From: Keith Busch <kbusch@kernel.org>
Date: Tue, 22 Oct 2024 22:48:50 +0000 (-0700)
Subject: PCI: Convert __pci_walk_bus() to be recursive
X-Git-Tag: microblaze-v6.16~472^2~24^2~1
X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=ee061da777f704976c6d3fdc1707788d11a052c5;p=linux-2.6-microblaze.git

PCI: Convert __pci_walk_bus() to be recursive

The original implementation of __pci_walk_bus() chose a non-recursive walk,
presumably as a precaution on stack use. We do recursive bus walking in
other places though. For example:

  pci_bus_resettable()
  pci_stop_bus_device()
  pci_remove_bus_device()
  pci_bus_allocate_dev_resources()

So recursive pci bus walking is well tested and safe, and is easier to
follow.

Convert __pci_walk_bus() to be recursive to make it easier to introduce
finer grain locking in the future.

Link: https://lore.kernel.org/r/20241022224851.340648-5-kbusch@meta.com
Signed-off-by: Keith Busch <kbusch@kernel.org>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 7c07a141e877..8491e9c7f058 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -389,37 +389,23 @@ void pci_bus_add_devices(const struct pci_bus *bus)
 }
 EXPORT_SYMBOL(pci_bus_add_devices);
 
-static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
-			   void *userdata)
+static int __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
+			  void *userdata)
 {
 	struct pci_dev *dev;
-	struct pci_bus *bus;
-	struct list_head *next;
-	int retval;
+	int ret = 0;
 
-	bus = top;
-	next = top->devices.next;
-	for (;;) {
-		if (next == &bus->devices) {
-			/* end of this bus, go up or finish */
-			if (bus == top)
+	list_for_each_entry(dev, &top->devices, bus_list) {
+		ret = cb(dev, userdata);
+		if (ret)
+			break;
+		if (dev->subordinate) {
+			ret = __pci_walk_bus(dev->subordinate, cb, userdata);
+			if (ret)
 				break;
-			next = bus->self->bus_list.next;
-			bus = bus->self->bus;
-			continue;
 		}
-		dev = list_entry(next, struct pci_dev, bus_list);
-		if (dev->subordinate) {
-			/* this is a pci-pci bridge, do its devices next */
-			next = dev->subordinate->devices.next;
-			bus = dev->subordinate;
-		} else
-			next = dev->bus_list.next;
-
-		retval = cb(dev, userdata);
-		if (retval)
-			break;
 	}
+	return ret;
 }
 
 /**