The patch titled
Subject: mm/ksm: unmerge and clear VM_MERGEABLE when setting PR_SET_MEMORY_MERGE=0
has been added to the -mm mm-unstable branch. Its filename is
mm-ksm-unmerge-and-clear-vm_mergeable-when-setting-pr_set_memory_merge=0.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-ksm-unmerge-and-clear-vm_mergeable-when-setting-pr_set_memory_merge=0.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/ksm: unmerge and clear VM_MERGEABLE when setting PR_SET_MEMORY_MERGE=0
Date: Sat, 22 Apr 2023 22:54:18 +0200
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@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20230422205420.30372-2-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Stefan Roesch <shr@xxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Janosch Frank <frankja@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/ksm.h | 1
kernel/sys.c | 12 ++------
mm/ksm.c | 59 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 63 insertions(+), 9 deletions(-)
--- a/include/linux/ksm.h~mm-ksm-unmerge-and-clear-vm_mergeable-when-setting-pr_set_memory_merge=0
+++ a/include/linux/ksm.h
@@ -21,6 +21,7 @@ int ksm_madvise(struct vm_area_struct *v
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);
--- a/kernel/sys.c~mm-ksm-unmerge-and-clear-vm_mergeable-when-setting-pr_set_memory_merge=0
+++ a/kernel/sys.c
@@ -2695,16 +2695,10 @@ SYSCALL_DEFINE5(prctl, int, option, unsi
if (mmap_write_lock_killable(me->mm))
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);
mmap_write_unlock(me->mm);
break;
case PR_GET_MEMORY_MERGE:
--- a/mm/ksm.c~mm-ksm-unmerge-and-clear-vm_mergeable-when-setting-pr_set_memory_merge=0
+++ a/mm/ksm.c
@@ -2520,6 +2520,22 @@ static void __ksm_add_vma(struct vm_area
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_struc
__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 +2599,35 @@ int ksm_enable_merge_any(struct mm_struc
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)
{
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-ksm-unmerge-and-clear-vm_mergeable-when-setting-pr_set_memory_merge=0.patch
selftests-ksm-ksm_functional_tests-add-prctl-unmerge-test.patch
mm-ksm-move-disabling-ksm-from-s390-gmap-code-to-ksm-code.patch
