Re: 2.6.5-rc1 SCSI + st regressions (was: Linux 2.6.5-rc1)

[Kai Makisara]

On Tue, 16 Mar 2004, Matthias Andree wrote:

> On Tue, 16 Mar 2004, Matthew Wilcox wrote:
> 
> > On Tue, Mar 16, 2004 at 10:12:03PM +0100, Matthias Andree wrote:
> > > I have some SCSI troubles with 2.6.5-rc1 (from BK) that 2.6.4 didn't
> > > have.
> > > 
> > > Modprobe, loading the st driver, tries a NULL pointer dereference in
> > > kernel space and my 2nd tape drive isn't found: st1 is not shown. cat
> > > /proc/scsi/scsi (typed after the attempted zero page dereference) hangs
> > > in rwsem_down_read_failed with process state D.
> > 
> > I notice you're using the sym2 driver.  Could you try backing out the
> > changes made to it in 2.6.5-rc1, just to be sure we're looking at an st
> > problem, not a sym2 problem?
> 
I was able to reproduce this with the scsi_debug driver (you can use it 
for simple tape tests by changing TYPE_DISK to TYPE_TAPE). Reverting the 
patch:

# ChangeSet
#   2004/03/12 16:22:36-08:00 greg@xxxxxxxxx 
#   remove cdev_set_name completely as it is not needed.

(and editing drivers/char/tty_io.c to get the kernel to compile) solved 
the problem for me. st.c is using the name put into kobj.name in making 
the class file names. I will make a patch that removes this dependency.

While looking at this problem, I noticed that the naming changes already 
committed to BK had disappeared. Looking at st.c history revealed that the 
following change had been committed (sorry for wrapping) by greg@xxxxxxxxx 
46 hours ago:

--- 1.80+1.79.1.2/drivers/scsi/st.c	Wed Mar 17 12:25:28 2004
+++ 1.81/drivers/scsi/st.c	Wed Mar 17 12:25:28 2004
@@ -3896,11 +3896,6 @@
 				       dev_num);
 				goto out_free_tape;
 			}
-			/* Make sure that the minor numbers corresponding 
to the four
-			   first modes always get the same names */
-			i = mode << (4 - ST_NBR_MODE_BITS);
-			snprintf(cdev->kobj.name, KOBJ_NAME_LEN, "%s%s%s", 
j ? "n" : "",
-				 disk->disk_name, st_formats[i]);
 			cdev->owner = THIS_MODULE;
 			cdev->ops = &st_fops;

The change comment was "merge" and it resulted in st.c version 1.81. (I am 
not using Bitkeeper but trying to extract information from bkbits.net.)

	Kai

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