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From: Mike Rapoport <rppt@linux.ibm.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: akpm@linux-foundation.org, mhocko@suse.com,
	dan.j.williams@intel.com, pavel.tatashin@microsoft.com,
	jglisse@redhat.com, Jonathan.Cameron@huawei.com,
	rafael@kernel.org, david@redhat.com, linux-mm@kvack.org,
	Oscar Salvador <osalvador@suse.com>
Subject: Re: [PATCH v2 3/5] mm, memory_hotplug: Move zone/pages handling to offline stage
Date: Wed, 28 Nov 2018 09:52:38 +0200
Message-ID: <20181128075238.GD14414@rapoport-lnx> (raw)
In-Reply-To: <20181127162005.15833-4-osalvador@suse.de>

On Tue, Nov 27, 2018 at 05:20:03PM +0100, Oscar Salvador wrote:
> From: Oscar Salvador <osalvador@suse.com>
> 
> The current implementation accesses pages during hot-remove
> stage in order to get the zone linked to this memory-range.
> We use that zone for a) check if the zone is ZONE_DEVICE and
> b) to shrink the zone's spanned pages.
> 
> Accessing pages during this stage is problematic, as we might be
> accessing pages that were not initialized if we did not get to
> online the memory before removing it.
> 
> The only reason to check for ZONE_DEVICE in __remove_pages
> is to bypass the call to release_mem_region_adjustable(),
> since these regions are removed with devm_release_mem_region.
> 
> With patch#2, this is no longer a problem so we can safely
> call release_mem_region_adjustable().
> release_mem_region_adjustable() will spot that the region
> we are trying to remove was acquired by means of
> devm_request_mem_region, and will back off safely.
> 
> This allows us to remove all zone-related operations from
> hot-remove stage.
> 
> Because of this, zone's spanned pages are shrinked during
> the offlining stage in shrink_zone_pgdat().
> It would have been great to decrease also the spanned page
> for the node there, but we need them in try_offline_node().
> So we still decrease spanned pages for the node in the hot-remove
> stage.
> 
> The only particularity is that now
> find_smallest_section_pfn/find_biggest_section_pfn, when called from
> shrink_zone_span, will now check for online sections and not
> valid sections instead.
> To make this work with devm/HMM code, we need to call offline_mem_sections
> and online_mem_sections in that code path when we are adding memory.
> 
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
>  arch/powerpc/mm/mem.c          | 11 +----
>  arch/sh/mm/init.c              |  4 +-
>  arch/x86/mm/init_32.c          |  3 +-
>  arch/x86/mm/init_64.c          |  8 +---
>  include/linux/memory_hotplug.h |  8 ++--
>  kernel/memremap.c              | 14 +++++--
>  mm/memory_hotplug.c            | 95 ++++++++++++++++++++++++------------------
>  mm/sparse.c                    |  4 +-
>  8 files changed, 76 insertions(+), 71 deletions(-)
 
[ ... ]
 
>  /**
> - * __remove_pages() - remove sections of pages from a zone
> - * @zone: zone from which pages need to be removed
> + * __remove_pages() - remove sections of pages from a nid
> + * @nid: nid from which pages belong to

Nit: the description sounds a bit awkward.
Why not to keep the original one with s/zone/node/?

>   * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
>   * @nr_pages: number of pages to remove (must be multiple of section size)
>   * @altmap: alternative device page map or %NULL if default memmap is used
> @@ -547,35 +566,28 @@ static int __remove_section(struct zone *zone, struct mem_section *ms,
>   * sure that pages are marked reserved and zones are adjust properly by
>   * calling offline_pages().
>   */

-- 
Sincerely yours,
Mike.

  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-27 16:20 [PATCH v2 0/5] Do not touch pages in hot-remove path Oscar Salvador
2018-11-27 16:20 ` [PATCH v2 1/5] mm, memory_hotplug: Add nid parameter to arch_remove_memory Oscar Salvador
2018-11-27 16:20 ` [PATCH v2 2/5] kernel, resource: Check for IORESOURCE_SYSRAM in release_mem_region_adjustable Oscar Salvador
2018-11-27 16:20 ` [PATCH v2 3/5] mm, memory_hotplug: Move zone/pages handling to offline stage Oscar Salvador
2018-11-28  7:52   ` Mike Rapoport [this message]
2018-11-28 14:25     ` osalvador
2018-11-28 14:15   ` osalvador
2018-11-27 16:20 ` [PATCH v2 4/5] mm, memory-hotplug: Rework unregister_mem_sect_under_nodes Oscar Salvador
2019-03-24  6:48   ` Anshuman Khandual
2019-03-25  7:40     ` Oscar Salvador
2019-03-25  8:04       ` Michal Hocko
2019-03-25  8:14         ` Oscar Salvador
2018-11-27 16:20 ` [PATCH v2 5/5] mm, memory_hotplug: Refactor shrink_zone/pgdat_span Oscar Salvador
2018-11-28  6:50   ` Michal Hocko
2018-11-28  7:07     ` Oscar Salvador
2018-11-28 10:03       ` David Hildenbrand
2018-11-28 10:14       ` Michal Hocko
2018-11-28 11:00         ` osalvador
2018-11-28 12:31           ` Michal Hocko
2018-11-28 12:51             ` osalvador
2018-11-28 13:08               ` Michal Hocko
2018-11-28 13:18                 ` osalvador
2018-11-28 15:50                   ` Michal Hocko
2018-11-28 16:02                     ` osalvador
2018-11-29  9:29                     ` osalvador
2018-11-28 13:09               ` osalvador

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