[3.16.y-ckt stable] Patch "crush: ensuring at most num-rep osds are selected" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    crush: ensuring at most num-rep osds are selected

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 5e8a1326f728be726566b7eed73f210f61923ec1 Mon Sep 17 00:00:00 2001
From: Ilya Dryomov <idryomov at gmail.com>
Date: Tue, 14 Apr 2015 16:04:23 +0300
Subject: crush: ensuring at most num-rep osds are selected

commit 45002267e8d2699bf9b022315bee3dd13b044843 upstream.

Crush temporary buffers are allocated as per replica size configured
by the user.  When there are more final osds (to be selected as per
rule) than the replicas, buffer overlaps and it causes crash.  Now, it
ensures that at most num-rep osds are selected even if more number of
osds are allowed by the rule.

Reflects ceph.git commits 6b4d1aa99718e3b367496326c1e64551330fabc0,
                          234b066ba04976783d15ff2abc3e81b6cc06fb10.

Signed-off-by: Ilya Dryomov <idryomov at gmail.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ceph/crush/mapper.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/ceph/crush/mapper.c b/net/ceph/crush/mapper.c
index a1ef53c04415..b1f2d1f44d37 100644
--- a/net/ceph/crush/mapper.c
+++ b/net/ceph/crush/mapper.c
@@ -290,6 +290,7 @@ static int is_out(const struct crush_map *map,
  * @type: the type of item to choose
  * @out: pointer to output vector
  * @outpos: our position in that vector
+ * @out_size: size of the out vector
  * @tries: number of attempts to make
  * @recurse_tries: number of attempts to have recursive chooseleaf make
  * @local_retries: localized retries
@@ -304,6 +305,7 @@ static int crush_choose_firstn(const struct crush_map *map,
 			       const __u32 *weight, int weight_max,
 			       int x, int numrep, int type,
 			       int *out, int outpos,
+			       int out_size,
 			       unsigned int tries,
 			       unsigned int recurse_tries,
 			       unsigned int local_retries,
@@ -322,6 +324,7 @@ static int crush_choose_firstn(const struct crush_map *map,
 	int item = 0;
 	int itemtype;
 	int collide, reject;
+	int count = out_size;

 	dprintk("CHOOSE%s bucket %d x %d outpos %d numrep %d tries %d recurse_tries %d local_retries %d local_fallback_retries %d parent_r %d\n",
 		recurse_to_leaf ? "_LEAF" : "",
@@ -329,7 +332,7 @@ static int crush_choose_firstn(const struct crush_map *map,
 		tries, recurse_tries, local_retries, local_fallback_retries,
 		parent_r);

-	for (rep = outpos; rep < numrep; rep++) {
+	for (rep = outpos; rep < numrep && count > 0 ; rep++) {
 		/* keep trying until we get a non-out, non-colliding item */
 		ftotal = 0;
 		skip_rep = 0;
@@ -403,7 +406,7 @@ static int crush_choose_firstn(const struct crush_map *map,
 							 map->buckets[-1-item],
 							 weight, weight_max,
 							 x, outpos+1, 0,
-							 out2, outpos,
+							 out2, outpos, count,
 							 recurse_tries, 0,
 							 local_retries,
 							 local_fallback_retries,
@@ -463,6 +466,7 @@ reject:
 		dprintk("CHOOSE got %d\n", item);
 		out[outpos] = item;
 		outpos++;
+		count--;
 	}

 	dprintk("CHOOSE returns %d\n", outpos);
@@ -654,6 +658,7 @@ int crush_do_rule(const struct crush_map *map,
 	__u32 step;
 	int i, j;
 	int numrep;
+	int out_size;
 	/*
 	 * the original choose_total_tries value was off by one (it
 	 * counted "retries" and not "tries").  add one.
@@ -761,6 +766,7 @@ int crush_do_rule(const struct crush_map *map,
 						x, numrep,
 						curstep->arg2,
 						o+osize, j,
+						result_max-osize,
 						choose_tries,
 						recurse_tries,
 						choose_local_retries,
@@ -770,11 +776,13 @@ int crush_do_rule(const struct crush_map *map,
 						c+osize,
 						0);
 				} else {
+					out_size = ((numrep < (result_max-osize)) ?
+                                                    numrep : (result_max-osize));
 					crush_choose_indep(
 						map,
 						map->buckets[-1-w[i]],
 						weight, weight_max,
-						x, numrep, numrep,
+						x, out_size, numrep,
 						curstep->arg2,
 						o+osize, j,
 						choose_tries,
@@ -783,7 +791,7 @@ int crush_do_rule(const struct crush_map *map,
 						recurse_to_leaf,
 						c+osize,
 						0);
-					osize += numrep;
+					osize += out_size;
 				}
 			}