selftests: drv-net-hw: inject pp_alloc_fail errors in the right place

The tool pp_alloc_fail.py tested error recovery by injecting errors
into the function page_pool_alloc_pages(). The page pool allocation
function page_pool_dev_alloc() does not end up calling
page_pool_alloc_pages(). page_pool_alloc_netmems() seems to be the
function that is called by all of the page pool alloc functions in
the API, so move error injection to that function instead.

Signed-off-by: John Daley <johndale@cisco.com>
Link: https://patch.msgid.link/20250115181312.3544-2-johndale@cisco.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: johndale88

net/core/page_pool.c

@@ -595,13 +595,13 @@ netmem_ref page_pool_alloc_netmems(struct page_pool *pool, gfp_t gfp)
 	return netmem;
 }
 EXPORT_SYMBOL(page_pool_alloc_netmems);
+ALLOW_ERROR_INJECTION(page_pool_alloc_netmems, NULL);
 
 struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
 {
 	return netmem_to_page(page_pool_alloc_netmems(pool, gfp));
 }
 EXPORT_SYMBOL(page_pool_alloc_pages);
-ALLOW_ERROR_INJECTION(page_pool_alloc_pages, NULL);
 
 /* Calculate distance between two u32 values, valid if distance is below 2^(31)
  *  https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution

tools/testing/selftests/drivers/net/hw/pp_alloc_fail.py

@@ -21,9 +21,9 @@ def _enable_pp_allocation_fail():
     if not os.path.exists("/sys/kernel/debug/fail_function"):
         raise KsftSkipEx("Kernel built without function error injection (or DebugFS)")
 
-    if not os.path.exists("/sys/kernel/debug/fail_function/page_pool_alloc_pages"):
+    if not os.path.exists("/sys/kernel/debug/fail_function/page_pool_alloc_netmems"):
         with open("/sys/kernel/debug/fail_function/inject", "w") as fp:
-            fp.write("page_pool_alloc_pages\n")
+            fp.write("page_pool_alloc_netmems\n")
 
     _write_fail_config({
         "verbose": 0,
@@ -37,7 +37,7 @@ def _disable_pp_allocation_fail():
     if not os.path.exists("/sys/kernel/debug/fail_function"):
         return
 
-    if os.path.exists("/sys/kernel/debug/fail_function/page_pool_alloc_pages"):
+    if os.path.exists("/sys/kernel/debug/fail_function/page_pool_alloc_netmems"):
         with open("/sys/kernel/debug/fail_function/inject", "w") as fp:
             fp.write("\n")