In order to add mTHP support to khugepaged, we will often be checking if a
given order is (or is not) a PMD order. Some places in the kernel already
use this check, so lets create a simple helper function to keep the code
clean and readable.

Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Nico Pache <npache@redhat.com>
---
 include/linux/huge_mm.h | 5 +++++
 mm/huge_memory.c        | 2 +-
 mm/khugepaged.c         | 6 +++---
 mm/memory.c             | 2 +-
 mm/mempolicy.c          | 2 +-
 mm/page_alloc.c         | 4 ++--
 mm/shmem.c              | 3 +--
 7 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a4d9f964dfde..bd7f0e1d8094 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -771,6 +771,11 @@ static inline bool pmd_is_huge(pmd_t pmd)
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
+static inline bool is_pmd_order(unsigned int order)
+{
+	return order == HPAGE_PMD_ORDER;
+}
+
 static inline int split_folio_to_list_to_order(struct folio *folio,
 		struct list_head *list, int new_order)
 {
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 7d0a64033b18..9968cde6f820 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4122,7 +4122,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
 		i_mmap_unlock_read(mapping);
 out:
 	xas_destroy(&xas);
-	if (old_order == HPAGE_PMD_ORDER)
+	if (is_pmd_order(old_order))
 		count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
 	count_mthp_stat(old_order, !ret ? MTHP_STAT_SPLIT : MTHP_STAT_SPLIT_FAILED);
 	return ret;
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b7b4680d27ab..d3bdec4ec61b 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1532,7 +1532,7 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign
 	if (IS_ERR(folio))
 		return SCAN_PAGE_NULL;
 
-	if (folio_order(folio) != HPAGE_PMD_ORDER) {
+	if (!is_pmd_order(folio_order(folio))) {
 		result = SCAN_PAGE_COMPOUND;
 		goto drop_folio;
 	}
@@ -2015,7 +2015,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
 		 * we locked the first folio, then a THP might be there already.
 		 * This will be discovered on the first iteration.
 		 */
-		if (folio_order(folio) == HPAGE_PMD_ORDER) {
+		if (is_pmd_order(folio_order(folio))) {
 			result = SCAN_PTE_MAPPED_HUGEPAGE;
 			goto out_unlock;
 		}
@@ -2343,7 +2343,7 @@ static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm,
 			continue;
 		}
 
-		if (folio_order(folio) == HPAGE_PMD_ORDER) {
+		if (is_pmd_order(folio_order(folio))) {
 			result = SCAN_PTE_MAPPED_HUGEPAGE;
 			/*
 			 * PMD-sized THP implies that we can only try
diff --git a/mm/memory.c b/mm/memory.c
index 5c8bf1eb55f5..9ede3a31aa4e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5479,7 +5479,7 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio, struct page *pa
 	if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER))
 		return ret;
 
-	if (folio_order(folio) != HPAGE_PMD_ORDER)
+	if (!is_pmd_order(folio_order(folio)))
 		return ret;
 	page = &folio->page;
 
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 0e5175f1c767..e5528c35bbb8 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2449,7 +2449,7 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order,
 
 	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
 	    /* filter "hugepage" allocation, unless from alloc_pages() */
-	    order == HPAGE_PMD_ORDER && ilx != NO_INTERLEAVE_INDEX) {
+	    is_pmd_order(order) && ilx != NO_INTERLEAVE_INDEX) {
 		/*
 		 * For hugepage allocation and non-interleave policy which
 		 * allows the current node (or other explicitly preferred
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 75ee81445640..c500def16cc7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -652,7 +652,7 @@ static inline unsigned int order_to_pindex(int migratetype, int order)
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	bool movable;
 	if (order > PAGE_ALLOC_COSTLY_ORDER) {
-		VM_BUG_ON(order != HPAGE_PMD_ORDER);
+		VM_BUG_ON(!is_pmd_order(order));
 
 		movable = migratetype == MIGRATE_MOVABLE;
 
@@ -684,7 +684,7 @@ static inline bool pcp_allowed_order(unsigned int order)
 	if (order <= PAGE_ALLOC_COSTLY_ORDER)
 		return true;
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (order == HPAGE_PMD_ORDER)
+	if (is_pmd_order(order))
 		return true;
 #endif
 	return false;
diff --git a/mm/shmem.c b/mm/shmem.c
index d00044257401..4ecefe02881d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5532,8 +5532,7 @@ static ssize_t thpsize_shmem_enabled_store(struct kobject *kobj,
 		spin_unlock(&huge_shmem_orders_lock);
 	} else if (sysfs_streq(buf, "inherit")) {
 		/* Do not override huge allocation policy with non-PMD sized mTHP */
-		if (shmem_huge == SHMEM_HUGE_FORCE &&
-		    order != HPAGE_PMD_ORDER)
+		if (shmem_huge == SHMEM_HUGE_FORCE && !is_pmd_order(order))
 			return -EINVAL;
 
 		spin_lock(&huge_shmem_orders_lock);
-- 
2.53.0