1 files changed, 41 insertions, 15 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 17a66ea544e7..7b0b2229d4ed 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -852,7 +852,9 @@ noinline int __filemap_add_folio(struct address_space *mapping,
 		struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp)
 {
 	XA_STATE(xas, &mapping->i_pages, index);
-	bool huge = folio_test_hugetlb(folio);
+	void *alloced_shadow = NULL;
+	int alloced_order = 0;
+	bool huge;
 	long nr;
 
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
@@ -861,6 +863,7 @@ noinline int __filemap_add_folio(struct address_space *mapping,
 
 	VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
 	xas_set_order(&xas, index, folio_order(folio));
+	huge = folio_test_hugetlb(folio);
 	nr = folio_nr_pages(folio);
 
 	gfp &= GFP_RECLAIM_MASK;
@@ -868,16 +871,10 @@ noinline int __filemap_add_folio(struct address_space *mapping,
 	folio->mapping = mapping;
 	folio->index = xas.xa_index;
 
-	do {
-		unsigned int order = xa_get_order(xas.xa, xas.xa_index);
+	for (;;) {
+		int order = -1, split_order = 0;
 		void *entry, *old = NULL;
 
-		if (order > folio_order(folio)) {
-			xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
-					order, gfp);
-			if (xas_error(&xas))
-				goto error;
-		}
 		xas_lock_irq(&xas);
 		xas_for_each_conflict(&xas, entry) {
 			old = entry;
@@ -885,19 +882,33 @@ noinline int __filemap_add_folio(struct address_space *mapping,
 				xas_set_err(&xas, -EEXIST);
 				goto unlock;
 			}
+			/*
+			 * If a larger entry exists,
+			 * it will be the first and only entry iterated.
+			 */
+			if (order == -1)
+				order = xas_get_order(&xas);
+		}
+
+		/* entry may have changed before we re-acquire the lock */
+		if (alloced_order && (old != alloced_shadow || order != alloced_order)) {
+			xas_destroy(&xas);
+			alloced_order = 0;
 		}
 
 		if (old) {
-			if (shadowp)
-				*shadowp = old;
-			/* entry may have been split before we acquired lock */
-			order = xa_get_order(xas.xa, xas.xa_index);
-			if (order > folio_order(folio)) {
+			if (order > 0 && order > folio_order(folio)) {
 				/* How to handle large swap entries? */
 				BUG_ON(shmem_mapping(mapping));
+				if (!alloced_order) {
+					split_order = order;
+					goto unlock;
+				}
 				xas_split(&xas, old, order);
 				xas_reset(&xas);
 			}
+			if (shadowp)
+				*shadowp = old;
 		}
 
 		xas_store(&xas, folio);
@@ -913,9 +924,24 @@ noinline int __filemap_add_folio(struct address_space *mapping,
 				__lruvec_stat_mod_folio(folio,
 						NR_FILE_THPS, nr);
 		}
+
 unlock:
 		xas_unlock_irq(&xas);
-	} while (xas_nomem(&xas, gfp));
+
+		/* split needed, alloc here and retry. */
+		if (split_order) {
+			xas_split_alloc(&xas, old, split_order, gfp);
+			if (xas_error(&xas))
+				goto error;
+			alloced_shadow = old;
+			alloced_order = split_order;
+			xas_reset(&xas);
+			continue;
+		}
+
+		if (!xas_nomem(&xas, gfp))
+			break;
+	}
 
 	if (xas_error(&xas))
 		goto error;