Hi,
The way file ide-disk.c handles usage count, it seems to me that its
concurrency bug.
In open method and release, it uses code as follows


static int idedisk_open(struct inode *inode, struct file *filp)
{
        ide_drive_t *drive = inode->i_bdev->bd_disk->private_data;
        drive->usage++;
        if (drive->removable && drive->usage == 1) {
                ide_task_t args;
                memset(&args, 0, sizeof(ide_task_t));
                args.tfRegister[IDE_COMMAND_OFFSET] = WIN_DOORLOCK;
                args.command_type = IDE_DRIVE_TASK_NO_DATA;
                args.handler      = &task_no_data_intr;
                check_disk_change(inode->i_bdev);
                /*
                 * Ignore the return code from door_lock,
                 * since the open() has already succeeded,
                 * and the door_lock is irrelevant at this point.
                 */
                if (drive->doorlocking && ide_raw_taskfile(drive, &args, NULL))
                        drive->doorlocking = 0;
        }
        return 0;
}


Here, if drive->usage=0 initially and two process concurrently executes 
drive->usage++, then drive->usage will become 2.  Both of them will
think that drive is already initialized. Something similar can happen
in case of release.
                      I think a semaphore need to be added in
ide_drive_t structure and method should be modified as

static int idedisk_open(struct inode *inode, struct file *filp)
{
        ide_drive_t *drive = inode->i_bdev->bd_disk->private_data;
        if(down_interruptible(&drive->sem)){
                    /*error handling code*/
        } 
        drive->usage++;
        if (drive->removable && drive->usage == 1) {
                ide_task_t args;
                memset(&args, 0, sizeof(ide_task_t));
                args.tfRegister[IDE_COMMAND_OFFSET] = WIN_DOORLOCK;
                args.command_type = IDE_DRIVE_TASK_NO_DATA;
                args.handler      = &task_no_data_intr;
                check_disk_change(inode->i_bdev);
                /*
                 * Ignore the return code from door_lock,
                 * since the open() has already succeeded,
                 * and the door_lock is irrelevant at this point.
                 */
                if (drive->doorlocking && ide_raw_taskfile(drive, &args, NULL))
                        drive->doorlocking = 0;
        }
         up(&drive->sem);
        return 0;
}
Similar modifications are also required in release.

Please let me know if there is anything wrong in above code. Also let
me know to whom I should offer patches for this.

-- 
Regards,
Tushar
--------------------
It's not a problem, it's an opportunity for improvement. Lets improve.
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