bcache: Add btree_map() functions

Lots of stuff has been open coding its own btree traversal - which is
generally pretty simple code, but there are a few subtleties.

This adds new new functions, bch_btree_map_nodes() and
bch_btree_map_keys(), which do the traversal for you. Everything that's
open coding btree traversal now (with the exception of garbage
collection) is slowly going to be converted to these two functions;
being able to write other code at a higher level of abstraction  is a
big improvement w.r.t. overall code quality.

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

5 files changed, 186 insertions, 97 deletions

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 674e2f42e778..20fe96c121d9 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -384,8 +384,6 @@ struct keybuf_key {
         void                    *private;
 };
 
-typedef bool (keybuf_pred_fn)(struct keybuf *, struct bkey *);
-
 struct keybuf {
         struct bkey             last_scanned;
         spinlock_t              lock;
diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index d0512e451dda..14c2a23d3884 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -842,6 +842,13 @@ struct bkey *__bch_bset_search(struct btree *b, struct bset_tree *t,
 
 /* Btree iterator */
 
+/*
+ * Returns true if l > r - unless l == r, in which case returns true if l is
+ * older than r.
+ *
+ * Necessary for btree_sort_fixup() - if there are multiple keys that compare
+ * equal in different sets, we have to process them newest to oldest.
+ */
 static inline bool btree_iter_cmp(struct btree_iter_set l,
                                   struct btree_iter_set r)
 {
@@ -1146,16 +1153,16 @@ out:
 /* Sysfs stuff */
 
 struct bset_stats {
+        struct btree_op op;
         size_t nodes;
         size_t sets_written, sets_unwritten;
         size_t bytes_written, bytes_unwritten;
         size_t floats, failed;
 };
 
-static int bch_btree_bset_stats(struct btree *b, struct btree_op *op,
-                            struct bset_stats *stats)
+static int btree_bset_stats(struct btree_op *op, struct btree *b)
 {
-        struct bkey *k;
+        struct bset_stats *stats = container_of(op, struct bset_stats, op);
         unsigned i;
 
         stats->nodes++;
@@ -1180,30 +1187,20 @@ static int bch_btree_bset_stats(struct btree *b, struct btree_op *op,
                 }
         }
 
-        if (b->level) {
-                struct btree_iter iter;
-
-                for_each_key_filter(b, k, &iter, bch_ptr_bad) {
-                        int ret = btree(bset_stats, k, b, op, stats);
-                        if (ret)
-                                return ret;
-                }
-        }
-
-        return 0;
+        return MAP_CONTINUE;
 }
 
 int bch_bset_print_stats(struct cache_set *c, char *buf)
 {
-        struct btree_op op;
         struct bset_stats t;
         int ret;
 
-        bch_btree_op_init_stack(&op);
         memset(&t, 0, sizeof(struct bset_stats));
+        bch_btree_op_init_stack(&t.op);
+        t.op.c = c;
 
-        ret = btree_root(bset_stats, c, &op, &t);
-        if (ret)
+        ret = bch_btree_map_nodes(&t.op, c, &ZERO_KEY, btree_bset_stats);
+        if (ret < 0)
                 return ret;
 
         return snprintf(buf, PAGE_SIZE,
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 17bfd87fc8f4..cfbdcf349b7f 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -2296,6 +2296,82 @@ int bch_btree_search_recurse(struct btree *b, struct btree_op *op)
         return ret;
 }
 
+/* Map across nodes or keys */
+
+static int bch_btree_map_nodes_recurse(struct btree *b, struct btree_op *op,
+                                       struct bkey *from,
+                                       btree_map_nodes_fn *fn, int flags)
+{
+        int ret = MAP_CONTINUE;
+
+        if (b->level) {
+                struct bkey *k;
+                struct btree_iter iter;
+
+                bch_btree_iter_init(b, &iter, from);
+
+                while ((k = bch_btree_iter_next_filter(&iter, b,
+                                                       bch_ptr_bad))) {
+                        ret = btree(map_nodes_recurse, k, b,
+                                    op, from, fn, flags);
+                        from = NULL;
+
+                        if (ret != MAP_CONTINUE)
+                                return ret;
+                }
+        }
+
+        if (!b->level || flags == MAP_ALL_NODES)
+                ret = fn(op, b);
+
+        return ret;
+}
+
+int __bch_btree_map_nodes(struct btree_op *op, struct cache_set *c,
+                          struct bkey *from, btree_map_nodes_fn *fn, int flags)
+{
+        int ret = btree_root(map_nodes_recurse, c, op, from, fn, flags);
+        if (closure_blocking(&op->cl))
+                closure_sync(&op->cl);
+        return ret;
+}
+
+static int bch_btree_map_keys_recurse(struct btree *b, struct btree_op *op,
+                                      struct bkey *from, btree_map_keys_fn *fn,
+                                      int flags)
+{
+        int ret = MAP_CONTINUE;
+        struct bkey *k;
+        struct btree_iter iter;
+
+        bch_btree_iter_init(b, &iter, from);
+
+        while ((k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad))) {
+                ret = !b->level
+                        ? fn(op, b, k)
+                        : btree(map_keys_recurse, k, b, op, from, fn, flags);
+                from = NULL;
+
+                if (ret != MAP_CONTINUE)
+                        return ret;
+        }
+
+        if (!b->level && (flags & MAP_END_KEY))
+                ret = fn(op, b, &KEY(KEY_INODE(&b->key),
+                                     KEY_OFFSET(&b->key), 0));
+
+        return ret;
+}
+
+int bch_btree_map_keys(struct btree_op *op, struct cache_set *c,
+                       struct bkey *from, btree_map_keys_fn *fn, int flags)
+{
+        int ret = btree_root(map_keys_recurse, c, op, from, fn, flags);
+        if (closure_blocking(&op->cl))
+                closure_sync(&op->cl);
+        return ret;
+}
+
 /* Keybuf code */
 
