mm/khugepaged: convert alloc_charge_hpage() to use folios

Also remove count_memcg_page_event now that its last caller no longer uses
it and reword hpage_collapse_alloc_page() to hpage_collapse_alloc_folio().

This removes 1 call to compound_head() and helps convert khugepaged to
use folios throughout.

Link: https://lkml.kernel.org/r/20231020183331.10770-5-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: VMoola

include/linux/memcontrol.h

@@ -1087,15 +1087,6 @@ static inline void count_memcg_events(struct mem_cgroup *memcg,
 	local_irq_restore(flags);
 }
 
-static inline void count_memcg_page_event(struct page *page,
-					  enum vm_event_item idx)
-{
-	struct mem_cgroup *memcg = page_memcg(page);
-
-	if (memcg)
-		count_memcg_events(memcg, idx, 1);
-}
-
 static inline void count_memcg_folio_events(struct folio *folio,
 		enum vm_event_item idx, unsigned long nr)
 {
@@ -1598,11 +1589,6 @@ static inline void __count_memcg_events(struct mem_cgroup *memcg,
 {
 }
 
-static inline void count_memcg_page_event(struct page *page,
-					  int idx)
-{
-}
-
 static inline void count_memcg_folio_events(struct folio *folio,
 		enum vm_event_item idx, unsigned long nr)
 {

mm/khugepaged.c

@@ -888,16 +888,16 @@ static int hpage_collapse_find_target_node(struct collapse_control *cc)
 }
 #endif
 
-static bool hpage_collapse_alloc_page(struct page **hpage, gfp_t gfp, int node,
+static bool hpage_collapse_alloc_folio(struct folio **folio, gfp_t gfp, int node,
 				      nodemask_t *nmask)
 {
-	*hpage = __alloc_pages(gfp, HPAGE_PMD_ORDER, node, nmask);
-	if (unlikely(!*hpage)) {
+	*folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, nmask);
+
+	if (unlikely(!*folio)) {
 		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
 		return false;
 	}
 
-	folio_prep_large_rmappable((struct folio *)*hpage);
 	count_vm_event(THP_COLLAPSE_ALLOC);
 	return true;
 }
@@ -1064,17 +1064,20 @@ static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
 	int node = hpage_collapse_find_target_node(cc);
 	struct folio *folio;
 
-	if (!hpage_collapse_alloc_page(hpage, gfp, node, &cc->alloc_nmask))
+	if (!hpage_collapse_alloc_folio(&folio, gfp, node, &cc->alloc_nmask)) {
+		*hpage = NULL;
 		return SCAN_ALLOC_HUGE_PAGE_FAIL;
+	}
 
-	folio = page_folio(*hpage);
 	if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
 		folio_put(folio);
 		*hpage = NULL;
 		return SCAN_CGROUP_CHARGE_FAIL;
 	}
-	count_memcg_page_event(*hpage, THP_COLLAPSE_ALLOC);
 
+	count_memcg_folio_events(folio, THP_COLLAPSE_ALLOC, 1);
+
+	*hpage = folio_page(folio, 0);
 	return SCAN_SUCCEED;
 }