[PATCH] erofs: fix compacted_2b if compacted_4b_initial > totalidx

Yue Hu
2021-09-14T04:00:05Z

From: Yue Hu <huyue2@yulong.com>

Currently, the whole indexes will only be compacted 4B if
compacted_4b_initial > totalidx. So, the calculated compacted_2b
is worthless for that case. It may waste CPU resources.

No need to update compacted_4b_initial as mkfs since it's used to
fulfill the alignment of the 1st compacted_2b pack and would handle
the case above.

We also need to clarify compacted_4b_end here. It's used for the
last lclusters which aren't fitted in the previous compacted_2b
packs.

Some messages are from Xiang.

Signed-off-by: Yue Hu <huyue2@yulong.com>
---
fs/erofs/zmap.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 9fb98d8..aeed404 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -369,7 +369,8 @@ static int compacted_load_cluster_from_disk(struct z_erofs_maprecorder *m,
if (compacted_4b_initial == 32 / 4)
compacted_4b_initial = 0;

- if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
+ if ((vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B) &&
+ compacted_4b_initial <= totalidx) {
compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
else
compacted_2b = 0;
--
1.9.1