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s390/qeth: fix underestimated count of buffer elements

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For a memory range/skb where the last byte falls onto a page boundary
(ie. 'end' is of the form xxx...xxx001), the PFN_UP() part of the
calculation currently doesn't round up to the next PFN due to an
off-by-one error.
Thus qeth believes that the skb occupies one page less than it
actually does, and may select a IO buffer that doesn't have enough spare
buffer elements to fit all of the skb's data.
HW detects this as a malformed buffer descriptor, and raises an
exception which then triggers device recovery.

Fixes: 2863c61334 ("qeth: refactor calculation of SBALE count")
Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ursula Braun 2018-02-09 11:03:49 +01:00 committed by David S. Miller
parent 0bf7800f17
commit 89271c65ed
1 changed files with 1 additions and 1 deletions
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2
drivers/s390/net/qeth_core.h
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@ -846,7 +846,7 @@ struct qeth_trap_id {
*/
static inline int qeth_get_elements_for_range(addr_t start, addr_t end)
{
return PFN_UP(end - 1) - PFN_DOWN(start);
return PFN_UP(end) - PFN_DOWN(start);
}
static inline int qeth_get_micros(void)