On Mon, Apr 04, 2022 at 10:05:00AM -0400, Zi Yan wrote: > On 4 Apr 2022, at 9:29, Naoya Horiguchi wrote: > > I found that the below VM_BUG_ON_FOLIO is triggered on v5.18-rc1 > > (and also reproducible with mmotm on 3/31). > > I have no idea about the bug's mechanism, but it seems not to be > > shared in LKML yet, so let me just share. config.gz is attached. > > > > [ 48.206424] page:0000000021452e3a refcount:6 mapcount:0 mapping:000000003aaf5253 index:0x0 pfn:0x14e600 > > [ 48.213316] head:0000000021452e3a order:9 compound_mapcount:0 compound_pincount:0 > > [ 48.218830] aops:xfs_address_space_operations [xfs] ino:dee dentry name:"libc.so.6" > > [ 48.225098] flags: 0x57ffffc0012027(locked|referenced|uptodate|active|private|head|node=1|zone=2|lastcpupid=0x1fffff) > > [ 48.232792] raw: 0057ffffc0012027 0000000000000000 dead000000000122 ffff8a0dc9a376b8 > > [ 48.238464] raw: 0000000000000000 ffff8a0dc6b23d20 00000006ffffffff 0000000000000000 > > [ 48.244109] page dumped because: VM_BUG_ON_FOLIO(folio_nr_pages(old) != nr_pages) > > [ 48.249196] ------------[ cut here ]------------ > > [ 48.251240] kernel BUG at mm/memcontrol.c:6857! > > [ 48.260535] RIP: 0010:mem_cgroup_migrate+0x217/0x320 > > [ 48.286942] Call Trace: > > [ 48.287665] <TASK> > > [ 48.288255] iomap_migrate_page+0x64/0x190 > > [ 48.289366] move_to_new_page+0xa3/0x470 > > Is it because migration code assumes all THPs have order=HPAGE_PMD_ORDER? > Would the patch below fix the issue? This looks entirely plausible to me! I do have changes in this area, but clearly I should have submitted them earlier. Let's get these fixes in as they are. Is there a test suite that tests page migration? I usually use xfstests and it does no page migration at all (at least 'git grep migrate' finds nothing useful).
