firewire: core: stop using page private to store DMA mapping address

There is a long discussion about the use of private field in page
structure between Linux kernel developers.

This commit stop using page private to store DMA mapping address for
isochronous context, to prepare for mm future change.

Link: https://lore.kernel.org/r/20260110013911.19160-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

1 files changed, 25 insertions, 23 deletions

diff --git a/drivers/firewire/core-iso.c b/drivers/firewire/core-iso.c
index f2e35ac7a476..3f36243ec0c1 100644
--- a/drivers/firewire/core-iso.c
+++ b/drivers/firewire/core-iso.c
@@ -55,25 +55,32 @@ int fw_iso_buffer_alloc(struct fw_iso_buffer *buffer, int page_count)
 int fw_iso_buffer_map_dma(struct fw_iso_buffer *buffer, struct fw_card *card,
 			  enum dma_data_direction direction)
 {
-	dma_addr_t address;
+	dma_addr_t *dma_addrs __free(kfree) = kcalloc(buffer->page_count, sizeof(dma_addrs[0]),
+						      GFP_KERNEL);
 	int i;
 
-	buffer->direction = direction;
+	if (!dma_addrs)
+		return -ENOMEM;
 
 	// 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))
+		dma_addr_t dma_addr = dma_map_page(card->device, buffer->pages[i], 0, PAGE_SIZE,
+						   direction);
+		if (dma_mapping_error(card->device, dma_addr))
 			break;
 
-		set_page_private(buffer->pages[i], address);
+		dma_addrs[i] = dma_addr;
 	}
-	buffer->page_count_mapped = i;
-	if (i < buffer->page_count)
+	if (i < buffer->page_count) {
+		while (i-- > 0)
+			dma_unmap_page(card->device, dma_addrs[i], PAGE_SIZE, buffer->direction);
 		return -ENOMEM;
+	}
+
+	buffer->direction = direction;
+	buffer->dma_addrs = no_free_ptr(dma_addrs);
 
 	return 0;
 }
@@ -98,13 +105,13 @@ EXPORT_SYMBOL(fw_iso_buffer_init);
 void fw_iso_buffer_destroy(struct fw_iso_buffer *buffer,
 			   struct fw_card *card)
 {
-	int i;
-	dma_addr_t address;
-
-	for (i = 0; i < buffer->page_count_mapped; i++) {
-		address = page_private(buffer->pages[i]);
-		dma_unmap_page(card->device, address,
-			       PAGE_SIZE, buffer->direction);
+	if (buffer->dma_addrs) {
+		for (int i = 0; i < buffer->page_count; ++i) {
+			dma_addr_t dma_addr = buffer->dma_addrs[i];
+			dma_unmap_page(card->device, dma_addr, PAGE_SIZE, buffer->direction);
+		}
+		kfree(buffer->dma_addrs);
+		buffer->dma_addrs = NULL;
 	}
 
 	if (buffer->pages) {
@@ -114,20 +121,15 @@ void fw_iso_buffer_destroy(struct fw_iso_buffer *buffer,
 	}
 
 	buffer->page_count = 0;
-	buffer->page_count_mapped = 0;
 }
 EXPORT_SYMBOL(fw_iso_buffer_destroy);
 
 /* Convert DMA address to offset into virtually contiguous buffer. */
 size_t fw_iso_buffer_lookup(struct fw_iso_buffer *buffer, dma_addr_t completed)
 {
-	size_t i;
-	dma_addr_t address;
-	ssize_t offset;
-
-	for (i = 0; i < buffer->page_count; i++) {
-		address = page_private(buffer->pages[i]);
-		offset = (ssize_t)completed - (ssize_t)address;
+	for (int i = 0; i < buffer->page_count; i++) {
+		dma_addr_t dma_addr = buffer->dma_addrs[i];
+		ssize_t offset = (ssize_t)completed - (ssize_t)dma_addr;
 		if (offset > 0 && offset <= PAGE_SIZE)
 			return (i << PAGE_SHIFT) + offset;
 	}