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

[Alexandru Elisei]

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@xxxxxxx>
---
 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);
+			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