[PATCH 2/2] nvme-tcp: delay nvme_tcp_reclassify_socket()

[Shin'ichiro Kawasaki]

From: Eric Dumazet <edumazet at google.com>

Commit 841aee4d75f1 ("nvme-tcp: lockdep: annotate in-kernel sockets")
introduced nvme_tcp_reclassify_socket() to resolve a lockdep WARN by
distinguishing userspace sockets from nvme-tcp sockets. After that, TLS
encryption support was introduced to nvme-tcp and it added another lock
dependency on userspace socket handling by tlshd, which resulted in a
new lockdep WARN. This WARN was hidden by the commit 19bdb70c77d3
("nvme-tcp: lockdep: use dynamic lockdep keys per socket instance").
However, it turned out the commit 19bdb70c77d3 has a bug of lockdep key
lifetime management, and it is to be reverted by another patch in this
series. After the revert, the WARN was unveiled and observed at the
blktests test case nvme/062:

  WARNING: possible circular locking dependency detected
  7.3.0-rc2+ #455 Tainted: G        W
  ------------------------------------------------------
  tlshd/75867 is trying to acquire lock:
  ffffffff91ada5e0 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x64/0x6d0

  but task is already holding lock:
  ffff888197808258 (sk_lock-AF_INET-NVME){+.+.}-{0:0}, at: do_tcp_setsockopt+0x499/0x26a0

  which lock already depends on the new lock.

To fix the lockdep WARN caused by the TLS encryption support, delay the
reclassification of the nvme-tcp sockets. Currently the reclassification
happens before the TLS handshake starts, which pulls in the additional
lock dependencies related to tlshd. Reclassify the sockets after the TLS
handshake instead, to cut that dependency.

Link: https://lore.kernel.org/lkml/CANn89i+wnTLC==UnXCpjsS4YxvEfhe5oK0N7fttbqr1zKyqdug@mail.gmail.com/
Signed-off-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki at wdc.com>
---
 drivers/nvme/host/tcp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 0666bb469c0a..7eec983c0ead 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1869,7 +1869,6 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
 	}
 
 	sk_net_refcnt_upgrade(queue->sock->sk);
-	nvme_tcp_reclassify_socket(queue->sock);
 
 	/* Single syn retry */
 	tcp_sock_set_syncnt(queue->sock->sk, 1);
@@ -1958,6 +1957,8 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
 			goto err_init_connect;
 	}
 
+	nvme_tcp_reclassify_socket(queue->sock);
+
 	ret = nvme_tcp_init_connection(queue);
 	if (ret)
 		goto err_init_connect;
-- 
2.54.0