Re: [PATCH] tests/qtest/migrate-test: Use regular file file for shared-memory tests

[Fabiano Rosas <farosas@suse.de>]

Nicholas Piggin <npiggin@gmail.com> writes:

> There is no need to use /dev/shm for file-backed memory devices, and
> it is too small to be usable in gitlab CI. Switch to using a regular
> file in /tmp/ which will usually have more space available.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
> Am I missing something? AFAIKS there is not even any point using
> /dev/shm aka tmpfs anyway, there is not much special about it as a
> filesystem. This applies on top of the series just sent, and passes
> gitlab CI qtests including aarch64.

/dev/shm however will be mounted on tmpfs while /tmp may not. I don't
know if this has any implication to this test. Probably not.

>
> Thanks,
> Nick
>
>  tests/qtest/migration-test.c | 41 ++++++++++++------------------------
>  1 file changed, 13 insertions(+), 28 deletions(-)
>
> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> index 45830eb213..86eace354e 100644
> --- a/tests/qtest/migration-test.c
> +++ b/tests/qtest/migration-test.c
> @@ -552,7 +552,7 @@ typedef struct {
>       * unconditionally, because it means the user would like to be verbose.
>       */
>      bool hide_stderr;
> -    bool use_shmem;
> +    bool use_memfile;
>      /* only launch the target process */
>      bool only_target;
>      /* Use dirty ring if true; dirty logging otherwise */
> @@ -672,29 +672,14 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>      g_autofree gchar *cmd_source = NULL;
>      g_autofree gchar *cmd_target = NULL;
>      const gchar *ignore_stderr;
> -    g_autofree char *shmem_opts = NULL;
> -    g_autofree char *shmem_path = NULL;
> +    g_autofree char *memfile_opts = NULL;
> +    g_autofree char *memfile_path = NULL;
>      const char *kvm_opts = NULL;
>      const char *arch = qtest_get_arch();
>      const char *memory_size;
>      const char *machine_alias, *machine_opts = "";
>      g_autofree char *machine = NULL;
>  
> -    if (args->use_shmem) {
> -        if (!g_file_test("/dev/shm", G_FILE_TEST_IS_DIR)) {
> -            g_test_skip("/dev/shm is not supported");
> -            return -1;
> -        }
> -        if (getenv("GITLAB_CI")) {
> -            /*
> -             * Gitlab runners are limited to 64MB shm size. See:
> -             * https://lore.kernel.org/all/87ttq5fvh7.fsf@suse.de/
> -             */
> -            g_test_skip("/dev/shm is not supported in Gitlab CI environment");
> -            return -1;
> -        }
> -    }
> -
>      dst_state = (QTestMigrationState) { };
>      src_state = (QTestMigrationState) { };
>      bootfile_create(tmpfs, args->suspend_me);
> @@ -754,12 +739,12 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>          ignore_stderr = "";
>      }
>  
> -    if (args->use_shmem) {
> -        shmem_path = g_strdup_printf("/dev/shm/qemu-%d", getpid());
> -        shmem_opts = g_strdup_printf(
> +    if (args->use_memfile) {
> +        memfile_path = g_strdup_printf("/%s/qemu-%d", tmpfs, getpid());

The variable tmpfs already contains the leading slash. Strictly speaking
we don't need the pid because 'tmpfs' is unique for each migration-test
run. If you use a fixed string such as qemu-mem, you can then clean it
up at test_migrate_end() along with the others.

> +        memfile_opts = g_strdup_printf(
>              "-object memory-backend-file,id=mem0,size=%s"
>              ",mem-path=%s,share=on -numa node,memdev=mem0",
> -            memory_size, shmem_path);
> +            memory_size, memfile_path);
>      }
>  
>      if (args->use_dirty_ring) {
> @@ -788,7 +773,7 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>                                   memory_size, tmpfs,
>                                   arch_opts ? arch_opts : "",
>                                   arch_source ? arch_source : "",
> -                                 shmem_opts ? shmem_opts : "",
> +                                 memfile_opts ? memfile_opts : "",
>                                   args->opts_source ? args->opts_source : "",
>                                   ignore_stderr);
>      if (!args->only_target) {
> @@ -810,7 +795,7 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>                                   memory_size, tmpfs, uri,
>                                   arch_opts ? arch_opts : "",
>                                   arch_target ? arch_target : "",
> -                                 shmem_opts ? shmem_opts : "",
> +                                 memfile_opts ? memfile_opts : "",
>                                   args->opts_target ? args->opts_target : "",
>                                   ignore_stderr);
>      *to = qtest_init_with_env(QEMU_ENV_DST, cmd_target);
> @@ -822,8 +807,8 @@ static int test_migrate_start(QTestState **from, QTestState **to,
>       * Remove shmem file immediately to avoid memory leak in test failed case.
>       * It's valid because QEMU has already opened this file
>       */

I'm not sure what memory leak this referred to. When a test fails
anywhere outside test_migrate_end(), the /tmp/migration-test-XXXX
directory will stay behind with all the files used during the test. We
probably don't need the special case for this one file.

$ ls /tmp/migration-test-*/
/tmp/migration-test-GFO6N2/:
tlscredsx5090

/tmp/migration-test-QH2MO2/:
bootsect  dest_serial  src_serial

> -    if (args->use_shmem) {
> -        unlink(shmem_path);
> +    if (args->use_memfile) {
> +        unlink(memfile_path);
>      }
>  
>      return 0;
> @@ -1875,7 +1860,7 @@ static void test_ignore_shared(void)
>      g_autofree char *uri = g_strdup_printf("unix:%s/migsocket", tmpfs);
>      QTestState *from, *to;
>      MigrateStart args = {
> -        .use_shmem = true,
> +        .use_memfile = true,
>      };
>  
>      if (test_migrate_start(&from, &to, uri, &args)) {
> @@ -2033,7 +2018,7 @@ static void test_mode_reboot(void)
>      g_autofree char *uri = g_strdup_printf("file:%s/%s", tmpfs,
>                                             FILE_TEST_FILENAME);
>      MigrateCommon args = {
> -        .start.use_shmem = true,
> +        .start.use_memfile = true,
>          .connect_uri = uri,
>          .listen_uri = "defer",
>          .start_hook = test_mode_reboot_start