floppy: fix open(O_ACCMODE) for ioctl-only open

Commit 09954bad4 ("floppy: refactor open() flags handling"), as a
side-effect, causes open(/dev/fdX, O_ACCMODE) to fail. It turns out that
this is being used setfdprm userspace for ioctl-only open().

Reintroduce back the original behavior wrt !(FMODE_READ|FMODE_WRITE)
modes, while still keeping the original O_NDELAY bug fixed.

Cc: stable@vger.kernel.org # v4.5+
Reported-by: Wim Osterholt <wim@djo.tudelft.nl>
Tested-by: Wim Osterholt <wim@djo.tudelft.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/block/floppy.c

@@ -3663,11 +3663,6 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
 
 	opened_bdev[drive] = bdev;
 
-	if (!(mode & (FMODE_READ|FMODE_WRITE))) {
-		res = -EINVAL;
-		goto out;
-	}
-
 	res = -ENXIO;
 
 	if (!floppy_track_buffer) {
@@ -3711,13 +3706,15 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
 	if (UFDCS->rawcmd == 1)
 		UFDCS->rawcmd = 2;
 
-	UDRS->last_checked = 0;
-	clear_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags);
-	check_disk_change(bdev);
-	if (test_bit(FD_DISK_CHANGED_BIT, &UDRS->flags))
-		goto out;
-	if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags))
-		goto out;
+	if (mode & (FMODE_READ|FMODE_WRITE)) {
+		UDRS->last_checked = 0;
+		clear_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags);
+		check_disk_change(bdev);
+		if (test_bit(FD_DISK_CHANGED_BIT, &UDRS->flags))
+			goto out;
+		if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags))
+			goto out;
+	}
 
 	res = -EROFS;