[PATCH 4/9] cgroups: add res counter common ancestor searching

Dwight Engen dwight.engen at oracle.com
Thu Dec 12 21:35:13 UTC 2013


From: "Kirill A. Shutemov" <kirill at shutemov.name>

Add a new API to find the common ancestor between two resource counters.
This includes the passed resource counter themselves.

Signed-off-by: Kirill A. Shutemov <kirill at shutemov.name>
Signed-off-by: Frederic Weisbecker <fweisbec at gmail.com>
Cc: Li Zefan <lizf at cn.fujitsu.com>
Cc: Paul Menage <paul at paulmenage.org>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: Aditya Kali <adityakali at google.com>
Cc: Oleg Nesterov <oleg at redhat.com>
Cc: Tim Hockin <thockin at hockin.org>
Cc: Tejun Heo <htejun at gmail.com>
Cc: Containers <containers at lists.linux-foundation.org>
Cc: Glauber Costa <glommer at gmail.com>
Cc: Cgroups <cgroups at vger.kernel.org>
Cc: Daniel J Walsh <dwalsh at redhat.com>
Cc: "Daniel P. Berrange" <berrange at redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
Cc: Max Kellermann <mk at cm4all.com>
Cc: Mandeep Singh Baines <msb at chromium.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---
 include/linux/res_counter.h |  4 ++++
 kernel/res_counter.c        | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index 9721fde..4addc7a 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -144,6 +144,10 @@ u64 res_counter_uncharge(struct res_counter *counter, unsigned long val);
 u64 res_counter_uncharge_until(struct res_counter *counter,
 			       struct res_counter *top,
 			       unsigned long val);
+
+struct res_counter *res_counter_common_ancestor(struct res_counter *l,
+						struct res_counter *r);
+
 /**
  * res_counter_margin - calculate chargeable space of a counter
  * @cnt: the counter
diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index dadb16e..8c16224 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -132,6 +132,40 @@ u64 res_counter_uncharge(struct res_counter *counter, unsigned long val)
 	return res_counter_uncharge_until(counter, NULL, val);
 }
 
+/*
+ * Walk through r1 and r2 parents and try to find the closest common one
+ * between both. If none is found, it returns NULL.
+ */
+struct res_counter *
+res_counter_common_ancestor(struct res_counter *r1, struct res_counter *r2)
+{
+	struct res_counter *iter;
+	int r1_depth = 0, r2_depth = 0;
+
+	for (iter = r1; iter; iter = iter->parent)
+		r1_depth++;
+
+	for (iter = r2; iter; iter = iter->parent)
+		r2_depth++;
+
+	while (r1_depth > r2_depth) {
+		r1 = r1->parent;
+		r1_depth--;
+	}
+
+	while (r2_depth > r1_depth) {
+		r2 = r2->parent;
+		r2_depth--;
+	}
+
+	while (r1 != r2) {
+		r1 = r1->parent;
+		r2 = r2->parent;
+	}
+
+	return r1;
+}
+
 static inline unsigned long long *
 res_counter_member(struct res_counter *counter, int member)
 {
-- 
1.8.3.1



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