Patch series "Fixes for compaction_test", v2. The compaction_test memory selftest introduces fragmentation in memory and then tries to allocate as many hugepages as possible. This series addresses some problems. On Aarch64, if nr_hugepages == 0, then the test trivially succeeds since compaction_index becomes 0, which is less than 3, due to no division by zero exception being raised. We fix that by checking for division by zero. Secondly, correctly set the number of hugepages to zero before trying to set a large number of them. Now, consider a situation in which, at the start of the test, a non-zero number of hugepages have been already set (while running the entire selftests/mm suite, or manually by the admin). The test operates on 80% of memory to avoid OOM-killer invocation, and because some memory is already blocked by hugepages, it would increase the chance of OOM-killing. Also, since mem_free used in check_compaction() is the value before we set nr_hugepages to zero, the chance that the compaction_index will be small is very high if the preset nr_hugepages was high, leading to a bogus test success. This patch (of 3): Currently, if at runtime we are not able to allocate a huge page, the test will trivially pass on Aarch64 due to no exception being raised on division by zero while computing compaction_index. Fix that by checking for nr_hugepages == 0. Anyways, in general, avoid a division by zero by exiting the program beforehand. While at it, fix a typo, and handle the case where the number of hugepages may overflow an integer. Link: https://lkml.kernel.org/r/20240521074358.675031-1-dev.jain@xxxxxxx Link: https://lkml.kernel.org/r/20240521074358.675031-2-dev.jain@xxxxxxx Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory") Signed-off-by: Dev Jain <dev.jain@xxxxxxx> Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Cc: Sri Jayaramappa <sjayaram@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> diff --git a/tools/testing/selftests/mm/compaction_test.c b/tools/testing/selftests/mm/compaction_test.c index 4f42eb7d7636..0b249a06a60b 100644 --- a/tools/testing/selftests/mm/compaction_test.c +++ b/tools/testing/selftests/mm/compaction_test.c @@ -82,12 +82,13 @@ int prereq(void) return -1; } -int check_compaction(unsigned long mem_free, unsigned int hugepage_size) +int check_compaction(unsigned long mem_free, unsigned long hugepage_size) { + unsigned long nr_hugepages_ul; int fd, ret = -1; int compaction_index = 0; - char initial_nr_hugepages[10] = {0}; - char nr_hugepages[10] = {0}; + char initial_nr_hugepages[20] = {0}; + char nr_hugepages[20] = {0}; /* We want to test with 80% of available memory. Else, OOM killer comes in to play */ @@ -134,7 +135,12 @@ int check_compaction(unsigned long mem_free, unsigned int hugepage_size) /* We should have been able to request at least 1/3 rd of the memory in huge pages */ - compaction_index = mem_free/(atoi(nr_hugepages) * hugepage_size); + nr_hugepages_ul = strtoul(nr_hugepages, NULL, 10); + if (!nr_hugepages_ul) { + ksft_print_msg("ERROR: No memory is available as huge pages\n"); + goto close_fd; + } + compaction_index = mem_free/(nr_hugepages_ul * hugepage_size); lseek(fd, 0, SEEK_SET); @@ -145,11 +151,11 @@ int check_compaction(unsigned long mem_free, unsigned int hugepage_size) goto close_fd; } - ksft_print_msg("Number of huge pages allocated = %d\n", - atoi(nr_hugepages)); + ksft_print_msg("Number of huge pages allocated = %lu\n", + nr_hugepages_ul); if (compaction_index > 3) { - ksft_print_msg("ERROR: Less that 1/%d of memory is available\n" + ksft_print_msg("ERROR: Less than 1/%d of memory is available\n" "as huge pages\n", compaction_index); goto close_fd; }
