Re: [PATCH v3 1/3] mm/hmm: make full use of walk_page_range()

From: Jason Gunthorpe <jgg@mellanox.com>
To: Ralph Campbell <rcampbell@nvidia.com>,
	Jerome Glisse <jglisse@redhat.com>,
	Christoph Hellwig <hch@lst.de>
Cc: John Hubbard <jhubbard@nvidia.com>,
	"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 1/3] mm/hmm: make full use of walk_page_range()
Date: Tue, 29 Oct 2019 17:40:39 +0000	[thread overview]
Message-ID: <20191029174036.GR22766@mellanox.com> (raw)
In-Reply-To: <20191023195515.13168-2-rcampbell@nvidia.com>

On Wed, Oct 23, 2019 at 12:55:13PM -0700, Ralph Campbell wrote:
> hmm_range_fault() calls find_vma() and walk_page_range() in a loop.
> This is unnecessary duplication since walk_page_range() calls find_vma()
> in a loop already.
> Simplify hmm_range_fault() by defining a walk_test() callback function
> to filter unhandled vmas.
> This also fixes a bug where hmm_range_fault() was not checking
> start >= vma->vm_start before checking vma->vm_flags so hmm_range_fault()
> could return an error based on the wrong vma for the requested range.
> It also fixes a bug when the vma has no read access and the caller did
> not request a fault, there shouldn't be any error return code.
> 
> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Cc: Jason Gunthorpe <jgg@mellanox.com>
> Cc: Christoph Hellwig <hch@lst.de>
>  mm/hmm.c | 126 +++++++++++++++++++++++++++----------------------------
>  1 file changed, 63 insertions(+), 63 deletions(-)

This is looking OK, can we get an ack from Jerome? Christoph?

I recall my first worry was that walk->vma could now be null, as
ops->pte_hole is set. But it looks like that is all handled now?

Thanks,
Jason