Re: [PATCH RFC 20/37] mm: compaction: Reserve metadata storage in compaction_alloc()

Peter Collingbourne
2023-11-21T04:49:44Z

Hi Alexandru,

On Wed, Aug 23, 2023 at 6:16 AM Alexandru Elisei
<alexandru.elisei@arm.com> wrote:
>
> If the source page being migrated has metadata associated with it, make
> sure to reserve the metadata storage when choosing a suitable destination
> page from the free list.
>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
> mm/compaction.c | 9 +++++++++
> mm/internal.h | 1 +
> 2 files changed, 10 insertions(+)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index cc0139fa0cb0..af2ee3085623 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -570,6 +570,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
> bool locked = false;
> unsigned long blockpfn = *start_pfn;
> unsigned int order;
> + int ret;
>
> /* Strict mode is for isolation, speed is secondary */
> if (strict)
> @@ -626,6 +627,11 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
>
> /* Found a free page, will break it into order-0 pages */
> order = buddy_order(page);
> + if (metadata_storage_enabled() && cc->reserve_metadata) {
> + ret = reserve_metadata_storage(page, order, cc->gfp_mask);

At this point the zone lock is held and preemption is disabled, which
makes it invalid to call reserve_metadata_storage.

Peter

> + if (ret)
> + goto isolate_fail;
> + }
> isolated = __isolate_free_page(page, order);
> if (!isolated)
> break;
> @@ -1757,6 +1763,9 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
> struct compact_control *cc = (struct compact_control *)data;
> struct folio *dst;
>
> + if (metadata_storage_enabled())
> + cc->reserve_metadata = folio_has_metadata(src);
> +
> if (list_empty(&cc->freepages)) {
> isolate_freepages(cc);
>
> diff --git a/mm/internal.h b/mm/internal.h
> index d28ac0085f61..046cc264bfbe 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -492,6 +492,7 @@ struct compact_control {
> */
> bool alloc_contig; /* alloc_contig_range allocation */
> bool source_has_metadata; /* source pages have associated metadata */
> + bool reserve_metadata;
> };
>
> /*
> --
> 2.41.0
>