linux-kernel - Re: [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap

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Message-ID: <20180927122537.GA20378@techadventures.net>
Date:   Thu, 27 Sep 2018 14:25:37 +0200
From:   Oscar Salvador <osalvador@...hadventures.net>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        pavel.tatashin@...rosoft.com, dave.jiang@...el.com,
        dave.hansen@...el.com, jglisse@...hat.com, rppt@...ux.vnet.ibm.com,
        dan.j.williams@...el.com, logang@...tatee.com, mingo@...nel.org,
        kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the
 point where we init pgmap

On Thu, Sep 27, 2018 at 01:09:26PM +0200, Michal Hocko wrote:
> > So there were a few things I wasn't sure we could pull outside of the
> > hotplug lock. One specific example is the bits related to resizing the pgdat
> > and zone. I wanted to avoid pulling those bits outside of the hotplug lock.
> 
> Why would that be a problem. There are dedicated locks for resizing.

True is that move_pfn_range_to_zone() manages the locks for pgdat/zone resizing,
but it also takes care of calling init_currently_empty_zone() in case the zone is empty.
Could not that be a problem if we take move_pfn_range_to_zone() out of the lock?

-- 
Oscar Salvador
SUSE L3