linux-ext4 - [PATCH] highmem: memcpy_{from,to}

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Message-Id: <20230802144354.1023099-1-agruenba@redhat.com>
Date:   Wed,  2 Aug 2023 16:43:54 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        David Sterba <dsterba@...e.com>, linux-fsdevel@...r.kernel.org,
        Pankaj Raghav <p.raghav@...sung.com>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
        ntfs3@...ts.linux.dev, Theodore Tso <tytso@....edu>,
        Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
        Andreas Gruenbacher <agruenba@...hat.com>
Subject: [PATCH] highmem: memcpy_{from,to}_folio() fix

memcpy_to_folio() and memcpy_from_folio() compute the size of the chunk
of memory they can copy for each page, but then they don't use the chunk
size in the actual memcpy.  Fix that.

Also, git rid of superfluous parentheses in these two functions.

Fixes: 520a10fe2d72 ("highmem: add memcpy_to_folio() and memcpy_from_folio()")
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
---
 include/linux/highmem.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 0280f57d4744..99c474de800d 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -445,13 +445,13 @@ static inline void memcpy_from_folio(char *to, struct folio *folio,
 	VM_BUG_ON(offset + len > folio_size(folio));
 
 	do {
-		char *from = kmap_local_folio(folio, offset);
+		const char *from = kmap_local_folio(folio, offset);
 		size_t chunk = len;
 
 		if (folio_test_highmem(folio) &&
-		    (chunk > (PAGE_SIZE - offset_in_page(offset))))
+		    chunk > PAGE_SIZE - offset_in_page(offset))
 			chunk = PAGE_SIZE - offset_in_page(offset);
-		memcpy(to, from, len);
+		memcpy(to, from, chunk);
 		kunmap_local(from);
 
 		from += chunk;
@@ -470,9 +470,9 @@ static inline void memcpy_to_folio(struct folio *folio, size_t offset,
 		size_t chunk = len;
 
 		if (folio_test_highmem(folio) &&
-		    (chunk > (PAGE_SIZE - offset_in_page(offset))))
+		    chunk > PAGE_SIZE - offset_in_page(offset))
 			chunk = PAGE_SIZE - offset_in_page(offset);
-		memcpy(to, from, len);
+		memcpy(to, from, chunk);
 		kunmap_local(to);
 
 		from += chunk;
-- 
2.40.1