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authorIlya Dryomov <ilya.dryomov@inktank.com>2014-03-19 16:58:36 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-05-13 13:32:52 +0200
commite24b7822c7fea8d23d30baea8aabf96ec8522936 (patch)
tree4bd2bc8e42e6f0cfbb1a6319629c28193a962305
parent2d1871289ce4af1bdee5eb46992f0ad3e005a508 (diff)
downloadlwn-e24b7822c7fea8d23d30baea8aabf96ec8522936.tar.gz
lwn-e24b7822c7fea8d23d30baea8aabf96ec8522936.zip
crush: fix off-by-one errors in total_tries refactor
commit 48a163dbb517eba13643bf404a0d695c1ab0a60d upstream. Back in 27f4d1f6bc32c2ed7b2c5080cbd58b14df622607 we refactored the CRUSH code to allow adjustment of the retry counts on a per-pool basis. That commit had an off-by-one bug: the previous "tries" counter was a *retry* count, not a *try* count, but the new code was passing in 1 meaning there should be no retries. Fix the ftotal vs tries comparison to use < instead of <= to fix the problem. Note that the original code used <= here, which means the global "choose_total_tries" tunable is actually counting retries. Compensate for that by adding 1 in crush_do_rule when we pull the tunable into the local variable. This was noticed looking at output from a user provided osdmap. Unfortunately the map doesn't illustrate the change in mapping behavior and I haven't managed to construct one yet that does. Inspection of the crush debug output now aligns with prior versions, though. Reflects ceph.git commit 795704fd615f0b008dcc81aa088a859b2d075138. Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com> Reviewed-by: Josh Durgin <josh.durgin@inktank.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/ceph/crush/mapper.c46
1 files changed, 27 insertions, 19 deletions
diff --git a/net/ceph/crush/mapper.c b/net/ceph/crush/mapper.c
index b703790b4e44..074bb2a5e675 100644
--- a/net/ceph/crush/mapper.c
+++ b/net/ceph/crush/mapper.c
@@ -292,8 +292,8 @@ static int is_out(const struct crush_map *map,
* @outpos: our position in that vector
* @tries: number of attempts to make
* @recurse_tries: number of attempts to have recursive chooseleaf make
- * @local_tries: localized retries
- * @local_fallback_tries: localized fallback retries
+ * @local_retries: localized retries
+ * @local_fallback_retries: localized fallback retries
* @recurse_to_leaf: true if we want one device under each item of given type (chooseleaf instead of choose)
* @out2: second output vector for leaf items (if @recurse_to_leaf)
*/
@@ -304,8 +304,8 @@ static int crush_choose_firstn(const struct crush_map *map,
int *out, int outpos,
unsigned int tries,
unsigned int recurse_tries,
- unsigned int local_tries,
- unsigned int local_fallback_tries,
+ unsigned int local_retries,
+ unsigned int local_fallback_retries,
int recurse_to_leaf,
int *out2)
{
@@ -344,9 +344,9 @@ static int crush_choose_firstn(const struct crush_map *map,
reject = 1;
goto reject;
}
- if (local_fallback_tries > 0 &&
+ if (local_fallback_retries > 0 &&
flocal >= (in->size>>1) &&
- flocal > local_fallback_tries)
+ flocal > local_fallback_retries)
item = bucket_perm_choose(in, x, r);
else
item = crush_bucket_choose(in, x, r);
@@ -393,8 +393,8 @@ static int crush_choose_firstn(const struct crush_map *map,
x, outpos+1, 0,
out2, outpos,
recurse_tries, 0,
- local_tries,
- local_fallback_tries,
+ local_retries,
+ local_fallback_retries,
0,
NULL) <= outpos)
/* didn't get leaf */
@@ -420,14 +420,14 @@ reject:
ftotal++;
flocal++;
- if (collide && flocal <= local_tries)
+ if (collide && flocal <= local_retries)
/* retry locally a few times */
retry_bucket = 1;
- else if (local_fallback_tries > 0 &&
- flocal <= in->size + local_fallback_tries)
+ else if (local_fallback_retries > 0 &&
+ flocal <= in->size + local_fallback_retries)
/* exhaustive bucket search */
retry_bucket = 1;
- else if (ftotal <= tries)
+ else if (ftotal < tries)
/* then retry descent */
retry_descent = 1;
else
@@ -640,10 +640,18 @@ int crush_do_rule(const struct crush_map *map,
__u32 step;
int i, j;
int numrep;
- int choose_tries = map->choose_total_tries;
- int choose_local_tries = map->choose_local_tries;
- int choose_local_fallback_tries = map->choose_local_fallback_tries;
+ /*
+ * the original choose_total_tries value was off by one (it
+ * counted "retries" and not "tries"). add one.
+ */
+ int choose_tries = map->choose_total_tries + 1;
int choose_leaf_tries = 0;
+ /*
+ * the local tries values were counted as "retries", though,
+ * and need no adjustment
+ */
+ int choose_local_retries = map->choose_local_tries;
+ int choose_local_fallback_retries = map->choose_local_fallback_tries;
if ((__u32)ruleno >= map->max_rules) {
dprintk(" bad ruleno %d\n", ruleno);
@@ -677,12 +685,12 @@ int crush_do_rule(const struct crush_map *map,
case CRUSH_RULE_SET_CHOOSE_LOCAL_TRIES:
if (curstep->arg1 > 0)
- choose_local_tries = curstep->arg1;
+ choose_local_retries = curstep->arg1;
break;
case CRUSH_RULE_SET_CHOOSE_LOCAL_FALLBACK_TRIES:
if (curstep->arg1 > 0)
- choose_local_fallback_tries = curstep->arg1;
+ choose_local_fallback_retries = curstep->arg1;
break;
case CRUSH_RULE_CHOOSELEAF_FIRSTN:
@@ -734,8 +742,8 @@ int crush_do_rule(const struct crush_map *map,
o+osize, j,
choose_tries,
recurse_tries,
- choose_local_tries,
- choose_local_fallback_tries,
+ choose_local_retries,
+ choose_local_fallback_retries,
recurse_to_leaf,
c+osize);
} else {