Re: [RFC PATCH v2 for 4.15 08/14] Provide cpu_opv system call

----- On Nov 6, 2017, at 9:07 PM, Boqun Feng boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:

On Mon, Nov 06, 2017 at 03:56:38PM -0500, Mathieu Desnoyers wrote:
[...]

quoted

+static int cpu_op_pin_pages(unsigned long addr, unsigned long len,
+		struct page ***pinned_pages_ptr, size_t *nr_pinned,
+		int write)
+{
+	struct page *pages[2];
+	int ret, nr_pages;
+
+	if (!len)
+		return 0;
+	nr_pages = cpu_op_range_nr_pages(addr, len);
+	BUG_ON(nr_pages > 2);
+	if (*nr_pinned + nr_pages > NR_PINNED_PAGES_ON_STACK) {

Is this a bug? Seems you will kzalloc() every time if *nr_pinned is
bigger than NR_PINNED_PAGES_ON_STACK, which will result in memory
leaking.

I think the logic here is complex enough for us to introduce a
structure, like:

struct cpu_opv_page_pinner {
	int nr_pinned;
	bool is_kmalloc;
	struct page **pinned_pages;
};

Thoughts?

Good catch !

How about the attached diff ? I'll fold it into the rseq/dev tree.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com