linux-kernel - [PATCH 1/2] mm/PAGE_IDLE_FLAG: Set PAGE

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Date:   Fri,  6 Aug 2021 09:51:52 +0000
From:   SeongJae Park <sj38.park@...il.com>
To:     akpm@...ux-foundation.org
Cc:     SeongJae Park <sjpark@...zon.de>, rdunlap@...radead.org,
        broonie@...nel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-next@...r.kernel.org, mhocko@...e.cz,
        mm-commits@...r.kernel.org, sfr@...b.auug.org.au,
        willy@...radead.org, linux-damon@...zon.com
Subject: [PATCH 1/2] mm/PAGE_IDLE_FLAG: Set PAGE_EXTENSION for none-64BIT

From: SeongJae Park <sjpark@...zon.de>

Commit 128fd80c4c07 ("mm/idle_page_tracking: Make PG_idle reusable") of
linux-mm[1] allows PAGE_IDLE_FLAG to be set without PAGE_EXTENSION
while 64BIT is not set.  This makes 'enum page_ext_flags' undefined, so
build fails as below for the config (!64BIT, !PAGE_EXTENSION, and
IDLE_PAGE_FLAG).

    $ make ARCH=i386 allnoconfig
    $ echo 'CONFIG_PAGE_IDLE_FLAG=y' >> .config
    $ make olddefconfig
    $ make ARCH=i386
    [...]
    ../include/linux/page_idle.h: In function ‘folio_test_young’:
    ../include/linux/page_idle.h:25:18: error: ‘PAGE_EXT_YOUNG’ undeclared (first use in this function); did you mean ‘PAGEOUTRUN’?
       return test_bit(PAGE_EXT_YOUNG, &page_ext->flags);
    [...]

This commit fixes this issue by making PAGE_EXTENSION to be set when
64BIT is not set and PAGE_IDLE_FLAG is set.

[1] https://github.com/hnaz/linux-mm/commit/128fd80c4c07

Fixes: 128fd80c4c07 ("mm/idle_page_tracking: Make PG_idle reusable")
Reported-by: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: SeongJae Park <sjpark@...zon.de>
---
 mm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index d0b85dc12429..50ca602edeb6 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -741,6 +741,7 @@ config DEFERRED_STRUCT_PAGE_INIT
 
 config PAGE_IDLE_FLAG
 	bool "Add PG_idle and PG_young flags"
+	select PAGE_EXTENSION if !64BIT
 	help
 	  This feature adds PG_idle and PG_young flags in 'struct page'.  PTE
 	  Accessed bit writers can set the state of the bit in the flags to let
@@ -749,7 +750,6 @@ config PAGE_IDLE_FLAG
 config IDLE_PAGE_TRACKING
 	bool "Enable idle page tracking"
 	depends on SYSFS && MMU && BROKEN
-	select PAGE_EXTENSION if !64BIT
 	select PAGE_IDLE_FLAG
 	help
 	  This feature allows to estimate the amount of user pages that have
-- 
2.17.1