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 <[email protected]>
Acked-by: David Hildenbrand (Arm) <[email protected]>
Reviewed-by: Lance Yang <[email protected]>
Reviewed-by: Nico Pache <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: David Sterba <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
---
 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


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