linux-stable/drivers/s390
Julian Wiedmann 12472af896 s390/qeth: fix overestimated count of buffer elements
qeth_get_elements_for_range() doesn't know how to handle a 0-length
range (ie. start == end), and returns 1 when it should return 0.
Such ranges occur on TSO skbs, where the L2/L3/L4 headers (and thus all
of the skb's linear data) are skipped when mapping the skb into regular
buffer elements.

This overestimation may cause several performance-related issues:
1. sub-optimal IO buffer selection, where the next buffer gets selected
   even though the skb would actually still fit into the current buffer.
2. forced linearization, if the element count for a non-linear skb
   exceeds QETH_MAX_BUFFER_ELEMENTS.

Rather than modifying qeth_get_elements_for_range() and adding overhead
to every caller, fix up those callers that are in risk of passing a
0-length range.

Fixes: 2863c61334 ("qeth: refactor calculation of SBALE count")
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-02-28 11:13:12 -05:00
..
block vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
char vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
cio s390/cio: fix kernel-doc usage 2018-02-05 07:34:52 +01:00
crypto treewide: Use DEVICE_ATTR_RO 2018-01-09 16:34:34 +01:00
net s390/qeth: fix overestimated count of buffer elements 2018-02-28 11:13:12 -05:00
scsi s390: add a few more SPDX identifiers 2017-12-05 07:51:09 +01:00
virtio virtio/s390: implement PM operations for virtio_ccw 2018-02-14 14:34:09 +02:00
Makefile s390: add a few more SPDX identifiers 2017-12-05 07:51:09 +01:00