[Patch v2] mm/khugepaged: unify pmd folio installation with map_anon_folio_pmd()

[Wei Yang <richard.weiyang@gmail.com>]

Currently we install pmd folio with map_anon_folio_pmd() in
__do_huge_pmd_anonymous_page() and do_huge_zero_wp_pmd(). While in
collapse_huge_page(), it is done with identical code except statistics
adjustment.

Unify the process with map_anon_folio_pmd() to install pmd folio. Split
it to map_anon_folio_pmd_pf() and map_anon_folio_pmd_nopf() to be used
in page fault or not respectively.

No functional change is intended.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>

---
v2:
  * split to map_anon_folio_pmd_[no]pf() suggested by Matthew
---
 include/linux/huge_mm.h |  6 ++++++
 mm/huge_memory.c        | 14 ++++++++++----
 mm/khugepaged.c         |  9 +--------
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index e3ed008a076a..277ade3b7640 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -539,6 +539,8 @@ void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
 			   pmd_t *pmd, bool freeze);
 bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
 			   pmd_t *pmdp, struct folio *folio);
+void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd,
+		struct vm_area_struct *vma, unsigned long haddr);
 
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 
@@ -629,6 +631,10 @@ static inline bool unmap_huge_pmd_locked(struct vm_area_struct *vma,
 	return false;
 }
 
+void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd,
+		struct vm_area_struct *vma, unsigned long haddr)
+{}
+
 #define split_huge_pud(__vma, __pmd, __address)	\
 	do { } while (0)
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f13de93637bf..88960530b1d5 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1217,7 +1217,7 @@ static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma,
 	return folio;
 }
 
-static void map_anon_folio_pmd(struct folio *folio, pmd_t *pmd,
+void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd,
 		struct vm_area_struct *vma, unsigned long haddr)
 {
 	pmd_t entry;
@@ -1228,11 +1228,17 @@ static void map_anon_folio_pmd(struct folio *folio, pmd_t *pmd,
 	folio_add_lru_vma(folio, vma);
 	set_pmd_at(vma->vm_mm, haddr, pmd, entry);
 	update_mmu_cache_pmd(vma, haddr, pmd);
+	deferred_split_folio(folio, false);
+}
+
+static void map_anon_folio_pmd_pf(struct folio *folio, pmd_t *pmd,
+		struct vm_area_struct *vma, unsigned long haddr)
+{
+	map_anon_folio_pmd_nopf(folio, pmd, vma, haddr);
 	add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 	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)
@@ -1271,7 +1277,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 			return ret;
 		}
 		pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
-		map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
+		map_anon_folio_pmd_pf(folio, vmf->pmd, vma, haddr);
 		mm_inc_nr_ptes(vma->vm_mm);
 		spin_unlock(vmf->ptl);
 	}
@@ -1877,7 +1883,7 @@ static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf)
 	if (ret)
 		goto release;
 	(void)pmdp_huge_clear_flush(vma, haddr, vmf->pmd);
-	map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
+	map_anon_folio_pmd_pf(folio, vmf->pmd, vma, haddr);
 	goto unlock;
 release:
 	folio_put(folio);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f4f57ba69d72..ce7181b6ae4e 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1224,17 +1224,10 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 	__folio_mark_uptodate(folio);
 	pgtable = pmd_pgtable(_pmd);
 
-	_pmd = folio_mk_pmd(folio, vma->vm_page_prot);
-	_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
-
 	spin_lock(pmd_ptl);
 	BUG_ON(!pmd_none(*pmd));
-	folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE);
-	folio_add_lru_vma(folio, vma);
 	pgtable_trans_huge_deposit(mm, pmd, pgtable);
-	set_pmd_at(mm, address, pmd, _pmd);
-	update_mmu_cache_pmd(vma, address, pmd);
-	deferred_split_folio(folio, false);
+	map_anon_folio_pmd_nopf(folio, pmd, vma, address);
 	spin_unlock(pmd_ptl);
 
 	folio = NULL;
-- 
2.34.1