linux-kernel - [PATCH] mm/sparse: clarify pgdat_to

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Message-ID: <20210630092309.17654-1-miles.chen@mediatek.com>
Date:   Wed, 30 Jun 2021 17:23:09 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <wsd_upstream@...iatek.com>,
        Miles Chen <miles.chen@...iatek.com>
Subject: [PATCH] mm/sparse: clarify pgdat_to_phys

clarify pgdat_to_phys() by wrapping pgdat_to_phys
with CONFIG_NUMA. (the same config as contig_page_data)

No functional change intended.

Comment from Mark [1]:
"
... and I reckon it'd be clearer and more robust to define
pgdat_to_phys() in the same ifdefs as contig_page_data so
that these, stay in-sync. e.g. have:

| #ifdef CONFIG_NUMA
| #define pgdat_to_phys(x)	virt_to_phys(x)
| #else /* CONFIG_NUMA */
|
| extern struct pglist_data contig_page_data;
| ...
| #define pgdat_to_phys(x)	__pa_symbol(&contig_page_data)
|
| #endif /* CONIFIG_NUMA */
"

[1] https://lore.kernel.org/linux-arm-kernel/20210615131902.GB47121@C02TD0UTHF1T.local/

Cc: Mark Rutland <mark.rutland@....com>
Signed-off-by: Miles Chen <miles.chen@...iatek.com>
---
 mm/sparse.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 7272f7a1449d..62c21ec28e33 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -344,14 +344,15 @@ size_t mem_section_usage_size(void)
 	return sizeof(struct mem_section_usage) + usemap_size();
 }
 
-static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat)
-{
-#ifndef CONFIG_NUMA
-	return __pa_symbol(pgdat);
-#else
-	return __pa(pgdat);
-#endif
-}
+#ifdef CONFIG_NUMA
+#define pgdat_to_phys(pgdat) __pa(pgdat)
+#else /* CONFIG_NUMA */
+/*
+ * When !CONFIG_NUMA, we only expect pgdat == &contig_page_data,
+ * and use __pa_symbol().
+ */
+#define pgdat_to_phys(pgdat) __pa_symbol(pgdat)
+#endif /* CONFIG_NUMA */
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 static struct mem_section_usage * __init
-- 
2.18.0