David Hildenbrand <david@xxxxxxxxxx> writes:
> On 13.09.22 07:22, Alistair Popple wrote:
>> As noted by John Hubbard the original test relied on side effects of the
>> implementation of migrate_vma_setup() to detect if pages had been
>> swapped to disk or not. This is subject to change in future so
>> explicitly check for swap entries via pagemap instead. Fix a spelling
>> mistake while we're at it.
>> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
>> Fixes: 5cc88e844e87 ("selftests/hmm-tests: add test for dirty bits")
>> ---
>> tools/testing/selftests/vm/hmm-tests.c | 50 +++++++++++++++++++++++---
>> 1 file changed, 46 insertions(+), 4 deletions(-)
>> diff --git a/tools/testing/selftests/vm/hmm-tests.c
>> b/tools/testing/selftests/vm/hmm-tests.c
>> index 70fdb49b59ed..b5f6a7dc1f12 100644
>> --- a/tools/testing/selftests/vm/hmm-tests.c
>> +++ b/tools/testing/selftests/vm/hmm-tests.c
>> @@ -1261,9 +1261,47 @@ static int destroy_cgroup(void)
>> return 0;
>> }
>> +static uint64_t get_pfn(int fd, uint64_t ptr)
>> +{
>> + uint64_t pfn;
>> + int ret;
>> +
>> + ret = pread(fd, &pfn, sizeof(ptr),
>> + (uint64_t) ptr / getpagesize() * sizeof(ptr));
>> + if (ret != sizeof(ptr))
>> + return 0;
>> +
>> + return pfn;
>> +}
>> +
>> +#define PAGEMAP_SWAPPED (1ULL << 62)
>> +
>> +/* Returns true if at least one page in the range is on swap */
>> +static bool pages_swapped(void *ptr, unsigned long pages)
>> +{
>> + uint64_t pfn;
>> + int fd = open("/proc/self/pagemap", O_RDONLY);
>> + unsigned long i;
>> +
>> + if (fd < 0)
>> + return false;
>> +
>> + for (i = 0; i < pages; i++) {
>> + pfn = get_pfn(fd, (uint64_t) ptr + i * getpagesize());
>> +
>> + if (pfn & PAGEMAP_SWAPPED) {
>> + close(fd);
>> + return true;
>> + }
>
> We do have pagemap_get_entry() in vm_util.c to query the pagemap entry.
Thanks. I'd missed that, although `grep pagemap
tools/testing/selftests/vm` suggests I'm not the first to follow a
tradition of open-coding this :-)
But there's no need to perpetuate that tradition, so will redo this to
use vm_util.c instead.
> Can you further, add pagemap_is_swapped() to vm_util.c?
>
> I'll be also needing that (including a variant for testing a range) in anon COW
> tests.
