bcachefs: CONFIG_BCACHEFS_INJECT_TRANSACTION_RESTARTS

Incorrectly handled transaction restarts can be a source of heisenbugs;
add a mode where we randomly inject them to shake them out.

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

diff --git a/fs/bcachefs/Kconfig b/fs/bcachefs/Kconfig
index 85eea7a4dea30bae294d33b2d05f5ae7308df43a..fc7efd0a7525e0d44779b4947a8ea251f225995d 100644 (file)
--- a/fs/bcachefs/Kconfig
+++ b/fs/bcachefs/Kconfig
@@ -61,6 +61,13 @@ config BCACHEFS_DEBUG
        The resulting code will be significantly slower than normal; you
        probably shouldn't select this option unless you're a developer.
 
+config BCACHEFS_INJECT_TRANSACTION_RESTARTS
+       bool "Randomly inject transaction restarts"
+       depends on BCACHEFS_DEBUG
+       help
+       Randomly inject transaction restarts in a few core paths - may have a
+       significant performance penalty
+
 config BCACHEFS_TESTS
        bool "bcachefs unit and performance tests"
        depends on BCACHEFS_FS

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 5988219c690849974bd8ece6d6f846c87142fe43..e32fce4fd25832b1d021d58f9acffc7c778df4ef 100644 (file)
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -2357,6 +2357,12 @@ struct bkey_s_c bch2_btree_iter_peek_max(struct btree_iter *iter, struct bpos en
        bch2_btree_iter_verify_entry_exit(iter);
        EBUG_ON((iter->flags & BTREE_ITER_filter_snapshots) && bkey_eq(end, POS_MAX));
 
+       ret = trans_maybe_inject_restart(trans, _RET_IP_);
+       if (unlikely(ret)) {
+               k = bkey_s_c_err(ret);
+               goto out_no_locked;
+       }
+
        if (iter->update_path) {
                bch2_path_put_nokeep(trans, iter->update_path,
                                     iter->flags & BTREE_ITER_intent);
@@ -2622,6 +2628,12 @@ struct bkey_s_c bch2_btree_iter_peek_prev_min(struct btree_iter *iter, struct bp
        bch2_btree_iter_verify_entry_exit(iter);
        EBUG_ON((iter->flags & BTREE_ITER_filter_snapshots) && bpos_eq(end, POS_MIN));
 
+       int ret = trans_maybe_inject_restart(trans, _RET_IP_);
+       if (unlikely(ret)) {
+               k = bkey_s_c_err(ret);
+               goto out_no_locked;
+       }
+
        while (1) {
                k = __bch2_btree_iter_peek_prev(iter, search_key);
                if (unlikely(!k.k))
@@ -2749,6 +2761,12 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
        bch2_btree_iter_verify_entry_exit(iter);
        EBUG_ON(btree_iter_path(trans, iter)->level && (iter->flags & BTREE_ITER_with_key_cache));
 
+       ret = trans_maybe_inject_restart(trans, _RET_IP_);
+       if (unlikely(ret)) {
+               k = bkey_s_c_err(ret);
+               goto out_no_locked;
+       }
+
        /* extents can't span inode numbers: */
        if ((iter->flags & BTREE_ITER_is_extents) &&
            unlikely(iter->pos.offset == KEY_OFFSET_MAX)) {
@@ -3106,6 +3124,10 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size)
 
        WARN_ON_ONCE(new_bytes > BTREE_TRANS_MEM_MAX);
 
+       ret = trans_maybe_inject_restart(trans, _RET_IP_);
+       if (ret)
+               return ERR_PTR(ret);
+
        struct btree_transaction_stats *s = btree_trans_stats(trans);
        s->max_mem = max(s->max_mem, new_bytes);
 
@@ -3163,7 +3185,8 @@ out_new_mem:
 
        if (old_bytes) {
                trace_and_count(c, trans_restart_mem_realloced, trans, _RET_IP_, new_bytes);
-               return ERR_PTR(btree_trans_restart(trans, BCH_ERR_transaction_restart_mem_realloced));
+               return ERR_PTR(btree_trans_restart_ip(trans,
+                                       BCH_ERR_transaction_restart_mem_realloced, _RET_IP_));
        }
 out_change_top:
        p = trans->mem + trans->mem_top;
@@ -3271,6 +3294,14 @@ u32 bch2_trans_begin(struct btree_trans *trans)
 
        trans->last_begin_ip = _RET_IP_;
 
+#ifdef CONFIG_BCACHEFS_INJECT_TRANSACTION_RESTARTS
+       if (trans->restarted) {
+               trans->restart_count_this_trans++;
+       } else {
+               trans->restart_count_this_trans = 0;
+       }
+#endif
+
        trans_set_locked(trans, false);
 
        if (trans->restarted) {

diff --git a/fs/bcachefs/btree_iter.h b/fs/bcachefs/btree_iter.h
index b9538e6e6d65eeb8f5aa5c2aa259f6a1372b60f0..8c16d9a3ec1d81013d319f04f3b07ee673a99f39 100644 (file)
--- a/fs/bcachefs/btree_iter.h
+++ b/fs/bcachefs/btree_iter.h
@@ -355,6 +355,18 @@ static int btree_trans_restart(struct btree_trans *trans, int err)
        return btree_trans_restart_ip(trans, err, _THIS_IP_);
 }
 
+static inline int trans_maybe_inject_restart(struct btree_trans *trans, unsigned long ip)
+{
+#ifdef CONFIG_BCACHEFS_INJECT_TRANSACTION_RESTARTS
+       if (!(ktime_get_ns() & ~(~0ULL << min(63, (10 + trans->restart_count_this_trans))))) {
+               trace_and_count(trans->c, trans_restart_injected, trans, ip);
+               return btree_trans_restart_ip(trans,
+                                       BCH_ERR_transaction_restart_fault_inject, ip);
+       }
+#endif
+       return 0;
+}
+
 bool bch2_btree_node_upgrade(struct btree_trans *,
                             struct btree_path *, unsigned);
 

diff --git a/fs/bcachefs/btree_trans_commit.c b/fs/bcachefs/btree_trans_commit.c
index 2760dd9569ed91666fd2f0c615ee55807720366c..c4f524b2ca9a07213459b5ffd0df3a8e5035d174 100644 (file)
--- a/fs/bcachefs/btree_trans_commit.c
+++ b/fs/bcachefs/btree_trans_commit.c
@@ -999,6 +999,10 @@ int __bch2_trans_commit(struct btree_trans *trans, unsigned flags)
 
        bch2_trans_verify_not_unlocked_or_in_restart(trans);
 
+       ret = trans_maybe_inject_restart(trans, _RET_IP_);
+       if (unlikely(ret))
+               goto out_reset;
+
        if (!trans->nr_updates &&
            !trans->journal_entries_u64s)
                goto out_reset;

diff --git a/fs/bcachefs/btree_types.h b/fs/bcachefs/btree_types.h
index a6f251eb416469f429546229de4e37150e4ada8c..a09cbe9cd94f11d32be767a28ba96ec096d2994f 100644 (file)
--- a/fs/bcachefs/btree_types.h
+++ b/fs/bcachefs/btree_types.h
@@ -509,6 +509,9 @@ struct btree_trans {
        bool                    notrace_relock_fail:1;
        enum bch_errcode        restarted:16;
        u32                     restart_count;
+#ifdef CONFIG_BCACHEFS_INJECT_TRANSACTION_RESTARTS
+       u32                     restart_count_this_trans;
+#endif
 
        u64                     last_begin_time;
        unsigned long           last_begin_ip;