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Subject[PATCH v2 05/22] powerpc/book3s64/hash: Use the pte_t address from the caller
Date
Don't fetch the pte value using lockless page table walk. Instead use the value from the
caller. hash_preload is called with ptl lock held. So it is safe to use the
pte_t address directly.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
arch/powerpc/mm/book3s64/hash_utils.c | 27 +++++----------------------
1 file changed, 5 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index e2a7873c7760..81b4130ceb05 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1545,14 +1545,11 @@ static bool should_hash_preload(struct mm_struct *mm, unsigned long ea)
}
#endif

-static void hash_preload(struct mm_struct *mm, unsigned long ea,
+static void hash_preload(struct mm_struct *mm, pte_t *ptep, unsigned long ea,
bool is_exec, unsigned long trap)
{
- int hugepage_shift;
unsigned long vsid;
pgd_t *pgdir;
- pte_t *ptep;
- unsigned long flags;
int rc, ssize, update_flags = 0;
unsigned long access = _PAGE_PRESENT | _PAGE_READ | (is_exec ? _PAGE_EXEC : 0);

@@ -1574,30 +1571,18 @@ static void hash_preload(struct mm_struct *mm, unsigned long ea,
vsid = get_user_vsid(&mm->context, ea, ssize);
if (!vsid)
return;
- /*
- * Hash doesn't like irqs. Walking linux page table with irq disabled
- * saves us from holding multiple locks.
- */
- local_irq_save(flags);

- /*
- * THP pages use update_mmu_cache_pmd. We don't do
- * hash preload there. Hence can ignore THP here
- */
- ptep = find_current_mm_pte(pgdir, ea, NULL, &hugepage_shift);
- if (!ptep)
- goto out_exit;
-
- WARN_ON(hugepage_shift);
#ifdef CONFIG_PPC_64K_PAGES
/* If either H_PAGE_4K_PFN or cache inhibited is set (and we are on
* a 64K kernel), then we don't preload, hash_page() will take
* care of it once we actually try to access the page.
* That way we don't have to duplicate all of the logic for segment
* page size demotion here
+ * Called with PTL held, hence can be sure the value won't change in
+ * between.
*/
if ((pte_val(*ptep) & H_PAGE_4K_PFN) || pte_ci(*ptep))
- goto out_exit;
+ return;
#endif /* CONFIG_PPC_64K_PAGES */

/* Is that local to this CPU ? */
@@ -1622,8 +1607,6 @@ static void hash_preload(struct mm_struct *mm, unsigned long ea,
mm_ctx_user_psize(&mm->context),
mm_ctx_user_psize(&mm->context),
pte_val(*ptep));
-out_exit:
- local_irq_restore(flags);
}

/*
@@ -1674,7 +1657,7 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
return;
}

- hash_preload(vma->vm_mm, address, is_exec, trap);
+ hash_preload(vma->vm_mm, ptep, address, is_exec, trap);
}

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
--
2.24.1
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