linux-kernel - [tip: x86/cache] x86/resctrl: Factor rdtgroup lock for multi-file ops

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Message-ID: <168613512832.404.10934762057759711815.tip-bot2@tip-bot2>
Date:   Wed, 07 Jun 2023 10:52:08 -0000
From:   "tip-bot2 for Peter Newman" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Peter Newman <peternewman@...gle.com>,
        "Borislav Petkov (AMD)" <bp@...en8.de>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Babu Moger <babu.moger@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/cache] x86/resctrl: Factor rdtgroup lock for multi-file ops

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

Commit-ID:     c45c06d4ae63a0714efbfa435c5a8f64a5f35b9b
Gitweb:        https://git.kernel.org/tip/c45c06d4ae63a0714efbfa435c5a8f64a5f35b9b
Author:        Peter Newman <peternewman@...gle.com>
AuthorDate:    Wed, 19 Apr 2023 14:50:13 +02:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Wed, 07 Jun 2023 12:15:18 +02:00

x86/resctrl: Factor rdtgroup lock for multi-file ops

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@...gle.com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Tested-by: Babu Moger <babu.moger@....com>
Link: https://lore.kernel.org/r/20230419125015.693566-2-peternewman@google.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 61cdd9b..653d258 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2305,6 +2305,26 @@ 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);
@@ -2312,8 +2332,7 @@ 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);
 
@@ -2332,17 +2351,7 @@ 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,