linux-kernel - [PATCH v1 1/2] mm: introduce pmd

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Date:   Sat, 28 Aug 2021 12:23:05 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     akpm@...ux-foundation.org, tglx@...utronix.de, hannes@...xchg.org,
        mhocko@...nel.org, vdavydov.dev@...il.com,
        kirill.shutemov@...ux.intel.com, mika.penttila@...tfour.com,
        david@...hat.com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, songmuchun@...edance.com,
        Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH v1 1/2] mm: introduce pmd_install() helper

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@...edance.com>
Reviewed-by: David Hildenbrand <david@...hat.com>
---
 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 a3cc83d64564..0af420a7e382 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2463,6 +2463,7 @@ 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 c90b6e4984c9..923cbba1bf37 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3209,15 +3209,8 @@ 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() */
-- 
2.11.0