On Wed, Sep 22, 2021 at 05:06:53PM +0800, Li Wang wrote:

Hi,

Li,

I confirmed this patch (applied on 5.14) gets rid of the below userfaultfd test failure.

# ./userfaultfd anon 16 2 nr_pages: 4096, nr_pages_per_cpu: 256 bounces: 1, mode: rnd read, userfaults: 313 missing (51+34+37+26+41+28+15+20+16+12+13+7+10+2+0+1) 995 wp (121+79+96+53+90+104+48+61+56+82+56+41+49+26+11+22) bounces: 0, mode: read, userfaults: 64 missing (15+8+10+6+5+2+4+3+3+1+4+0+0+2+0+1) 2157 wp (223+274+189+141+116+132+203+153+143+126+110+114+101+66+42+24) testing uffd-wp with pagemap (pgsize=4096): done testing uffd-wp with pagemap (pgsize=2097152): done testing UFFDIO_ZEROPAGE: done. testing signal delivery: done. testing events (fork, remap, remove): ERROR: nr 3933 memory corruption 0 1 (errno=0, line=963) ERROR: faulting process failed (errno=0, line=1117)

Just to keep a record within this thread - my understanding is above issue is a separate issue from what Nadav has fixed. The other fix could be:

https://lore.kernel.org/lkml/20210923232512.210092-1-peterx@redhat.com/

When verify with Nadav's patch, please check whether you have thp enabled globally:

# echo always > /sys/kernel/mm/transparent_hugepage/enabled

Thanks,