erofs-utils: zero out garbage trailing data for non-0padding cases
When "-E legacy-compress" is used, lz4 0padding feature will be
disabled by default in order to support old kernels (< Linux v5.3).
In that case, the current mkfs leaves previous garbage data after
valid compressed data if the length becomes shorter. This doesn't
matter for kernels >= v5.0 since LZ4_decompress_safe_partial() is used.
However, for staging erofs v4.19, it used an in-house customized
lz4 implemention due to LZ4_decompress_safe_partial() didn't work
as expected at that time, yet it doesn't allow trailing random
data in practice or decompression failure could happen.
I don't think it really matters since "obsoleted_mkfs" works perfectly
for such old staging versions (v4.19). Anyway, trailing garbage data
sounds unreasonable, so let's zero out it now.
Link: https://lore.kernel.org/r/20210430040345.17120-4-xiang@kernel.org
Fixes: 66653ef10a7f ("erofs-utils: introduce compression for regular files")
Reviewed-by: Li Guifu <bluce.lee@aliyun.com>
Signed-off-by: Gao Xiang <xiang@kernel.org>
1 file changed