Re: [PATCH v1 3/6] mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()

Baoquan He
2020-07-29T13:24:29Z

On 06/30/20 at 04:26pm, David Hildenbrand wrote:
> Inside has_unmovable_pages(), we have a comment describing how unmovable
> data could end up in ZONE_MOVABLE - via "movable_core". Also, besides
~~~ 'movablecore'
> checking if the first page in the pageblock is reserved, we don't
> perform any further checks in case of ZONE_MOVABLE.
>
> In case of memory offlining, we set REPORT_FAILURE, properly
> dump_page() the page and handle the error gracefully.
> alloc_contig_pages() users currently never allocate from ZONE_MOVABLE.
> E.g., hugetlb uses alloc_contig_pages() for the allocation of gigantic
> pages only, which will never end up on the MOVABLE zone
> (see htlb_alloc_mask()).
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> mm/page_isolation.c | 16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 553b49a34cf71..02a01bff6b219 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -58,16 +58,12 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
> spin_unlock_irqrestore(&zone->lock, flags);
> if (!ret) {
> drain_all_pages(zone);
> - } else {
> - WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> -
> - if ((isol_flags & REPORT_FAILURE) && unmovable)
> - /*
> - * printk() with zone->lock held will likely trigger a
> - * lockdep splat, so defer it here.
> - */
> - dump_page(unmovable, "unmovable page");
> - }
> + } else if ((isol_flags & REPORT_FAILURE) && unmovable)

This else if branch should be enclosed in brace?

> + /*
> + * printk() with zone->lock held will likely trigger a
> + * lockdep splat, so defer it here.
> + */
> + dump_page(unmovable, "unmovable page");
>
> return ret;
> }

Otherwise, the patch looks good to me.

Reviewed-by: Baoquan He <bhe@redhat.com>