block-map: add __GFP_ZERO flag for alloc_page in function bio_copy_kern

block-map: add __GFP_ZERO flag for alloc_page in function bio_copy_kern

[ Upstream commit cc8f7fe1f5eab010191aa4570f27641876fa1267 ]

Add __GFP_ZERO flag for alloc_page in function bio_copy_kern to initialize
the buffer of a bio.

Signed-off-by: Haimin Zhang <tcs.kernel@gmail.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220216084038.15635-1-tcs.kernel@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>