On 7/22/26 2:41 PM, Muhammad Usama Anjum wrote:
> The hole_punch case verifies that guard regions survive MADV_REMOVE and
> that the backing range is punched out. MADV_REMOVE delegates the hole
> punch to the backing filesystem, which may reject the operation with
> EOPNOTSUPP.
>
> That result means the test cannot establish the state whose guard
> semantics it intends to validate. Treating the missing filesystem
> capability as a guard-region failure creates a false regression.
>
> Unmap the range and skip only when MADV_REMOVE fails with EOPNOTSUPP.
> Preserve the assertion for all other errors so failures on supported
> configurations remain visible.
>
> Signed-off-by: Muhammad Usama Anjum <[email protected]>
I tested this patch on a QEMU by mounting ramfs over /tmp and then
running guard-regions from /tmp.
Before the patch:
# RUN guard_regions.file.hole_punch ...
# guard-regions.c:1947:hole_punch:Expected madvise(&ptr[3 * page_size],
4 * page_size, MADV_REMOVE) (-1) == 0 (0)
# hole_punch: Test terminated by assertion
# FAIL guard_regions.file.hole_punch
not ok 84 guard_regions.file.hole_punch
After the patch:
# RUN guard_regions.file.hole_punch ...
# SKIP MADV_REMOVE not supported by filesystem
# OK guard_regions.file.hole_punch
ok 84 guard_regions.file.hole_punch # SKIP MADV_REMOVE not supported by
filesystem
Tested-by: Sarthak Sharma <[email protected]>
> ---
> tools/testing/selftests/mm/guard-regions.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/guard-regions.c
> b/tools/testing/selftests/mm/guard-regions.c
> index b21df3040b1c7..5c8ec3ca75d7d 100644
> --- a/tools/testing/selftests/mm/guard-regions.c
> +++ b/tools/testing/selftests/mm/guard-regions.c
> @@ -1912,7 +1912,7 @@ TEST_F(guard_regions, hole_punch)
> {
> const unsigned long page_size = self->page_size;
> char *ptr;
> - int i;
> + int i, ret;
>
> if (variant->backing == ANON_BACKED)
> SKIP(return, "Truncation test specific to file-backed");
> @@ -1944,8 +1944,12 @@ TEST_F(guard_regions, hole_punch)
> }
>
> /* Now hole punch the guarded region. */
> - ASSERT_EQ(madvise(&ptr[3 * page_size], 4 * page_size,
> - MADV_REMOVE), 0);
> + ret = madvise(&ptr[3 * page_size], 4 * page_size, MADV_REMOVE);
> + if (ret == -1 && errno == EOPNOTSUPP) {
> + ASSERT_EQ(munmap(ptr, 10 * page_size), 0);
> + SKIP(return, "MADV_REMOVE not supported by filesystem");
> + }
> + ASSERT_EQ(ret, 0);
>
> /* Ensure guard regions remain. */
> for (i = 0; i < 10; i++) {
