[usbip-devel] Fwd: BUG_ON missing transfer_buffer

[Ziemowit Z. <zie...@gm...>]

Hello again,

The cause for the bug described before is a buffer allocation in highmem,
without a mapping to kernel CPU space.  It should not happen in drivers
without DMA, but apparently occurs on some machines then and now.
(Using Suse 10.3 - Kernel 2.6.22)

The bad point is, we don't get the DMA address either, until we register
as DMA device. Therefore we can't map the buffer and this transfer is
lost - blocking the device.
When registering as DMA device, about half of the buffers are mapped
to highmem only - lowering the performance significantly.
This seems to be a storage driver problem, as I didn't see it in any other
context.

Has anyone seen this behavior before?
Is there any solution?
Is it fixed in newer kernel releases?

Thanks for any response!
                                    Ziemowit

---------- Forwarded message ----------
From: Ziemowit Zglinski <zie...@gm...>
Date: 2008/7/17
Subject: BUG_ON missing transfer_buffer
To: usb...@li...


Hello,

When using USBIP, I run against the line 534 in vhci_hcd.c:

    /* patch to usb_sg_init() is in 2.5.60 */
    BUG_ON (!urb->transfer_buffer && urb->transfer_buffer_length);

unfortunately my computer with Suse 10.3 runs regularly into this bug, when
using a pen-drive.
To be correct, this happens only on some PCs, and not on others!

Do you know any solution to this problem?

Best regards,
                        Ziemowit