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s390/css: Prevent unnecessary allocation in subchannel loop 

Subchannel looping function for_each_subchannel_staged() allocates a
subchannel-ID-bitmap to efficiently iterate over the list of known
and unknown subchannels. Since this function is also used to iterate
over known-subchannels only, optimize that case by not requiring the
ID-bitmap allocation and falling back to simple bus_for_each_dev()
looping.

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Peter Oberparleiter 2013-11-26 14:59:21 +01:00 committed by Martin Schwidefsky
parent 175746eb06
commit 47d30674d6
1 changed files with 9 additions and 1 deletions
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10
drivers/s390/cio/css.c
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@ -69,7 +69,8 @@ static int call_fn_known_sch(struct device *dev, void *data)
struct cb_data *cb = data;
int rc = 0;
idset_sch_del(cb->set, sch->schid);
if (cb->set)
idset_sch_del(cb->set, sch->schid);
if (cb->fn_known_sch)
rc = cb->fn_known_sch(sch, cb->data);
return rc;
@ -115,6 +116,13 @@ int for_each_subchannel_staged(int (*fn_known)(struct subchannel *, void *),
cb.fn_known_sch = fn_known;
cb.fn_unknown_sch = fn_unknown;
if (fn_known && !fn_unknown) {
/* Skip idset allocation in case of known-only loop. */
cb.set = NULL;
return bus_for_each_dev(&css_bus_type, NULL, &cb,
call_fn_known_sch);
}
cb.set = idset_sch_new();
if (!cb.set)
/* fall back to brute force scanning in case of oom */