linux-kernel - [PATCH 4.20 42/92] CIFS: Fix credits calculation for cancelled requests

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Message-Id: <20190218133458.644177463@linuxfoundation.org>
Date:   Mon, 18 Feb 2019 14:42:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pavel Shilovsky <pshilov@...rosoft.com>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.20 42/92] CIFS: Fix credits calculation for cancelled requests

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 8a26f0f781f56d3016b34a2217e346973d067e7b ]

If a request is cancelled, we can't assume that the server returns
1 credit back. Instead we need to wait for a response and process
the number of credits granted by the server.

Create a separate mid callback for cancelled request, parse the number
of credits in a response buffer and add them to the client's credits.
If the didn't get a response (no response buffer available) assume
0 credits granted. The latter most probably happens together with
session reconnect, so the client's credits are adjusted anyway.

Signed-off-by: Pavel Shilovsky <pshilov@...rosoft.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/cifsglob.h  |  1 +
 fs/cifs/transport.c | 28 ++++++++++++++++++++++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 38ab0fca49e1..7a4fae0dc566 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1426,6 +1426,7 @@ struct mid_q_entry {
 	int mid_state;	/* wish this were enum but can not pass to wait_event */
 	unsigned int mid_flags;
 	__le16 command;		/* smb command code */
+	unsigned int optype;	/* operation type */
 	bool large_buf:1;	/* if valid response, is pointer to large buf */
 	bool multiRsp:1;	/* multiple trans2 responses for one request  */
 	bool multiEnd:1;	/* both received */
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index d51064c1ba42..4dbf62bb51b2 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -785,6 +785,24 @@ cifs_noop_callback(struct mid_q_entry *mid)
 {
 }
 
+static void
+cifs_cancelled_callback(struct mid_q_entry *mid)
+{
+	struct TCP_Server_Info *server = mid->server;
+	unsigned int optype = mid->optype;
+	unsigned int credits_received = 0;
+
+	if (mid->mid_state == MID_RESPONSE_RECEIVED) {
+		if (mid->resp_buf)
+			credits_received = server->ops->get_credits(mid);
+		else
+			cifs_dbg(FYI, "Bad state for cancelled MID\n");
+	}
+
+	DeleteMidQEntry(mid);
+	add_credits(server, credits_received, optype);
+}
+
 int
 compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 		   const int flags, const int num_rqst, struct smb_rqst *rqst,
@@ -860,6 +878,7 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 		}
 
 		midQ[i]->mid_state = MID_REQUEST_SUBMITTED;
+		midQ[i]->optype = optype;
 		/*
 		 * We don't invoke the callback compounds unless it is the last
 		 * request.
@@ -894,15 +913,20 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
 
 	for (i = 0; i < num_rqst; i++) {
 		rc = wait_for_response(ses->server, midQ[i]);
-		if (rc != 0) {
+		if (rc != 0)
+			break;
+	}
+	if (rc != 0) {
+		for (; i < num_rqst; i++) {
 			cifs_dbg(VFS, "Cancelling wait for mid %llu cmd: %d\n",
 				 midQ[i]->mid, le16_to_cpu(midQ[i]->command));
 			send_cancel(ses->server, &rqst[i], midQ[i]);
 			spin_lock(&GlobalMid_Lock);
 			if (midQ[i]->mid_state == MID_REQUEST_SUBMITTED) {
 				midQ[i]->mid_flags |= MID_WAIT_CANCELLED;
-				midQ[i]->callback = DeleteMidQEntry;
+				midQ[i]->callback = cifs_cancelled_callback;
 				cancelled_mid[i] = true;
+				credits[i] = 0;
 			}
 			spin_unlock(&GlobalMid_Lock);
 		}
-- 
2.19.1