 static inline int keybuf_cmp(struct keybuf_key *l, struct keybuf_key *r)
@@ -2314,74 +2390,70 @@ static inline int keybuf_nonoverlapping_cmp(struct keybuf_key *l,
         return clamp_t(int64_t, bkey_cmp(&l->key, &r->key), -1, 1);
 }
 
-static int bch_btree_refill_keybuf(struct btree *b, struct btree_op *op,
-                                   struct keybuf *buf, struct bkey *end,
-                                   keybuf_pred_fn *pred)
-{
-        struct btree_iter iter;
-        bch_btree_iter_init(b, &iter, &buf->last_scanned);
-
-        while (!array_freelist_empty(&buf->freelist)) {
-                struct bkey *k = bch_btree_iter_next_filter(&iter, b,
-                                                            bch_ptr_bad);
-
-                if (!b->level) {
-                        if (!k) {
-                                buf->last_scanned = b->key;
-                                break;
-                        }
+struct refill {
+        struct btree_op op;
+        struct keybuf   *buf;
+        struct bkey     *end;
+        keybuf_pred_fn  *pred;
+};
 
-                        buf->last_scanned = *k;
-                        if (bkey_cmp(&buf->last_scanned, end) >= 0)
-                                break;
+static int refill_keybuf_fn(struct btree_op *op, struct btree *b,
+                            struct bkey *k)
+{
+        struct refill *refill = container_of(op, struct refill, op);
+        struct keybuf *buf = refill->buf;
+        int ret = MAP_CONTINUE;
 
-                        if (pred(buf, k)) {
-                                struct keybuf_key *w;
+        if (bkey_cmp(k, refill->end) >= 0) {
+                ret = MAP_DONE;
+                goto out;
+        }
 
-                                spin_lock(&buf->lock);
+        if (!KEY_SIZE(k)) /* end key */
+                goto out;
 
-                                w = array_alloc(&buf->freelist);
+        if (refill->pred(buf, k)) {
+                struct keybuf_key *w;
 
-                                w->private = NULL;
-                                bkey_copy(&w->key, k);
+                spin_lock(&buf->lock);
 
-                                if (RB_INSERT(&buf->keys, w, node, keybuf_cmp))
-                                        array_free(&buf->freelist, w);
+                w = array_alloc(&buf->freelist);
+                if (!w) {
+                        spin_unlock(&buf->lock);
+                        return MAP_DONE;
+                }
 
-                                spin_unlock(&buf->lock);
-                        }
-                } else {
-                        if (!k)
-                                break;
+                w->private = NULL;
+                bkey_copy(&w->key, k);
 
-                        btree(refill_keybuf, k, b, op, buf, end, pred);
-                        /*
-                         * Might get an error here, but can't really do anything
-                         * and it'll get logged elsewhere. Just read what we
-                         * can.
-                         */
+                if (RB_INSERT(&buf->keys, w, node, keybuf_cmp))
+                        array_free(&buf->freelist, w);
 
-                        if (bkey_cmp(&buf->last_scanned, end) >= 0)
-                                break;
+                if (array_freelist_empty(&buf->freelist))
+                        ret = MAP_DONE;
 
-                        cond_resched();
-                }
+                spin_unlock(&buf->lock);
         }
-
-        return 0;
+out:
+        buf->last_scanned = *k;
+        return ret;
 }
 
 void bch_refill_keybuf(struct cache_set *c, struct keybuf *buf,
                        struct bkey *end, keybuf_pred_fn *pred)
 {
         struct bkey start = buf->last_scanned;
-        struct btree_op op;
-        bch_btree_op_init_stack(&op);
+        struct refill refill;
 
         cond_resched();
 
