ext4: use memcpy_to_page() in pagecache_write()

[ Upstream commit bd256fda

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Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210207190425.38107-7-chaitanya.kulkarni@wdc.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Stable-dep-of: 956510c0

 ("fs: ext4: initialize fsdata in pagecache_write()")
Signed-off-by: Sasha Levin <sashal@kernel.org>