bcachefs: bch2_path_put_nokeep()

The btree iterator code may allocate extra btree paths, temporarily,
that do not refer to keys being returned: we don't need to wait until
transaction restart to drop these, when they're not referenced they
should be deleted right away.

This fixes a transaction path overflow bug.

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

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index baf8ed40280ce7ccb4cfd8f5c24bbcd8a556fb90..283764225d133337d629589985a36904fbb0b319 100644 (file)
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -1299,6 +1299,18 @@ void bch2_path_put(struct btree_trans *trans, struct btree_path *path, bool inte
        __bch2_path_free(trans, path);
 }
 
+static void bch2_path_put_nokeep(struct btree_trans *trans, struct btree_path *path,
+                                bool intent)
+{
+       EBUG_ON(trans->paths + path->idx != path);
+       EBUG_ON(!path->ref);
+
+       if (!__btree_path_put(path, intent))
+               return;
+
+       __bch2_path_free(trans, path);
+}
+
 noinline __cold
 void bch2_trans_updates_to_text(struct printbuf *buf, struct btree_trans *trans)
 {
@@ -1962,8 +1974,8 @@ struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos e
        EBUG_ON(iter->flags & BTREE_ITER_ALL_LEVELS);
 
        if (iter->update_path) {
-               bch2_path_put(trans, iter->update_path,
-                             iter->flags & BTREE_ITER_INTENT);
+               bch2_path_put_nokeep(trans, iter->update_path,
+                                    iter->flags & BTREE_ITER_INTENT);
                iter->update_path = NULL;
        }
 
@@ -1994,8 +2006,8 @@ struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos e
 
                if (iter->update_path &&
                    bkey_cmp(iter->update_path->pos, k.k->p)) {
-                       bch2_path_put(trans, iter->update_path,
-                                     iter->flags & BTREE_ITER_INTENT);
+                       bch2_path_put_nokeep(trans, iter->update_path,
+                                            iter->flags & BTREE_ITER_INTENT);
                        iter->update_path = NULL;
                }
 
@@ -2237,7 +2249,7 @@ struct bkey_s_c bch2_btree_iter_peek_prev(struct btree_iter *iter)
                                 * that candidate
                                 */
                                if (saved_path && bkey_cmp(k.k->p, saved_k.p)) {
-                                       bch2_path_put(trans, iter->path,
+                                       bch2_path_put_nokeep(trans, iter->path,
                                                      iter->flags & BTREE_ITER_INTENT);
                                        iter->path = saved_path;
                                        saved_path = NULL;
@@ -2250,7 +2262,7 @@ struct bkey_s_c bch2_btree_iter_peek_prev(struct btree_iter *iter)
                                                              iter->snapshot,
                                                              k.k->p.snapshot)) {
                                        if (saved_path)
-                                               bch2_path_put(trans, saved_path,
+                                               bch2_path_put_nokeep(trans, saved_path,
                                                      iter->flags & BTREE_ITER_INTENT);
                                        saved_path = btree_path_clone(trans, iter->path,
                                                                iter->flags & BTREE_ITER_INTENT);
@@ -2294,7 +2306,7 @@ got_key:
        btree_path_set_should_be_locked(iter->path);
 out_no_locked:
        if (saved_path)
-               bch2_path_put(trans, saved_path, iter->flags & BTREE_ITER_INTENT);
+               bch2_path_put_nokeep(trans, saved_path, iter->flags & BTREE_ITER_INTENT);
 
        bch2_btree_iter_verify_entry_exit(iter);
        bch2_btree_iter_verify(iter);
@@ -2584,7 +2596,7 @@ void bch2_trans_iter_exit(struct btree_trans *trans, struct btree_iter *iter)
                bch2_path_put(trans, iter->path,
                              iter->flags & BTREE_ITER_INTENT);
        if (iter->update_path)
-               bch2_path_put(trans, iter->update_path,
+               bch2_path_put_nokeep(trans, iter->update_path,
                              iter->flags & BTREE_ITER_INTENT);
        if (iter->key_cache_path)
                bch2_path_put(trans, iter->key_cache_path,