mm/huge_memory: remove folio split check for READ_ONLY_THP_FOR_FS

Without READ_ONLY_THP_FOR_FS, large file-backed folios cannot be created
by a FS without large folio support.  The check is no longer needed.

Link: https://lore.kernel.org/20260517135416.1434539-9-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
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: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
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>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2fc3356d0a3c3206776636c1b2c35b66be7be283..74bdf6ecd0cdfd92880aa6830133e3e9d3114aa9 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3763,33 +3763,9 @@ int folio_check_splittable(struct folio *folio, unsigned int new_order,
        if (!folio->mapping && !folio_test_anon(folio))
                return -EBUSY;
 
-       if (folio_test_anon(folio)) {
-               /* order-1 is not supported for anonymous THP. */
-               if (new_order == 1)
-                       return -EINVAL;
-       } else if (split_type == SPLIT_TYPE_NON_UNIFORM || new_order) {
-               if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
-                   !mapping_large_folio_support(folio->mapping)) {
-                       /*
-                        * We can always split a folio down to a single page
-                        * (new_order == 0) uniformly.
-                        *
-                        * For any other scenario
-                        *   a) uniform split targeting a large folio
-                        *      (new_order > 0)
-                        *   b) any non-uniform split
-                        * we must confirm that the file system supports large
-                        * folios.
-                        *
-                        * Note that we might still have THPs in such
-                        * mappings, which is created from khugepaged when
-                        * CONFIG_READ_ONLY_THP_FOR_FS is enabled. But in that
-                        * case, the mapping does not actually support large
-                        * folios properly.
-                        */
-                       return -EINVAL;
-               }
-       }
+       /* order-1 is not supported for anonymous THP. */
+       if (folio_test_anon(folio) && new_order == 1)
+               return -EINVAL;
 
        /*
         * swapcache folio could only be split to order 0