linux-kernel - Re: [PATCH v5] mm: don't allow deferred pages with NEED_PER_CPU

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Message-Id: <20180515141240.c7587ed53a0ff32ff984e3d2@linux-foundation.org>
Date:   Tue, 15 May 2018 14:12:40 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mhocko@...e.com,
        linux-mm@...ck.org, mgorman@...hsingularity.net, mingo@...nel.org,
        peterz@...radead.org, rostedt@...dmis.org, fengguang.wu@...el.com,
        dennisszhou@...il.com
Subject: Re: [PATCH v5] mm: don't allow deferred pages with NEED_PER_CPU_KM

On Tue, 15 May 2018 13:51:24 -0400 Pavel Tatashin <pasha.tatashin@...cle.com> wrote:

> It is unsafe to do virtual to physical translations before mm_init() is
> called if struct page is needed in order to determine the memory section
> number (see SECTION_IN_PAGE_FLAGS). This is because only in mm_init() we
> initialize struct pages for all the allocated memory when deferred struct
> pages are used.
> 
> My recent fix exposed this problem,

"my recent fix" isn't very useful.  I changed this to identify
c9e97a1997 ("mm: initialize pages on demand during boot"), yes?

> 
> Fixes: 3a80a7fa7989 ("mm: meminit: initialise a subset of struct pages if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set")
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>

And I added cc:stable.