[PATCH 4.15 034/122] dax: fix vma_is_fsdax() helper

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@xxxxxxxxx>

commit 230f5a8969d8345fc9bbe3683f068246cf1be4b8 upstream.

Gerd reports that ->i_mode may contain other bits besides S_IFCHR. Use
S_ISCHR() instead. Otherwise, get_user_pages_longterm() may fail on
device-dax instances when those are meant to be explicitly allowed.

Fixes: 2bb6d2837083 ("mm: introduce get_user_pages_longterm")
Cc: <stable@xxxxxxxxxxxxxxx>
Reported-by: Gerd Rausch <gerd.rausch@xxxxxxxxxx>
Acked-by: Jane Chu <jane.chu@xxxxxxxxxx>
Reported-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/linux/fs.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3204,7 +3204,7 @@ static inline bool vma_is_fsdax(struct v
 	if (!vma_is_dax(vma))
 		return false;
 	inode = file_inode(vma->vm_file);
-	if (inode->i_mode == S_IFCHR)
+	if (S_ISCHR(inode->i_mode))
 		return false; /* device-dax */
 	return true;
 }