RE: [RFC PATCH] mm: move xa forward when run across zombie page

["Pulavarty, Badari" <badari.pulavarty@intel.com>]

Thanks for the suggestion. 

With 6.1-rc3, I am able to run my test to completion 😊

I will now back out all my debug and try it again.

Thanks,
Badari

-----Original Message-----
From: Hugh Dickins <hughd@google.com> 
Sent: Monday, October 31, 2022 12:39 PM
To: Pulavarty, Badari <badari.pulavarty@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>; david@fromorbit.com; akpm@linux-foundation.org; bfoster@redhat.com; huangzhaoyang@gmail.com; ke.wang@unisoc.com; linux-fsdevel@vger.kernel.org; linux-mm@kvack.org; zhaoyang.huang@unisoc.com; Shutemov, Kirill <kirill.shutemov@intel.com>; Tang, Feng <feng.tang@intel.com>; Huang, Ying <ying.huang@intel.com>; Yin, Fengwei <fengwei.yin@intel.com>; Hansen, Dave <dave.hansen@intel.com>; Zanussi, Tom <tom.zanussi@intel.com>
Subject: RE: [RFC PATCH] mm: move xa forward when run across zombie page

On Mon, 31 Oct 2022, Pulavarty, Badari wrote:

> Hi,
> 
> Just want to give an update on the issue, hoping to get more thoughts/suggestions.
> 
> I have been adding lot of debug to try to root cause the issue.
> When I enabled CONFIG_VM_DEBUG, I run into following assertion failure:
> 
> [ 1810.282055] entry: 0 folio: ffe6dfc30e428040 [ 1810.282059] page 
> dumped because: VM_BUG_ON_PAGE(entry != folio) [ 1810.282062] BUG: 
...
> [ 1810.282310]  __delete_from_swap_cache.cold.20+0x33/0x35
> [ 1810.282321]  delete_from_swap_cache+0x50/0xa0 [ 1810.282330]  
> folio_free_swap+0xab/0xe0 [ 1810.282339]  free_swap_cache+0x8a/0xa0 [ 
> 1810.282346]  free_page_and_swap_cache+0x12/0xb0
> [ 1810.282356]  split_huge_page_to_list+0xf13/0x10d0     <<<<<<<<<<<<<<<<<<
> [ 1810.282365]  madvise_cold_or_pageout_pte_range+0x528/0x1390
> [ 1810.282374]  walk_pgd_range+0x5fe/0xa10 [ 1810.282383]  
> __walk_page_range+0x184/0x190 [ 1810.282391]  
> walk_page_range+0x120/0x190 [ 1810.282398]  
> madvise_pageout+0x10b/0x2a0 [ 1810.282406]  ? 
> set_track_prepare+0x48/0x70 [ 1810.282415]  
> madvise_vma_behavior+0x2f2/0xb10 [ 1810.282422]  ? 
> find_vma_prev+0x72/0xc0 [ 1810.282431]  do_madvise+0x21b/0x440 [ 
> 1810.282439]  damon_va_apply_scheme+0x76/0xa0 [ 1810.282448]  
> kdamond_fn+0xbe9/0xe10 [ 1810.282456]  ? 
> damon_split_region_at+0x70/0x70 [ 1810.282675]  kthread+0xfc/0x130 [ 
> 1810.282837]  ? kthread_complete_and_exit+0x20/0x20
> 
> Since I am not using hugepages explicitly..  I recompiled the kernel 
> with
> 
> CONFIG_TRANSPARENT_HUGEPAGE=n
> 
> And my problem went away (including the original issue).

For that one, please try with 6.1-rc3 (and CONFIG_TRANSPARENT_HUGEPAGE back to y).  Mel put a fix to that kind of thing into 6.1-rc2, then I fixed its warning in 6.1-rc3 (git log -n2 mm/huge_memory.c tells more).

Hugh