Mikael Pettersson posted the following to the linux-kernel
mailing list. His patch includes a fix that Willem Riede
spotted as well (no driver_unregister() in ide.c). Willem
also had other changes in ide-scsi.c which are still pending.
See attached file.


Doug Gilbert


Mikael Pettersson wrote on lkml:
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

In 2.5 (the bug's been there since 2.5.42), rmmod:ing a
modular IDE subdriver like ide-cd or ide-scsi and then
rebooting causes an oops in device_shutdown(). This is because
the IDE layer doesn't reset the drive->gendev.driver pointer
that it previously set up to point to data structures in the
subdriver module. device_shutdown() sees a non-NULL ->driver,
dereferences it, and oopses.

The patch below for 2.5.54 fixes two generic bugs related to
unloading of modular IDE subdrivers, and one specific to ide-scsi:

1. ata_attach() needs to set drive->gendev.driver = NULL
    when no specific driver claims the drive. This prevents a
    drive previously owned by a subdriver module from keeping
    its ->gendev.driver pointing into that module.

2. ide_unregister_driver() needs to unregister &driver->gen_driver;
    this is to balance the corresponding register call in
    ide_register_driver(). [This part of the patch is originally
    by Patrick Mochel.]

3. ide-scsi.c abuses ide_driver_t's busy field as a counter
    while the field in fact is a single-bit boolean. This causes
    the busyness of the driver to be incorrect while the driver
    is active. (From my recent patch for 2.4.20-ac2/2.4.21-pre2.)

With these three fixes modular ide-cd and ide-scsi work quite
reliably for me in 2.5.54.

/Mikael

diff -ruN linux-2.5.54/drivers/ide/ide.c 
linux-2.5.54.ide-fixes/drivers/ide/ide.c
--- linux-2.5.54/drivers/ide/ide.c	2003-01-02 14:27:55.000000000 +0100
+++ linux-2.5.54.ide-fixes/drivers/ide/ide.c	2003-01-04 
02:34:02.000000000 +0100
@@ -1346,6 +1346,7 @@
  	spin_unlock(&drivers_lock);
  	spin_lock(&drives_lock);
  	list_add_tail(&drive->list, &ata_unused);
+	drive->gendev.driver = NULL;
  	spin_unlock(&drives_lock);
  	return 1;
  }
@@ -2308,6 +2309,8 @@
  	list_del(&driver->drivers);
  	spin_unlock(&drivers_lock);

+	driver_unregister(&driver->gen_driver);
+
  	while(!list_empty(&driver->drives)) {
  		drive = list_entry(driver->drives.next, ide_drive_t, list);
  		if (driver->cleanup(drive)) {
diff -ruN linux-2.5.54/drivers/scsi/ide-scsi.c 
linux-2.5.54.ide-fixes/drivers/scsi/ide-scsi.c
--- linux-2.5.54/drivers/scsi/ide-scsi.c	2002-12-24 13:53:50.000000000 +0100
+++ linux-2.5.54.ide-fixes/drivers/scsi/ide-scsi.c	2003-01-04 
02:34:02.000000000 +0100
@@ -590,6 +590,7 @@
  	set_bit(IDESCSI_LOG_CMD, &scsi->log);
  #endif /* IDESCSI_DEBUG_LOG */
  	idescsi_add_settings(drive);
+	DRIVER(drive)->busy--;
  }

  static int idescsi_cleanup (ide_drive_t *drive)
@@ -995,7 +996,7 @@
  	for (id = 0; id < MAX_HWIFS * MAX_DRIVES; id++) {
  		drive = idescsi_drives[id];
  		if (drive)
-			DRIVER(drive)->busy--;
+			DRIVER(drive)->busy = 0;
  	}
  	scsi_unregister   (idescsi_host);
  	device_unregister(&idescsi_primary);
-
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^