On 30 May 2022, at 7:50, Anshuman Khandual wrote:
> HugeTLB allocation (32MB pages on 4K base page) via sysfs on arm64 platform
> is getting stuck in isolate_single_pageblock(), because of an infinite loop
> Because head_pfn always evaluate the same, so does pfn, and the outer loop
> never exits. Dropping the relevant code block, which seems redundant, makes
> the problem go away.
Thanks for the report.
>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Zi Yan <ziy@xxxxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity")
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> I am not sure about this fix, and also did not find much time today to
> debug any further. There are much code changes around this function in
> recent days. This problem is present on latest mainline kernel.
>
> - Anshuman
>
> mm/page_isolation.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 6021f8444b5a..b0922fee75c1 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -389,10 +389,6 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
> struct page *head = compound_head(page);
> unsigned long head_pfn = page_to_pfn(head);
>
> - if (head_pfn + nr_pages <= boundary_pfn) {
> - pfn = head_pfn + nr_pages;
> - continue;
> - }
> #if defined CONFIG_COMPACTION || defined CONFIG_CMA
> /*
> * hugetlb, lru compound (THP), and movable compound pages
> --
> 2.20.1
Can you try the patch below to see if it fixes the issue? Thanks.
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 6021f8444b5a..d200d41ad0d3 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -385,9 +385,9 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
* above do the rest. If migration is not possible, just fail.
*/
if (PageCompound(page)) {
- unsigned long nr_pages = compound_nr(page);
struct page *head = compound_head(page);
unsigned long head_pfn = page_to_pfn(head);
+ unsigned long nr_pages = compound_nr(head);
if (head_pfn + nr_pages <= boundary_pfn) {
pfn = head_pfn + nr_pages;
--
Best Regards,
Yan, Zi
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