[PATCH] fs/resctrl: Fix CLOSID propagation when reparenting monitor groups

[Jinjie Ruan]

Renaming a monitor group to move it below a different control group
changes the CLOSID of every task in that monitor group. mongrp_reparent()
updates rdtgrp->mon.parent and rdtgrp->closid before calling
rdt_move_group_tasks() to propagate the new CLOSID to the tasks.

rdt_move_group_tasks() uses its first argument to identify the tasks to
move. For a monitor group this is is_rmid_match(), which on MPAM compares
both the PARTID and the PMG of the task with the parent control group's
CLOSID and the monitor group's RMID. After rdtgrp->mon.parent and
rdtgrp->closid have been updated, the match uses the new CLOSID, so no
task in the monitor group matches and none is moved. The tasks keep the
old PARTID and continue to use the old control group's allocation.

x86 matches on the RMID alone, so it is unaffected. Now only arm64 mpam
affected.

Save the monitor group state before it is modified and use the saved state
as the source of the task move. The updated group remains the destination,
so matching tasks are moved to the new CLOSID and RMID.

Fixes: 8da2b938eb7e ("x86/resctrl: Implement rename op for mon groups")
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 7.1.x
---
 fs/resctrl/rdtgroup.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 57ab090072c2..33b23b59a6de 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -4322,6 +4322,7 @@ static void mongrp_reparent(struct rdtgroup *rdtgrp,
 			    cpumask_var_t cpus)
 {
 	struct rdtgroup *prdtgrp = rdtgrp->mon.parent;
+	struct rdtgroup old_rdtgrp = *rdtgrp;
 
 	WARN_ON(rdtgrp->type != RDTMON_GROUP);
 	WARN_ON(new_prdtgrp->type != RDTCTRL_GROUP);
@@ -4338,7 +4339,7 @@ static void mongrp_reparent(struct rdtgroup *rdtgrp,
 	rdtgrp->closid = new_prdtgrp->closid;
 
 	/* Propagate updated closid to all tasks in this group. */
-	rdt_move_group_tasks(rdtgrp, rdtgrp, cpus);
+	rdt_move_group_tasks(&old_rdtgrp, rdtgrp, cpus);
 
 	update_closid_rmid(cpus, NULL);
 }
-- 
2.43.0