firewire: core: use common kernel API to allocate and release a batch of pages

The pair of alloc_pages_bulk() and release_pages() are convenient to
allocate and release a batch of pages.

This commit utilizes the pair to maintain pages for isochronous DMA
context.

Link: https://lore.kernel.org/r/20260110013911.19160-5-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

diff --git a/drivers/firewire/core-iso.c b/drivers/firewire/core-iso.c
index e678ffba5de245ef2bdca1bc9f23dd18e5986780..f2e35ac7a47606daaaf4b77bf24446909d899863 100644 (file)
--- a/drivers/firewire/core-iso.c
+++ b/drivers/firewire/core-iso.c
@@ -31,22 +31,18 @@
 int fw_iso_buffer_alloc(struct fw_iso_buffer *buffer, int page_count)
 {
        struct page **page_array __free(kfree) = kcalloc(page_count, sizeof(page_array[0]), GFP_KERNEL);
-       int i;
 
        if (!page_array)
                return -ENOMEM;
 
-       for (i = 0; i < page_count; ++i) {
-               struct page *page = alloc_page(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO);
-
-               if (!page)
-                       break;
-               page_array[i] = page;
-       }
-
-       if (i < page_count) {
-               while (i-- > 0)
-                       __free_page(page_array[i]);
+       // Retrieve noncontiguous pages. The descriptors for 1394 OHCI isochronous DMA contexts
+       // have a set of address and length per each, while the reason to use pages is the
+       // convenience to map them into virtual address space of user process.
+       unsigned long nr_populated = alloc_pages_bulk(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO,
+                                                     page_count, page_array);
+       if (nr_populated != page_count) {
+               // Assuming the above call fills page_array sequentially from the beginning.
+               release_pages(page_array, nr_populated);
                return -ENOMEM;
        }
 
@@ -64,7 +60,10 @@ int fw_iso_buffer_map_dma(struct fw_iso_buffer *buffer, struct fw_card *card,
 
        buffer->direction = direction;
 
+       // Retrieve DMA mapping addresses for the pages. They are not contiguous. Maintain the cache
+       // coherency for the pages by hand.
        for (i = 0; i < buffer->page_count; i++) {
+               // The dma_map_phys() with a physical address per page is available here, instead.
                address = dma_map_page(card->device, buffer->pages[i],
                                       0, PAGE_SIZE, direction);
                if (dma_mapping_error(card->device, address))
@@ -109,8 +108,7 @@ void fw_iso_buffer_destroy(struct fw_iso_buffer *buffer,
        }
 
        if (buffer->pages) {
-               for (int i = 0; i < buffer->page_count; ++i)
-                       __free_page(buffer->pages[i]);
+               release_pages(buffer->pages, buffer->page_count);
                kfree(buffer->pages);
                buffer->pages = NULL;
        }