On Fri, 22 Jun 2007, Marc Pignat wrote: > from: Marc Pignat <[EMAIL PROTECTED]> > > kunmap must be called on the pointer returned by kmap.
Not necessarily: an offset within the same page is acceptable. > > Signed-off-by: Marc Pignat <[EMAIL PROTECTED]> > > --- > > N.B: This is the same patch as yesterday, with proper Signed-off-by and more > comments. > > The buffer variable is used this way: > buffer = kmap_atomic(sg->page, KM_BIO_SRC_IRQ) + sg->offset; > So we can't do > kunmap_atomic(buffer, KM_BIO_SRC_IRQ); > we must do > kunmap_atomic(buffer - sg->offset, KM_BIO_SRC_IRQ); > > Strangely this misuse showed no problem using CONFIG_SLAB, but oops using > CONFIG_SLUB, (lkml ''Oops in a driver while using SLUB as a SLAB allocator"). Aren't you just guessing there? Those kunmap_atomics in at91_mci.c may look wrong to you, but they're not incorrect (so long as sg->offset falls within the page, as it must do here to make sense of the page). Especially not on ARM, where kunmap_atomic actually has no interest in the argument passed. And the oops was in the flush_dcache_page. If you actually reproduced Nicolas' problem on ARM, and verified that your patch then fixes it, please let us know: that will be remarkably interesting. I believe I posted the correct fix last night (or at least a safe fix for now: Christoph Lameter may prefer to undo it and change ARM's dma_mapping at leisure later), checking PageSlab in page_mapping; and Linus has already put that one into his git tree. But it would be good to hear from Nicolas whether that indeed fixes his oops: I couldn't actually try my patch on ARM either. Hugh > > Regards > > Marc > > --- drivers/mmc/host/at91_mci.c-2.6.22-rc5.orig 2007-06-21 > 16:27:31.000000000 +0200 > +++ drivers/mmc/host/at91_mci.c-2.6.22-rc5 2007-06-21 16:42:48.000000000 > +0200 > @@ -164,7 +164,7 @@ static inline void at91mci_sg_to_dma(str > else > memcpy(dmabuf, sgbuffer, amount); > > - kunmap_atomic(sgbuffer, KM_BIO_SRC_IRQ); > + kunmap_atomic(sgbuffer - sg->offset, KM_BIO_SRC_IRQ); > > if (size == 0) > break; > @@ -293,7 +293,7 @@ static void at91mci_post_dma_read(struct > buffer[index] = swab32(buffer[index]); > } > > - kunmap_atomic(buffer, KM_BIO_SRC_IRQ); > + kunmap_atomic(buffer - sg->offset, KM_BIO_SRC_IRQ); > flush_dcache_page(sg->page); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
