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| author |   Julian Wiedmann <jwi@linux.vnet.ibm.com> | 2018-02-27 18:58:12 +0100 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2018-02-28 11:13:12 -0500 |
| commit | 12472af89632beb1ed8dea29d4efe208ca05b06a (patch) | |
| tree | 7ff331b71a1d91c8614d0c7630cd8deba11c83bc /drivers/s390/net/qeth_l3_main.c | |
| parent | gianfar: Fix Rx byte accounting for ndev stats (diff) | |
| download | linux-dev-12472af89632beb1ed8dea29d4efe208ca05b06a.tar.xz linux-dev-12472af89632beb1ed8dea29d4efe208ca05b06a.zip | |
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: 2863c61334aa ("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>
Diffstat (limited to '')
| -rw-r--r-- | drivers/s390/net/qeth_l3_main.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c index b0c888e86cd4..3421893c37a4 100644 --- a/drivers/s390/net/qeth_l3_main.c +++ b/drivers/s390/net/qeth_l3_main.c @@ -2450,11 +2450,12 @@ static void qeth_tso_fill_header(struct qeth_card *card, static int qeth_l3_get_elements_no_tso(struct qeth_card *card, struct sk_buff *skb, int extra_elems) { - addr_t tcpdptr = (addr_t)tcp_hdr(skb) + tcp_hdrlen(skb); - int elements = qeth_get_elements_for_range( - tcpdptr, - (addr_t)skb->data + skb_headlen(skb)) + - qeth_get_elements_for_frags(skb); + addr_t start = (addr_t)tcp_hdr(skb) + tcp_hdrlen(skb); + addr_t end = (addr_t)skb->data + skb_headlen(skb); + int elements = qeth_get_elements_for_frags(skb); + + if (start != end) + elements += qeth_get_elements_for_range(start, end); if ((elements + extra_elems) > QETH_MAX_BUFFER_ELEMENTS(card)) { QETH_DBF_MESSAGE(2, |