2.4.21-pre3 hdparm -X violates IDE locking

This bug impacts all versions of the kernel that I have looked at including 2.4.18 and above. It probably impacts many other versions as well.

hdparm -X issues a drive command ioctl which eventually issue a command to the drive bypassing all of the normal locking. The net effect is that a command can be set to the drive when the drive is not ready. Some drives lock up when this happens.

The call chain is

ide_ioctl calls
ide_cmd_ioctl

If the command is a set features to change the communications speed, after the command is complete, ide_cmd_ioctl calls

ide_set_xfer_rate

ide_set_xfer_rate then calls drive->speedproc.

Most speedprocs then call ide_config_drive_speed ide_config_drive_speed issue a set features command. and busy waits on it.

The easiest fix is to probably modify execute_drive_command to update drive->current_speed when it issues the appropriate SET FEATURES command, and then have ide_config_drive_speed do nothing if speed == current_speed.

I did a much bigger modification that handles changing drive speed specially and immediately. I'll make patches for either one, but I wanted to get some opinions before I did so.

Ross