[PATCH v10 02/15] fs/resctrl: Skip monitor context allocation when force-freeing RMIDs

[Jinjie Ruan]

From: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>

__check_limbo() allocates the architecture monitor context before the
scan loop, even when force_free is set. The force-free path never reads
occupancy and never uses the context.

If the allocation fails, the function returns early and leaves the limbo
list unflushed. Callers such as the unmount path then silently fail to
return the RMIDs to the free list, leaving stale CLOSIDs in limbo that
are re-interpreted with the CDP state of the next mount.

Only allocate and free the monitor context when occupancy will be read.

Fixes: fa7d949337cc ("x86/resctrl: Rename and move rdt files to a separate directory")
Cc: James Morse <james.morse@xxxxxxx>
Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 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 da883adc3adc..ffa9c67c9f00 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -142,11 +142,13 @@ void __check_limbo(struct rdt_l3_mon_domain *d, bool force_free)
 	u64 val = 0;
 
 	arch_priv = mon_event_all[QOS_L3_OCCUP_EVENT_ID].arch_priv;
-	arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, QOS_L3_OCCUP_EVENT_ID);
-	if (IS_ERR(arch_mon_ctx)) {
-		pr_warn_ratelimited("Failed to allocate monitor context: %pe",
-				    arch_mon_ctx);
-		return;
+	if (!force_free) {
+		arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, QOS_L3_OCCUP_EVENT_ID);
+		if (IS_ERR(arch_mon_ctx)) {
+			pr_warn_ratelimited("Failed to allocate monitor context: %pe",
+					    arch_mon_ctx);
+			return;
+		}
 	}
 
 	/*
@@ -192,7 +194,8 @@ void __check_limbo(struct rdt_l3_mon_domain *d, bool force_free)
 		cur_idx = idx + 1;
 	}
 
-	resctrl_arch_mon_ctx_free(r, QOS_L3_OCCUP_EVENT_ID, arch_mon_ctx);
+	if (!force_free)
+		resctrl_arch_mon_ctx_free(r, QOS_L3_OCCUP_EVENT_ID, arch_mon_ctx);
 }
 
 bool has_busy_rmid(struct rdt_l3_mon_domain *d)
-- 
2.43.0