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libceph: don't allow bidirectional swap of pg-upmap-items 

This reverts most of commit f53b7665c8 ("libceph: upmap semantic
changes").

We need to prevent duplicates in the final result.  For example, we
can currently take

  [1,2,3] and apply [(1,2)] and get [2,2,3]

or

  [1,2,3] and apply [(3,2)] and get [1,2,2]

The rest of the system is not prepared to handle duplicates in the
result set like this.

The reverted piece was intended to allow

  [1,2,3] and [(1,2),(2,1)] to get [2,1,3]

to reorder primaries.  First, this bidirectional swap is hard to
implement in a way that also prevents dups.  For example, [1,2,3] and
[(1,4),(2,3),(3,4)] would give [4,3,4] but would we just drop the last
step we'd have [4,3,3] which is also invalid, etc.  Simpler to just not
handle bidirectional swaps.  In practice, they are not needed: if you
just want to choose a different primary then use primary_affinity, or
pg_upmap (not pg_upmap_items).

Cc: stable@vger.kernel.org # 4.13
Link: http://tracker.ceph.com/issues/21410
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
This commit is contained in:
Ilya Dryomov 2017-09-18 12:21:37 +02:00
parent 2bd6bf03f4
commit 29a0cfbf91
1 changed files with 24 additions and 9 deletions
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33
net/ceph/osdmap.c
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@ -2445,19 +2445,34 @@ static void apply_upmap(struct ceph_osdmap *osdmap,
pg = lookup_pg_mapping(&osdmap->pg_upmap_items, pgid);
if (pg) {
for (i = 0; i < raw->size; i++) {
for (j = 0; j < pg->pg_upmap_items.len; j++) {
int from = pg->pg_upmap_items.from_to[j][0];
int to = pg->pg_upmap_items.from_to[j][1];
/*
* Note: this approach does not allow a bidirectional swap,
* e.g., [[1,2],[2,1]] applied to [0,1,2] -> [0,2,1].
*/
for (i = 0; i < pg->pg_upmap_items.len; i++) {
int from = pg->pg_upmap_items.from_to[i][0];
int to = pg->pg_upmap_items.from_to[i][1];
int pos = -1;
bool exists = false;
if (from == raw->osds[i]) {
if (!(to != CRUSH_ITEM_NONE &&
to < osdmap->max_osd &&
osdmap->osd_weight[to] == 0))
raw->osds[i] = to;
/* make sure replacement doesn't already appear */
for (j = 0; j < raw->size; j++) {
int osd = raw->osds[j];
if (osd == to) {
exists = true;
break;
}
/* ignore mapping if target is marked out */
if (osd == from && pos < 0 &&
!(to != CRUSH_ITEM_NONE &&
to < osdmap->max_osd &&
osdmap->osd_weight[to] == 0)) {
pos = j;
}
}
if (!exists && pos >= 0)
raw->osds[pos] = to;
}
}
}