linux-kernel - [PATCH] mm: sparse: clarify a variable name and its value

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Date: Sun,  9 Jun 2024 00:21:14 +0900
From: Leesoo Ahn <lsahn@...eel.net>
To: lsahn@...eel.net
Cc: Leesoo Ahn <lsahn@...akecorp.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mm: sparse: clarify a variable name and its value

Setting 'limit' variable to 0 might seem like it means "no limit". But
in the memblock API, 0 actually means the 'MEMBLOCK_ALLOC_ACCESSIBLE'
enum, which limits the physical address range based on
'memblock.current_limit'. This can be confusing.

To make things clearer, I suggest renaming the variable to
'limit_or_flag'. This name shows that the variable can either be a
number for limits or an enum for a flag. This way, readers will easily
understand what kind of value is being passed to the memblock API and
how it works without needing to look into the API details.

Signed-off-by: Leesoo Ahn <lsahn@...eel.net>
---
 mm/sparse.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index de40b2c73406..80e50ba26f24 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -333,7 +333,7 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
 					 unsigned long size)
 {
 	struct mem_section_usage *usage;
-	unsigned long goal, limit;
+	unsigned long goal, limit_or_flag;
 	int nid;
 	/*
 	 * A page may contain usemaps for other sections preventing the
@@ -346,12 +346,13 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
 	 * this problem.
 	 */
 	goal = pgdat_to_phys(pgdat) & (PAGE_SECTION_MASK << PAGE_SHIFT);
-	limit = goal + (1UL << PA_SECTION_SHIFT);
+	limit_or_flag = goal + (1UL << PA_SECTION_SHIFT);
 	nid = early_pfn_to_nid(goal >> PAGE_SHIFT);
 again:
-	usage = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal, limit, nid);
-	if (!usage && limit) {
-		limit = 0;
+	usage = memblock_alloc_try_nid(size, SMP_CACHE_BYTES, goal,
+				limit_or_flag, nid);
+	if (!usage && (limit_or_flag != MEMBLOCK_ALLOC_ACCESSIBLE)) {
+		limit_or_flag = MEMBLOCK_ALLOC_ACCESSIBLE;
 		goto again;
 	}
 	return usage;
-- 
2.34.1