On Wed 21-09-16 16:38:37, Li Zhong wrote:
> Commit 9bb627be47a5 ("mem-hotplug: don't clear the only node in
> new_node_page()") prevents allocating from an empty nodemask, but as David
> points out, it is still wrong. As node_online_map may include memoryless
> nodes, only allocating from these nodes is meaningless.
>
> This patch uses node_states[N_MEMORY] mask to prevent the above case.
>
OK, this is much better
I believe this should have
Fixes: 9bb627be47a5 ("mem-hotplug: don't clear the only node in new_node_page()")
Fixes: 394e31d2ceb4 ("mem-hotplug: alloc new page from a nearest neighbor node when mem-offline")
Fortunatelly everything is 4.8 so we do not need any backporting to
stable. Anyway this just shows that the hotplug patches need much better
review. E.g. 394e31d2ceb4 didn't have a single ack or r-b. Sigh
> Signed-off-by: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
> ---
> mm/memory_hotplug.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index b58906b..9d29ba0 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1555,8 +1555,8 @@ static struct page *new_node_page(struct page *page, unsigned long private,
> {
> gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;
> int nid = page_to_nid(page);
> - nodemask_t nmask = node_online_map;
> - struct page *new_page;
> + nodemask_t nmask = node_states[N_MEMORY];
> + struct page *new_page = NULL;
>
> /*
> * TODO: allocate a destination hugepage from a nearest neighbor node,
> @@ -1567,14 +1567,14 @@ static struct page *new_node_page(struct page *page, unsigned long private,
> return alloc_huge_page_node(page_hstate(compound_head(page)),
> next_node_in(nid, nmask));
>
> - if (nid != next_node_in(nid, nmask))
> - node_clear(nid, nmask);
> + node_clear(nid, nmask);
>
> if (PageHighMem(page)
> || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
> gfp_mask |= __GFP_HIGHMEM;
>
> - new_page = __alloc_pages_nodemask(gfp_mask, 0,
> + if (!nodes_empty(nmask))
> + new_page = __alloc_pages_nodemask(gfp_mask, 0,
> node_zonelist(nid, gfp_mask), &nmask);
> if (!new_page)
> new_page = __alloc_pages(gfp_mask, 0,
>
--
Michal Hocko
SUSE Labs
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