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Subject[ 17/21] NTB: Correctly handle receive buffers of the minimal size
Date
3.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jon Mason <jon.mason@intel.com>

commit c9d534c8cbaedbb522a1d2cb037c6c394f610317 upstream.

The ring logic of the NTB receive buffer/transmit memory window requires
there to be at least 2 payload sized allotments. For the minimal size
case, split the buffer into two and set the transport_mtu to the
appropriate size.

Signed-off-by: Jon Mason <jon.mason@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/ntb/ntb_transport.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -490,11 +490,12 @@ static void ntb_transport_setup_qp_mw(st
rx_size -= sizeof(struct ntb_rx_info);

qp->rx_buff = qp->remote_rx_info + 1;
- qp->rx_max_frame = min(transport_mtu, rx_size);
+ /* Due to housekeeping, there must be atleast 2 buffs */
+ qp->rx_max_frame = min(transport_mtu, rx_size / 2);
qp->rx_max_entry = rx_size / qp->rx_max_frame;
qp->rx_index = 0;

- qp->remote_rx_info->entry = qp->rx_max_entry;
+ qp->remote_rx_info->entry = qp->rx_max_entry - 1;

/* setup the hdr offsets with 0's */
for (i = 0; i < qp->rx_max_entry; i++) {
@@ -818,7 +819,8 @@ static void ntb_transport_init_queue(str
tx_size -= sizeof(struct ntb_rx_info);

qp->tx_mw = qp->rx_info + 1;
- qp->tx_max_frame = min(transport_mtu, tx_size);
+ /* Due to housekeeping, there must be atleast 2 buffs */
+ qp->tx_max_frame = min(transport_mtu, tx_size / 2);
qp->tx_max_entry = tx_size / qp->tx_max_frame;

if (nt->debugfs_dir) {



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