Revert "floppy: reintroduce O_NDELAY fix"

commit c7e9d0020361f4308a70cdfd6d5335e273eb8717 upstream.

The patch breaks userspace implementations (e.g. fdutils) and introduces
regressions in behaviour. Previously, it was possible to O_NDELAY open a
floppy device with no media inserted or with write protected media without
an error. Some userspace tools use this particular behavior for probing.

It's not the first time when we revert this patch. Previous revert is in
commit f2791e7 (Revert "floppy: refactor open() flags handling").

This reverts commit 8a0c014cd20516ade9654fc13b51345ec58e7be8.

Link: https://lore.kernel.org/linux-block/de10cb47-34d1-5a88-7751-225ca380f735@compro.net/
Reported-by: Mark Hounschell <markh@compro.net>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Wim Osterholt <wim@djo.tudelft.nl>
Cc: Kurt Garloff <kurt@garloff.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: evdenis

drivers/block/floppy.c

@@ -4067,22 +4067,21 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
 	if (UFDCS->rawcmd == 1)
 		UFDCS->rawcmd = 2;
 
-	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))
+	if (!(mode & FMODE_NDELAY)) {
+		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;
+		if ((mode & FMODE_WRITE) &&
+		    !test_bit(FD_DISK_WRITABLE_BIT, &UDRS->flags))
 			goto out;
 	}
-
-	res = -EROFS;
-
-	if ((mode & FMODE_WRITE) &&
-			!test_bit(FD_DISK_WRITABLE_BIT, &UDRS->flags))
-		goto out;
-
 	mutex_unlock(&open_lock);
 	mutex_unlock(&floppy_mutex);
 	return 0;