Commit b8649efa authored by Ursula Braun's avatar Ursula Braun Committed by David S. Miller
Browse files

net/smc: fix sender_free computation 



In some scenarios a separate consumer cursor update is necessary.
The decision is made in smc_tx_consumer_cursor_update(). The
sender_free computation could be wrong:

The rx confirmed cursor is always smaller than or equal to the
rx producer cursor. The parameters in the smc_curs_diff() call
have to be exchanged, otherwise sender_free might even be negative.

And if more data arrives local_rx_ctrl.prod might be updated, enabling
a cursor difference between local_rx_ctrl.prod and rx confirmed cursor
larger than the RMB size. This case is not covered by smc_curs_diff().
Thus function smc_curs_diff_large() is introduced here.

If a recvmsg() is processed in parallel, local_tx_ctrl.cons might
change during smc_cdc_msg_send. Make sure rx_curs_confirmed is updated
with the actually sent local_tx_ctrl.cons value.

Fixes: e82f2e31 ("net/smc: optimize consumer cursor updates")
Signed-off-by: default avatarUrsula Braun <ubraun@linux.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ad6f317f

net/smc/smc_cdc.c

+3 −2
Original line number Diff line number Diff line
@@ -91,6 +91,7 @@ int smc_cdc_msg_send(struct smc_connection *conn, 
		     struct smc_wr_buf *wr_buf,

		     struct smc_cdc_tx_pend *pend)

{

	union smc_host_cursor cfed;

	struct smc_link *link;

	int rc;
@@ -102,10 +103,10 @@ int smc_cdc_msg_send(struct smc_connection *conn, 
	conn->local_tx_ctrl.seqno = conn->tx_cdc_seq;

	smc_host_msg_to_cdc((struct smc_cdc_msg *)wr_buf,

			    &conn->local_tx_ctrl, conn);

	smc_curs_copy(&cfed, &((struct smc_host_cdc_msg *)wr_buf)->cons, conn);

	rc = smc_wr_tx_send(link, (struct smc_wr_tx_pend_priv *)pend);

	if (!rc)

		smc_curs_copy(&conn->rx_curs_confirmed,

			      &conn->local_tx_ctrl.cons, conn);

		smc_curs_copy(&conn->rx_curs_confirmed, &cfed, conn);



	return rc;

}

net/smc/smc_cdc.h

+25 −1
Original line number Diff line number Diff line
@@ -160,7 +160,9 @@ static inline void smcd_curs_copy(union smcd_cdc_cursor *tgt, 
#endif

}



/* calculate cursor difference between old and new, where old <= new */

/* calculate cursor difference between old and new, where old <= new and

 * difference cannot exceed size

 */

static inline int smc_curs_diff(unsigned int size,

				union smc_host_cursor *old,

				union smc_host_cursor *new)
@@ -185,6 +187,28 @@ static inline int smc_curs_comp(unsigned int size, 
	return smc_curs_diff(size, old, new);

}



/* calculate cursor difference between old and new, where old <= new and

 * difference may exceed size

 */

static inline int smc_curs_diff_large(unsigned int size,

				      union smc_host_cursor *old,

				      union smc_host_cursor *new)

{

	if (old->wrap < new->wrap)

		return min_t(int,

			     (size - old->count) + new->count +

			     (new->wrap - old->wrap - 1) * size,

			     size);



	if (old->wrap > new->wrap) /* wrap has switched from 0xffff to 0x0000 */

		return min_t(int,

			     (size - old->count) + new->count +

			     (new->wrap + 0xffff - old->wrap) * size,

			     size);



	return max_t(int, 0, (new->count - old->count));

}



static inline void smc_host_cursor_to_cdc(union smc_cdc_cursor *peer,

					  union smc_host_cursor *local,

					  struct smc_connection *conn)

net/smc/smc_tx.c

+2 −1
Original line number Diff line number Diff line
@@ -595,7 +595,8 @@ void smc_tx_consumer_update(struct smc_connection *conn, bool force) 
	if (to_confirm > conn->rmbe_update_limit) {

		smc_curs_copy(&prod, &conn->local_rx_ctrl.prod, conn);

		sender_free = conn->rmb_desc->len -

			      smc_curs_diff(conn->rmb_desc->len, &prod, &cfed);

			      smc_curs_diff_large(conn->rmb_desc->len,

						  &cfed, &prod);

	}



	if (conn->local_rx_ctrl.prod_flags.cons_curs_upd_req ||

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