On Tue, 2012-11-20 at 09:18 +1100, NeilBrown wrote: > On Mon, 19 Nov 2012 05:22:25 +0000 Dan Williams <[email protected]> wrote: > > > > > > > On 11/18/12 5:06 PM, "NeilBrown" <[email protected]> wrote: > > > > > > > >Hi Dan, > > > could you comment on this please? Would it make sense to arrange for > > >errors > > > to propagate up? Or should we arrange to do a software-fallback in the > > >dma > > > engine is a problem? What sort of things can cause error here anyway? > > > > Propagating up is missing reliable "dma abort" operation. > > > > In these cases the engine failed to complete due to hardware hang / driver > > bug, or has hit a memory error (uncorrectable even with software > > fallback). This originally should have been using async_tx_quiesce() > > which also does the panic. > > > > The engines that I have worked with have either lacked support for > > aborting, or were otherwise unable to recover from a hardware hang. > > However, for engines that do support error recovery they should be able to > > hide the failure from the upper layers. > > > > So maybe I could: > > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index ac09fa4..ffbf0ca 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -3268,7 +3268,7 @@ static void handle_stripe_expansion(struct r5conf > *conf, struct stripe_head *sh) > /* done submitting copies, wait for them to complete */ > if (tx) { > async_tx_ack(tx); > - dma_wait_for_async_tx(tx); > + async_tx_quiesce(&tx); > } > } > > > > and then the panic would be somebody else's problem? > > I note that handle_stripe_expansion has: > > async_tx_ack(tx); > dma_wait_for_async_tx(tx); > > while async_tx_quiesce() has: > > if (dma_wait_for_async_tx(*tx) == DMA_ERROR) > panic("DMA_ERROR waiting for transaction\n"); > async_tx_ack(*tx); > > > i.e. the same two functions called in the reverse order. Is the order > important? Is handle_stripe_expansion wrong? Should the patch I apply > actually be: > > > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index ac09fa4..e51d903 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -3266,10 +3266,7 @@ static void handle_stripe_expansion(struct r5conf > *conf, struct stripe_head *sh) > > } > /* done submitting copies, wait for them to complete */ > - if (tx) { > - async_tx_ack(tx); > - dma_wait_for_async_tx(tx); > - } > + async_tx_quiesce(&tx); > } >
Yes, this one, handles it like the other cases of needing to do a synchronous wait and does not care if tx is NULL. -- Dan -- 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/
