ceph: gracefully avoid empty crush buckets

This avoids a divide by zero when the input and/or map are
malformed.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/fs/ceph/crush/mapper.c b/fs/ceph/crush/mapper.c
index 0f0730c..c268393 100644 (file)
--- a/fs/ceph/crush/mapper.c
+++ b/fs/ceph/crush/mapper.c
@@ -299,7 +299,7 @@ static int crush_choose(struct crush_map *map,
        struct crush_bucket *in = bucket;
        int r;
        int i;
-       int item;
+       int item = 0;
        int itemtype;
        int collide, reject;
        const int orig_tries = 5; /* attempts before we fall back to search */
@@ -316,6 +316,7 @@ static int crush_choose(struct crush_map *map,
                        /* choose through intervening buckets */
                        flocal = 0;
                        do {
+                               collide = 0;
                                retry_bucket = 0;
                                r = rep;
                                if (in->alg == CRUSH_BUCKET_UNIFORM) {
@@ -340,6 +341,10 @@ static int crush_choose(struct crush_map *map,
                                }
 
                                /* bucket choose */
+                               if (in->size == 0) {
+                                       reject = 1;
+                                       goto reject;
+                               }
                                if (flocal >= (in->size>>1) &&
                                    flocal > orig_tries)
                                        item = bucket_perm_choose(in, x, r);
@@ -363,7 +368,6 @@ static int crush_choose(struct crush_map *map,
                                }
 
                                /* collision? */
-                               collide = 0;
                                for (i = 0; i < outpos; i++) {
                                        if (out[i] == item) {
                                                collide = 1;
@@ -388,6 +392,7 @@ static int crush_choose(struct crush_map *map,
                                                reject = 0;
                                }
 
+reject:
                                if (reject || collide) {
                                        ftotal++;
                                        flocal++;