Hi dear all,
It seems that scan_curseg_cache will not update free_nid_bitmap (call add_free_nid with update==false). The consequence is that the free_nid_root might not match the free_nid_bitmap. Is this normal? Many thanks!

Hi guys,
I found this really an issue, we assume that an NID==X
1. is marked as used in NAT
2. but marked as free in NAT journal
The above assumption hold when NAT cache of X was flushed to NAT journal in stead of NAT
With this assumption , at mount time , in building free NIDs, f2fs will
1. first scan NAT (scan_nat_page), found X is used
2. then scan NAT journal (scan_curseg_cache), found X is free , add it to free NIDs , BUT does not update free_nid_bitmap!

as an comparison , when NAT cache of X is flushed , the flushing code path will update free_nid_bitmap.

Found the reason , at unmount time , NAT cache will not flush to NAT journal but all flush to NAT, so the NAT at the next mount time is the most up to date.

if so this line should be guarded like this

But wait. If f2fs does not unmount normally . The scenario in post#2 still exist!!