On 4 Apr 2022, at 10:29, Matthew Wilcox wrote: > 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). https://github.com/linux-test-project/ltp has some migrate_pages and move_pages tests. You can run them after install ltp: sudo ./runltp -f syscalls -s migrate_pages and sudo ./runltp -f sys calls -s move_pages -- Best Regards, Yan, Zi
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