[PATCH v8 next 07/10] fs/resctrl: Add rmid_entry state helpers

Zeng Heng
2026-04-13T08:55:25Z

Introduce helper functions for rmid_entry management, in preparation
for upcoming patches supporting dynamic monitoring group allocation:

* rmid_is_occupied(): Query whether a RMID entry is currently allocated
by checking if its list node has been removed from the free list.

* rmid_entry_reassign_closid(): Update the closid associated with a RMID
entry.

Fix list node initialization in alloc_rmid() and dom_data_init() by
using list_del_init() instead of list_del(). This ensures list_empty()
checks in rmid_is_occupied() work correctly without encountering
LIST_POISON values.

Signed-off-by: Zeng Heng <zengheng4@huawei.com>
---
fs/resctrl/monitor.c | 18 ++++++++++++++++--
include/linux/resctrl.h | 21 +++++++++++++++++++++
2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
index 9fd901c78dc6..7473c43600cf 100644
--- a/fs/resctrl/monitor.c
+++ b/fs/resctrl/monitor.c
@@ -286,7 +286,7 @@ int alloc_rmid(u32 closid)
if (IS_ERR(entry))
return PTR_ERR(entry);

- list_del(&entry->list);
+ list_del_init(&entry->list);
return entry->rmid;
}

@@ -346,6 +346,20 @@ void free_rmid(u32 closid, u32 rmid)
list_add_tail(&entry->list, &rmid_free_lru);
}

+bool rmid_is_occupied(u32 closid, u32 rmid)
+{
+ u32 idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+
+ return list_empty(&rmid_ptrs[idx].list);
+}
+
+void rmid_entry_reassign_closid(u32 closid, u32 rmid)
+{
+ u32 idx = resctrl_arch_rmid_idx_encode(closid, rmid);
+
+ rmid_ptrs[idx].closid = closid;
+}
+
static struct mbm_state *get_mbm_state(struct rdt_l3_mon_domain *d, u32 closid,
u32 rmid, enum resctrl_event_id evtid)
{
@@ -945,7 +959,7 @@ int setup_rmid_lru_list(void)
idx = resctrl_arch_rmid_idx_encode(RESCTRL_RESERVED_CLOSID,
RESCTRL_RESERVED_RMID);
entry = __rmid_entry(idx);
- list_del(&entry->list);
+ list_del_init(&entry->list);

return 0;
}
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 006e57fd7ca5..b636e7250c20 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -702,6 +702,27 @@ bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r);
extern unsigned int resctrl_rmid_realloc_threshold;
extern unsigned int resctrl_rmid_realloc_limit;

+/**
+ * rmid_is_occupied() - Check whether the specified rmid has been
+ * allocated.
+ * @closid: Specify the closid that matches the rmid.
+ * @rmid: Specify the rmid entry to check status.
+ *
+ * This function checks if the rmid_entry is currently allocated by testing
+ * whether its list node is empty (removed from the free list).
+ *
+ * Return:
+ * True if the specified rmid is still in use.
+ */
+bool rmid_is_occupied(u32 closid, u32 rmid);
+
+/**
+ * rmid_entry_reassign_closid() - Update the closid field of a rmid_entry.
+ * @closid: Specify the reassigned closid.
+ * @rmid: Specify the rmid entry to update closid.
+ */
+void rmid_entry_reassign_closid(u32 closid, u32 rmid);
+
int resctrl_init(void);
void resctrl_exit(void);

--
2.25.1