Messages in this thread | | | Subject | Re: [PATCH 1/3] mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters | From | David Hildenbrand <> | Date | Tue, 27 Oct 2020 10:03:34 +0100 |
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On 26.10.20 18:33, Vlastimil Babka wrote: > Enabling page_poison=1 together with init_on_alloc=1 or init_on_free=1 produces > a warning in dmesg that page_poison takes precendence. However, as these > warnings are printed in early_param handlers for init_on_alloc/free, they are > not printed if page_poison is enabled later on the command line (handlers are > called in the order of their parameters), or when init_on_alloc/free is always > enabled by the respective config option - before the page_poison early param > handler is called, it is not considered to be enabled. This is inconsistent. > > We can remove the dependency on order by making the init_on_* parameters only > set a boolean variable, and postponing the evaluation after all early params > have been processed. Introduce a new init_mem_debugging() function for that, > and move the related debug_pagealloc processing there as well.
init_mem_debugging() is somewhat sub-optimal - init_on_alloc=1 or init_on_free=1 are rather security hardening mechanisms.
... I wondered if this could be the place to initialize any kind of mm parameters in the future. Like init_mem_params() or so.
> > As a result init_mem_debugging() knows always accurately if init_on_* and/or > page_poison options were enabled. Thus we can also optimize want_init_on_alloc() > and want_init_on_free(). We don't need to check page_poisoning_enabled() there, > we can instead not enable the init_on_* tracepoint at all, if page poisoning is > enabled. This results in a simpler and more effective code.
LGTM
Reviewed-by: David Hildenbrand <david@redhat.com>
-- Thanks,
David / dhildenb
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