linux-kernel - [PATCH hotfix 6.12 2/2] tools: testing: add expand-only mode VMA test

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Message-ID: <d2f88330254a6448092412bf7dfe077a579ab0dc.1729174352.git.lorenzo.stoakes@oracle.com>
Date: Thu, 17 Oct 2024 15:31:46 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Oliver Sang <oliver.sang@...el.com>
Subject: [PATCH hotfix 6.12 2/2] tools: testing: add expand-only mode VMA test

Add a test to assert that VMG_FLAG_JUST_EXPAND functions as expected - that
is, when the VMA iterator is positioned at the previous VMA and no VMAs
proceed it, we observe an expansion with all state as expected.

Explicitly place a prior VMA that would otherwise fail this test if the
mode were not enabled (as it would traverse to the previous-previous VMA).

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 tools/testing/vma/vma.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tools/testing/vma/vma.c b/tools/testing/vma/vma.c
index c53f220eb6cc..b33b47342d41 100644
--- a/tools/testing/vma/vma.c
+++ b/tools/testing/vma/vma.c
@@ -1522,6 +1522,45 @@ static bool test_copy_vma(void)
 	return true;
 }

+static bool test_expand_only_mode(void)
+{
+	unsigned long flags = VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE;
+	struct mm_struct mm = {};
+	VMA_ITERATOR(vmi, &mm, 0);
+	struct vm_area_struct *vma_prev, *vma;
+	VMG_STATE(vmg, &mm, &vmi, 0x5000, 0x9000, flags, 5);
+
+	/*
+	 * Place a VMA prior to the one we're expanding so we assert that we do
+	 * not erroneously try to traverse to the previous VMA even though we
+	 * have, through the use of VMG_FLAG_JUST_EXPAND, indicated we do not
+	 * need to do so.
+	 */
+	alloc_and_link_vma(&mm, 0, 0x2000, 0, flags);
+
+	/*
+	 * We will be positioned at the prev VMA, but looking to expand to
+	 * 0x9000.
+	 */
+	vma_iter_set(&vmi, 0x3000);
+	vma_prev = alloc_and_link_vma(&mm, 0x3000, 0x5000, 3, flags);
+	vmg.prev = vma_prev;
+	vmg.merge_flags = VMG_FLAG_JUST_EXPAND;
+
+	vma = vma_merge_new_range(&vmg);
+	ASSERT_NE(vma, NULL);
+	ASSERT_EQ(vma, vma_prev);
+	ASSERT_EQ(vmg.state, VMA_MERGE_SUCCESS);
+	ASSERT_EQ(vma->vm_start, 0x3000);
+	ASSERT_EQ(vma->vm_end, 0x9000);
+	ASSERT_EQ(vma->vm_pgoff, 3);
+	ASSERT_TRUE(vma_write_started(vma));
+	ASSERT_EQ(vma_iter_addr(&vmi), 0x3000);
+
+	cleanup_mm(&mm, &vmi);
+	return true;
+}
+
 int main(void)
 {
 	int num_tests = 0, num_fail = 0;
@@ -1553,6 +1592,7 @@ int main(void)
 	TEST(vmi_prealloc_fail);
 	TEST(merge_extend);
 	TEST(copy_vma);
+	TEST(expand_only_mode);

 #undef TEST

--
2.46.2