fs/sync.c: remove unnecessary NULL f_mapping check in sync_file_range

fsync codepath assumes that f_mapping can never be NULL, but
sync_file_range has a check for that.

Remove the one from sync_file_range as I don't see how you'd ever get a
NULL pointer in here.

Link: http://lkml.kernel.org/r/20170525110509.9434-1-jlayton@redhat.com
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/sync.c

@@ -335,11 +335,6 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 		goto out_put;
 
 	mapping = f.file->f_mapping;
-	if (!mapping) {
-		ret = -EINVAL;
-		goto out_put;
-	}
-
 	ret = 0;
 	if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
 		ret = filemap_fdatawait_range(mapping, offset, endbyte);