[PATCH v6 03/14] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled()

[Zi Yan]

Replace it with a check on the max folio order of the file's address space
mapping, making sure PMD folio is supported.  Keep the inode
open-for-write check, since even if collapse_file() now makes sure all
to-be-collapsed folios are clean and the created PMD file THP can be
handled by FSes properly, the filemap_flush() could perform undesirable
write back.

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
Reviewed-by: Lance Yang <lance.yang@xxxxxxxxx>
Reviewed-by: Nico Pache <npache@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Barry Song <baohua@xxxxxxxxxx>
Cc: Chris Mason <clm@xxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: David Sterba <dsterba@xxxxxxxx>
Cc: Dev Jain <dev.jain@xxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Liam Howlett <liam@xxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <ljs@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxxxxx>
---
 mm/huge_memory.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3e9eabc74c6c3..ccd623b9501b5 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -86,9 +86,6 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma)
 {
 	struct inode *inode;
 
-	if (!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS))
-		return false;
-
 	if (!vma->vm_file)
 		return false;
 
@@ -97,6 +94,9 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma)
 	if (IS_ANON_FILE(inode))
 		return false;
 
+	if (!mapping_pmd_folio_support(vma->vm_file->f_mapping))
+		return false;
+
 	return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode);
 }
 
-- 
2.53.0