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Re: Kernel 2.6.19.2 New RAID 5 Bug (oops when writing Samba -> RAID5)

To: Andrew Morton <akpm@xxxxxxxx>
Subject: Re: Kernel 2.6.19.2 New RAID 5 Bug (oops when writing Samba -> RAID5)
From: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Date: Fri, 26 Jan 2007 07:31:50 -0500 (EST)
Cc: Chuck Ebbert <cebbert@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, linux-raid@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, Neil Brown <neilb@xxxxxxx>
In-reply-to: <20070126012505.d8cb07f2.akpm@xxxxxxxx>
References: <Pine.LNX.4.64.0701200718290.29223@xxxxxxxxxxxxxxxx> <45B5261B.1050104@xxxxxxxxxx> <Pine.LNX.4.64.0701241836590.2930@xxxxxxxxxxxxxxxx> <20070126012505.d8cb07f2.akpm@xxxxxxxx>
Sender: xfs-bounce@xxxxxxxxxxx
Just re-ran the test 4-5 times, could not reproduce this one, but I'll 
keep running this kernel w/patch for a while and see if it happens again.

On Fri, 26 Jan 2007, Andrew Morton wrote:

> On Wed, 24 Jan 2007 18:37:15 -0500 (EST)
> Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote:
> 
> > > Without digging too deeply, I'd say you've hit the same bug Sami Farin and
> > > others
> > > have reported starting with 2.6.19: pages mapped with kmap_atomic() become
> > > unmapped
> > > during memcpy() or similar operations.  Try disabling preempt -- that 
> > > seems to
> > > be the
> > > common factor.
> > > 
> > > 
> > > -
> > > To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> > > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > 
> > > 
> > 
> > After I run some other tests, I am going to re-run this test and see if it 
> > OOPSes again with PREEMPT off.
> 
> Strange.  The below debug patch might catch it - please run with this
> applied.  
> 
> 
> --- a/arch/i386/mm/highmem.c~kmap_atomic-debugging
> +++ a/arch/i386/mm/highmem.c
> @@ -30,7 +30,43 @@ void *kmap_atomic(struct page *page, enu
>  {
>       enum fixed_addresses idx;
>       unsigned long vaddr;
> +     static unsigned warn_count = 10;
>  
> +     if (unlikely(warn_count == 0))
> +             goto skip;
> +
> +     if (unlikely(in_interrupt())) {
> +             if (in_irq()) {
> +                     if (type != KM_IRQ0 && type != KM_IRQ1 &&
> +                         type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
> +                         type != KM_BOUNCE_READ) {
> +                             WARN_ON(1);
> +                             warn_count--;
> +                     }
> +             } else if (!irqs_disabled()) {  /* softirq */
> +                     if (type != KM_IRQ0 && type != KM_IRQ1 &&
> +                         type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
> +                         type != KM_SKB_SUNRPC_DATA &&
> +                         type != KM_SKB_DATA_SOFTIRQ &&
> +                         type != KM_BOUNCE_READ) {
> +                             WARN_ON(1);
> +                             warn_count--;
> +                     }
> +             }
> +     }
> +
> +     if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ) {
> +             if (!irqs_disabled()) {
> +                     WARN_ON(1);
> +                     warn_count--;
> +             }
> +     } else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
> +             if (irq_count() == 0 && !irqs_disabled()) {
> +                     WARN_ON(1);
> +                     warn_count--;
> +             }
> +     }
> +skip:
>       /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
>       pagefault_disable();
>       if (!PageHighMem(page))
> _
> 


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