cifs: mangle existing header for SMB_COM_NT_CANCEL

The NT_CANCEL command looks just like the original command, except for a
few small differences. The send_nt_cancel function however currently takes
a tcon, which we don't have in SendReceive and SendReceive2.

Instead of "respinning" the entire header for an NT_CANCEL, just mangle
the existing header by replacing just the fields we need. This means we
don't need a tcon and allows us to call it from other places.

Reviewed-by: Pavel Shilovsky <piastryyy@gmail.com>
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 38 insertions, 25 deletions

diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index fe92c4cb75f5..c8e2808cd5e6 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -464,6 +464,43 @@ sync_mid_result(struct mid_q_entry *mid, struct TCP_Server_Info *server)
         return rc;
 }
 
+/*
+ * An NT cancel request header looks just like the original request except:
+ *
+ * The Command is SMB_COM_NT_CANCEL
+ * The WordCount is zeroed out
+ * The ByteCount is zeroed out
+ *
+ * This function mangles an existing request buffer into a
+ * SMB_COM_NT_CANCEL request and then sends it.
+ */
+static int
+send_nt_cancel(struct TCP_Server_Info *server, struct smb_hdr *in_buf,
+                struct mid_q_entry *mid)
+{
+        int rc = 0;
+
+        /* -4 for RFC1001 length and +2 for BCC field */
+        in_buf->smb_buf_length = sizeof(struct smb_hdr) - 4  + 2;
+        in_buf->Command = SMB_COM_NT_CANCEL;
+        in_buf->WordCount = 0;
+        BCC_LE(in_buf) = 0;
+
+        mutex_lock(&server->srv_mutex);
+        rc = cifs_sign_smb(in_buf, server, &mid->sequence_number);
+        if (rc) {
+                mutex_unlock(&server->srv_mutex);
+                return rc;
+        }
+        rc = smb_send(server, in_buf, in_buf->smb_buf_length);
+        mutex_unlock(&server->srv_mutex);
+
+        cFYI(1, "issued NT_CANCEL for mid %u, rc = %d",
+                in_buf->Mid, rc);
+
+        return rc;
+}
+
 int
 SendReceive2(const unsigned int xid, struct cifsSesInfo *ses,
              struct kvec *iov, int n_vec, int *pRespBufType /* ret */,
@@ -753,29 +790,6 @@ out:
         return rc;
 }
 
-/* Send an NT_CANCEL SMB to cause the POSIX blocking lock to return. */
-
-static int
-send_nt_cancel(struct cifsTconInfo *tcon, struct smb_hdr *in_buf,
-                struct mid_q_entry *midQ)
-{
-        int rc = 0;
-        struct cifsSesInfo *ses = tcon->ses;
-        __u16 mid = in_buf->Mid;
-
-        header_assemble(in_buf, SMB_COM_NT_CANCEL, tcon, 0);
-        in_buf->Mid = mid;
-        mutex_lock(&ses->server->srv_mutex);
-        rc = cifs_sign_smb(in_buf, ses->server, &midQ->sequence_number);
-        if (rc) {
-                mutex_unlock(&ses->server->srv_mutex);
-                return rc;
-        }
-        rc = smb_send(ses->server, in_buf, in_buf->smb_buf_length);
-        mutex_unlock(&ses->server->srv_mutex);
-        return rc;
-}
-
 /* We send a LOCKINGX_CANCEL_LOCK to cause the Windows
    blocking lock to return. */
 
@@ -890,8 +904,7 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifsTconInfo *tcon,
                 if (in_buf->Command == SMB_COM_TRANSACTION2) {
                         /* POSIX lock. We send a NT_CANCEL SMB to cause the
                            blocking lock to return. */
-
-                        rc = send_nt_cancel(tcon, in_buf, midQ);
+                        rc = send_nt_cancel(ses->server, in_buf, midQ);
                         if (rc) {
                                 delete_mid(midQ);
                                 return rc;