From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A8F27361657; Mon, 14 Sep 2026 03:37:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789357044; cv=none; b=oQ/SXEcNUzRM3OKqSwPJ+mRwc6AuIHFIj5NfS0mGnjDNwH7+nASlChFMlL+Jhhw2xRIAfLbGaxuvW+sAcFKb8dx8v9Gris3qAjUOsc1+ft9sNbXLUxHm/EqDBm8sJJMqz4yizvRfIF6zVfvkXO3RkBLvSADUwQoeT+kcFvkurqM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789357044; c=relaxed/simple; bh=OTH6AfbNxskT7yZ3KCdKmkuXajcikKb8jaUc2JD3p8I=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=JkE7ep+EdU9pQr5VBgIxfjCsRYgQUyAMjSD2TqRKE4I7LPjiUYhiJuQxhlqIf1Umo88UMamL1XlscNstS+OubZ2eSjhWUzGBVmHQF+XWrVNKxFFxLSbWfPYO+p/+JM0bZW/Ju7XSNGxuV7Fjw1qStT40JDwCbOeB5nJVb9DOtbM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R4Kh+vIa; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R4Kh+vIa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FB771F0089B; Mon, 14 Sep 2026 03:37:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789357042; bh=GHz7MaJJD5Da48g8xLhkAEKvKJoXLSs0Yrbsx7IqwWo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=R4Kh+vIaYoT83j9eCXiBo5nKZJIFMeiFindUg470Tu8zBc4AorPKRPKNKk03l7KjT 7LrWHGXYXE436fYIeOFV94QiUq2/wzPK79elW2yN6FZhXovKfo14+M539tGgXaPcL0 7eWLXA8R1XzzR9pKrCTz+eHxYWpwPnif9vMBvGr1g3LWcqcxCvVeUDVDFYBRJT3c/g ofOO5JZpwEHECirMpmn0jU2YOOJ2VnXYHC5sfHKwkuzNPNAbgjScSUF6eFMNKp24n5 eJYsfpzn1VO1faZDrWW5k60UsljZa23iIM5jFfPtYMuBE+QhOgQKki2qHBMBsQ9Q22 XCG87ekrG71JA== From: Allison Henderson To: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, pabeni@redhat.com, edumazet@google.com, kuba@kernel.org, horms@kernel.org Cc: achender@kernel.org, nicoyip.dev@gmail.com Subject: [PATCH net-next v3 04/13] net/rds: make rds_destroy_pending() cover single-connection destroy Date: Sun, 13 Sep 2026 20:37:10 -0700 Message-Id: <20260914033719.138057-5-achender@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260914033719.138057-1-achender@kernel.org> References: <20260914033719.138057-1-achender@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rds_conn_destroy() cancels the path works and then destroys the per-path workqueue. However, nothing currently stops the work-requeueing sites from queueing new work on the connection while that happens. The existing code would suggest that this protection is supposed to come from rds_destroy_pending(), since all of those sites guard the queueing with rds_destroy_pending() under rcu_read_lock() (the last stragglers were converted by the previous patch), and rds_conn_destroy() already issues a synchronize_rcu() after unhashing the connection. But the predicate only tests for the two global teardown cases (netns destruction via check_net(), module unload via ->t_unloading). Because the conn itself lacks any indication that a destroy is in progress, the predicate does not cover the destruction of a single connection outside these two cases. rds_conn_destroy() is not limited to the global paths: rds_ib_cm_connect_complete() destroys a single connection whose peer negotiated an unsupported protocol version. (The other per-transport caller, rds_ib_destroy_nodev_conns(), is only reached from rds_ib_exit(), where ->t_unloading already covers it.) While that destroy runs, a concurrent rds_cong_queue_updates() can still find the connection on the congestion map's m_conn_list (the conn is only removed from it after the paths are torn down) and call queue_delayed_work() on a cp_wq that destroy_workqueue() has already freed. Additionally, the other requeueing sites can likewise re-arm works that live in the about-to-be-freed connection unless rds_destroy_pending() has something to guard it with. The version-mismatch path used to be covered: commit c90ecbfaf50d2 ("rds: Use atomic flag to track connections being destroyed") introduced the RDS_DESTROY_PENDING cp_flags bit for exactly this, and after commit ebeeb1ad9b8ad ("rds: tcp: use rds_destroy_pending() to synchronize netns/module teardown and