Re: [Intel-gfx] [PATCH rdma-next v3 1/2] lib/scatterlist: Add support in dynamic allocation of SG table from pages

From: Jason Gunthorpe <jgg@nvidia.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: linux-rdma@vger.kernel.org, intel-gfx@lists.freedesktop.org,
	Roland Scheidegger <sroland@vmware.com>,
	dri-devel@lists.freedesktop.org,
	Maor Gottlieb <maorg@mellanox.com>,
	David Airlie <airlied@linux.ie>,
	Doug Ledford <dledford@redhat.com>,
	VMware Graphics <linux-graphics-maintainer@vmware.com>,
	Maor Gottlieb <maorg@nvidia.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [Intel-gfx] [PATCH rdma-next v3 1/2] lib/scatterlist: Add support in dynamic allocation of SG table from pages
Date: Fri, 25 Sep 2020 08:55:44 -0300	[thread overview]
Message-ID: <20200925115544.GY9475@nvidia.com> (raw)
In-Reply-To: <20200925071330.GA2280698@unreal>

On Fri, Sep 25, 2020 at 10:13:30AM +0300, Leon Romanovsky wrote:
> > > diff --git a/tools/testing/scatterlist/main.c b/tools/testing/scatterlist/main.c
> > > index 0a1464181226..4899359a31ac 100644
> > > +++ b/tools/testing/scatterlist/main.c
> > > @@ -55,14 +55,13 @@ int main(void)
> > >   	for (i = 0, test = tests; test->expected_segments; test++, i++) {
> > >   		struct page *pages[MAX_PAGES];
> > >   		struct sg_table st;
> > > -		int ret;
> > > +		struct scatterlist *sg;
> > >
> > >   		set_pages(pages, test->pfn, test->num_pages);
> > >
> > > -		ret = __sg_alloc_table_from_pages(&st, pages, test->num_pages,
> > > -						  0, test->size, test->max_seg,
> > > -						  GFP_KERNEL);
> > > -		assert(ret == test->alloc_ret);
> > > +		sg = __sg_alloc_table_from_pages(&st, pages, test->num_pages, 0,
> > > +				test->size, test->max_seg, NULL, 0, GFP_KERNEL);
> > > +		assert(PTR_ERR_OR_ZERO(sg) == test->alloc_ret);
> >
> > Some test coverage for relatively complex code would be very welcomed. Since
> > the testing framework is already there, even if it bit-rotted a bit, but
> > shouldn't be hard to fix.
> >
> > A few tests to check append/grow works as expected, in terms of how the end
> > table looks like given the initial state and some different page patterns
> > added to it. And both crossing and not crossing into sg chaining scenarios.
> 
> This function is basic for all RDMA devices and we are pretty confident
> that the old and new flows are tested thoroughly.

Well, since 0-day is reporting that __i915_gem_userptr_alloc_pages is
crashing on this, it probably does need some tests :\

Jason
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