[PATCH 7.2 v3 04/12] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check in hugepage_pmd_enabled()

[Zi Yan]

Remove READ_ONLY_THP_FOR_FS and khugepaged for file-backed pmd-sized
hugepages are enabled by the global transparent hugepage control.
khugepaged can still be enabled by per-size control for anon and shmem when
the global control is off.

Add shmem_hpage_pmd_enabled() stub for !CONFIG_SHMEM to remove
IS_ENABLED(SHMEM) in hugepage_pmd_enabled().

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 include/linux/shmem_fs.h |  2 +-
 mm/khugepaged.c          | 28 ++++++++++++++++------------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 1a345142af7d..dff8fb6ddac0 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -127,7 +127,7 @@ int shmem_writeout(struct folio *folio, struct swap_iocb **plug,
 void shmem_truncate_range(struct inode *inode, loff_t start, uoff_t end);
 int shmem_unuse(unsigned int type);
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SHMEM)
 unsigned long shmem_allowable_huge_orders(struct inode *inode,
 				struct vm_area_struct *vma, pgoff_t index,
 				loff_t write_end, bool shmem_huge_force);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 1c0fdc81d276..718a2d06d1e6 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -406,18 +406,8 @@ static inline int collapse_test_exit_or_disable(struct mm_struct *mm)
 		mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm);
 }
 
-static bool hugepage_pmd_enabled(void)
+static inline bool anon_hpage_pmd_enabled(void)
 {
-	/*
-	 * We cover the anon, shmem and the file-backed case here; file-backed
-	 * hugepages, when configured in, are determined by the global control.
-	 * Anon pmd-sized hugepages are determined by the pmd-size control.
-	 * Shmem pmd-sized hugepages are also determined by its pmd-size control,
-	 * except when the global shmem_huge is set to SHMEM_HUGE_DENY.
-	 */
-	if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
-	    hugepage_global_enabled())
-		return true;
 	if (test_bit(PMD_ORDER, &huge_anon_orders_always))
 		return true;
 	if (test_bit(PMD_ORDER, &huge_anon_orders_madvise))
@@ -425,7 +415,21 @@ static bool hugepage_pmd_enabled(void)
 	if (test_bit(PMD_ORDER, &huge_anon_orders_inherit) &&
 	    hugepage_global_enabled())
 		return true;
-	if (IS_ENABLED(CONFIG_SHMEM) && shmem_hpage_pmd_enabled())
+	return false;
+}
+
+static bool hugepage_pmd_enabled(void)
+{
+	/*
+	 * Anon, shmem and file-backed pmd-size hugepages are all determined by
+	 * the global control. If the global control is off, anon and shmem
+	 * pmd-sized hugepages are also determined by its per-size control.
+	 */
+	if (hugepage_global_enabled())
+		return true;
+	if (anon_hpage_pmd_enabled())
+		return true;
+	if (shmem_hpage_pmd_enabled())
 		return true;
 	return false;
 }
-- 
2.43.0