On Mon, Jan 04, 2016 at 09:28:52AM -0800, Dan Williams wrote: > On Sun, Jan 3, 2016 at 5:33 PM, NeilBrown <neilb@xxxxxxxx> wrote: > > On Mon, Dec 28 2015, Stanislav Samsonov wrote: > > > >> On 24 December 2015 at 00:46, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > >>> > >>> On Wed, Dec 23, 2015 at 2:39 PM, NeilBrown <neilb@xxxxxxxx> wrote: > >>> > On Thu, Dec 24 2015, Dan Williams wrote: > >>> >>> Changing the GFP_NOIO to GFP_ATOMIC in all the calls to > >>> >>> dmaengine_get_unmap_data() in crypto/async_tx/ would probably fix the > >>> >>> issue... or make it crash even worse :-) > >>> >>> > >>> >>> Dan: do you have any wisdom here? The xor is using the percpu data in > >>> >>> raid5, so it cannot be sleep, but GFP_NOIO allows sleep. > >>> >>> Does the code handle failure to get_unmap_data() safely? It looks like > >>> >>> it probably does. > >>> >> > >>> >> Those GFP_NOIO should move to GFP_NOWAIT. We don't want GFP_ATOMIC > >>> >> allocations to consume emergency reserves for a performance > >>> >> optimization. Longer term async_tx needs to be merged into md > >>> >> directly as we can allocate this unmap data statically per-stripe > >>> >> rather than per request. This asyntc_tx re-write has been on the todo > >>> >> list for years, but never seems to make it to the top. > >>> > > >>> > So the following maybe? > >>> > If I could get an acked-by from you Dan, and a Tested-by: from you > >>> > Slava, I'll submit upstream. > >>> > > >>> > Thanks, > >>> > NeilBrown > >>> > > >>> > From: NeilBrown <neilb@xxxxxxxx> > >>> > Date: Thu, 24 Dec 2015 09:35:18 +1100 > >>> > Subject: [PATCH] async_tx: use GFP_NOWAIT rather than GFP_IO > >>> > > >>> > These async_XX functions are called from md/raid5 in an atomic > >>> > section, between get_cpu() and put_cpu(), so they must not sleep. > >>> > So use GFP_NOWAIT rather than GFP_IO. > >>> > > >>> > Dan Williams writes: Longer term async_tx needs to be merged into md > >>> > directly as we can allocate this unmap data statically per-stripe > >>> > rather than per request. > >>> > > >>> > Reported-by: Stanislav Samsonov <slava@xxxxxxxxxxxxxxxxx> > >>> > Signed-off-by: NeilBrown <neilb@xxxxxxxx> > >>> > >>> Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx> > >> > >> Tested-by: Slava Samsonov <slava@xxxxxxxxxxxxxxxxx> > > > > Thanks. > > > > I guess this was problem was introduced by > > Commit: 7476bd79fc01 ("async_pq: convert to dmaengine_unmap_data") > > in 3.13. > > Yes. > > > Do we think it deserves to go to -stable? > > I think so, yes. > > > (I just realised that this is really Dan's code more than mine, > > so why am I submitting it ??? > > True! I was grateful for your offer, but I should have taken over > coordination... > > > But we are here now so it may as well go > > in through the md tree.) > > That or Vinod is maintaining drivers/dma/ these days (added Cc's). I can queue it up, pls send me the patch with ACKs. Looks like this might be 4.4 material, I am finalizing that in next day or so :) -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html