[PATCH v2] fs/resctrl: Ensure default group reports tasks on monitor-only systems

[PATCH v2] fs/resctrl: Ensure default group reports tasks on monitor-only systems

[Tony Luck]

resctrl can be mounted on a system that supports monitoring but not allocation.

On such a system reading the "tasks" file in the default group reports no
tasks, even when there are tasks assigned to the default group. This problem
occurs because the check for whether a task belongs to a CTRL_MON group is
gated by a check for whether the system supports allocation.

The resctrl_arch_alloc_capable() check in is_closid_match() breaks task
reporting for the default group on monitor-only systems so remove this
check. On systems that support allocation the check is redundant.

Fixes: e6b2fac36fcc ("x86/resctrl: Use is_closid_match() in more places")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260831174421.13921-1-tony.luck%40intel.com?part=9
Signed-off-by: Tony Luck <tony.luck@intel.com>
---
Changes since https://lore.kernel.org/all/20261008234311.17702-1-tony.luck@intel.com/

        Dropped Assisted-by: tag. The LLM was only used for commit wordsmithing
        and I've now discarded everything it wrote.

        Rewrote commit in 3-paragraph (context, problem, solution)
        format per Documentation/process/maintainer-tip.rst guidelines.
---
 fs/resctrl/rdtgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 68be9b903ac6..57ab090072c2 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -685,7 +685,7 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
 
 static bool is_closid_match(struct task_struct *t, struct rdtgroup *r)
 {
-	return (resctrl_arch_alloc_capable() && (r->type == RDTCTRL_GROUP) &&
+	return (r->type == RDTCTRL_GROUP &&
 		resctrl_arch_match_closid(t, r->closid));
 }
 
-- 
2.56.0

Re: [PATCH v2] fs/resctrl: Ensure default group reports tasks on monitor-only systems

[Reinette Chatre]

On 10/9/26 12:39 PM, Tony Luck wrote:
> resctrl can be mounted on a system that supports monitoring but not allocation.
> 
> On such a system reading the "tasks" file in the default group reports no
> tasks, even when there are tasks assigned to the default group. This problem
> occurs because the check for whether a task belongs to a CTRL_MON group is
> gated by a check for whether the system supports allocation.
> 
> The resctrl_arch_alloc_capable() check in is_closid_match() breaks task
> reporting for the default group on monitor-only systems so remove this
> check. On systems that support allocation the check is redundant.
> 
> Fixes: e6b2fac36fcc ("x86/resctrl: Use is_closid_match() in more places")
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Closes: https://sashiko.dev/#/patchset/20260831174421.13921-1-tony.luck%40intel.com?part=9
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>

Reinette

[tip: x86/cache] fs/resctrl: Ensure default group reports tasks on monitor-only systems

[tip-bot2 for Tony Luck]

The following commit has been merged into the x86/cache branch of tip:

Commit-ID:     2c10b3fa5bdf61e344bc522e6c2e00d870ce7ab8
Gitweb:        https://git.kernel.org/tip/2c10b3fa5bdf61e344bc522e6c2e00d870ce7ab8
Author:        Tony Luck <tony.luck@intel.com>
AuthorDate:    Fri, 09 Oct 2026 12:39:23 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 09 Oct 2026 17:43:05 -07:00

fs/resctrl: Ensure default group reports tasks on monitor-only systems

resctrl can be mounted on a system that supports monitoring but not allocation.

On such a system reading the "tasks" file in the default group reports no
tasks, even when there are tasks assigned to the default group. This problem
occurs because the check for whether a task belongs to a CTRL_MON group is
gated by a check for whether the system supports allocation.

The resctrl_arch_alloc_capable() check in is_closid_match() breaks task
reporting for the default group on monitor-only systems so remove this check.
On systems that support allocation the check is redundant.

Fixes: e6b2fac36fcc ("x86/resctrl: Use is_closid_match() in more places")
Closes: https://sashiko.dev/#/patchset/20260831174421.13921-1-tony.luck%40intel.com?part=9
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://patch.msgid.link/20261009193923.15498-1-tony.luck@intel.com
---
 fs/resctrl/rdtgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 68be9b9..57ab090 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -685,7 +685,7 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
 
 static bool is_closid_match(struct task_struct *t, struct rdtgroup *r)
 {
-	return (resctrl_arch_alloc_capable() && (r->type == RDTCTRL_GROUP) &&
+	return (r->type == RDTCTRL_GROUP &&
 		resctrl_arch_match_closid(t, r->closid));
 }