bcache: fix for gc and writeback race

Garbage collector needs to check keys in the writeback keybuf to
make sure it's not invalidating buckets to which the writeback
keys point to.

Signed-off-by: Nicholas Swenson <nks@daterainc.com>
Signed-off-by: Kent Overstreet <kmo@daterainc.com>

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index c36745e5986ab2746582bf464120041197df0096..31bb53fcc67a40806cf73659a596f98297d36128 100644 (file)
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1561,6 +1561,28 @@ size_t bch_btree_gc_finish(struct cache_set *c)
                SET_GC_MARK(PTR_BUCKET(c, &c->uuid_bucket, i),
                            GC_MARK_METADATA);
 
+       /* don't reclaim buckets to which writeback keys point */
+       rcu_read_lock();
+       for (i = 0; i < c->nr_uuids; i++) {
+               struct bcache_device *d = c->devices[i];
+               struct cached_dev *dc;
+               struct keybuf_key *w, *n;
+               unsigned j;
+
+               if (!d || UUID_FLASH_ONLY(&c->uuids[i]))
+                       continue;
+               dc = container_of(d, struct cached_dev, disk);
+
+               spin_lock(&dc->writeback_keys.lock);
+               rbtree_postorder_for_each_entry_safe(w, n,
+                                       &dc->writeback_keys.keys, node)
+                       for (j = 0; j < KEY_PTRS(&w->key); j++)
+                               SET_GC_MARK(PTR_BUCKET(c, &w->key, j),
+                                           GC_MARK_DIRTY);
+               spin_unlock(&dc->writeback_keys.lock);
+       }
+       rcu_read_unlock();
+
        for_each_cache(ca, c, i) {
                uint64_t *i;