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DateSun, 8 Mar 1998 23:58:20 -0500 (EST)
FromEric Youngdale <>
SubjectRe: Important: fs corruption with 2.0.33 and removable media
	Ahh, I think I see the problem.  Never mind my previous response.
Please try the enclosed (and completely untested) patch.  I believe that
it will correct the problem provided that I have correctly understood what
the problem is.

-Eric


"The world was a library, and its books were the stones, leaves,
 brooks, grass, and the birds of the earth.   We learned to do what only
 a student of nature ever learns, and that was to feel beauty."
			Chief Luther Standing Bear - Teton Sioux
On Tue, 3 Mar 1998, Richard Waltham wrote:

Index: sg.c
===================================================================
RCS file: /mnt/ide/home/eric/CVSROOT/linux/drivers/scsi/sg.c,v
retrieving revision 1.5
diff -c -r1.5 sg.c
*** sg.c	1997/12/08 01:15:56	1.5
--- sg.c	1998/03/09 04:00:59
***************
*** 350,355 ****
--- 350,367 ----
        break;
      }
+     if (driver_byte(result) != 0
+         && (SCpnt->sense_buffer[0] & 0x7f) == 0x70
+         && (SCpnt->sense_buffer[2] & 0xf) == UNIT_ATTENTION
+         && device->removable)
+       {
+         /* 
+          * detected disc change.  Set the bit - this may be used if there
+          * are filesystems using this device.
+          */
+         device->changed = 1;
+       }
+     
      /*
       * Now wake up the process that is waiting for the
       * result.
> Wolfram@informatik.uni-bonn.de wrote:
> > 
> > There is a very disastrous bug in 2.0.33 (untested with 2.1.x):
> > The disc change detection with removable media is not 100% working !
> > This has a destroying effect if your computer has enough RAM for caching.
> > [tested... :-(((( ]
> > 
> > Please test the following with your hardware: (reproduce able for me)
> > -mount the media and unmount it
> > -eject the media
> > -insert another media
> > -wait ~ 30 min. without doing anything at your computer (important !)
> > -mount this media (better mount it ro for safety !)
> > -no disc change detection.... (look at the kernel logs)
> > 
> > It looks like the disc change has been forgotten in these 30 min.
> > The disc change detection works normal if the change and mount happens within
> > less time.
> > 
> > The hardware: Fujitsu M2512A2 (230MB MO Drive & 230MB Media)
> >               ncr53c825 SCSI interface (with Gerard Roudier's driver)
> > 
> > 
> > Is this reproduce able by other people ?
> > 
> > Is there any possibility to fix this bug inside the kernel ?
> > E.g. test every minute for disc change detection ?
> > 
> 
> No problem here - but I'm not using an M2512A. Using an Iomega jaz shows no
> problems trying the above. Also using ncr53c8xx driver;)
> 
> Disk change is dependent on the drive reporting that the media has changed
> when it gets a SCSI command to do something. Its not something that the
> kernel keeps a track of.
> 
> Is your drive set to automatically spin down? I have tried one of these
> drives (a really old one) on this machine but cannot remember if it's always
> set to automatically spin down or whether it is set by one of the switches.
> 
> Could this be a bug in the drive firmware? eg remove media, load new, let it
> sit for sometime - maybe drive spins down and forgets disk change - mount
> new media, spins up and no disk change notification.
> 
> This really sounds like a drive problem even if it is not set to spin down.
> It is the drives job to say the media has changed.
> 
> Bye for now
> Richard
> 
> -- 
>  Richard Waltham   |               Work: richard@digtalinterface.demon.co.uk
>    At home in      |               Home:       dormouse@farsrobt.demon.co.uk
>  Southampton UK    |                              100421.1276@compuserve.com
> 
> -
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