On Thu, Jun 18, 2020 at 11:37:51AM -0700, Matthew Wilcox wrote:

On Thu, Jun 18, 2020 at 08:23:33PM +0200, Uladzislau Rezki wrote:

quoted

quoted

+void vfree_bulk(size_t count, void **addrs)
+{
+	unsigned int i;
+
+	BUG_ON(in_nmi());
+	might_sleep_if(!in_interrupt());
+
+	for (i = 0; i < count; i++) {
+		void *addr = addrs[i];
+		kmemleak_free(addr);
+		if (addr)
+			__vfree(addr);
+	}
+}
+EXPORT_SYMBOL(vfree_bulk);
+

Can we just do addrs[i] all over the loop?

Also, we can just call vfree() instead that has all checking we
need: NMI, kmemleak, might_sleep.

Of course we _can_.  But would we want to?  This way, we only do these
checks once instead of once per pointer, which is rather the point
of batching.

Ahh, right. I briefly looked at it and missed that point. Right you
are we do not want the vfree() here!

I might actually go further and hoist the in_interrupt() check into
this function ...

Why do you need it? Just to inline below code:

<snip>
 if (unlikely(in_interrupt()))
  __vfree_deferred(addr);
 else
  __vunmap(addr, 1);
<snip>

and bypass the __vfree() call(that is not marked as inline one)?
I mean to inline above into  vfree_bulk().

I suspect the RCU code always runs in_interrupt()
and so we always call vfree_deferred().

No. We release the memory from workqueue context.

--
Vlad Rezki