On Wed 31-01-18 11:21:04, Darrick J. Wong wrote:
> On Wed, Jan 24, 2018 at 10:26:49AM +0100, Michal Hocko wrote:
[...]
> > - I would also love to talk to some FS people and convince them to move
> > away from GFP_NOFS in favor of the new scope API. I know this just
> > means to send patches but the existing code is quite complex and it
> > really requires somebody familiar with the specific FS to do that
> > work.
>
> Hm, are you talking about setting PF_MEMALLOC_NOFS instead of passing
> *_NOFS to allocation functions and whatnot?
yes memalloc_nofs_{save,restore}
> Right now XFS will set it
> on any thread which has a transaction open, but that doesn't help for
> fs operations that don't have transactions (e.g. reading metadata,
> opening files). I suppose we could just set the flag any time someone
> stumbles into the fs code from userspace, though you're right that seems
> daunting.
I would really love to see the code to take the nofs scope
(memalloc_nofs_save) at the point where the FS "critical" section starts
(from the reclaim recursion POV). This would both document the context
and also limit NOFS allocations to bare minumum.
--
Michal Hocko
SUSE Labs
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