Re: [PATCH 00/29] Speculative page faults (anon vmas only)

[Michel Lespinasse]

Hi Ted,

On Sat, May 01, 2021 at 03:56:23PM -0400, Theodore Ts'o wrote:
> I tried running xfstests against the spf branch, and I've noticed it's
> causing regression for generic/619.  It's failing due to a umount
> failure due to a busy mount point:
> 
> QA output created by 619
> umount: /vdc: target is busy.
> 
> I haven't had a chance to investigate, but I thought I should let you know.

Thanks for the report. I think the issue is likely caused by commit
06adfeb8150d "mm: rcu safe vma->vm_file freeing", which will defer
fput on mapped files for one rcu grace period. I expect adding
synchronize_rcu to the proper place (I'm not sure exactly where though)
when unmounting file systems would be a workable fix.

Note though - at this point I am only submitting the anon part of the
patchset for inclusion. That is, the v5.12-spf-anon branch, rather
than the v5.12-spf branch which has the additional / less mature
changes for file mapped vma faults.

--
Michel "walken" Lespinasse