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From: chenguanxi11234@163.com
To: rafael@kernel.org
Cc: pavel@ucw.cz, len.brown@intel.com, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Chen Haonan <chen.haonan2@zte.com.cn>
Subject: [PATCH linux-next] kernel/power: Use kmap_local_page() in snapshot.c
Date: Mon, 11 Dec 2023 22:52:24 +0800	[thread overview]
Message-ID: <b2fd8c52429b51fc0c060753e6b616f1edf81d92.1702020689.git.chen.haonan2@zte.com.cn> (raw)

From: Chen Haonan <chen.haonan2@zte.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@zte.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


WARNING: multiple messages have this Message-ID (diff)
From: chenguanxi11234@163.com
To: rafael@kernel.org
Cc: pavel@ucw.cz, len.brown@intel.com, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Chen Haonan <chen.haonan2@zte.com.cn>
Subject: [PATCH linux-next v2] kernel/power: Use kmap_local_page() in snapshot.c
Date: Tue, 12 Dec 2023 23:37:36 +0800	[thread overview]
Message-ID: <b2fd8c52429b51fc0c060753e6b616f1edf81d92.1702020689.git.chen.haonan2@zte.com.cn> (raw)
Message-ID: <20231212153736.FUg21bzqc_9C3K1CEKNn1B7tO5Uyxtn4DyNTeFPlftY@z> (raw)

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

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

kmap_atomic() disables page-faults and preemption (the latter 
only for !PREEMPT_RT kernels).The code between the mapping and 
un-mapping in this patch does not depend on the above-mentioned 
side effects.So simply replaced kmap_atomic() with kmap_local_page().

Signed-off-by: Chen Haonan <chen.haonan2@zte.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


             reply	other threads:[~2023-12-11 15:08 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-11 14:52 chenguanxi11234 [this message]
2023-12-12 15:37 ` [PATCH linux-next v2] kernel/power: Use kmap_local_page() in snapshot.c chenguanxi11234
2023-12-11 16:04 ` [PATCH linux-next] " Rafael J. Wysocki
2023-12-12 14:38   ` chenguanxi11234
2023-12-12 15:01     ` Rafael J. Wysocki
2023-12-12 15:47       ` chenguanxi11234

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