On Mon, 31 Jan 2011 14:41:31 -0800
Andrew Morton [off-list ref] wrote:

On Mon, 31 Jan 2011 15:03:54 +0100
Johannes Weiner [off-list ref] wrote:

quoted

+static inline bool res_counter_check_margin(struct res_counter *cnt,
+					    unsigned long bytes)
+{
+	bool ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cnt->lock, flags);
+	ret = cnt->limit - cnt->usage >= bytes;
+	spin_unlock_irqrestore(&cnt->lock, flags);
+	return ret;
+}
+
 static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
 {
 	bool ret;

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 73ea323..c28072f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -1111,6 +1111,15 @@ static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem)
 	return false;
 }
 
+static bool mem_cgroup_check_margin(struct mem_cgroup *mem, unsigned long bytes)
+{
+	if (!res_counter_check_margin(&mem->res, bytes))
+		return false;
+	if (do_swap_account && !res_counter_check_margin(&mem->memsw, bytes))
+		return false;
+	return true;
+}

argh.

If you ever have a function with the string "check" in its name, it's a
good sign that you did something wrong.

Check what?  Against what?  Returning what?

mem_cgroup_check_under_limit() isn't toooo bad - the name tells you
what's being checked and tells you what to expect the return value to
mean.

But "res_counter_check_margin" and "mem_cgroup_check_margin" are just
awful.  Something like

	bool res_counter_may_charge(counter, bytes)

would be much clearer.

If we really want to stick with the "check" names (perhaps as an ironic
reference to res_counter's past mistakes) then please at least document
the sorry things?

Ah, I ack the concept of patch.

Acked-by: KAMEZAWA Hiroyuki <redacted>

Johannes, could you change name ? I'm sorry.



 

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