[PATCH v6 5/7] fs/resctrl: Continue counter allocation after failure

[Ben Horgan]

In mbm_event mode, with mbm_assign_on_mkdir set to 1, when a user creates a
new CTRL_MON or MON group resctrl attempts to allocate counters for each of
the supported MBM events on each resctrl domain. As counters are limited,
such allocation may fail and when it does counter allocations for the
remaining domains are skipped even if the domains have available counters.

Since a counter allocation failure may result in counter allocation being
skipped on other domains the user needs to view the resource group's
mbm_L3_assignments file to get an accurate view of counter assignment in a
new resource group and then manually create counters in the skipped domains
with available counters.

Writes to mbm_L3_assignments using the wildcard format, <event>:*=e, also
skip counter allocation in other domains after a counter allocation
failure.

When handling a request to create counters in all domains it is unnecessary
for a counter allocation in one domain to prevent counter allocation in
other domains. Always attempt to allocate all the counters requested.

Signed-off-by: Ben Horgan <ben.horgan@xxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
---
Changes since v4:
Update commit message (Reinette)

Changes since v5:
files -> file in commit message
Add Reinette's R-b
---
 fs/resctrl/monitor.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index 5fbcc64e50ce..0e6a389a16bf 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -1211,9 +1211,10 @@ static int rdtgroup_alloc_assign_cntr(struct rdt_resource *r, struct rdt_l3_mon_
  * NULL; otherwise, assign the counter to the specified domain @d.
  *
  * If all counters in a domain are already in use, rdtgroup_alloc_assign_cntr()
- * will fail. The assignment process will abort at the first failure encountered
- * during domain traversal, which may result in the event being only partially
- * assigned.
+ * will fail. When attempting to assign counters to all domains, carry on trying
+ * to assign counters after a failure since only some domains may have counters
+ * and the goal is to assign counters where possible. If any counter assignment
+ * fails, return the error from the last failing assignment.
  *
  * Return:
  * 0 on success, < 0 on failure.
@@ -1226,9 +1227,11 @@ static int rdtgroup_assign_cntr_event(struct rdt_l3_mon_domain *d, struct rdtgro
 
 	if (!d) {
 		list_for_each_entry(d, &r->mon_domains, hdr.list) {
-			ret = rdtgroup_alloc_assign_cntr(r, d, rdtgrp, mevt);
-			if (ret)
-				return ret;
+			int err;
+
+			err = rdtgroup_alloc_assign_cntr(r, d, rdtgrp, mevt);
+			if (err)
+				ret = err;
 		}
 	} else {
 		ret = rdtgroup_alloc_assign_cntr(r, d, rdtgrp, mevt);
-- 
2.43.0