[PATCH v5 03/14] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled()

Zi Yan
2026-04-29T15:30:28Z

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@nvidia.com>
---
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 2f3fcb4dd1ef8..3b324f03e9283 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