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>

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index c36745e5986a..31bb53fcc67a 100644
--- 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;