On Mon, 19 Nov 2012 18:23:57 -0800 Dan Williams <djbw@xxxxxx> wrote:
> On Tue, 2012-11-20 at 09:18 +1100, NeilBrown wrote:
> > On Mon, 19 Nov 2012 05:22:25 +0000 Dan Williams <djbw@xxxxxx> wrote:
> >
> > >
> > >
> > > On 11/18/12 5:06 PM, "NeilBrown" <neilb@xxxxxxx> 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.
Thanks. Following is now in my for-next branch.
NeilBrown
From e25a8de38d6584ffd042dbef3a5a8eb518b8813b Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Tue, 20 Nov 2012 14:11:15 +1100
Subject: [PATCH] md/raid5: use async_tx_quiesce() instead of open-coding it.
handle_stripe_expansion contains:
if (tx) {
async_tx_ack(tx);
dma_wait_for_async_tx(tx);
}
which is very similar to the body of async_tx_quiesce(),
except that the later handles an error from dma_wait_for_async_tx()
(admittedly by panicing, but that decision belongs in the dma
code, not the md code).
So just us async_tx_quiesce().
Acked-by: Dan Williams <djbw@xxxxxx>
Reported-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
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);
}
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