linux-kernel - [PATCH V3 1/3] arm64/mm/hotplug: Register boot memory hot remove notifier earlier

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Date:   Mon, 21 Sep 2020 17:35:06 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will@...nel.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Will Deacon <will@...nel.com>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>,
        Steve Capper <steve.capper@....com>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH V3 1/3] arm64/mm/hotplug: Register boot memory hot remove notifier earlier

This moves memory notifier registration earlier in the boot process from
device_initcall() to early_initcall() which will help in guarding against
potential early boot memory offline requests. Even though there should not
be any actual offlinig requests till memory block devices are initialized
with memory_dev_init() but then generic init sequence might just change in
future. Hence an early registration for the memory event notifier would be
helpful. While here, just skip the registration if CONFIG_MEMORY_HOTREMOVE
is not enabled and also call out when memory notifier registration fails.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Steve Capper <steve.capper@....com>
Cc: Mark Brown <broonie@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 arch/arm64/mm/mmu.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 75df62fea1b6..df3b7415b128 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1499,7 +1499,17 @@ static struct notifier_block prevent_bootmem_remove_nb = {
 
 static int __init prevent_bootmem_remove_init(void)
 {
-	return register_memory_notifier(&prevent_bootmem_remove_nb);
+	int ret = 0;
+
+	if (!IS_ENABLED(CONFIG_MEMORY_HOTREMOVE))
+		return ret;
+
+	ret = register_memory_notifier(&prevent_bootmem_remove_nb);
+	if (!ret)
+		return ret;
+
+	pr_err("Notifier registration failed - boot memory can be removed\n");
+	return ret;
 }
-device_initcall(prevent_bootmem_remove_init);
+early_initcall(prevent_bootmem_remove_init);
 #endif
-- 
2.20.1