bcache: Refactor btree io
The most significant change is that btree reads are now done
synchronously, instead of asynchronously and doing the post read stuff
from a workqueue.
This was originally done because we can't block on IO under
generic_make_request(). But - we already have a mechanism to punt cache
lookups to workqueue if needed, so if we just use that we don't have to
deal with the complexity of doing things asynchronously.
The main benefit is this makes the locking situation saner; we can hold
our write lock on the btree node until we're finished reading it, and we
don't need that btree_node_read_done() flag anymore.
Also, for writes, btree_write() was broken out into btree_node_write()
and btree_leaf_dirty() - the old code with the boolean argument was dumb
and confusing.
The prio_blocked mechanism was improved a bit too, now the only counter
is in struct btree_write, we don't mess with transfering a count from
struct btree anymore.
This required changing garbage collection to block prios at the start
and unblock when it finishes, which is cleaner than what it was doing
anyways (the old code had mostly the same effect, but was doing it in a
convoluted way)
And the btree iter btree_node_read_done() uses was converted to a real
mempool.
Signed-off-by: Kent Overstreet <koverstreet@google.com>
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 166c8dd..ad4957b 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -819,10 +819,9 @@
/*
* A btree node on disk could have too many bsets for an iterator to fit
- * on the stack - this is a single element mempool for btree_read_work()
+ * on the stack - have to dynamically allocate them
*/
- struct mutex fill_lock;
- struct btree_iter *fill_iter;
+ mempool_t *fill_iter;
/*
* btree_sort() is a merge sort and requires temporary space - single