[PATCH 04/11] powerpc: mm: Call ctor/dtor for kernel PTEs

Kevin Brodsky
2025-03-17T14:21:49Z

The generic implementation of pte_{alloc_one,free}_kernel now calls
the [cd]tor, without initialising the ptlock needlessly as
pagetable_pte_ctor() skips it for init_mm.

On powerpc, all functions related to PTE allocation are implemented
by common helpers, which are passed a boolean to differentiate user
from kernel pgtables. This patch aligns the powerpc implementation
with the generic one by calling pagetable_pte_[cd]tor()
unconditionally in those helpers.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
arch/powerpc/mm/pgtable-frag.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
index 387e9b1fe12c..77e55eac16e4 100644
--- a/arch/powerpc/mm/pgtable-frag.c
+++ b/arch/powerpc/mm/pgtable-frag.c
@@ -56,19 +56,17 @@ static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel)
{
void *ret = NULL;
struct ptdesc *ptdesc;
+ gfp_t gfp = PGALLOC_GFP;

- if (!kernel) {
- ptdesc = pagetable_alloc(PGALLOC_GFP | __GFP_ACCOUNT, 0);
- if (!ptdesc)
- return NULL;
- if (!pagetable_pte_ctor(mm, ptdesc)) {
- pagetable_free(ptdesc);
- return NULL;
- }
- } else {
- ptdesc = pagetable_alloc(PGALLOC_GFP, 0);
- if (!ptdesc)
- return NULL;
+ if (!kernel)
+ gfp |= __GFP_ACCOUNT;
+
+ ptdesc = pagetable_alloc(gfp, 0);
+ if (!ptdesc)
+ return NULL;
+ if (!pagetable_pte_ctor(mm, ptdesc)) {
+ pagetable_free(ptdesc);
+ return NULL;
}

atomic_set(&ptdesc->pt_frag_refcount, 1);
@@ -124,12 +122,10 @@ void pte_fragment_free(unsigned long *table, int kernel)

BUG_ON(atomic_read(&ptdesc->pt_frag_refcount) <= 0);
if (atomic_dec_and_test(&ptdesc->pt_frag_refcount)) {
- if (kernel)
- pagetable_free(ptdesc);
- else if (folio_test_clear_active(ptdesc_folio(ptdesc)))
- call_rcu(&ptdesc->pt_rcu_head, pte_free_now);
- else
+ if (kernel || !folio_test_clear_active(ptdesc_folio(ptdesc)))
pte_free_now(&ptdesc->pt_rcu_head);
+ else
+ call_rcu(&ptdesc->pt_rcu_head, pte_free_now);
}
}

--
2.47.0