Re: [PATCH v3 1/4] selftests/mm: virtual_address_range: mmap() without PROT_WRITE

[Dev Jain <dev.jain@arm.com>]

On 13/01/25 6:45 pm, Thomas Weißschuh wrote:
> When mapping a larger chunk than physical memory is available with
> PROT_WRITE and overcommit is disabled, the mapping will fail.
> This will prevent the test from running on systems with less then ~1GiB
> of memory and triggering an inscrutinable test failure.
> As the mappings are never written to anyways, the flag can be removed.
> 
> Fixes: 010409649885 ("selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()")
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> Acked-by: David Hildenbrand <david@redhat.com>
> Acked-by: Dev Jain <dev.jain@arm.com>
> ---
>   tools/testing/selftests/mm/virtual_address_range.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/virtual_address_range.c b/tools/testing/selftests/mm/virtual_address_range.c
> index 2a2b69e91950a37999f606847c9c8328d79890c2..ea6ccf49ef4c552f26317c2a40b09bca1a677f8f 100644
> --- a/tools/testing/selftests/mm/virtual_address_range.c
> +++ b/tools/testing/selftests/mm/virtual_address_range.c
> @@ -166,7 +166,7 @@ int main(int argc, char *argv[])
>   	ksft_set_plan(1);
>   
>   	for (i = 0; i < NR_CHUNKS_LOW; i++) {
> -		ptr[i] = mmap(NULL, MAP_CHUNK_SIZE, PROT_READ | PROT_WRITE,
> +		ptr[i] = mmap(NULL, MAP_CHUNK_SIZE, PROT_READ,
>   			      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>   
>   		if (ptr[i] == MAP_FAILED) {
> @@ -186,7 +186,7 @@ int main(int argc, char *argv[])
>   
>   	for (i = 0; i < NR_CHUNKS_HIGH; i++) {
>   		hint = hint_addr();
> -		hptr[i] = mmap(hint, MAP_CHUNK_SIZE, PROT_READ | PROT_WRITE,
> +		hptr[i] = mmap(hint, MAP_CHUNK_SIZE, PROT_READ,
>   			       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>   
>   		if (hptr[i] == MAP_FAILED)
> 

Just noticed a thing: I believe the fix commit you are looking for is
4e5ce33ceb32. My commit which you mention is not responsible for 
introducing the problem you are solving.