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Date:   Wed, 19 Apr 2023 14:50:13 +0200
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Subject: [PATCH v6 1/3] x86/resctrl: Factor rdtgroup lock for multi-file ops
From:   Peter Newman <peternewman@google.com>
To:     fenghua.yu@intel.com, reinette.chatre@intel.com
Cc:     Babu.Moger@amd.com, bp@alien8.de, dave.hansen@linux.intel.com,
        eranian@google.com, gupasani@google.com, hpa@zytor.com,
        james.morse@arm.com, linux-kernel@vger.kernel.org,
        mingo@redhat.com, skodak@google.com, tglx@linutronix.de,
        tony.luck@intel.com, x86@kernel.org,
        Peter Newman <peternewman@google.com>
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Precedence: bulk

rdtgroup_kn_lock_live() can only release a kernfs reference for a single
file before waiting on the rdtgroup_mutex, limiting its usefulness for
operations on multiple files, such as rename.

Factor the work needed to respectively break and unbreak active
protection on an individual file into rdtgroup_kn_{get,put}().

No functional change.

Signed-off-by: Peter Newman <peternewman@google.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 35 ++++++++++++++++----------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 6ad33f355861..51b869149e76 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2301,6 +2301,26 @@ static struct rdtgroup *kernfs_to_rdtgroup(struct kernfs_node *kn)
 	}
 }
 
+static void rdtgroup_kn_get(struct rdtgroup *rdtgrp, struct kernfs_node *kn)
+{
+	atomic_inc(&rdtgrp->waitcount);
+	kernfs_break_active_protection(kn);
+}
+
+static void rdtgroup_kn_put(struct rdtgroup *rdtgrp, struct kernfs_node *kn)
+{
+	if (atomic_dec_and_test(&rdtgrp->waitcount) &&
+	    (rdtgrp->flags & RDT_DELETED)) {
+		if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP ||
+		    rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED)
+			rdtgroup_pseudo_lock_remove(rdtgrp);
+		kernfs_unbreak_active_protection(kn);
+		rdtgroup_remove(rdtgrp);
+	} else {
+		kernfs_unbreak_active_protection(kn);
+	}
+}
+
 struct rdtgroup *rdtgroup_kn_lock_live(struct kernfs_node *kn)
 {
 	struct rdtgroup *rdtgrp = kernfs_to_rdtgroup(kn);
@@ -2308,8 +2328,7 @@ struct rdtgroup *rdtgroup_kn_lock_live(struct kernfs_node *kn)
 	if (!rdtgrp)
 		return NULL;
 
-	atomic_inc(&rdtgrp->waitcount);
-	kernfs_break_active_protection(kn);
+	rdtgroup_kn_get(rdtgrp, kn);
 
 	mutex_lock(&rdtgroup_mutex);
 
@@ -2328,17 +2347,7 @@ void rdtgroup_kn_unlock(struct kernfs_node *kn)
 		return;
 
 	mutex_unlock(&rdtgroup_mutex);
-
-	if (atomic_dec_and_test(&rdtgrp->waitcount) &&
-	    (rdtgrp->flags & RDT_DELETED)) {
-		if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP ||
-		    rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED)
-			rdtgroup_pseudo_lock_remove(rdtgrp);
-		kernfs_unbreak_active_protection(kn);
-		rdtgroup_remove(rdtgrp);
-	} else {
-		kernfs_unbreak_active_protection(kn);
-	}
+	rdtgroup_kn_put(rdtgrp, kn);
 }
 
 static int mkdir_mondata_all(struct kernfs_node *parent_kn,
-- 
2.40.0.634.g4ca3ef3211-goog