On Fri, 26 Jan 2007, Andrew Morton wrote:
> On Wed, 24 Jan 2007 18:37:15 -0500 (EST)
> Justin Piszcz <[email protected]> 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 [email protected]
> > > 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))
> _
>
>
The RAID5 bug may be hard to trigger, I have only made it happen once so
far (but only tried it once, don't like locking up the raid :)), I will
re-run the test after applying this patch.
Justin.
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