Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-27 Thread Logan Gunthorpe
On 27/04/17 12:53 AM, Christoph Hellwig wrote: > I think you'll need to follow the existing kmap semantics and never > fail the iomem version either. Otherwise you'll have a special case > that's almost never used that has a different error path. > > Again, wrong way. Suddenly making things

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-27 Thread Logan Gunthorpe
On 27/04/17 09:27 AM, Jason Gunthorpe wrote: > On Thu, Apr 27, 2017 at 08:53:38AM +0200, Christoph Hellwig wrote: > How about first switching as many call sites as possible to use > sg_copy_X_buffer instead of kmap? Yeah, I could look at doing that first. One problem is we might get more Naks

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-27 Thread Jason Gunthorpe
On Thu, Apr 27, 2017 at 08:53:38AM +0200, Christoph Hellwig wrote: > > The main difficulty we > > have now is that neither of those functions are expected to fail and we > > need them to be able to in cases where the page doesn't map to system > > RAM. This patch series is trying to address it

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-27 Thread Christoph Hellwig
On Wed, Apr 26, 2017 at 12:11:33PM -0600, Logan Gunthorpe wrote: > Ok, well for starters I think you are mistaken about kmap being able to > fail. I'm having a hard time finding many users of that function that > bother to check for an error when calling it. A quick audit of the arch code shows

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-27 Thread Logan Gunthorpe
On 26/04/17 01:44 AM, Christoph Hellwig wrote: > I think we'll at least need a draft of those to make sense of these > patches. Otherwise they just look very clumsy. Ok, what follows is a draft patch attempting to show where I'm thinking of going with this. Obviously it will not compile because

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-26 Thread Logan Gunthorpe
On 26/04/17 02:59 AM, wrote: > Good to know that somebody is working on this. Those problems troubled > us as well. Thanks Christian. It's a daunting problem and a there's a lot of work to do before we will ever be where we need to be so any help, even an ack, is greatly appreciated. Logan

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-26 Thread Logan Gunthorpe
On 26/04/17 01:44 AM, Christoph Hellwig wrote: > I think we'll at least need a draft of those to make sense of these > patches. Otherwise they just look very clumsy. Ok, I'll work up a draft proposal and send it in a couple days. But without a lot of cleanup such as this series it's not going

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-26 Thread Christoph Hellwig
On Tue, Apr 25, 2017 at 12:20:48PM -0600, Logan Gunthorpe wrote: > This patch introduces functions which kmap the pages inside an sgl. > These functions replace a common pattern of kmap(sg_page(sg)) that is > used in more than 50 places within the kernel. > > The motivation for this work is to

Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-26 Thread Christian König
Am 25.04.2017 um 20:20 schrieb Logan Gunthorpe: This patch introduces functions which kmap the pages inside an sgl. These functions replace a common pattern of kmap(sg_page(sg)) that is used in more than 50 places within the kernel. The motivation for this work is to eventually safely support

[PATCH v2 01/21] scatterlist: Introduce sg_map helper functions

2017-04-25 Thread Logan Gunthorpe
This patch introduces functions which kmap the pages inside an sgl. These functions replace a common pattern of kmap(sg_page(sg)) that is used in more than 50 places within the kernel. The motivation for this work is to eventually safely support sgls that contain io memory. In order for that to