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Subject[PATCH] 2.5.54 fix ide-cd/ide-scsi oopses after module unload
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);
-
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