mm/khugepaged: remove READ_ONLY_THP_FOR_FS check in hugepage_enabled()

Remove the READ_ONLY_THP_FOR_FS gate 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_enabled().

Clean up hugepage_enabled() by moving anon code to anon_hpage_enabled().

Link: https://lore.kernel.org/20260517135416.1434539-5-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Nico Pache <npache@redhat.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Sterba <dsterba@suse.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 17 insertions, 11 deletions

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 93a0ba872ebe..acb8dd961b45 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 eca22f1185d9..d8fdcc7882ad 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -503,26 +503,32 @@ static inline int collapse_test_exit_or_disable(struct mm_struct *mm)
 		mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm);
 }
 
+static inline bool anon_hpage_enabled(void)
+{
+	if (READ_ONCE(huge_anon_orders_always))
+		return true;
+	if (READ_ONCE(huge_anon_orders_madvise))
+		return true;
+	if (READ_ONCE(huge_anon_orders_inherit) &&
+	    hugepage_global_enabled())
+		return true;
+	return false;
+}
+
 static bool hugepage_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.
+	 * hugepages are determined by the global control.
 	 * Anon hugepages are determined by its per-size mTHP 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 (READ_ONCE(huge_anon_orders_always))
+	if (hugepage_global_enabled())
 		return true;
-	if (READ_ONCE(huge_anon_orders_madvise))
-		return true;
-	if (READ_ONCE(huge_anon_orders_inherit) &&
-	    hugepage_global_enabled())
+	if (anon_hpage_enabled())
 		return true;
-	if (IS_ENABLED(CONFIG_SHMEM) && shmem_hpage_pmd_enabled())
+	if (shmem_hpage_pmd_enabled())
 		return true;
 	return false;
 }