[PATCH 2/3] mm: use folio_headpage() instead of folio_page()

[SeongJae Park]

Several code in mm is using 'folio_page(folio, 0)' for getting the head
pages of folios.  It's not the standard idiom and inefficient.  Replace
the calls to 'folio_headpage()'.

Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
 mm/shmem.c       | 4 ++--
 mm/slab.c        | 6 +++---
 mm/slab_common.c | 4 ++--
 mm/slub.c        | 4 ++--
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index bc5c156ef470..8ae73973a7fc 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3211,7 +3211,7 @@ static const char *shmem_get_link(struct dentry *dentry,
 		folio = filemap_get_folio(inode->i_mapping, 0);
 		if (!folio)
 			return ERR_PTR(-ECHILD);
-		if (PageHWPoison(folio_page(folio, 0)) ||
+		if (PageHWPoison(folio_headpage(folio)) ||
 		    !folio_test_uptodate(folio)) {
 			folio_put(folio);
 			return ERR_PTR(-ECHILD);
@@ -3222,7 +3222,7 @@ static const char *shmem_get_link(struct dentry *dentry,
 			return ERR_PTR(error);
 		if (!folio)
 			return ERR_PTR(-ECHILD);
-		if (PageHWPoison(folio_page(folio, 0))) {
+		if (PageHWPoison(folio_headpage(folio))) {
 			folio_unlock(folio);
 			folio_put(folio);
 			return ERR_PTR(-ECHILD);
diff --git a/mm/slab.c b/mm/slab.c
index 7a269db050ee..a6f8f95678c9 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1373,7 +1373,7 @@ static struct slab *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
 	/* Make the flag visible before any changes to folio->mapping */
 	smp_wmb();
 	/* Record if ALLOC_NO_WATERMARKS was set when allocating the slab */
-	if (sk_memalloc_socks() && page_is_pfmemalloc(folio_page(folio, 0)))
+	if (sk_memalloc_socks() && page_is_pfmemalloc(folio_headpage(folio)))
 		slab_set_pfmemalloc(slab);
 
 	return slab;
@@ -1389,7 +1389,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab)
 
 	BUG_ON(!folio_test_slab(folio));
 	__slab_clear_pfmemalloc(slab);
-	page_mapcount_reset(folio_page(folio, 0));
+	page_mapcount_reset(folio_headpage(folio));
 	folio->mapping = NULL;
 	/* Make the mapping reset visible before clearing the flag */
 	smp_wmb();
@@ -1398,7 +1398,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab)
 	if (current->reclaim_state)
 		current->reclaim_state->reclaimed_slab += 1 << order;
 	unaccount_slab(slab, order, cachep);
-	__free_pages(folio_page(folio, 0), order);
+	__free_pages(folio_headpage(folio), order);
 }
 
 static void kmem_rcu_free(struct rcu_head *head)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index bf4e777cfe90..34a0b9988d12 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -939,9 +939,9 @@ void free_large_kmalloc(struct folio *folio, void *object)
 	kasan_kfree_large(object);
 	kmsan_kfree_large(object);
 
-	mod_lruvec_page_state(folio_page(folio, 0), NR_SLAB_UNRECLAIMABLE_B,
+	mod_lruvec_page_state(folio_headpage(folio), NR_SLAB_UNRECLAIMABLE_B,
 			      -(PAGE_SIZE << order));
-	__free_pages(folio_page(folio, 0), order);
+	__free_pages(folio_headpage(folio), order);
 }
 
 static void *__kmalloc_large_node(size_t size, gfp_t flags, int node);
diff --git a/mm/slub.c b/mm/slub.c
index 13459c69095a..1f0cbb4c2288 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1859,7 +1859,7 @@ static inline struct slab *alloc_slab_page(gfp_t flags, int node,
 	__folio_set_slab(folio);
 	/* Make the flag visible before any changes to folio->mapping */
 	smp_wmb();
-	if (page_is_pfmemalloc(folio_page(folio, 0)))
+	if (page_is_pfmemalloc(folio_headpage(folio)))
 		slab_set_pfmemalloc(slab);
 
 	return slab;
@@ -2066,7 +2066,7 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab)
 	if (current->reclaim_state)
 		current->reclaim_state->reclaimed_slab += pages;
 	unaccount_slab(slab, order, s);
-	__free_pages(folio_page(folio, 0), order);
+	__free_pages(folio_headpage(folio), order);
 }
 
 static void rcu_free_slab(struct rcu_head *h)
-- 
2.25.1