Re: [PATCH v2 1/9] mm: introduce pmd_install() helper

From: David Hildenbrand
Date: Tue Aug 24 2021 - 12:26:56 EST


On 19.08.21 05:18, Qi Zheng wrote:
Currently we have three times the same few lines repeated in the
code. Deduplicate them by newly introduced pmd_install() helper.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
include/linux/mm.h | 1 +
mm/filemap.c | 11 ++---------
mm/memory.c | 34 ++++++++++++++++------------------
3 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ce8fc0fd6d6e..57e48217bd71 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2471,6 +2471,7 @@ static inline spinlock_t *pud_lock(struct mm_struct *mm, pud_t *pud)
return ptl;
}
+extern void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte);
extern void __init pagecache_init(void);
extern void __init free_area_init_memoryless_node(int nid);
extern void free_initmem(void);
diff --git a/mm/filemap.c b/mm/filemap.c
index 53913fced7ae..9f773059c6dc 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3210,15 +3210,8 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page)
}
}
- if (pmd_none(*vmf->pmd)) {
- vmf->ptl = pmd_lock(mm, vmf->pmd);
- if (likely(pmd_none(*vmf->pmd))) {
- mm_inc_nr_ptes(mm);
- pmd_populate(mm, vmf->pmd, vmf->prealloc_pte);
- vmf->prealloc_pte = NULL;
- }
- spin_unlock(vmf->ptl);
- }
+ if (pmd_none(*vmf->pmd))
+ pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);
/* See comment in handle_pte_fault() */
if (pmd_devmap_trans_unstable(vmf->pmd)) {
diff --git a/mm/memory.c b/mm/memory.c
index 39e7a1495c3c..ef7b1762e996 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -433,9 +433,20 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
}
}
+void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte)
+{
+ spinlock_t *ptl = pmd_lock(mm, pmd);
+
+ if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
+ mm_inc_nr_ptes(mm);
+ pmd_populate(mm, pmd, *pte);
+ *pte = NULL;
+ }
+ spin_unlock(ptl);
+}
+
int __pte_alloc(struct mm_struct *mm, pmd_t *pmd)
{
- spinlock_t *ptl;
pgtable_t new = pte_alloc_one(mm);
if (!new)
return -ENOMEM;
@@ -455,13 +466,7 @@ int __pte_alloc(struct mm_struct *mm, pmd_t *pmd)
*/
smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
- ptl = pmd_lock(mm, pmd);
- if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
- mm_inc_nr_ptes(mm);
- pmd_populate(mm, pmd, new);
- new = NULL;
- }
- spin_unlock(ptl);
+ pmd_install(mm, pmd, &new);
if (new)
pte_free(mm, new);
return 0;
@@ -4027,17 +4032,10 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
return ret;
}
- if (vmf->prealloc_pte) {
- vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
- if (likely(pmd_none(*vmf->pmd))) {
- mm_inc_nr_ptes(vma->vm_mm);
- pmd_populate(vma->vm_mm, vmf->pmd, vmf->prealloc_pte);
- vmf->prealloc_pte = NULL;
- }
- spin_unlock(vmf->ptl);
- } else if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd))) {
+ if (vmf->prealloc_pte)
+ pmd_install(vma->vm_mm, vmf->pmd, &vmf->prealloc_pte);
+ else if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd)))
return VM_FAULT_OOM;
- }
}
/* See comment in handle_pte_fault() */


Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>

That's mostly unrelated to the remaining part of the series and can be picked up early.

--
Thanks,

David / dhildenb