On Mon, Oct 26, 2020 at 06:33:56PM +0100, 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
^ precedence
> 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.
>
> 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.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
With two more nits below fixed
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> ---
> include/linux/mm.h | 20 ++--------
> init/main.c | 2 +-
> mm/page_alloc.c | 94 +++++++++++++++++++++++-----------------------
> 3 files changed, 50 insertions(+), 66 deletions(-)
>
...
> @@ -792,6 +752,44 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
> unsigned int order, int migratetype) {}
> #endif
>
> +/*
> + * Enable static keys related to various memory debugging and hardening options.
> + * Some override others, and depend on early params that are evaluated in the
> + * order of appearance. So we need to first gather the full picture of what was
> + * enabled, and then make decisions.
> + */
> +void init_mem_debugging()
Shouldn't it be init_mem_debug(void)?
Or whatever a new name would be :)
> +{
> + if (_init_on_alloc_enabled_early) {
> + if (page_poisoning_enabled()) {
> + pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> + "will take precedence over init_on_alloc\n");
> + } else {
> + static_branch_enable(&init_on_alloc);
> + }
> + }
> + if (_init_on_free_enabled_early) {
> + if (page_poisoning_enabled()) {
> + pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> + "will take precedence over init_on_free\n");
> + } else {
> + static_branch_enable(&init_on_free);
> + }
> + }
I think the braces for the inner ifs are not required.
> +
> +#ifdef CONFIG_DEBUG_PAGEALLOC
> + if (!debug_pagealloc_enabled())
> + return;
> +
> + static_branch_enable(&_debug_pagealloc_enabled);
> +
> + if (!debug_guardpage_minorder())
> + return;
> +
> + static_branch_enable(&_debug_guardpage_enabled);
> +#endif
> +}
> +
> static inline void set_buddy_order(struct page *page, unsigned int order)
> {
> set_page_private(page, order);
> --
> 2.29.0
>
>
--
Sincerely yours,
Mike.
