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

[Ralph Campbell]

> From: Alistair Popple <apopple@xxxxxxxxxx>
> Sent: Thursday, February 25, 2021 11:19 PM
> To: linux-mm@xxxxxxxxx; nouveau@xxxxxxxxxxxxxxxxxxxxx;
> bskeggs@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx
> Cc: linux-doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; dri-
> devel@xxxxxxxxxxxxxxxxxxxxx; John Hubbard <jhubbard@xxxxxxxxxx>; Ralph
> Campbell <rcampbell@xxxxxxxxxx>; jglisse@xxxxxxxxxx; Jason Gunthorpe
> <jgg@xxxxxxxxxx>; hch@xxxxxxxxxxxxx; daniel@xxxxxxxx; Alistair Popple
> <apopple@xxxxxxxxxx>
> Subject: [PATCH v3 6/8] mm: Selftests for exclusive device memory
> 
> Adds some selftests for exclusive device memory.
> 
> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>

One minor nit below, but you can add
Tested-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>

> +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.