fs: fix reporting supported extra file attributes for statx()

statx(2) notes that any attribute that is not indicated as supported
by stx_attributes_mask has no usable value.  Commits 801e5237
("fs: move generic stat response attr handling to vfs_getattr_nosec")
and 712b2698 ("fs/stat: Define DAX statx attribute") sets
STATX_ATTR_AUTOMOUNT and STATX_ATTR_DAX, respectively, without setting
stx_attributes_mask, which can cause xfstests generic/532 to fail.

Fix this in the same way as commit 1b9598c8 ("xfs: fix reporting
supported extra file attributes for statx()")

Fixes: 801e5237 ("fs: move generic stat response attr handling to vfs_getattr_nosec")
Fixes: 712b2698 ("fs/stat: Define DAX statx attribute")
Cc: stable@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/stat.c

@@ -86,12 +86,20 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
 	/* SB_NOATIME means filesystem supplies dummy atime value */
 	if (inode->i_sb->s_flags & SB_NOATIME)
 		stat->result_mask &= ~STATX_ATIME;
+
+	/*
+	 * Note: If you add another clause to set an attribute flag, please
+	 * update attributes_mask below.
+	 */
 	if (IS_AUTOMOUNT(inode))
 		stat->attributes |= STATX_ATTR_AUTOMOUNT;
 
 	if (IS_DAX(inode))
 		stat->attributes |= STATX_ATTR_DAX;
 
+	stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
+				  STATX_ATTR_DAX);
+
 	mnt_userns = mnt_user_ns(path->mnt);
 	if (inode->i_op->getattr)
 		return inode->i_op->getattr(mnt_userns, path, stat,