linux-kernel - [RFC PATCH v1 12/57] cgroup: Remove PAGE_SIZE compile-time constant assumption

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Message-ID: <20241014105912.3207374-12-ryan.roberts@arm.com>
Date: Mon, 14 Oct 2024 11:58:19 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Michal Koutný <mkoutny@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	David Hildenbrand <david@...hat.com>,
	Greg Marsden <greg.marsden@...cle.com>,
	Ivan Ivanov <ivan.ivanov@...e.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Kalesh Singh <kaleshsingh@...gle.com>,
	Marc Zyngier <maz@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Matthias Brugger <mbrugger@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Tejun Heo <tj@...nel.org>,
	Will Deacon <will@...nel.org>,
	Zefan Li <lizefan.x@...edance.com>
Cc: Ryan Roberts <ryan.roberts@....com>,
	cgroups@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [RFC PATCH v1 12/57] cgroup: Remove PAGE_SIZE compile-time constant assumption

To prepare for supporting boot-time page size selection, refactor code
to remove assumptions about PAGE_SIZE being compile-time constant. Code
intended to be equivalent when compile-time page size is active.

Wrap global variables that are initialized with PAGE_SIZE derived values
using DEFINE_GLOBAL_PAGE_SIZE_VAR() so their initialization can be
deferred for boot-time page size builds.

Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---

***NOTE***
Any confused maintainers may want to read the cover note here for context:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/

 kernel/cgroup/cgroup.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index c8e4b62b436a4..1e9c96210821d 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4176,16 +4176,16 @@ static int cgroup_seqfile_show(struct seq_file *m, void *arg)
 	return 0;
 }
 
-static struct kernfs_ops cgroup_kf_single_ops = {
+static DEFINE_GLOBAL_PAGE_SIZE_VAR(struct kernfs_ops, cgroup_kf_single_ops, {
 	.atomic_write_len	= PAGE_SIZE,
 	.open			= cgroup_file_open,
 	.release		= cgroup_file_release,
 	.write			= cgroup_file_write,
 	.poll			= cgroup_file_poll,
 	.seq_show		= cgroup_seqfile_show,
-};
+});
 
-static struct kernfs_ops cgroup_kf_ops = {
+static DEFINE_GLOBAL_PAGE_SIZE_VAR(struct kernfs_ops, cgroup_kf_ops, {
 	.atomic_write_len	= PAGE_SIZE,
 	.open			= cgroup_file_open,
 	.release		= cgroup_file_release,
@@ -4195,7 +4195,7 @@ static struct kernfs_ops cgroup_kf_ops = {
 	.seq_next		= cgroup_seqfile_next,
 	.seq_stop		= cgroup_seqfile_stop,
 	.seq_show		= cgroup_seqfile_show,
-};
+});
 
 static void cgroup_file_notify_timer(struct timer_list *timer)
 {
-- 
2.43.0