rds connection/workq management") it was set right before that rds_conn_destroy() call and tested via rds_ib_is_unloading(). Commit cdc306a5c9cd3 ("rds: make v3.1 as compat version") then removed the last set_bit while leaving the test behind, so the bit has been dead ever since and per-conn destroy has run unguarded. Bring the protection back at the connection level: set conn->c_destroy_in_prog before the unhash + synchronize_rcu() sequence in rds_conn_destroy() and test it in rds_destroy_pending(). The existing rcu_read_lock() around every check-and-queue site pairs with that synchronize_rcu(): once it returns, every new reader observes the flag and refuses to queue, and anything queued before it is flushed or cancelled by the existing teardown. Drop the now-unreferenced RDS_DESTROY_PENDING bit and its dead test. In the Oracle UEK kernel the equivalent conn->c_destroy_in_prog flag is part of the larger connection refcounting rework ("net/rds: Add krefs to struct rds_connection"), including ("net/rds: Merge uses of conn->c_destroy_in_prog & RDS_DESTROY_PENDING"). This ports the missing pieces of the requeue guard, which stand on their own. Fixes: cdc306a5c9cd3 ("rds: make v3.1 as compat version") Suggested-by: Sharath Srinivasan Assisted-by: Claude-Code:claude-fable-5 Signed-off-by: Allison Henderson --- net/rds/connection.c | 8 ++++++++ net/rds/ib.c | 5 +---- net/rds/rds.h | 12 ++++++++++-- 3 files changed, 19 insertions(+), 6 deletions(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index a96569a3ee9a..242ca0570a47 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -579,6 +579,14 @@ void rds_conn_destroy(struct rds_connection *conn) "%pI4\n", conn, &conn->c_laddr, &conn->c_faddr); + /* Make rds_destroy_pending() true for this conn. Together with + * the synchronize_rcu() below this stops the work-requeueing + * sites (which all test rds_destroy_pending() under + * rcu_read_lock()) from queueing new work on the path + * workqueues once we start cancelling and destroying them. + */ + WRITE_ONCE(conn->c_destroy_in_prog, true); + /* Ensure conn will not be scheduled for reconnect */ spin_lock_irq(&rds_conn_lock); hlist_del_init_rcu(&conn->c_hash_node); diff --git a/net/rds/ib.c b/net/rds/ib.c index 786f39169bc1..9fe3b9951bd3 100644 --- a/net/rds/ib.c +++ b/net/rds/ib.c @@ -525,10 +525,7 @@ static void rds_ib_set_unloading(void) static bool rds_ib_is_unloading(struct rds_connection *conn) { - struct rds_conn_path *cp = &conn->c_path[0]; - - return (test_bit(RDS_DESTROY_PENDING, &cp->cp_flags) || - atomic_read(&rds_ib_unloading) != 0); + return atomic_read(&rds_ib_unloading) != 0; } void rds_ib_exit(void) diff --git a/net/rds/rds.h b/net/rds/rds.h index 2db49573dacd..50b08c28ab86 100644 --- a/net/rds/rds.h +++ b/net/rds/rds.h @@ -89,7 +89,6 @@ enum { #define RDS_RECONNECT_PENDING 1 #define RDS_IN_XMIT 2 #define RDS_RECV_REFILL 3 -#define RDS_DESTROY_PENDING 4 /* Max number of multipaths per RDS connection. Must be a power of 2 */ #define RDS_MPATH_WORKERS 8 @@ -148,6 +147,14 @@ struct rds_connection { c_pad_to_32:29; int c_npaths; bool c_with_sport_idx; + /* Set once, by rds_conn_destroy(), before it cancels the path + * works; read through rds_destroy_pending(). A site that arms + * a path work must test the predicate and queue the work inside + * one rcu_read_lock() section: the synchronize_rcu() that + * follows the store is what keeps a queue issued after the + * cancellation from landing on a destroyed workqueue. + */ + bool c_destroy_in_prog; struct rds_connection *c_passive; struct rds_transport *c_trans; @@ -994,7 +1001,8 @@ void __rds_put_mr_final(struct kref *kref); static inline bool rds_destroy_pending(struct rds_connection *conn) { - return !check_net(rds_conn_net(conn)) || + return READ_ONCE(conn->c_destroy_in_prog) || + !check_net(rds_conn_net(conn)) || (conn->c_trans->t_unloading && conn->c_trans->t_unloading(conn)); } -- 2.25.1