ide: fix races in handling of user-space SET XFER commands

* Make cmd->tf_flags field 'u16' and add IDE_TFLAG_SET_XFER taskfile flag.

* Update ide_finish_cmd() to set xfer / re-read id if the new flag is set.

* Convert set_xfer_rate() (write handler for /proc/ide/hd?/current_speed)
  and ide_cmd_ioctl() (HDIO_DRIVE_CMD ioctl handler) to use the new flag.

* Remove no longer needed disable_irq_nosync() + enable_irq() from
  ide_config_drive_speed().

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ide/ide-ioctls.c

diff --git a/drivers/ide/ide-ioctls.c b/drivers/ide/ide-ioctls.c
index e246d3d..d3440b50 100644
--- a/drivers/ide/ide-ioctls.c
+++ b/drivers/ide/ide-ioctls.c
@@ -167,6 +167,8 @@
 			err = -EINVAL;
 			goto abort;
 		}
+
+		cmd.tf_flags |= IDE_TFLAG_SET_XFER;
 	}
 
 	err = ide_raw_taskfile(drive, &cmd, buf, args[3]);
@@ -174,12 +176,6 @@
 	args[0] = tf->status;
 	args[1] = tf->error;
 	args[2] = tf->nsect;
-
-	if (!err && xfer_rate) {
-		/* active-retuning-calls future */
-		ide_set_xfer_rate(drive, xfer_rate);
-		ide_driveid_update(drive);
-	}
 abort:
 	if (copy_to_user((void __user *)arg, &args, 4))
 		err = -EFAULT;