[PATCH v3 5/6] dax: short circuit vma_is_fsdax() in the CONFIG_FS_DAX=n case

[Dan Williams <dan.j.williams@xxxxxxxxx>]

Do not bother looking up the file type in the case when Filesystem-DAX
is disabled at build time.

Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 include/linux/fs.h |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7418341578a3..c97fc4dbaae1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3197,6 +3197,8 @@ static inline bool vma_is_fsdax(struct vm_area_struct *vma)
 
 	if (!vma->vm_file)
 		return false;
+	if (!IS_ENABLED(CONFIG_FS_DAX))
+		return false;
 	if (!vma_is_dax(vma))
 		return false;
 	inode = file_inode(vma->vm_file);