linux-kernel - [PATCH RFC 4/4] mitigations: Add flock cache accounting to 'mitigations=off'

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Date: Wed, 17 Jan 2024 08:14:46 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
	Jeff Layton <jlayton@...nel.org>,
	Chuck Lever <chuck.lever@...cle.com>,
	Shakeel Butt <shakeelb@...gle.com>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>,
	Tejun Heo <tj@...nel.org>,
	Vasily Averin <vasily.averin@...ux.dev>,
	Michal Koutny <mkoutny@...e.com>,
	Waiman Long <longman@...hat.com>,
	Muchun Song <muchun.song@...ux.dev>,
	Jiri Kosina <jikos@...nel.org>,
	cgroups@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH RFC 4/4] mitigations: Add flock cache accounting to 'mitigations=off'

Allow flock cache accounting to be disabled with 'mitigations=off', as
it fits the profile for that option: trusted user space combined with a
performance-impacting mitigation.

Also, for consistency with the other CONFIG_MITIGATION_* options, rename
CONFIG_FLOCK_ACCOUNTING to CONFIG_MITIGATION_FLOCK_ACCOUNTING.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 4 ++++
 fs/Kconfig                                      | 2 +-
 fs/locks.c                                      | 5 +++--
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 24e873351368..b31fe7433b48 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3427,6 +3427,10 @@
 					       ssbd=force-off [ARM64]
 					       tsx_async_abort=off [X86]
 
+					       Software mitigations:
+					       ---------------------
+					       flock_accounting=off [KNL]
+
 				Exceptions:
 					       This does not have any effect on
 					       kvm.nx_huge_pages when
diff --git a/fs/Kconfig b/fs/Kconfig
index 591f54a03059..4345b79d3b40 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -129,7 +129,7 @@ config FILE_LOCKING
           for filesystems like NFS and for the flock() system
           call. Disabling this option saves about 11k.
 
-config FLOCK_ACCOUNTING
+config MITIGATION_FLOCK_ACCOUNTING
 	bool "Enable kernel memory accounting for file locks" if EXPERT
 	depends on FILE_LOCKING
 	default y
diff --git a/fs/locks.c b/fs/locks.c
index e2799a18c4e8..fd4157ccd504 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -64,6 +64,7 @@
 #include <linux/hashtable.h>
 #include <linux/percpu.h>
 #include <linux/sysctl.h>
+#include <linux/mitigations.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/filelock.h>
@@ -2905,7 +2906,7 @@ static int __init proc_locks_init(void)
 fs_initcall(proc_locks_init);
 #endif
 
-static bool flock_accounting __ro_after_init = IS_ENABLED(CONFIG_FLOCK_ACCOUNTING);
+static bool flock_accounting __ro_after_init = IS_ENABLED(CONFIG_MITIGATION_FLOCK_ACCOUNTING);
 
 static int __init flock_accounting_cmdline(char *str)
 {
@@ -2930,7 +2931,7 @@ static int __init filelock_init(void)
 	int i;
 	slab_flags_t flags = SLAB_PANIC;
 
-	if (!flock_accounting)
+	if (mitigations_off() || !flock_accounting)
 		pr_err(FLOCK_ACCOUNTING_MSG);
 	else
 		flags |= SLAB_ACCOUNT;
-- 
2.43.0