linux-kernel - [PATCH linux-next] kernel/power: Use kmap_local

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Date:   Mon, 11 Dec 2023 22:52:24 +0800
From:   chenguanxi11234@....com
To:     rafael@...nel.org
Cc:     pavel@....cz, len.brown@...el.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Chen Haonan <chen.haonan2@....com.cn>
Subject: [PATCH linux-next] kernel/power: Use kmap_local_page() in snapshot.c

From: Chen Haonan <chen.haonan2@....com.cn>

kmap_atomic() has been deprecated in favor of kmap_local_page().

Each call to kmap_atomic() in the kernel creates a non-preemptable
segment and disables the missing page exception. This can be one of
the sources of unexpected latency. Therefore users should choose
kmap_local_page() over kmap_atomic().

Signed-off-by: Chen Haonan <chen.haonan2@....com.cn>
---
 kernel/power/snapshot.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 50a15408c3fc..feef0d4d3288 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1487,11 +1487,11 @@ static bool copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
 	s_page = pfn_to_page(src_pfn);
 	d_page = pfn_to_page(dst_pfn);
 	if (PageHighMem(s_page)) {
-		src = kmap_atomic(s_page);
-		dst = kmap_atomic(d_page);
+		src = kmap_local_page(s_page);
+		dst = kmap_local_page(d_page);
 		zeros_only = do_copy_page(dst, src);
-		kunmap_atomic(dst);
-		kunmap_atomic(src);
+		kunmap_local(dst);
+		kunmap_local(src);
 	} else {
 		if (PageHighMem(d_page)) {
 			/*
@@ -1499,9 +1499,9 @@ static bool copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
 			 * data modified by kmap_atomic()
 			 */
 			zeros_only = safe_copy_page(buffer, s_page);
-			dst = kmap_atomic(d_page);
+			dst = kmap_local_page(d_page);
 			copy_page(dst, buffer);
-			kunmap_atomic(dst);
+			kunmap_local(dst);
 		} else {
 			zeros_only = safe_copy_page(page_address(d_page), s_page);
 		}
-- 
2.25.1