Commit 9de6c087 authored by Julian Wiedmann's avatar Julian Wiedmann Committed by Vasily Gorbik
Browse files

s390/qdio: simplify overlap calculation on Input refill 



Refilling the Input Queue requires additional checks, as the refilled
SBALs can overlap with the ACKs that qdio maintains on the queue.

This code path is way too complex, and does a whole bunch of wrap-around
checks that the modulo arithmetic in sub_buf() takes care of by itself.
So shrink down all that code into a few lines of equivalent
functionality.

Signed-off-by: default avatarJulian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent fee36576

drivers/s390/cio/qdio_main.c

+7 −43
Original line number Diff line number Diff line
@@ -1438,24 +1438,6 @@ out: 
}

EXPORT_SYMBOL_GPL(qdio_activate);



static inline int buf_in_between(int bufnr, int start, int count)

{

	int end = add_buf(start, count);



	if (end > start) {

		if (bufnr >= start && bufnr < end)

			return 1;

		else

			return 0;

	}



	/* wrap-around case */

	if (bufnr >= start || bufnr < end)

		return 1;

	else

		return 0;

}



/**

 * handle_inbound - reset processed input buffers

 * @q: queue containing the buffers
@@ -1466,36 +1448,18 @@ static inline int buf_in_between(int bufnr, int start, int count) 
static int handle_inbound(struct qdio_q *q, unsigned int callflags,

			  int bufnr, int count)

{

	int diff;

	int overlap;



	qperf_inc(q, inbound_call);



	if (!q->u.in.ack_count)

		goto set;



	/* protect against stop polling setting an ACK for an emptied slsb */

	if (count == QDIO_MAX_BUFFERS_PER_Q) {

		/* overwriting everything, just delete polling status */

		q->u.in.ack_count = 0;

		goto set;

	} else if (buf_in_between(q->u.in.ack_start, bufnr, count)) {

		if (is_qebsm(q)) {

			/* partial overwrite, just update ack_start */

			diff = add_buf(bufnr, count);

			diff = sub_buf(diff, q->u.in.ack_start);

			q->u.in.ack_count -= diff;

			if (q->u.in.ack_count <= 0) {

				q->u.in.ack_count = 0;

				goto set;

			}

			q->u.in.ack_start = add_buf(q->u.in.ack_start, diff);

		} else {

			/* the only ACK will be deleted */

			q->u.in.ack_count = 0;

		}

	/* If any ACKed SBALs are returned to HW, adjust ACK tracking: */

	overlap = min(count - sub_buf(q->u.in.ack_start, bufnr),

		      q->u.in.ack_count);

	if (overlap > 0) {

		q->u.in.ack_start = add_buf(q->u.in.ack_start, overlap);

		q->u.in.ack_count -= overlap;

	}



set:

	count = set_buf_states(q, bufnr, SLSB_CU_INPUT_EMPTY, count);

	atomic_add(count, &q->nr_buf_used);

CRA Git | Maintained and supported by SUSTech CRA and CCSE