[PATCH v4 04/24] x86/resctrl: Move rmid allocation out of mkdir_rdt_prepare()

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

RMID are allocated for each monitor or control group directory, because
each of these needs its own RMID. For control groups,
rdtgroup_mkdir_ctrl_mon() later goes on to allocate the CLOSID.

MPAM's equivalent of RMID is 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 out of mkdir_rdt_prepare() to occur in its caller,
after the mkdir_rdt_prepare() call. This allows the RMID allocator to
know the CLOSID.

Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v2:
 * Moved kernfs_activate() later to preserve atomicity of files being visible
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 35 +++++++++++++++++++-------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 05774b185eec..8346a8f2ff9f 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3176,6 +3176,12 @@ static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
 	return 0;
 }
 
+static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp)
+{
+	if (rdt_mon_capable)
+		free_rmid(rgrp->closid, rgrp->mon.rmid);
+}
+
 static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 			     const char *name, umode_t mode,
 			     enum rdt_group_type rtype, struct rdtgroup **r)
@@ -3241,12 +3247,6 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 		goto out_destroy;
 	}
 
-	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
-	if (ret)
-		goto out_destroy;
-
-	kernfs_activate(kn);
-
 	/*
 	 * The caller unlocks the parent_kn upon success.
 	 */
@@ -3265,7 +3265,6 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 static void mkdir_rdt_prepare_clean(struct rdtgroup *rgrp)
 {
 	kernfs_remove(rgrp->kn);
-	free_rmid(rgrp->closid, rgrp->mon.rmid);
 	rdtgroup_remove(rgrp);
 }
 
@@ -3287,12 +3286,21 @@ static int rdtgroup_mkdir_mon(struct kernfs_node *parent_kn,
 	prgrp = rdtgrp->mon.parent;
 	rdtgrp->closid = prgrp->closid;
 
+	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
+	if (ret) {
+		mkdir_rdt_prepare_clean(rdtgrp);
+		goto out_unlock;
+	}
+
+	kernfs_activate(rdtgrp->kn);
+
 	/*
 	 * Add the rdtgrp to the list of rdtgrps the parent
 	 * ctrl_mon group has to track.
 	 */
 	list_add_tail(&rdtgrp->mon.crdtgrp_list, &prgrp->mon.crdtgrp_list);
 
+out_unlock:
 	rdtgroup_kn_unlock(parent_kn);
 	return ret;
 }
@@ -3323,10 +3331,17 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 	ret = 0;
 
 	rdtgrp->closid = closid;
-	ret = rdtgroup_init_alloc(rdtgrp);
-	if (ret < 0)
+
+	ret = mkdir_rdt_prepare_rmid_alloc(rdtgrp);
+	if (ret)
 		goto out_id_free;
 
+	kernfs_activate(rdtgrp->kn);
+
+	ret = rdtgroup_init_alloc(rdtgrp);
+	if (ret < 0)
+		goto out_rmid_free;
+
 	list_add(&rdtgrp->rdtgroup_list, &rdt_all_groups);
 
 	if (rdt_mon_capable) {
@@ -3345,6 +3360,8 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
 
 out_del_list:
 	list_del(&rdtgrp->rdtgroup_list);
+out_rmid_free:
+	mkdir_rdt_prepare_rmid_free(rdtgrp);
 out_id_free:
 	closid_free(closid);
 out_common_fail:
-- 
2.39.2