linux-kernel - [PATCH] f2fs: Use memcpy_page() in f2fs_copy

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Message-Id: <20220716204353.22049-1-fmdefrancesco@gmail.com>
Date:   Sat, 16 Jul 2022 22:43:53 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
        Nick Terrell <terrelln@...com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Ira Weiny <ira.weiny@...el.com>
Subject: [PATCH] f2fs: Use memcpy_page() in f2fs_copy_page()

The use of kmap() is being deprecated in favor of kmap_local_page().

Two main problems with kmap(): (1) It comes with an overhead as mapping
space is restricted and protected by a global lock for synchronization and
(2) it also requires global TLB invalidation when the kmap’s pool wraps
and it might block when the mapping space is fully utilized until a slot
becomes available.

Therefore, replace kmap() with kmap_local_page() in f2fs_copy_page() and
use memcpy_page() instead of open coding kmap_local_page() + memcpy().

Suggested-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
---
 fs/f2fs/f2fs.h | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d9bbecd008d2..f04e760bb1c1 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2698,12 +2698,8 @@ static inline struct page *f2fs_pagecache_get_page(
 
 static inline void f2fs_copy_page(struct page *src, struct page *dst)
 {
-	char *src_kaddr = kmap(src);
-	char *dst_kaddr = kmap(dst);
 
-	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
-	kunmap(dst);
-	kunmap(src);
+	memcpy_page(dst, 0, src, 0, PAGE_SIZE);
 }
 
 static inline void f2fs_put_page(struct page *page, int unlock)
-- 
2.37.1