bcachefs: Fix gap buffer bug in bch2_journal_key_insert_take()

Multiple bug fixes for journal iters:

 - When the journal keys gap buffer is resized, we have to adjust the
   iterators for moving the gap to the end
 - We don't want to rewind iterators to point to the key we just
   inserted if it's not for the correct btree/level

Also, add some new assertions.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/btree_journal_iter.c b/fs/bcachefs/btree_journal_iter.c
index 5cbcbfe85235b8de3777ae82b120d4627f99c8d7..a6413a8747d3c442d2890e34b238cd5e454a146b 100644 (file)
--- a/fs/bcachefs/btree_journal_iter.c
+++ b/fs/bcachefs/btree_journal_iter.c
@@ -130,12 +130,30 @@ struct bkey_i *bch2_journal_keys_peek_slot(struct bch_fs *c, enum btree_id btree
        return bch2_journal_keys_peek_upto(c, btree_id, level, pos, pos, &idx);
 }
 
+static void journal_iter_verify(struct journal_iter *iter)
+{
+       struct journal_keys *keys = iter->keys;
+       size_t gap_size = keys->size - keys->nr;
+
+       BUG_ON(iter->idx >= keys->gap &&
+              iter->idx <  keys->gap + gap_size);
+
+       if (iter->idx < keys->size) {
+               struct journal_key *k = keys->data + iter->idx;
+
+               int cmp = cmp_int(k->btree_id,  iter->btree_id) ?:
+                         cmp_int(k->level,     iter->level);
+               BUG_ON(cmp < 0);
+       }
+}
+
 static void journal_iters_fix(struct bch_fs *c)
 {
        struct journal_keys *keys = &c->journal_keys;
        /* The key we just inserted is immediately before the gap: */
        size_t gap_end = keys->gap + (keys->size - keys->nr);
-       struct btree_and_journal_iter *iter;
+       struct journal_key *new_key = &keys->data[keys->gap - 1];
+       struct journal_iter *iter;
 
        /*
         * If an iterator points one after the key we just inserted, decrement
@@ -143,9 +161,14 @@ static void journal_iters_fix(struct bch_fs *c)
         * decrement was unnecessary, bch2_btree_and_journal_iter_peek() will
         * handle that:
         */
-       list_for_each_entry(iter, &c->journal_iters, journal.list)
-               if (iter->journal.idx == gap_end)
-                       iter->journal.idx = keys->gap - 1;
+       list_for_each_entry(iter, &c->journal_iters, list) {
+               journal_iter_verify(iter);
+               if (iter->idx           == gap_end &&
+                   new_key->btree_id   == iter->btree_id &&
+                   new_key->level      == iter->level)
+                       iter->idx = keys->gap - 1;
+               journal_iter_verify(iter);
+       }
 }
 
 static void journal_iters_move_gap(struct bch_fs *c, size_t old_gap, size_t new_gap)
@@ -192,7 +215,12 @@ int bch2_journal_key_insert_take(struct bch_fs *c, enum btree_id id,
        if (idx > keys->gap)
                idx -= keys->size - keys->nr;
 
+       size_t old_gap = keys->gap;
+
        if (keys->nr == keys->size) {
+               journal_iters_move_gap(c, old_gap, keys->size);
+               old_gap = keys->size;
+
                struct journal_keys new_keys = {
                        .nr                     = keys->nr,
                        .size                   = max_t(size_t, keys->size, 8) * 2,
@@ -216,7 +244,7 @@ int bch2_journal_key_insert_take(struct bch_fs *c, enum btree_id id,
                keys->gap       = keys->nr;
        }
 
-       journal_iters_move_gap(c, keys->gap, idx);
+       journal_iters_move_gap(c, old_gap, idx);
 
        move_gap(keys, idx);
 
@@ -301,16 +329,21 @@ static void bch2_journal_iter_advance(struct journal_iter *iter)
 
 static struct bkey_s_c bch2_journal_iter_peek(struct journal_iter *iter)
 {
-       struct journal_key *k = iter->keys->data + iter->idx;
+       journal_iter_verify(iter);
+
+       while (iter->idx < iter->keys->size) {
+               struct journal_key *k = iter->keys->data + iter->idx;
+
+               int cmp = cmp_int(k->btree_id,  iter->btree_id) ?:
+                         cmp_int(k->level,     iter->level);
+               if (cmp > 0)
+                       break;
+               BUG_ON(cmp);
 
-       while (k < iter->keys->data + iter->keys->size &&
-              k->btree_id      == iter->btree_id &&
-              k->level         == iter->level) {
                if (!k->overwritten)
                        return bkey_i_to_s_c(k->k);
 
                bch2_journal_iter_advance(iter);
-               k = iter->keys->data + iter->idx;
        }
 
        return bkey_s_c_null;
@@ -330,6 +363,8 @@ static void bch2_journal_iter_init(struct bch_fs *c,
        iter->level     = level;
        iter->keys      = &c->journal_keys;
        iter->idx       = bch2_journal_key_search(&c->journal_keys, id, level, pos);
+
+       journal_iter_verify(iter);
 }
 
 static struct bkey_s_c bch2_journal_iter_peek_btree(struct btree_and_journal_iter *iter)