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mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL 

Patch series "mm_slot: fix the usage of mm_slot_entry", v2.

When using mm_slot in ksm, there is code like:

     slot = mm_slot_lookup(mm_slots_hash, mm);
     mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
     if (mm_slot && ..) {
     }

The mm_slot_entry() won't return a valid value if slot is NULL generally. 
But currently it works since slot is the first element of struct
ksm_mm_slot.

To reduce the ambiguity and make it robust, access mm_slot_entry() when
slot is !NULL.

Link: https://lkml.kernel.org/r/20250919071244.17020-1-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20250919071244.17020-2-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Kiryl Shutsemau <kirill@shutemov.name>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Wei Yang 2025-09-19 07:12:43 +00:00 committed by Andrew Morton
parent 3dfd02c900
commit 08498be43e
1 changed files with 11 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
mm/ksm.c
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@ -2936,8 +2936,9 @@ void __ksm_exit(struct mm_struct *mm)
spin_lock(&ksm_mmlist_lock);
slot = mm_slot_lookup(mm_slots_hash, mm);
if (slot) {
mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
if (mm_slot && ksm_scan.mm_slot != mm_slot) {
if (ksm_scan.mm_slot != mm_slot) {
if (!mm_slot->rmap_list) {
hash_del(&slot->hash);
list_del(&slot->mm_node);
@ -2947,6 +2948,7 @@ void __ksm_exit(struct mm_struct *mm)
&ksm_scan.mm_slot->slot.mm_node);
}
}
}
spin_unlock(&ksm_mmlist_lock);
if (easy_to_free) {