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Commit 7030fd62 authored by Bart Van Assche's avatar Bart Van Assche Committed by Robert Love
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libfc: Do not invoke the response handler after fc_exch_done() 



While the FCoE initiator driver invokes fc_exch_done() from inside
the libfc response handler, FCoE target drivers typically invoke
fc_exch_done() from outside the libfc response handler. The object
fc_exch.arg points at may disappear as soon as fc_exch_done() has
finished. So it's important not to invoke the response handler
function after fc_exch_done() has finished. Modify libfc such that
this guarantee is provided if fc_exch_done() is invoked from
outside a response handler. This patch fixes a sporadic crash in
FCoE target implementations after a command has been aborted.

Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: default avatarRobert Love <robert.w.love@intel.com>
parent f95b35cf

drivers/scsi/libfc/fc_exch.c

+92 −39
Original line number Diff line number Diff line
@@ -381,6 +381,8 @@ static void fc_exch_timer_set(struct fc_exch *ep, unsigned int timer_msec) 
/**

 * fc_exch_done_locked() - Complete an exchange with the exchange lock held

 * @ep: The exchange that is complete

 *

 * Note: May sleep if invoked from outside a response handler.

 */

static int fc_exch_done_locked(struct fc_exch *ep)

{
@@ -392,7 +394,6 @@ static int fc_exch_done_locked(struct fc_exch *ep) 
	 * ep, and in that case we only clear the resp and set it as

	 * complete, so it can be reused by the timer to send the rrq.

	 */

	ep->resp = NULL;

	if (ep->state & FC_EX_DONE)

		return rc;

	ep->esb_stat |= ESB_ST_COMPLETE;
@@ -589,6 +590,8 @@ static struct fc_seq *fc_seq_start_next(struct fc_seq *sp) 


/*

 * Set the response handler for the exchange associated with a sequence.

 *

 * Note: May sleep if invoked from outside a response handler.

 */

static void fc_seq_set_resp(struct fc_seq *sp,

			    void (*resp)(struct fc_seq *, struct fc_frame *,
@@ -596,8 +599,18 @@ static void fc_seq_set_resp(struct fc_seq *sp, 
			    void *arg)

{

	struct fc_exch *ep = fc_seq_exch(sp);

	DEFINE_WAIT(wait);



	spin_lock_bh(&ep->ex_lock);

	while (ep->resp_active && ep->resp_task != current) {

		prepare_to_wait(&ep->resp_wq, &wait, TASK_UNINTERRUPTIBLE);

		spin_unlock_bh(&ep->ex_lock);



		schedule();



		spin_lock_bh(&ep->ex_lock);

	}

	finish_wait(&ep->resp_wq, &wait);

	ep->resp = resp;

	ep->arg = arg;

	spin_unlock_bh(&ep->ex_lock);
@@ -680,6 +693,61 @@ static int fc_seq_exch_abort(const struct fc_seq *req_sp, 
	return error;

}



/**

 * fc_invoke_resp() - invoke ep->resp()

 *

 * Notes:

 * It is assumed that after initialization finished (this means the

 * first unlock of ex_lock after fc_exch_alloc()) ep->resp and ep->arg are

 * modified only via fc_seq_set_resp(). This guarantees that none of these

 * two variables changes if ep->resp_active > 0.

 *

 * If an fc_seq_set_resp() call is busy modifying ep->resp and ep->arg when

 * this function is invoked, the first spin_lock_bh() call in this function

 * will wait until fc_seq_set_resp() has finished modifying these variables.

 *

 * Since fc_exch_done() invokes fc_seq_set_resp() it is guaranteed that that

 * ep->resp() won't be invoked after fc_exch_done() has returned.

 *

 * The response handler itself may invoke fc_exch_done(), which will clear the

 * ep->resp pointer.

 *

 * Return value:

 * Returns true if and only if ep->resp has been invoked.

 */

static bool fc_invoke_resp(struct fc_exch *ep, struct fc_seq *sp,

			   struct fc_frame *fp)

{

	void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);

	void *arg;

	bool res = false;



	spin_lock_bh(&ep->ex_lock);

	ep->resp_active++;

	if (ep->resp_task != current)

		ep->resp_task = !ep->resp_task ? current : NULL;

	resp = ep->resp;

	arg = ep->arg;

	spin_unlock_bh(&ep->ex_lock);



	if (resp) {

		resp(sp, fp, arg);

		res = true;

	} else if (!IS_ERR(fp)) {

		fc_frame_free(fp);

