Luck, Tony [tony.luck@xxxxxxxxx] wrote:
> Starting with the next-20100927 tag of linux-next I saw this error
> while booting ia64:
>
> Unable to handle kernel NULL pointer dereference (address 0000000000000020)
> usb-stor-scan[5915]: Oops 8813272891392 [1]
> Modules linked in: dm_mod usb_storage sg container button usbhid uhci_hcd ehci_hcd usbcore fan processor thermal thermal_sys
>
> Pid: 5915, CPU 0, comm: usb-stor-scan
> psr : 00001010085a6010 ifs : 8000000000000894 ip : [<a00000010012a630>] Not tainted (2.6.36-rc5-generic-smp-next-20100927)
> ip is at mempool_alloc+0x70/0x200
>
> The problem was that "page_pool" was NULL, but blk_queue_bounce()
> had decided to use it! The code in mm/bounce.c looks quite
> fragile here as there are several places where page_pool is used, but
> it is only initialized inside #ifdef CONFIG_HIGHMEM (which is not
> set on ia64).
>
> Reverting this patch so that the old rules for setting
> q->limits.bounce_pfn are used cures the immediate problem.
> But I think there must be some deeper issues involved.
>
> I think that reverting means that I take the fast exit
> from blk_queue_bounce():
>
> if (queue_bounce_pfn(q) >= blk_max_pfn)
> return;
Let me know if this fixes the problem. Thank you very much.
diff -r 1a48e21f1e50 drivers/scsi/scsi_lib.c
--- a/drivers/scsi/scsi_lib.c Fri Sep 24 09:44:52 2010 -0700
+++ b/drivers/scsi/scsi_lib.c Tue Sep 28 15:55:10 2010 -0700
@@ -1590,7 +1590,7 @@ static void scsi_request_fn(struct reque
u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
{
struct device *host_dev;
- u64 bounce_limit = 0xffffffff;
+ u64 bounce_limit = BLK_BOUNCE_HIGH;
if (shost->unchecked_isa_dma)
return BLK_BOUNCE_ISA;
--
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