From e242b92af5ef74cdf40b237c9e904034c081b144 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Thu, 15 Dec 2022 21:44:32 -0500 Subject: [PATCH] bcachefs: Fix for long running btree transactions & key cache While a btree transaction is running, we hold a SRCU read lock on the btree key cache that prevents btree key cache keys from being freed - this is so that relock() operations won't access freed memory. The downside of this is that long running btree transactions prevent memory from being freed from the key cache. This adds a check in bch2_trans_begin() - if the transaction has been running longer than 1 second, drop and retake the SRCU read lock and zero out pointers to unlock key cache paths. Signed-off-by: Kent Overstreet --- fs/bcachefs/btree_iter.c | 18 ++++++++++++++++++ fs/bcachefs/btree_types.h | 1 + fs/bcachefs/errcode.h | 1 + 3 files changed, 20 insertions(+) diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c index c6ccf3add7338..669d2b0b384ae 100644 --- a/fs/bcachefs/btree_iter.c +++ b/fs/bcachefs/btree_iter.c @@ -2756,6 +2756,20 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size) return p; } +static noinline void bch2_trans_reset_srcu_lock(struct btree_trans *trans) +{ + struct bch_fs *c = trans->c; + struct btree_path *path; + + trans_for_each_path(trans, path) + if (path->cached && !btree_node_locked(path, 0)) + path->l[0].b = ERR_PTR(-BCH_ERR_no_btree_node_srcu_reset); + + srcu_read_unlock(&c->btree_trans_barrier, trans->srcu_idx); + trans->srcu_idx = srcu_read_lock(&c->btree_trans_barrier); + trans->srcu_lock_time = jiffies; +} + /** * bch2_trans_begin() - reset a transaction after a interrupted attempt * @trans: transaction to reset @@ -2811,6 +2825,9 @@ u32 bch2_trans_begin(struct btree_trans *trans) bch2_trans_relock(trans); } + if (unlikely(time_after(jiffies, trans->srcu_lock_time + HZ))) + bch2_trans_reset_srcu_lock(trans); + trans->last_restarted_ip = _RET_IP_; if (trans->restarted) bch2_btree_path_traverse_all(trans); @@ -2897,6 +2914,7 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_ trans->nr_max_paths = s->nr_max_paths; trans->srcu_idx = srcu_read_lock(&c->btree_trans_barrier); + trans->srcu_lock_time = jiffies; if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG_TRANSACTIONS)) { struct btree_trans *pos; diff --git a/fs/bcachefs/btree_types.h b/fs/bcachefs/btree_types.h index e47fd252c3fb9..390cfe63fbe87 100644 --- a/fs/bcachefs/btree_types.h +++ b/fs/bcachefs/btree_types.h @@ -411,6 +411,7 @@ struct btree_trans { enum bch_errcode restarted:16; u32 restart_count; unsigned long last_restarted_ip; + unsigned long srcu_lock_time; /* * For when bch2_trans_update notices we'll be splitting a compressed diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h index dc388864be6f0..5f0f757267842 100644 --- a/fs/bcachefs/errcode.h +++ b/fs/bcachefs/errcode.h @@ -53,6 +53,7 @@ x(BCH_ERR_no_btree_node, no_btree_node_down) \ x(BCH_ERR_no_btree_node, no_btree_node_init) \ x(BCH_ERR_no_btree_node, no_btree_node_cached) \ + x(BCH_ERR_no_btree_node, no_btree_node_srcu_reset) \ x(0, btree_insert_fail) \ x(BCH_ERR_btree_insert_fail, btree_insert_btree_node_full) \ x(BCH_ERR_btree_insert_fail, btree_insert_need_mark_replicas) \ -- 2.30.2