Index: sys/vm/swap_pager.c
===================================================================
--- sys/vm/swap_pager.c
+++ sys/vm/swap_pager.c
@@ -2201,7 +2201,8 @@
 	struct swblk *sb;
 	daddr_t blk;
 	vm_pindex_t offset, last;
-	int i, limit, start;
+	daddr_t d[SWAP_META_PAGES];
+	int i, failed, limit, start;
 
 	VM_OBJECT_ASSERT_WLOCKED(srcobject);
 	VM_OBJECT_ASSERT_WLOCKED(dstobject);
@@ -2210,39 +2211,53 @@
 		return;
 
 	swp_pager_init_freerange(&range);
+	failed = 0;
 	offset = pindex;
 	last = pindex + count;
 	sb = swblk_start_limit(srcobject, pindex, last);
 	start = (sb != NULL && sb->p < pindex) ? pindex - sb->p : 0;
 	for (; sb != NULL;
 	    sb = swblk_start_limit(srcobject, pindex, last), start = 0) {
-		limit = MIN(last - sb->p, SWAP_META_PAGES);
+		pindex = sb->p;
+		limit = MIN(last - pindex, SWAP_META_PAGES);
 		for (i = start; i < limit; i++) {
 			if (sb->d[i] == SWAPBLK_NONE)
 				continue;
 			blk = swp_pager_meta_build(dstobject,
-			    sb->p + i - offset, sb->d[i], true);
+			    pindex + i - offset, sb->d[i], true);
 			if (blk == sb->d[i]) {
 				/*
-				 * Destination has no swapblk and is not
-				 * resident, so transfer source.
-				 * swp_pager_meta_build() failed memory
-				 * allocation already, likely to sleep in retry.
+				 * Failed memory allocation stopped transfer;
+				 * save remaining blocks for transfer with lock
+				 * released.
 				 */
-				VM_OBJECT_WUNLOCK(srcobject);
-				swp_pager_meta_build(dstobject,
-				    sb->p + i - offset, sb->d[i], false);
-				VM_OBJECT_WLOCK(srcobject);
+				d[i++] = blk;
+				for (failed = i; i < limit; i++) {
+					d[i] = sb->d[i];
+					sb->d[i] = SWAPBLK_NONE;
+				}
 			} else if (blk != SWAPBLK_NONE)
 				swp_pager_update_freerange(&range, sb->d[i]);
 			sb->d[i] = SWAPBLK_NONE;
 		}
-		pindex = sb->p + SWAP_META_PAGES;
 		if (swp_pager_swblk_empty(sb, 0, start) &&
 		    swp_pager_swblk_empty(sb, limit, SWAP_META_PAGES)) {
 			swblk_lookup_remove(srcobject, sb);
 			uma_zfree(swblk_zone, sb);
 		}
+		if (failed > 0) {
+			/* Finish block transfer, with the lock released. */
+			VM_OBJECT_WUNLOCK(srcobject);
+			for (i = failed - 1; i < limit; i++) {
+				if (d[i] == SWAPBLK_NONE)
+					continue;
+				swp_pager_meta_build(dstobject,
+				    pindex + i - offset, d[i], false);
+			}
+			VM_OBJECT_WLOCK(srcobject);
+			failed = 0;
+		}
+		pindex += SWAP_META_PAGES;
 	}
 	swp_pager_freeswapspace(&range);
 }