Re: [LSF/MM TOPIC] proposals for topics

[Michal Hocko <mhocko@kernel.org>]

On Tue 26-01-16 00:08:28, Tetsuo Handa wrote:
[...]
> If it turned out that we are using GFP_NOFS from LSM hooks correctly,
> I'd expect such GFP_NOFS allocations retry unless SIGKILL is pending.
> Filesystems might be able to handle GFP_NOFS allocation failures. But
> userspace might not be able to handle system call failures caused by
> GFP_NOFS allocation failures; OOM-unkillable processes might unexpectedly
> terminate as if they are OOM-killed. Would you please add GFP_KILLABLE
> to list of the topics?

Are there so many places to justify a flag? Isn't it easier to check for
fatal_signal_pending in the failed path and do the retry otherwise? This
allows for a more flexible fallback strategy - e.g. drop the locks and
retry again, sleep for reasonable time, wait for some event etc... This
sounds much more extensible than a single flag burried down in the
allocator path. Besides that all allocations besides __GFP_NOFAIL and
GFP_NOFS are already killable. The first one by definition and the later
one because of the current implementation restrictions which we can
hopefully fix longterm.


-- 
Michal Hocko
SUSE Labs

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