bcachefs: Child btree iterators

This adds the ability for btree iterators to own child iterators - to be
used by an upcoming rework of bch2_btree_iter_peek_slot(), so we can
scan forwards while maintaining our current position.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 5c38562ab206e5c7788af8fba14e757213012287..eccc7a39df014c92dfd60a40ed96146d3e0ad620 100644 (file)
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -18,6 +18,9 @@
 #include <linux/prefetch.h>
 
 static void btree_iter_set_search_pos(struct btree_iter *, struct bpos);
+static struct btree_iter *btree_iter_child_alloc(struct btree_iter *, unsigned long);
+static struct btree_iter *btree_trans_iter_alloc(struct btree_trans *);
+static void btree_iter_copy(struct btree_iter *, struct btree_iter *);
 
 static inline struct bpos bkey_successor(struct btree_iter *iter, struct bpos p)
 {
@@ -1967,9 +1970,39 @@ static inline void bch2_btree_iter_init(struct btree_trans *trans,
 
 /* new transactional stuff: */
 
+static void btree_iter_child_free(struct btree_iter *iter)
+{
+       struct btree_iter *child = btree_iter_child(iter);
+
+       if (child) {
+               bch2_trans_iter_free(iter->trans, child);
+               iter->child_idx = U8_MAX;
+       }
+}
+
+static struct btree_iter *btree_iter_child_alloc(struct btree_iter *iter,
+                                                unsigned long ip)
+{
+       struct btree_trans *trans = iter->trans;
+       struct btree_iter *child = btree_iter_child(iter);
+
+       if (!child) {
+               child = btree_trans_iter_alloc(trans);
+               child->ip_allocated     = ip;
+               iter->child_idx         = child->idx;
+
+               trans->iters_live       |= 1ULL << child->idx;
+               trans->iters_touched    |= 1ULL << child->idx;
+       }
+
+       return child;
+}
+
 static inline void __bch2_trans_iter_free(struct btree_trans *trans,
                                          unsigned idx)
 {
+       btree_iter_child_free(&trans->iters[idx]);
+
        __bch2_btree_iter_unlock(&trans->iters[idx]);
        trans->iters_linked             &= ~(1ULL << idx);
        trans->iters_live               &= ~(1ULL << idx);
@@ -2037,6 +2070,7 @@ static void btree_trans_iter_alloc_fail(struct btree_trans *trans)
 
 static struct btree_iter *btree_trans_iter_alloc(struct btree_trans *trans)
 {
+       struct btree_iter *iter;
        unsigned idx;
 
        if (unlikely(trans->iters_linked ==
@@ -2044,21 +2078,28 @@ static struct btree_iter *btree_trans_iter_alloc(struct btree_trans *trans)
                btree_trans_iter_alloc_fail(trans);
 
        idx = __ffs64(~trans->iters_linked);
-
+       iter = &trans->iters[idx];
+
+       iter->trans             = trans;
+       iter->idx               = idx;
+       iter->child_idx         = U8_MAX;
+       iter->flags             = 0;
+       iter->nodes_locked      = 0;
+       iter->nodes_intent_locked = 0;
        trans->iters_linked     |= 1ULL << idx;
-       trans->iters[idx].idx    = idx;
-       trans->iters[idx].flags  = 0;
-       return &trans->iters[idx];
+       return iter;
 }
 
-static inline void btree_iter_copy(struct btree_iter *dst,
-                                  struct btree_iter *src)
+static void btree_iter_copy(struct btree_iter *dst, struct btree_iter *src)
 {
-       unsigned i, idx = dst->idx;
+       unsigned i, offset = offsetof(struct btree_iter, flags);
 
-       *dst = *src;
-       dst->idx = idx;
-       dst->flags &= ~BTREE_ITER_KEEP_UNTIL_COMMIT;
+       __bch2_btree_iter_unlock(dst);
+       btree_iter_child_free(dst);
+
+       memcpy((void *) dst + offset,
+              (void *) src + offset,
+              sizeof(struct btree_iter) - offset);
 
        for (i = 0; i < BTREE_MAX_DEPTH; i++)
                if (btree_node_locked(dst, i))
@@ -2365,6 +2406,13 @@ int bch2_trans_exit(struct btree_trans *trans)
        bch2_trans_unlock(trans);
 
 #ifdef CONFIG_BCACHEFS_DEBUG
+       if (trans->iters_live) {
+               struct btree_iter *iter;
+
+               trans_for_each_iter(trans, iter)
+                       btree_iter_child_free(iter);
+       }
+
        if (trans->iters_live) {
                struct btree_iter *iter;
 

diff --git a/fs/bcachefs/btree_iter.h b/fs/bcachefs/btree_iter.h
index a2ce711fd61f0b981df5c940cfb3eb0c01420c7e..18732ca531ec3d53a0a512a094c6e371af0a3a92 100644 (file)
--- a/fs/bcachefs/btree_iter.h
+++ b/fs/bcachefs/btree_iter.h
@@ -181,6 +181,12 @@ static inline void bch2_btree_iter_set_pos(struct btree_iter *iter, struct bpos
        iter->should_be_locked = false;
 }
 
+static inline struct btree_iter *btree_iter_child(struct btree_iter *iter)
+{
+       return iter->child_idx == U8_MAX ? NULL
+               : iter->trans->iters + iter->child_idx;
+}
+
 /* Sort order for locking btree iterators: */
 static inline int btree_iter_lock_cmp(const struct btree_iter *l,
                                      const struct btree_iter *r)

diff --git a/fs/bcachefs/btree_types.h b/fs/bcachefs/btree_types.h
index bb0f92e3b3abd8ed85e335fc3bb181304d0011f1..97e0216486856dfcae3d181da76223befab337d7 100644 (file)
--- a/fs/bcachefs/btree_types.h
+++ b/fs/bcachefs/btree_types.h
@@ -241,15 +241,20 @@ enum btree_iter_uptodate {
  */
 struct btree_iter {
        struct btree_trans      *trans;
-       struct bpos             pos;
-       /* what we're searching for/what the iterator actually points to: */
-       struct bpos             real_pos;
-       struct bpos             pos_after_commit;
+       unsigned long           ip_allocated;
+
+       u8                      idx;
+       u8                      child_idx;
+
+       /* btree_iter_copy starts here: */
+       u16                     flags;
+
        /* When we're filtering by snapshot, the snapshot ID we're looking for: */
        unsigned                snapshot;
 
-       u16                     flags;
-       u8                      idx;
+       struct bpos             pos;
+       struct bpos             real_pos;
+       struct bpos             pos_after_commit;
 
        enum btree_id           btree_id:4;
        enum btree_iter_uptodate uptodate:3;
@@ -276,7 +281,6 @@ struct btree_iter {
         * bch2_btree_iter_next_slot() can correctly advance pos.
         */
        struct bkey             k;
-       unsigned long           ip_allocated;
 };
 
 static inline enum btree_iter_type