Re: [PATCH v3 6/8] mm: Selftests for exclusive device memory

[Alistair Popple <apopple@nvidia.com>]

On Tuesday, 2 March 2021 10:14:56 AM AEDT Ralph Campbell wrote:
> > From: Alistair Popple <apopple@nvidia.com>
> > Sent: Thursday, February 25, 2021 11:19 PM
> > To: linux-mm@kvack.org; nouveau@lists.freedesktop.org;
> > bskeggs@redhat.com; akpm@linux-foundation.org
> > Cc: linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; dri-
> > devel@lists.freedesktop.org; John Hubbard <jhubbard@nvidia.com>; Ralph
> > Campbell <rcampbell@nvidia.com>; jglisse@redhat.com; Jason Gunthorpe
> > <jgg@nvidia.com>; hch@infradead.org; daniel@ffwll.ch; Alistair Popple
> > <apopple@nvidia.com>
> > Subject: [PATCH v3 6/8] mm: Selftests for exclusive device memory
> > 
> > Adds some selftests for exclusive device memory.
> > 
> > Signed-off-by: Alistair Popple <apopple@nvidia.com>
> 
> One minor nit below, but you can add

Thanks Ralph. Will fix that.

> Tested-by: Ralph Campbell <rcampbell@nvidia.com>
> Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
> 
> > +static int dmirror_exclusive(struct dmirror *dmirror,
> > +			     struct hmm_dmirror_cmd *cmd)
> > +{
> > +	unsigned long start, end, addr;
> > +	unsigned long size = cmd->npages << PAGE_SHIFT;
> > +	struct mm_struct *mm = dmirror->notifier.mm;
> > +	struct page *pages[64];
> > +	struct dmirror_bounce bounce;
> > +	unsigned long next;
> > +	int ret;
> > +
> > +	start = cmd->addr;
> > +	end = start + size;
> > +	if (end < start)
> > +		return -EINVAL;
> > +
> > +	/* Since the mm is for the mirrored process, get a reference first. */
> > +	if (!mmget_not_zero(mm))
> > +		return -EINVAL;
> > +
> > +	mmap_read_lock(mm);
> > +	for (addr = start; addr < end; addr = next) {
> > +		int i, mapped;
> > +
> > +		if (end < addr + (64 << PAGE_SHIFT))
> > +			next = end;
> > +		else
> > +			next = addr + (64 << PAGE_SHIFT);
> 
> I suggest using ARRAY_SIZE(pages) instead of '64' to make the meaning clear.
> 
>