linux-kernel - [PATCH] percpu: simplify the logic of pcpu_alloc_first

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Date: Tue, 23 Apr 2024 21:55:25 +0800
From: Yuntao Wang <ytcoode@...il.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Cc: Dennis Zhou <dennis@...nel.org>,
	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Yuntao Wang <ytcoode@...il.com>
Subject: [PATCH] percpu: simplify the logic of pcpu_alloc_first_chunk()

In the logic for hiding the end of the bitmap, there are several places
where the same value 'region_bits - offset_bits' is calculated over and
over again using different methods. Eliminate these redundant calculations
to improve code readability.

Signed-off-by: Yuntao Wang <ytcoode@...il.com>
---
 mm/percpu.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 4e11fc1e6def..2a051f00f68d 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1421,15 +1421,13 @@ static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr,
 	if (chunk->end_offset) {
 		/* hide the end of the bitmap */
 		offset_bits = chunk->end_offset / PCPU_MIN_ALLOC_SIZE;
-		bitmap_set(chunk->alloc_map,
-			   pcpu_chunk_map_bits(chunk) - offset_bits,
-			   offset_bits);
-		set_bit((start_offset + map_size) / PCPU_MIN_ALLOC_SIZE,
-			chunk->bound_map);
+		start_offset = region_bits - offset_bits;
+
+		bitmap_set(chunk->alloc_map, start_offset, offset_bits);
+		set_bit(start_offset, chunk->bound_map);
 		set_bit(region_bits, chunk->bound_map);
 
-		pcpu_block_update_hint_alloc(chunk, pcpu_chunk_map_bits(chunk)
-					     - offset_bits, offset_bits);
+		pcpu_block_update_hint_alloc(chunk, start_offset, offset_bits);
 	}
 
 	return chunk;
-- 
2.44.0