mm/huge_memory: add pmd folio to ds_queue in do_huge_zero_wp_pmd()

We add pmd folio into ds_queue on the first page fault in
__do_huge_pmd_anonymous_page(), so that we can split it in case of memory
pressure.  This should be the same for a pmd folio during wp page fault.

Commit 1ced09e0331f ("mm: allocate THP on hugezeropage wp-fault") miss to
add it to ds_queue, which means system may not reclaim enough memory in
case of memory pressure even the pmd folio is under used.

Move deferred_split_folio() into map_anon_folio_pmd() to make the pmd
folio installation consistent.

Link: https://lkml.kernel.org/r/20251008095453.18772-2-richard.weiyang@gmail.com
Fixes: 1ced09e0331f ("mm: allocate THP on hugezeropage wp-fault")
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Acked-by: Usama Arif <usamaarif642@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 671c4ec918be3dbdee88ff9674c6ebdb64223ac6..49f2ff9de1cad5a0a2a13d8d20158d95239fbf60 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1232,6 +1232,7 @@ static void map_anon_folio_pmd(struct folio *folio, pmd_t *pmd,
        count_vm_event(THP_FAULT_ALLOC);
        count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_ALLOC);
        count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
+       deferred_split_folio(folio, false);
 }
 
 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
@@ -1272,7 +1273,6 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
                pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
                map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
                mm_inc_nr_ptes(vma->vm_mm);
-               deferred_split_folio(folio, false);
                spin_unlock(vmf->ptl);
        }