[PATCH v6 03/24] x86/resctrl: Create helper for RMID allocation and mondata dir creation

[James Morse <james.morse@arm.com>]

When monitoring is supported, each monitor and control group is allocated
an RMID. For control groups, rdtgroup_mkdir_ctrl_mon() later goes on to
allocate the CLOSID.

MPAM's equivalent of RMID are not an independent number, so can't be
allocated until the CLOSID is known. An RMID allocation for one CLOSID
may fail, whereas another may succeed depending on how many monitor
groups a control group has.

The RMID allocation needs to move to be after the CLOSID has been
allocated.

Move the RMID allocation and mondata dir creation to a helper, this
makes a subsequent change easier to read.

Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Tested-By: Peter Newman <peternewman@google.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v4:
 * Fixed typo in commit message, moved some words around.
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 42 +++++++++++++++++---------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index a2158c266e41..7a7369a323b5 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3165,6 +3165,30 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
 	return ret;
 }
 
+static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
+{
+	int ret;
+
+	if (!rdt_mon_capable)
+		return 0;
+
+	ret = alloc_rmid();
+	if (ret < 0) {
+		rdt_last_cmd_puts("Out of RMIDs\n");
+		return ret;
+	}
+	rdtgrp->mon.rmid = ret;
+
+	ret = mkdir_mondata_all(rdtgrp->kn, rdtgrp, &rdtgrp->mon.mon_data_kn);
+	if (ret) {
+		rdt_last_cmd_puts("kernfs subdir error\n");
+		free_rmid(rdtgrp->mon.rmid);
+		return ret;
+	}
+
+	return 0;
+}
+
 static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 			     const char *name, umode_t mode,
 			     enum rdt_group_type rtype, struct rdtgroup **r)
@@ -3230,20 +3254,10 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 		goto out_destroy;
 	}
 
-	if (rdt_mon_capable) {
-		ret = alloc_rmid();
-		if (ret < 0) {
-			rdt_last_cmd_puts("Out of RMIDs\n");
-			goto out_destroy;
-		}
-		rdtgrp->mon.rmid = ret;
+	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
+	if (ret)
+		goto out_destroy;
 
-		ret = mkdir_mondata_all(kn, rdtgrp, &rdtgrp->mon.mon_data_kn);
-		if (ret) {
-			rdt_last_cmd_puts("kernfs subdir error\n");
-			goto out_idfree;
-		}
-	}
 	kernfs_activate(kn);
 
 	/*
@@ -3251,8 +3265,6 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 	 */
 	return 0;
 
-out_idfree:
-	free_rmid(rdtgrp->mon.rmid);
 out_destroy:
 	kernfs_put(rdtgrp->kn);
 	kernfs_remove(rdtgrp->kn);
-- 
2.39.2