	}



	spin_lock_bh(&ep->ex_lock);

	if (--ep->resp_active == 0)

		ep->resp_task = NULL;

	spin_unlock_bh(&ep->ex_lock);



	if (ep->resp_active == 0)

		wake_up(&ep->resp_wq);



	return res;

}



/**

 * fc_exch_timeout() - Handle exchange timer expiration

 * @work: The work_struct identifying the exchange that timed out
@@ -689,8 +757,6 @@ static void fc_exch_timeout(struct work_struct *work) 
	struct fc_exch *ep = container_of(work, struct fc_exch,

					  timeout_work.work);

	struct fc_seq *sp = &ep->seq;

	void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);

	void *arg;

	u32 e_stat;

	int rc = 1;
@@ -708,16 +774,13 @@ static void fc_exch_timeout(struct work_struct *work) 
			fc_exch_rrq(ep);

		goto done;

	} else {

		resp = ep->resp;

		arg = ep->arg;

		ep->resp = NULL;

		if (e_stat & ESB_ST_ABNORMAL)

			rc = fc_exch_done_locked(ep);

		spin_unlock_bh(&ep->ex_lock);

		if (!rc)

			fc_exch_delete(ep);

		if (resp)

			resp(sp, ERR_PTR(-FC_EX_TIMEOUT), arg);

		fc_invoke_resp(ep, sp, ERR_PTR(-FC_EX_TIMEOUT));

		fc_seq_set_resp(sp, NULL, ep->arg);

		fc_seq_exch_abort(sp, 2 * ep->r_a_tov);

		goto done;

	}
@@ -804,6 +867,8 @@ static struct fc_exch *fc_exch_em_alloc(struct fc_lport *lport, 
	ep->f_ctl = FC_FC_FIRST_SEQ;	/* next seq is first seq */

	ep->rxid = FC_XID_UNKNOWN;

	ep->class = mp->class;

	ep->resp_active = 0;

	init_waitqueue_head(&ep->resp_wq);

	INIT_DELAYED_WORK(&ep->timeout_work, fc_exch_timeout);

out:

	return ep;
@@ -864,6 +929,8 @@ static struct fc_exch *fc_exch_find(struct fc_exch_mgr *mp, u16 xid) 
 * fc_exch_done() - Indicate that an exchange/sequence tuple is complete and

 *		    the memory allocated for the related objects may be freed.

 * @sp: The sequence that has completed

 *

 * Note: May sleep if invoked from outside a response handler.

 */

static void fc_exch_done(struct fc_seq *sp)

{
@@ -873,6 +940,8 @@ static void fc_exch_done(struct fc_seq *sp) 
	spin_lock_bh(&ep->ex_lock);

	rc = fc_exch_done_locked(ep);

	spin_unlock_bh(&ep->ex_lock);



	fc_seq_set_resp(sp, NULL, ep->arg);

	if (!rc)

		fc_exch_delete(ep);

}
@@ -1436,9 +1505,7 @@ static void fc_exch_recv_req(struct fc_lport *lport, struct fc_exch_mgr *mp, 
		 * If new exch resp handler is valid then call that

		 * first.

		 */

		if (ep->resp)

			ep->resp(sp, fp, ep->arg);

		else

		if (!fc_invoke_resp(ep, sp, fp))

			lport->tt.lport_recv(lport, fp);

		fc_exch_release(ep);	/* release from lookup */

	} else {
@@ -1462,8 +1529,6 @@ static void fc_exch_recv_seq_resp(struct fc_exch_mgr *mp, struct fc_frame *fp) 
	struct fc_exch *ep;

	enum fc_sof sof;

	u32 f_ctl;

	void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);

	void *ex_resp_arg;

	int rc;



	ep = fc_exch_find(mp, ntohs(fh->fh_ox_id));
@@ -1506,14 +1571,11 @@ static void fc_exch_recv_seq_resp(struct fc_exch_mgr *mp, struct fc_frame *fp) 


	if (fc_sof_needs_ack(sof))

		fc_seq_send_ack(sp, fp);

	resp = ep->resp;

	ex_resp_arg = ep->arg;



	if (fh->fh_type != FC_TYPE_FCP && fr_eof(fp) == FC_EOF_T &&

	    (f_ctl & (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) ==

	    (FC_FC_LAST_SEQ | FC_FC_END_SEQ)) {

		spin_lock_bh(&ep->ex_lock);

		resp = ep->resp;

		rc = fc_exch_done_locked(ep);

		WARN_ON(fc_seq_exch(sp) != ep);

		spin_unlock_bh(&ep->ex_lock);
@@ -1534,10 +1596,8 @@ static void fc_exch_recv_seq_resp(struct fc_exch_mgr *mp, struct fc_frame *fp) 
	 * If new exch resp handler is valid then call that

	 * first.

