[PATCH AUTOSEL 4.19 4/5] cifs: add a warning when the in-flight count goes negative

[Sasha Levin <sashal@kernel.org>]

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

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index c07dcb2af2eb8..01ab4496cb897 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -79,6 +79,7 @@ smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
 		*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);
-- 
2.39.2