-        btree_root(refill_keybuf, c, &op, buf, end, pred);
-        closure_sync(&op.cl);
+        bch_btree_op_init_stack(&refill.op);
+        refill.buf = buf;
+        refill.end = end;
+        refill.pred = pred;
+
+        bch_btree_map_keys(&refill.op, c, &buf->last_scanned,
+                           refill_keybuf_fn, MAP_END_KEY);
 
         pr_debug("found %s keys from %llu:%llu to %llu:%llu",
                  RB_EMPTY_ROOT(&buf->keys) ? "no" :
@@ -2465,9 +2537,9 @@ struct keybuf_key *bch_keybuf_next(struct keybuf *buf)
 }
 
 struct keybuf_key *bch_keybuf_next_rescan(struct cache_set *c,
-                                             struct keybuf *buf,
-                                             struct bkey *end,
-                                             keybuf_pred_fn *pred)
+                                          struct keybuf *buf,
+                                          struct bkey *end,
+                                          keybuf_pred_fn *pred)
 {
         struct keybuf_key *ret;
 
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index fa9641aaed39..cafdeb01e219 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -400,9 +400,42 @@ static inline void wake_up_gc(struct cache_set *c)
                 wake_up_process(c->gc_thread);
 }
 
+#define MAP_DONE        0
+#define MAP_CONTINUE    1
+
+#define MAP_ALL_NODES   0
+#define MAP_LEAF_NODES  1
+
+#define MAP_END_KEY     1
+
+typedef int (btree_map_nodes_fn)(struct btree_op *, struct btree *);
+int __bch_btree_map_nodes(struct btree_op *, struct cache_set *,
+                          struct bkey *, btree_map_nodes_fn *, int);
+
+static inline int bch_btree_map_nodes(struct btree_op *op, struct cache_set *c,
+                                      struct bkey *from, btree_map_nodes_fn *fn)
+{
+        return __bch_btree_map_nodes(op, c, from, fn, MAP_ALL_NODES);
+}
+
+static inline int bch_btree_map_leaf_nodes(struct btree_op *op,
+                                           struct cache_set *c,
+                                           struct bkey *from,
+                                           btree_map_nodes_fn *fn)
+{
+        return __bch_btree_map_nodes(op, c, from, fn, MAP_LEAF_NODES);
+}
+
+typedef int (btree_map_keys_fn)(struct btree_op *, struct btree *,
+                                struct bkey *);
+int bch_btree_map_keys(struct btree_op *, struct cache_set *,
+                       struct bkey *, btree_map_keys_fn *, int);
+
+typedef bool (keybuf_pred_fn)(struct keybuf *, struct bkey *);
+
 void bch_keybuf_init(struct keybuf *);
-void bch_refill_keybuf(struct cache_set *, struct keybuf *, struct bkey *,
-                       keybuf_pred_fn *);
+void bch_refill_keybuf(struct cache_set *, struct keybuf *,
+                       struct bkey *, keybuf_pred_fn *);
 bool bch_keybuf_check_overlapping(struct keybuf *, struct bkey *,
                                   struct bkey *);
 void bch_keybuf_del(struct keybuf *, struct keybuf_key *);
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 4392f3f38d62..c68de9f12618 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -433,31 +433,17 @@ static int bch_writeback_thread(void *arg)
 
 /* Init */
 
-static int bch_btree_sectors_dirty_init(struct btree *b, struct btree_op *op,
-                                        struct cached_dev *dc)
+static int sectors_dirty_init_fn(struct btree_op *op, struct btree *b,
+                                 struct bkey *k)
 {
-        struct bkey *k;
-        struct btree_iter iter;
-
-        bch_btree_iter_init(b, &iter, &KEY(dc->disk.id, 0, 0));
-        while ((k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad)))
-                if (!b->level) {
-                        if (KEY_INODE(k) > dc->disk.id)
-                                break;
-
-                        if (KEY_DIRTY(k))
-                                bcache_dev_sectors_dirty_add(b->c, dc->disk.id,
-                                                             KEY_START(k),
-                                                             KEY_SIZE(k));
-                } else {
-                        btree(sectors_dirty_init, k, b, op, dc);
-                        if (KEY_INODE(k) > dc->disk.id)
-                                break;
-
-                        cond_resched();
-                }
+        if (KEY_INODE(k) > op->inode)
+                return MAP_DONE;
 
-        return 0;
+        if (KEY_DIRTY(k))
+                bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
+                                             KEY_START(k), KEY_SIZE(k));
+
+        return MAP_CONTINUE;
 }
 
 void bch_sectors_dirty_init(struct cached_dev *dc)
@@ -465,7 +451,10 @@ void bch_sectors_dirty_init(struct cached_dev *dc)
         struct btree_op op;
 
         bch_btree_op_init_stack(&op);
-        btree_root(sectors_dirty_init, dc->disk.c, &op, dc);
+        op.inode = dc->disk.id;
+
+        bch_btree_map_keys(&op, dc->disk.c, &KEY(op.inode, 0, 0),
+                           sectors_dirty_init_fn, 0);
 }
 
 int bch_cached_dev_writeback_init(struct cached_dev *dc)