linux-kernel - [PATCH AUTOSEL 5.4 4/6] cifs: add a warning when the in-flight count goes negative

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Date:   Tue, 29 Aug 2023 09:33:50 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Shyam Prasad N <sprasad@...rosoft.com>,
        Bharath SM <bharathsm@...rosoft.com>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>, pc@....nz,
        gregkh@...uxfoundation.org, lsahlber@...hat.com, pc@...guebit.com,
        vl@...ba.org, ematsumiya@...e.de
Subject: [PATCH AUTOSEL 5.4 4/6] cifs: add a warning when the in-flight count goes negative

From: Shyam Prasad N <sprasad@...rosoft.com>

[ Upstream commit e4645cc2f1e2d6f268bb8dcfac40997c52432aed ]

We've seen the in-flight count go into negative with some
internal stress testing in Microsoft.

Adding a WARN when this happens, in hope of understanding
why this happens when it happens.

Signed-off-by: Shyam Prasad N <sprasad@...rosoft.com>
Reviewed-by: Bharath SM <bharathsm@...rosoft.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/smb2ops.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index cd0030533bf7a..ad9b207432e10 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -79,6 +79,7 @@ smb2_add_credits(struct TCP_Server_Info *server,
 		*val = 65000; /* Don't get near 64K credits, avoid srv bugs */
 		printk_once(KERN_WARNING "server overflowed SMB3 credits\n");
 	}
+	WARN_ON_ONCE(server->in_flight == 0);
 	server->in_flight--;
 	if (server->in_flight == 0 && (optype & CIFS_OP_MASK) != CIFS_NEG_OP)
 		rc = change_conf(server);
-- 
2.40.1