linux-kernel - [RFC PATCH 06/18] mm: introduce CONFIG_FREE_USER

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Date:   Fri, 29 Apr 2022 21:35:40 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     akpm@...ux-foundation.org, tglx@...utronix.de,
        kirill.shutemov@...ux.intel.com, mika.penttila@...tfour.com,
        david@...hat.com, jgg@...dia.com, tj@...nel.org, dennis@...nel.org,
        ming.lei@...hat.com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, songmuchun@...edance.com,
        zhouchengming@...edance.com, Qi Zheng <zhengqi.arch@...edance.com>
Subject: [RFC PATCH 06/18] mm: introduce CONFIG_FREE_USER_PTE

This configuration variable will be used to build the code needed to
free user PTE page table pages.

The PTE page table setting and clearing functions(such as set_pte_at())
are in the architecture's files, and these functions will be hooked to
implement FREE_USER_PTE, so the architecture support is needed.

Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
---
 mm/Kconfig | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index 034d87953600..af99ed626732 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -909,6 +909,16 @@ config ANON_VMA_NAME
 	  area from being merged with adjacent virtual memory areas due to the
 	  difference in their name.
 
+config ARCH_SUPPORTS_FREE_USER_PTE
+	def_bool n
+
+config FREE_USER_PTE
+	bool "Free user PTE page tables"
+	default y
+	depends on ARCH_SUPPORTS_FREE_USER_PTE && MMU && SMP
+	help
+	  Try to free user PTE page table page when its all entries are none.
+
 source "mm/damon/Kconfig"
 
 endmenu
-- 
2.20.1