Re: [PATCH v2] tools/testing/vma: cover hole filling through __mmap_region()

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

On Tue, Sep 08, 2026 at 05:55:15PM +0800, Tianyi Chen wrote:
> The mmap tests extend existing mappings one neighbor at a time, while
> merge tests construct merge state directly. Neither exercises filling
> a hole between compatible mappings through the mmap setup and completion
> path.
>
> Fill a gap through __mmap_region() and require both neighbors to merge
> into one VMA. Repeat with only the new mapping's execute permission set
> and require three separate VMAs. Check boundaries, permissions, page
> offsets, map_count and cleanup.
>
> Signed-off-by: Tianyi Chen <hi@tychen.cc>

For future - please always send v2 patches not in-reply-to anything :P otherwise
mails get buried.

Otherwise all LGTM, thanks for addressing feedback! So:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> Assisted-by: Codex:GPT-6
> ---
> Changes in v2:
> - Rebase onto mm-unstable, preserving the new /dev/zero test.
> - Rename hole_flags to middle_flags and describe each mapping's address
>   and length in its comment.
> - Remove the redundant hole, per-page and outer-boundary iterator checks.
> - Use const bounds and named booleans for the middle VMA's expected execute
>   permission, and separate assertion groups for readability.
>
> Validation: all 29 VMA tests passed with ASan and UBSan enabled, built
> with clang 20 using the existing VMA Makefile.
>
> v1: https://lore.kernel.org/r/20260906144100.849288-1-hi@tychen.cc
> Review: https://lore.kernel.org/r/ap5pmX-RddQ-c90O@gremlin

Thanks! :) very nice.

>
>  tools/testing/vma/tests/mmap.c | 68 ++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)
>
> diff --git a/tools/testing/vma/tests/mmap.c b/tools/testing/vma/tests/mmap.c
> index fa73faff226..53e4abe6a63 100644
> --- a/tools/testing/vma/tests/mmap.c
> +++ b/tools/testing/vma/tests/mmap.c
> @@ -45,6 +45,72 @@ static bool test_mmap_region_basic(void)
>  	return true;
>  }
>
> +static bool mmap_region_fill_hole(bool merge)
> +{
> +	const vma_flags_t vma_flags = mk_vma_flags(VMA_READ_BIT, VMA_WRITE_BIT,
> +			VMA_MAYREAD_BIT, VMA_MAYWRITE_BIT, VMA_MAYEXEC_BIT);
> +	vma_flags_t middle_flags = vma_flags;
> +	struct mm_struct mm = {};
> +	struct vm_area_struct *vma;
> +	unsigned long addr;
> +	int count = 0;
> +	VMA_ITERATOR(vmi, &mm, 0);
> +
> +	current->mm = &mm;
> +	if (!merge)
> +		vma_flags_set(&middle_flags, VMA_EXEC_BIT);
> +
> +	/* Map at 0x300000, length 0x3000. */
> +	addr = __mmap_region(NULL, 0x300000, 0x3000, vma_flags, 0x300, NULL);
> +	ASSERT_EQ(addr, 0x300000);
> +
> +	/* Map at 0x306000, length 0x3000, leaving a hole. */
> +	addr = __mmap_region(NULL, 0x306000, 0x3000, vma_flags, 0x306, NULL);
> +	ASSERT_EQ(addr, 0x306000);
> +	ASSERT_EQ(mm.map_count, 2);
> +
> +	/* Map at 0x303000, length 0x3000, filling the hole. */
> +	addr = __mmap_region(NULL, 0x303000, 0x3000, middle_flags, 0x303, NULL);
> +	ASSERT_EQ(addr, 0x303000);
> +	ASSERT_EQ(mm.map_count, merge ? 1 : 3);
> +
> +	vma_iter_set(&vmi, 0);
> +	for_each_vma(vmi, vma) {
> +		const unsigned long start = 0x300000 + count * 0x3000;
> +		const unsigned long end = merge ? 0x309000 : start + 0x3000;
> +		/* Only the middle VMA in the non-merge case has VMA_EXEC. */
> +		const bool is_middle_vma = count == 1;
> +		const bool expect_exec_vma = is_middle_vma && !merge;
> +
> +		ASSERT_EQ(vma->vm_start, start);
> +		ASSERT_EQ(vma->vm_end, end);
> +		ASSERT_EQ(vma_start_pgoff(vma), start >> PAGE_SHIFT);
> +		ASSERT_EQ(vma_start_anon_pgoff(vma), start >> PAGE_SHIFT);
> +
> +		ASSERT_TRUE(vma_test_all(vma, VMA_READ_BIT, VMA_WRITE_BIT,
> +					 VMA_MAYREAD_BIT, VMA_MAYWRITE_BIT,
> +					 VMA_MAYEXEC_BIT));
> +		ASSERT_EQ(vma_test(vma, VMA_EXEC_BIT), expect_exec_vma);
> +
> +		count++;
> +	}
> +
> +	ASSERT_EQ(count, mm.map_count);
> +
> +	ASSERT_EQ(cleanup_mm(&mm, &vmi), count);
> +	return true;
> +}
> +
> +static bool test_mmap_region_fill_hole_merge(void)
> +{
> +	return mmap_region_fill_hole(true);
> +}
> +
> +static bool test_mmap_region_fill_hole_flags_mismatch(void)
> +{
> +	return mmap_region_fill_hole(false);
> +}
> +
>  static bool test_pure_anon_dev_zero(void)
>  {
>  	const vma_flags_t vma_flags = mk_vma_flags(VMA_READ_BIT, VMA_WRITE_BIT,
> @@ -84,5 +150,7 @@ static bool test_pure_anon_dev_zero(void)
>  static void run_mmap_tests(int *num_tests, int *num_fail)
>  {
>  	TEST(mmap_region_basic);
> +	TEST(mmap_region_fill_hole_merge);
> +	TEST(mmap_region_fill_hole_flags_mismatch);
>  	TEST(pure_anon_dev_zero);
>  }
> --
> 2.55.0
>

--
Cheers, Lorenzo