: Pointer to mm + * + * Returns 0 on success, otherwise error code + */ +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) { -- 2.43.0