Re: [PATCH] mm/mm_slot: make sure slot is the first element of its wrapper structure

[Wei Yang <richard.weiyang@gmail.com>]

On Mon, Sep 15, 2025 at 09:56:34AM +0200, David Hildenbrand wrote:
[...]
>diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>index 6b40bdfd224c3..70a32d59d7d2f 100644
>--- a/mm/khugepaged.c
>+++ b/mm/khugepaged.c
>@@ -488,11 +488,13 @@ void __khugepaged_exit(struct mm_struct *mm)
>        spin_lock(&khugepaged_mm_lock);
>        slot = mm_slot_lookup(mm_slots_hash, mm);
>-       mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
>-       if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
>-               hash_del(&slot->hash);
>-               list_del(&slot->mm_node);
>-               free = 1;
>+       if (slot) {
>+               mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
>+               if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
>+                       hash_del(&slot->hash);
>+                       list_del(&slot->mm_node);
>+                       free = 1;
>+               }
>        }

But... to be honest, for khugepaged_mm_slot, I'd prefer to remove the
definition of it. struct khugepaged_mm_slot just wrap struct mm_slot.

One un-convenient thing of this change is we cant use KMEM_CACHE() to define
the slab allocator. Have to convert to the old api.

-- 
Wei Yang
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