bcache: Explicitly track btree node's parent

This is prep work for the reworked btree insertion code.

The way we set b->parent is ugly and hacky... the problem is, when
btree_split() or garbage collection splits or rewrites a btree node, the
parent changes for all its (potentially already cached) children.

I may change this later and add some code to look through the btree node
cache and find all our cached child nodes and change the parent pointer
then...

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

2 files changed, 20 insertions, 10 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index d1734d9d9c79..87299baa8a1b 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -884,6 +884,7 @@ out:
 
         lock_set_subclass(&b->lock.dep_map, level + 1, _THIS_IP_);
         b->level        = level;
+        b->parent       = (void *) ~0UL;
 
         mca_reinit(b);
 
@@ -1898,7 +1899,7 @@ out:
 
 static int btree_split(struct btree *b, struct btree_op *op)
 {
-        bool split, root = b == b->c->root;
+        bool split;
         struct btree *n1, *n2 = NULL, *n3 = NULL;
         uint64_t start_time = local_clock();
 
@@ -1920,7 +1921,7 @@ static int btree_split(struct btree *b, struct btree_op *op)
                 if (IS_ERR(n2))
                         goto err_free1;
 
-                if (root) {
+                if (!b->parent) {
                         n3 = bch_btree_node_alloc(b->c, b->level + 1, &op->cl);
                         if (IS_ERR(n3))
                                 goto err_free2;
@@ -1928,7 +1929,8 @@ static int btree_split(struct btree *b, struct btree_op *op)
 
                 bch_btree_insert_keys(n1, op);
 
-                /* Has to be a linear search because we don't have an auxiliary
+                /*
+                 * Has to be a linear search because we don't have an auxiliary
                  * search tree yet
                  */
 
@@ -1960,6 +1962,8 @@ static int btree_split(struct btree *b, struct btree_op *op)
         bch_btree_node_write(n1, &op->cl);
 
         if (n3) {
+                /* Depth increases, make a new root */
+
                 bkey_copy_key(&n3->key, &MAX_KEY);
                 bch_btree_insert_keys(n3, op);
                 bch_btree_node_write(n3, &op->cl);
@@ -1967,7 +1971,9 @@ static int btree_split(struct btree *b, struct btree_op *op)
                 closure_sync(&op->cl);
                 bch_btree_set_root(n3);
                 rw_unlock(true, n3);
-        } else if (root) {
+        } else if (!b->parent) {
+                /* Root filled up but didn't need to be split */
+
                 op->keys.top = op->keys.bottom;
                 closure_sync(&op->cl);
                 bch_btree_set_root(n1);
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index 8a1c7e6bbbe3..6d2fb7550706 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -125,6 +125,7 @@ struct btree {
         unsigned long           seq;
         struct rw_semaphore     lock;
         struct cache_set        *c;
+        struct btree            *parent;
 
         unsigned long           flags;
         uint16_t                written;        /* would be nice to kill */
@@ -327,12 +328,13 @@ static inline void rw_unlock(bool w, struct btree *b)
 ({                                                                      \
         int _r, l = (b)->level - 1;                                     \
         bool _w = l <= (op)->lock;                                      \
-        struct btree *_b = bch_btree_node_get((b)->c, key, l, op);      \
-        if (!IS_ERR(_b)) {                                              \
-                _r = bch_btree_ ## fn(_b, op, ##__VA_ARGS__);           \
-                rw_unlock(_w, _b);                                      \
+        struct btree *_child = bch_btree_node_get((b)->c, key, l, op);  \
+        if (!IS_ERR(_child)) {                                          \
+                _child->parent = (b);                                   \
+                _r = bch_btree_ ## fn(_child, op, ##__VA_ARGS__);       \
+                rw_unlock(_w, _child);                                  \
         } else                                                          \
-                _r = PTR_ERR(_b);                                       \
+                _r = PTR_ERR(_child);                                   \
         _r;                                                             \
 })
 
@@ -350,8 +352,10 @@ static inline void rw_unlock(bool w, struct btree *b)
                 bool _w = insert_lock(op, _b);                          \
                 rw_lock(_w, _b, _b->level);                             \
                 if (_b == (c)->root &&                                  \
-                    _w == insert_lock(op, _b))                          \
+                    _w == insert_lock(op, _b)) {                        \
+                        _b->parent = NULL;                              \
                         _r = bch_btree_ ## fn(_b, op, ##__VA_ARGS__);   \
+                }                                                       \
                 rw_unlock(_w, _b);                                      \
                 bch_cannibalize_unlock(c, &(op)->cl);                   \
         } while (_r == -EINTR);                                         \