busdma_bounce: Add free_bounce_pages helper function.

Deduplicate code to iterate over the bpages list in a bus_dmamap_t
freeing bounce pages during bus_dmamap_unload.

Reviewed by:	imp
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D34967

sys/arm/arm/busdma_machdep.c

@@ -1178,14 +1178,10 @@ _bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
 void
 bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
-	struct bounce_page *bpage;
 	struct bounce_zone *bz;
 
 	if ((bz = dmat->bounce_zone) != NULL) {
-		while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
-			STAILQ_REMOVE_HEAD(&map->bpages, links);
-			free_bounce_page(dmat, bpage);
-		}
+		free_bounce_pages(dmat, map);
 
 		bz = dmat->bounce_zone;
 		bz->free_bpages += map->pagesreserved;

sys/arm64/arm64/busdma_bounce.c

@@ -969,13 +969,7 @@ bounce_bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
 static void
 bounce_bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
-	struct bounce_page *bpage;
-
-	while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
-		STAILQ_REMOVE_HEAD(&map->bpages, links);
-		free_bounce_page(dmat, bpage);
-	}
-
+	free_bounce_pages(dmat, map);
 	map->sync_count = 0;
 	map->flags &= ~DMAMAP_MBUF;
 }

sys/kern/subr_busdma_bounce.c

@@ -420,6 +420,17 @@ free_bounce_page(bus_dma_tag_t dmat, struct bounce_page *bpage)
 		wakeup(&bounce_map_callbacklist);
 }
 
+static void
+free_bounce_pages(bus_dma_tag_t dmat, bus_dmamap_t map)
+{
+	struct bounce_page *bpage;
+
+	while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
+		STAILQ_REMOVE_HEAD(&map->bpages, links);
+		free_bounce_page(dmat, bpage);
+	}
+}
+
 static void
 busdma_thread(void *dummy __unused)
 {

sys/powerpc/powerpc/busdma_machdep.c

@@ -801,17 +801,12 @@ _bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
 void
 bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
-	struct bounce_page *bpage;
-
 	if (dmat->iommu) {
 		IOMMU_UNMAP(dmat->iommu, map->segments, map->nsegs, dmat->iommu_cookie);
 		map->nsegs = 0;
 	}
 
-	while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
-		STAILQ_REMOVE_HEAD(&map->bpages, links);
-		free_bounce_page(dmat, bpage);
-	}
+	free_bounce_pages(dmat, map);
 }
 
 void

sys/riscv/riscv/busdma_bounce.c

@@ -810,13 +810,7 @@ bounce_bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
 static void
 bounce_bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
-	struct bounce_page *bpage;
-
-	while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
-		STAILQ_REMOVE_HEAD(&map->bpages, links);
-		free_bounce_page(dmat, bpage);
-	}
-
+	free_bounce_pages(dmat, map);
 	map->sync_count = 0;
 }
 

sys/x86/x86/busdma_bounce.c

@@ -907,15 +907,10 @@ bounce_bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
 static void
 bounce_bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
 {
-	struct bounce_page *bpage;
-
 	if (map == NULL)
 		return;
 
-	while ((bpage = STAILQ_FIRST(&map->bpages)) != NULL) {
-		STAILQ_REMOVE_HEAD(&map->bpages, links);
-		free_bounce_page(dmat, bpage);
-	}
+	free_bounce_pages(dmat, map);
 }
 
 static void