Re: [PATCH] scsi: take module reference during async scan

[John Garry <john.garry@huawei.com>]

On 07/09/2020 22:32, Douglas Gilbert wrote:

Hi Doug,

>   # insmod scsi_debug.ko
> 
> Gave errors like this:
> 
> [  140.115244] debugfs: Directory 'sde' with parent 'block' already 
> present!

As an aside, I thought that this issue was fixed...

> [  140.376426] debugfs: Directory 'sde' with parent 'block' already 
> present!
> [  140.420613] sd 3:0:0:0: [sde] tag#40 access beyond end of device
> [  140.426655] blk_update_request: I/O error, dev sde, sector 15984 op 
> 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0
> [  140.437319] sd 3:0:0:0: [sde] tag#41 access beyond end of device
> [  140.443368] blk_update_request: I/O error, dev sde, sector 15984 op 
> 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> ...
> 
> Which wasn't the scsi_debug driver directly as it doesn't use debugfs. So
> I suspect something is rotten in the mid-level.
> 
> When I tried to replicate John's config I couldn't even boot my Ubuntu
> 20.04 based system (with a MKP kernel). Seemed to fail/lockup before any
> kernel prints came out to the serial port (yes, still useful), perhaps in
> initrd. I'm guessing another, non-SCSI module caused the lockup. So I
> gave up and turned off that config setting.

You can also try this hack locally (without enabling that config), if 
you like:

--->8---

--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -496,6 +496,12 @@ static int really_probe(struct device *dev, struct 
device_driver *drv)
         int local_trigger_count = atomic_read(&deferred_trigger_count);
         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
                            !drv->suppress_bind_attrs;

+       if (strcmp(drv->name, "sd") == 0)
+               test_remove = 1;
+       else if (strcmp(drv->name, "scsi_debug") == 0)
+               test_remove = 1;

---8<---

Cheers,
john