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authorDavid Hildenbrand <david@redhat.com>2023-04-22 22:54:18 +0200
committerAndrew Morton <akpm@linux-foundation.org>2023-05-02 17:21:49 -0700
commit24139c07f413ef4b555482c758343d71392a19bc (patch)
tree59c520ceba8cfb5493d2154df6661f12a12459da /mm/ksm.c
parent70307b0e297a6634be855c49525ccbea50922a90 (diff)
mm/ksm: unmerge and clear VM_MERGEABLE when setting PR_SET_MEMORY_MERGE=0
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>
Diffstat (limited to 'mm/ksm.c')
-rw-r--r--mm/ksm.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index 9e48258985d2..823bb3475a68 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 +2599,35 @@ 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)
{