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Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence reclaim lockdep false positives

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On Tue 20-12-16 08:24:13, Dave Chinner wrote:
> On Thu, Dec 15, 2016 at 03:07:08PM +0100, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> > 
> > Now that the page allocator offers __GFP_NOLOCKDEP let's introduce
> > KM_NOLOCKDEP alias for the xfs allocation APIs. While we are at it
> > also change KM_NOFS users introduced by b17cb364dbbb ("xfs: fix missing
> > KM_NOFS tags to keep lockdep happy") and use the new flag for them
> > instead. There is really no reason to make these allocations contexts
> > weaker just because of the lockdep which even might not be enabled
> > in most cases.
> > 
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> I'd suggest that it might be better to drop this patch for now -
> it's not necessary for the context flag changeover but does
> introduce a risk of regressions if the conversion is wrong.
> 
> Hence I think this is better as a completely separate series
> which audits and changes all the unnecessary KM_NOFS allocations
> in one go. I've never liked whack-a-mole style changes like this -
> do it once, do it properly....

OK, fair enough. I thought it might be better to have an example user so
that others can follow but as you say, the risk of regression is really
there and these kind of changes definitely need a throughout review.

I am not sure I will be able to post more of those changes because that
requires an intimate knowledge of the fs so I hope somebody can take
over there and follow up.

Thanks!
-- 
Michal Hocko
SUSE Labs

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[PATCH 0/9 v2] scope GFP_NOFS api Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
  [PATCH 5/9] xfs: use memalloc_nofs_{save,restore} instead of memalloc_noio* Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
    Re: [PATCH 5/9] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* Brian Foster <bfoster@redhat.com> - 2016-12-16 17:40 +0100
      [PATCH 5/9 v2] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* Michal Hocko <mhocko@kernel.org> - 2016-12-16 23:10 +0100
  [PATCH 6/9] jbd2: mark the transaction context with the scope GFP_NOFS context Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
    Re: [PATCH 6/9] jbd2: mark the transaction context with the scope  GFP_NOFS context Jan Kara <jack@suse.cz> - 2016-12-19 10:40 +0100
  [PATCH 9/9] Revert "ext4: fix wrong gfp type under transaction" Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
    Re: [PATCH 9/9] Revert "ext4: fix wrong gfp type under transaction" Jan Kara <jack@suse.cz> - 2016-12-19 10:40 +0100
  [PATCH 3/9] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
    Re: [PATCH 3/9] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Brian Foster <bfoster@redhat.com> - 2016-12-16 17:40 +0100
  [PATCH 7/9] jbd2: make the whole kjournald2 kthread NOFS safe Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
    Re: [PATCH 7/9] jbd2: make the whole kjournald2 kthread NOFS safe Jan Kara <jack@suse.cz> - 2016-12-19 10:40 +0100
  [PATCH 4/9] mm: introduce memalloc_nofs_{save,restore} API Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
  [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
    [PATCH 2/9 v2] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-16 16:50 +0100
      Re: [PATCH 2/9 v2] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Brian Foster <bfoster@redhat.com> - 2016-12-16 17:40 +0100
        Re: [PATCH 2/9 v2] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-16 23:10 +0100
    Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Dave Chinner <david@fromorbit.com> - 2016-12-19 22:30 +0100
      Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-12-19 23:10 +0100
        Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Dave Chinner <david@fromorbit.com> - 2016-12-20 22:40 +0100
      Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-20 09:40 +0100
  [PATCH 1/9] lockdep: allow to disable reclaim lockup detection Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
  [DEBUG PATCH 0/2] debug explicit GFP_NO{FS,IO} usage from the scope context Michal Hocko <mhocko@kernel.org> - 2016-12-16 13:50 +0100
    [DEBUG PATCH 2/2] silent warnings which we cannot do anything about Michal Hocko <mhocko@kernel.org> - 2016-12-16 13:50 +0100
    [DEBUG PATCH 1/2] mm, debug: report when GFP_NO{FS,IO} is used explicitly from memalloc_no{fs,io}_{save,restore} context Michal Hocko <mhocko@kernel.org> - 2016-12-16 13:50 +0100
  Re: [PATCH 0/9 v2] scope GFP_NOFS api Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-12-16 16:20 +0100
    Re: [PATCH 0/9 v2] scope GFP_NOFS api Michal Hocko <mhocko@kernel.org> - 2016-12-16 16:40 +0100
      Re: [PATCH 0/9 v2] scope GFP_NOFS api Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-12-16 17:30 +0100
        Re: [PATCH 0/9 v2] scope GFP_NOFS api Jan Kara <jack@suse.cz> - 2016-12-19 10:30 +0100
  Re: [PATCH 0/9 v2] scope GFP_NOFS api Michal Hocko <mhocko@kernel.org> - 2016-12-22 10:40 +0100

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