linux-ext4 - [RFC PATCH 4/8] null_blk: use memcpy_page() in copy_from

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Date:   Sun,  7 Feb 2021 11:04:21 -0800
From:   Chaitanya Kulkarni <chaitanya.kulkarni@....com>
To:     linux-block@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org
Cc:     axboe@...nel.dk, tytso@....edu, adilger.kernel@...ger.ca,
        jaegeuk@...nel.org, chao@...nel.org, johannes.thumshirn@....com,
        damien.lemoal@....com, bvanassche@....org,
        chaitanya.kulkarni@....com, dongli.zhang@...cle.com, clm@...com,
        ira.weiny@...el.com, dsterba@...e.com, ebiggers@...nel.org,
        hch@...radead.org, dave.hansen@...el.com
Subject: [RFC PATCH 4/8] null_blk: use memcpy_page() in copy_from_nullb()

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@....com>
---
 drivers/block/null_blk/main.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index c9b6db82b07c..1c0e1a295e90 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1042,7 +1042,6 @@ static int copy_from_nullb(struct nullb *nullb, struct page *dest,
 	size_t temp, count = 0;
 	unsigned int offset;
 	struct nullb_page *t_page;
-	void *dst, *src;
 
 	while (count < n) {
 		temp = min_t(size_t, nullb->dev->blocksize, n - count);
@@ -1051,16 +1050,11 @@ static int copy_from_nullb(struct nullb *nullb, struct page *dest,
 		t_page = null_lookup_page(nullb, sector, false,
 			!null_cache_active(nullb));
 
-		dst = kmap_atomic(dest);
-		if (!t_page) {
-			memset(dst + off + count, 0, temp);
-			goto next;
-		}
-		src = kmap_atomic(t_page->page);
-		memcpy(dst + off + count, src + offset, temp);
-		kunmap_atomic(src);
-next:
-		kunmap_atomic(dst);
+		if (t_page)
+			memcpy_page(dest, off + count, t_page->page, offset,
+				    temp);
+		else
+			zero_user(dest, off + count, temp);
 
 		count += temp;
 		sector += temp >> SECTOR_SHIFT;
-- 
2.22.1