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erofs: ensure that the post-EOF tails are all zeroed 

commit e4c1cf523d upstream.

This was accidentally fixed up in commit e4c1cf523d but we can't
take the full change due to other dependancy issues, so here is just
the actual bugfix that is needed.

[Background]

keltargw reported an issue [1] that with mmaped I/Os, sometimes the
tail of the last page (after file ends) is not filled with zeroes.

The root cause is that such tail page could be wrongly selected for
inplace I/Os so the zeroed part will then be filled with compressed
data instead of zeroes.

A simple fix is to avoid doing inplace I/Os for such tail parts,
actually that was already fixed upstream in commit e4c1cf523d
("erofs: tidy up z_erofs_do_read_page()") by accident.

[1] https://lore.kernel.org/r/3ad8b469-25db-a297-21f9-75db2d6ad224@linux.alibaba.com

Reported-by: keltargw <keltar.gw@gmail.com>
Fixes: 3883a79abd ("staging: erofs: introduce VLE decompression support")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gao Xiang 2023-08-31 19:29:58 +08:00 committed by Greg Kroah-Hartman
parent babc8be398
commit 9535cd2119
1 changed files with 2 additions and 0 deletions
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2
fs/erofs/zdata.c
View File

@ -993,6 +993,8 @@ hitted:
cur = end - min_t(erofs_off_t, offset + end - map->m_la, end);
if (!(map->m_flags & EROFS_MAP_MAPPED)) {
zero_user_segment(page, cur, end);
++spiltted;
tight = false;
goto next_part;
}
if (map->m_flags & EROFS_MAP_FRAGMENT) {