linux-kernel - [PATCH 1/8] lib/test_vmalloc: add no_block_alloc

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Message-Id: <20250807075810.358714-2-urezki@gmail.com>
Date: Thu,  7 Aug 2025 09:58:03 +0200
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
To: linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>,
	Michal Hocko <mhocko@...nel.org>,
	Baoquan He <bhe@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Uladzislau Rezki <urezki@...il.com>
Subject: [PATCH 1/8] lib/test_vmalloc: add no_block_alloc_test case

Introduce a new test case "no_block_alloc_test" that verifies
non-blocking allocations using __vmalloc() with GFP_ATOMIC and
GFP_NOWAIT flags.

It is recommended to build kernel with CONFIG_DEBUG_ATOMIC_SLEEP
enabled to help catch "sleeping while atomic" issues. This test
ensures that memory allocation logic under atomic constraints
does not inadvertently sleep.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 lib/test_vmalloc.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c
index 2815658ccc37..aae5f4910aff 100644
--- a/lib/test_vmalloc.c
+++ b/lib/test_vmalloc.c
@@ -54,6 +54,7 @@ __param(int, run_test_mask, 7,
 		"\t\tid: 256,  name: kvfree_rcu_1_arg_vmalloc_test\n"
 		"\t\tid: 512,  name: kvfree_rcu_2_arg_vmalloc_test\n"
 		"\t\tid: 1024, name: vm_map_ram_test\n"
+		"\t\tid: 2048, name: no_block_alloc_test\n"
 		/* Add a new test case description here. */
 );
 
@@ -283,6 +284,30 @@ static int fix_size_alloc_test(void)
 	return 0;
 }
 
+static int no_block_alloc_test(void)
+{
+	void *ptr;
+	int i;
+
+	for (i = 0; i < test_loop_count; i++) {
+		bool use_atomic = !!(get_random_u8() % 2);
+		gfp_t gfp = use_atomic ? GFP_ATOMIC : GFP_NOWAIT;
+		unsigned long size = (nr_pages > 0 ? nr_pages : 1) * PAGE_SIZE;
+
+		preempt_disable();
+		ptr = __vmalloc(size, gfp);
+		preempt_enable();
+
+		if (!ptr)
+			return -1;
+
+		*((__u8 *)ptr) = 0;
+		vfree(ptr);
+	}
+
+	return 0;
+}
+
 static int
 pcpu_alloc_test(void)
 {
@@ -411,6 +436,7 @@ static struct test_case_desc test_case_array[] = {
 	{ "kvfree_rcu_1_arg_vmalloc_test", kvfree_rcu_1_arg_vmalloc_test, },
 	{ "kvfree_rcu_2_arg_vmalloc_test", kvfree_rcu_2_arg_vmalloc_test, },
 	{ "vm_map_ram_test", vm_map_ram_test, },
+	{ "no_block_alloc_test", no_block_alloc_test, true },
 	/* Add a new test case here. */
 };
 
-- 
2.39.5