this is a second version of the series previously posted . Tetsuo
has noticed a bug I've introduced during the rebase and also pointed
out reserves access changes on nommu arches which I have addressed
as well. Mel had some more feedback which is hopefully addressed as
well. There were no further comments so I am reposting and asking for
this is a part of a larger series I posted back in Oct last year . I
have dropped patch 3 because it was incorrect and patch 4 is not
applicable without it.
The primary reason to apply patch 1 is to remove a risk of the complete
memory depletion by oom victims. While this is a theoretical risk right
now there is a demand for memcg aware oom killer which might kill all
processes inside a memcg which can be a lot of tasks. That would make
the risk quite real.
This issue is addressed by limiting access to memory reserves. We no
longer use TIF_MEMDIE to grant the access and use tsk_is_oom_victim
instead. See Patch 1 for more details. Patch 2 is a trivial follow up
I would still like to get rid of TIF_MEMDIE completely but I do not have
time to do it now and it is not a pressing issue.