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Date:   Thu, 25 Aug 2022 08:27:52 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     lizhe.67@bytedance.com
Cc:     Jason@zx2c4.com, akpm@linux-foundation.org, corbet@lwn.net,
        keescook@chromium.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        lizefan.x@bytedance.com, mark-pk.tsai@mediatek.com,
        mhiramat@kernel.org, rostedt@goodmis.org, vbabka@suse.cz,
        yuanzhu@bytedance.com
Subject: Re: [PATCH v2] page_ext: introduce boot parameter 'early_page_ext'
Message-ID: <YwcWaO1Z5pSRRokc@dhcp22.suse.cz>
References: <YwXczj8Dh0uI0EA9@dhcp22.suse.cz>
 <20220825062129.92091-1-lizhe.67@bytedance.com>
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On Thu 25-08-22 14:21:29, lizhe.67@bytedance.com wrote:
> On 2022-08-24 8:09 UTC, mhocko@suse.com wrote:
[...]
> >> diff --git a/init/main.c b/init/main.c
> >> index 91642a4e69be..3760c0326525 100644
> >> --- a/init/main.c
> >> +++ b/init/main.c
> >> @@ -849,6 +849,8 @@ static void __init mm_init(void)
> >>  	pgtable_init();
> >>  	debug_objects_mem_init();
> >>  	vmalloc_init();
> >> +	/* Should be run after vmap initialization */
> >> +	page_ext_init(true);
> >
> >you can just 
> >	if (early_page_ext)
> >		page_ext_init();
> >
> >>  	/* Should be run before the first non-init thread is created */
> >>  	init_espfix_bsp();
> >>  	/* Should be run after espfix64 is set up. */
> >> @@ -1606,7 +1608,7 @@ static noinline void __init kernel_init_freeable(void)
> >>  	padata_init();
> >>  	page_alloc_init_late();
> >>  	/* Initialize page ext after all struct pages are initialized. */
> >> -	page_ext_init();
> >> +	page_ext_init(false);
> >
> >	if (!early_page_ext)
> >		page_ext_init();
> 
> I think we can use an inline function instead of 'early_page_ext' here. The
> reason is that if CONFIG_PAGE_EXTENSION=n, 'early_page_ext' is undefined.
> Thought we can #define early_page_ext as false, it is ugly.

Agreed!

-- 
Michal Hocko
SUSE Labs