diff mbox series

[136/212] mm/sparse: clarify pgdat_to_phys

Message ID 20210902215713.SjcwYIO6n%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [001/212] ia64: fix typo in a comment | expand

Commit Message

Andrew Morton Sept. 2, 2021, 9:57 p.m. UTC 
From: Miles Chen <miles.chen@mediatek.com>
Subject: mm/sparse: clarify pgdat_to_phys

Clarify pgdat_to_phys() by testing if
pgdat == &contig_page_data when CONFIG_NUMA=n.

We only expect contig_page_data in such case, so we
use &contig_page_data directly instead of pgdat.

No functional change intended when CONFIG_BUG_VM=n.

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/

Link: https://lkml.kernel.org/r/20210723123342.26406-1-miles.chen@mediatek.com
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/sparse.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

--- a/mm/sparse.c~mm-sparse-clarify-pgdat_to_phys
+++ a/mm/sparse.c
@@ -321,7 +321,8 @@  size_t mem_section_usage_size(void)
 static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat)
 {
 #ifndef CONFIG_NUMA
-	return __pa_symbol(pgdat);
+	VM_BUG_ON(pgdat != &contig_page_data);
+	return __pa_symbol(&contig_page_data);
 #else
 	return __pa(pgdat);
 #endif