smb3: add tracepoint to catch cases where credit refund of failed op overlaps reconnect

Add tracepoint to catch potential cases where a pending operation overlapping a
reconnect could fail and incorrectly refund its credits causing the client
to think it has more credits available than the server thinks it does.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 89985a0..831fa60 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -74,6 +74,12 @@ smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
        int *val, rc = 0;
        spin_lock(&server->req_lock);
        val = server->ops->get_credits_field(server, optype);
+
+       /* eg found case where write overlapping reconnect messed up credits */
+       if (((optype & CIFS_OP_MASK) == CIFS_NEG_OP) && (*val != 0))
+               trace_smb3_reconnect_with_invalid_credits(server->CurrentMid,
+                       server->hostname, *val);
+
        *val += add;
        if (*val > 65000) {
                *val = 65000; /* Don't get near 64K credits, avoid srv bugs */

diff --git a/fs/cifs/trace.h b/fs/cifs/trace.h
index d4aed52..43e5bd4 100644 (file)
--- a/fs/cifs/trace.h
+++ b/fs/cifs/trace.h
@@ -486,6 +486,36 @@ DEFINE_EVENT(smb3_reconnect_class, smb3_##name,  \
 DEFINE_SMB3_RECONNECT_EVENT(reconnect);
 DEFINE_SMB3_RECONNECT_EVENT(partial_send_reconnect);
 
+DECLARE_EVENT_CLASS(smb3_credit_class,
+       TP_PROTO(__u64  currmid,
+               char *hostname,
+               int credits),
+       TP_ARGS(currmid, hostname, credits),
+       TP_STRUCT__entry(
+               __field(__u64, currmid)
+               __field(char *, hostname)
+               __field(int, credits)
+       ),
+       TP_fast_assign(
+               __entry->currmid = currmid;
+               __entry->hostname = hostname;
+               __entry->credits = credits;
+       ),
+       TP_printk("server=%s current_mid=0x%llx credits=%d",
+               __entry->hostname,
+               __entry->currmid,
+               __entry->credits)
+)
+
+#define DEFINE_SMB3_CREDIT_EVENT(name)        \
+DEFINE_EVENT(smb3_credit_class, smb3_##name,  \
+       TP_PROTO(__u64  currmid,                \
+               char *hostname,                 \
+               int  credits),                  \
+       TP_ARGS(currmid, hostname, credits))
+
+DEFINE_SMB3_CREDIT_EVENT(reconnect_with_invalid_credits);
+
 #endif /* _CIFS_TRACE_H */
 
 #undef TRACE_INCLUDE_PATH