	 */

	if (resp)

		resp(sp, fp, ex_resp_arg);

	else

		fc_frame_free(fp);

	fc_invoke_resp(ep, sp, fp);



	fc_exch_release(ep);

	return;

rel:
@@ -1576,8 +1636,6 @@ static void fc_exch_recv_resp(struct fc_exch_mgr *mp, struct fc_frame *fp) 
 */

static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp)

{

	void (*resp)(struct fc_seq *, struct fc_frame *fp, void *arg);

	void *ex_resp_arg;

	struct fc_frame_header *fh;

	struct fc_ba_acc *ap;

	struct fc_seq *sp;
@@ -1622,9 +1680,6 @@ static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp) 
		break;

	}



	resp = ep->resp;

	ex_resp_arg = ep->arg;



	/* do we need to do some other checks here. Can we reuse more of

	 * fc_exch_recv_seq_resp

	 */
@@ -1636,17 +1691,14 @@ static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp) 
	    ntoh24(fh->fh_f_ctl) & FC_FC_LAST_SEQ)

		rc = fc_exch_done_locked(ep);

	spin_unlock_bh(&ep->ex_lock);



	fc_exch_hold(ep);

	if (!rc)

		fc_exch_delete(ep);



	if (resp)

		resp(sp, fp, ex_resp_arg);

	else

		fc_frame_free(fp);



	fc_invoke_resp(ep, sp, fp);

	if (has_rec)

		fc_exch_timer_set(ep, ep->r_a_tov);



	fc_exch_release(ep);

}



/**
@@ -1768,32 +1820,33 @@ static void fc_seq_ls_rjt(struct fc_frame *rx_fp, enum fc_els_rjt_reason reason, 
/**

 * fc_exch_reset() - Reset an exchange

 * @ep: The exchange to be reset

 *

 * Note: May sleep if invoked from outside a response handler.

 */

static void fc_exch_reset(struct fc_exch *ep)

{

	struct fc_seq *sp;

	void (*resp)(struct fc_seq *, struct fc_frame *, void *);

	void *arg;

	int rc = 1;



	spin_lock_bh(&ep->ex_lock);

	fc_exch_abort_locked(ep, 0);

	ep->state |= FC_EX_RST_CLEANUP;

	fc_exch_timer_cancel(ep);

	resp = ep->resp;

	ep->resp = NULL;

	if (ep->esb_stat & ESB_ST_REC_QUAL)

		atomic_dec(&ep->ex_refcnt);	/* drop hold for rec_qual */

	ep->esb_stat &= ~ESB_ST_REC_QUAL;

	arg = ep->arg;

	sp = &ep->seq;

	rc = fc_exch_done_locked(ep);

	spin_unlock_bh(&ep->ex_lock);



	fc_exch_hold(ep);



	if (!rc)

		fc_exch_delete(ep);



	if (resp)

		resp(sp, ERR_PTR(-FC_EX_CLOSED), arg);

	fc_invoke_resp(ep, sp, ERR_PTR(-FC_EX_CLOSED));

	fc_seq_set_resp(sp, NULL, ep->arg);

	fc_exch_release(ep);

}



/**

include/scsi/libfc.h

+9 −0
Original line number Diff line number Diff line
@@ -410,6 +410,12 @@ struct fc_seq { 
 * @fh_type:      The frame type

 * @class:        The class of service

 * @seq:          The sequence in use on this exchange

 * @resp_active:  Number of tasks that are concurrently executing @resp().

 * @resp_task:    If @resp_active > 0, either the task executing @resp(), the

 *                task that has been interrupted to execute the soft-IRQ

 *                executing @resp() or NULL if more than one task is executing

 *                @resp concurrently.

 * @resp_wq:      Waitqueue for the tasks waiting on @resp_active.

 * @resp:         Callback for responses on this exchange

 * @destructor:   Called when destroying the exchange

 * @arg:          Passed as a void pointer to the resp() callback
@@ -441,6 +447,9 @@ struct fc_exch { 
	u32		    r_a_tov;

	u32		    f_ctl;

	struct fc_seq       seq;

	int		    resp_active;

	struct task_struct  *resp_task;

	wait_queue_head_t   resp_wq;

	void		    (*resp)(struct fc_seq *, struct fc_frame *, void *);

	void		    *arg;

	void		    (*destructor)(struct fc_seq *, void *);