cifs: only wake the thread for the very last PDU in a compound (4e34feb5) · Commits · 戴 / test

For compounded PDUs we whould only wake the waiting thread for the very last PDU of the compound. We do this so that we are guaranteed that the demultiplex_thread will not process or access any of those MIDs any more once the send/recv thread starts processing. Else there is a race where at the end of the send/recv processing we will try to delete all the mids of the compound. If the multiplex thread still has other mids to process at this point for this compound this can lead to an oops. Needed to fix recent commit: commit ("cifs: update smb2_queryfs() to use compounding") Signed-off-by:

Ronnie Sahlberg <lsahlber@redhat.com> Signed-off-by:

Steve French <stfrench@microsoft.com> Reviewed-by:

Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/transport.c

+17 −1

Original line number	Diff line number	Diff line
		@@ -773,6 +773,11 @@ cifs_setup_request(struct cifs_ses ses, struct smb_rqst rqst)
		return mid;
		}

		static void
		cifs_noop_callback(struct mid_q_entry *mid)
		{
		}

		int
		compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
		const int flags, const int num_rqst, struct smb_rqst *rqst,
		@@ -827,8 +832,13 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
		}

		midQ[i]->mid_state = MID_REQUEST_SUBMITTED;
		/*
		* We don't invoke the callback compounds unless it is the last
		* request.
		*/
		if (i < num_rqst - 1)
		midQ[i]->callback = cifs_noop_callback;
		}

		cifs_in_send_inc(ses->server);
		rc = smb_send_rqst(ses->server, num_rqst, rqst, flags);
		cifs_in_send_dec(ses->server);
		@@ -909,6 +919,12 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
		midQ[i]->resp_buf = NULL;
		}
		out:
		/*
		* This will dequeue all mids. After this it is important that the
		* demultiplex_thread will not process any of these mids any futher.
		* This is prevented above by using a noop callback that will not
		* wake this thread except for the very last PDU.
		*/
		for (i = 0; i < num_rqst; i++)
		cifs_delete_mid(midQ[i]);
		add_credits(ses->server, credits, optype);

Admin message