tree b3d6d687fc3875724ff690084e5d026e898fdcaa
parent db9feb29c204b00e3507cf4840d31cda25386356
author Gao Xiang <xiang@kernel.org> 1619755424 +0800
committer Gao Xiang <xiang@kernel.org> 1619886401 +0800

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>