[PATCH v3] tmpfs: don't enable large folios if not supported

[Kefeng Wang <wangkefeng.wang@huawei.com>]

The tmpfs could support large folio, but there is some configurable
options(mount options and runtime deny/force) to enable/disable large
folio allocation, so there is a performance issue when perform write
without large folio, the issue is similar to commit 4e527d5841e2
("iomap: fault in smaller chunks for non-large folio mappings").

Don't call mapping_set_large_folios() in __shmem_get_inode() when
large folio is disabled to fix it.

Fixes: 9aac777aaf94 ("filemap: Convert generic_perform_write() to support large folios")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---

v3:
- don't enable large folio suppport in __shmem_get_inode() if disabled,
  suggested by Matthew.

v2:
- Don't use IOCB flags

 mm/shmem.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 0a2f78c2b919..2b859ac4ddc5 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2850,7 +2850,10 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
 	cache_no_acl(inode);
 	if (sbinfo->noswap)
 		mapping_set_unevictable(inode->i_mapping);
-	mapping_set_large_folios(inode->i_mapping);
+
+	if ((sbinfo->huge && shmem_huge != SHMEM_HUGE_DENY) ||
+	    shmem_huge == SHMEM_HUGE_FORCE)
+		mapping_set_large_folios(inode->i_mapping);
 
 	switch (mode & S_IFMT) {
 	default:
-- 
2.27.0