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SubjectRe: [lkp-robot] [mm, page_alloc] b7ef62aa8a: BUG:kernel_hang_in_boot_stage
> > BUG: kernel hang in boot stage
>
> Thanks, I was able to reproduce and debug this.
> Andrew, please apply the following -fix. There will be conflicts on later
> patches, but with trivial resolution (pages -> free_pages). Thanks!
>
> ...
>
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1977,6 +1977,9 @@ static void steal_suitable_fallback(struct zone *zone, struct page *page,
> goto single_page;
>
> pages = move_freepages_block(zone, page, start_type);
> + /* moving whole block can fail due to zone boundary conditions */
> + if (!pages)
> + goto single_page;
>
> /* Claim the whole block if over half of it is free */
> if (pages >= (1 << (pageblock_order-1)) ||

The result is a bit odd:

free_pages = move_freepages_block(zone, page, start_type,
&movable_pages);
/*
* Determine how many pages are compatible with our allocation.
* For movable allocation, it's the number of movable pages which
* we just obtained. For other types it's a bit more tricky.
*/
if (start_type == MIGRATE_MOVABLE) {
alike_pages = movable_pages;
} else {
/*
* If we are falling back a RECLAIMABLE or UNMOVABLE allocation
* to MOVABLE pageblock, consider all non-movable pages as
* compatible. If it's UNMOVABLE falling back to RECLAIMABLE or
* vice versa, be conservative since we can't distinguish the
* exact migratetype of non-movable pages.
*/
if (old_block_type == MIGRATE_MOVABLE)
alike_pages = pageblock_nr_pages
- (free_pages + movable_pages);
else
alike_pages = 0;
}

/* moving whole block can fail due to zone boundary conditions */
if (!free_pages)
goto single_page;

should we do `goto single_page' as soon as the move_freepages_block()
call fails?

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