linux-kernel - Re: [PATCH] x86/mm/hotplug: fix BUG

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Message-ID: <20170607104715.5niuwk42fhahbftk@node.shutemov.name>
Date:   Wed, 7 Jun 2017 13:47:15 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Jérôme Glisse <jglisse@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: Re: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove

On Tue, Jun 06, 2017 at 01:35:12PM -0400, Jérôme Glisse wrote:
> With commit af2cf278ef4f we no longer free pud so that we
> do not have synchronize all pgd on hotremove/vfree. But the
> new 5 level page table code re-added that code f2a6a705 and
> thus we now trigger a BUG_ON() l128 in sync_global_pgds()
> 
> This patch remove free_pud() like in af2cf278ef4f

Good catch. Thanks!

But I think we only need to skip free_pud_table() for 4-level paging.
If we don't we would leave 513 page tables around instead of one in
5-level paging case.

I don't think it's acceptable.

And please use patch subject lines along with commit hashes to simplify
reading commit message.

-- 
 Kirill A. Shutemov