Re: [PATCH 3/9] tests/qtest/migration: Fix file migration offset check

[Peter Xu <peterx@redhat.com>]

On Fri, Apr 26, 2024 at 11:20:36AM -0300, Fabiano Rosas wrote:
> When doing file migration, QEMU accepts an offset that should be
> skipped when writing the migration stream to the file. The purpose of
> the offset is to allow the management layer to put its own metadata at
> the start of the file.
> 
> We have tests for this in migration-test, but only testing that the
> migration stream starts at the correct offset and not that it actually
> leaves the data intact. Unsurprisingly, there's been a bug in that
> area that the tests didn't catch.
> 
> Fix the tests to write some data to the offset region and check that
> it's actually there after the migration.
> 
> Fixes: 3dc35470c8 ("tests/qtest: migration-test: Add tests for file-based migration")
> Signed-off-by: Fabiano Rosas <farosas@suse.de>
> ---
>  tests/qtest/migration-test.c | 70 +++++++++++++++++++++++++++++++++---
>  1 file changed, 65 insertions(+), 5 deletions(-)
> 
> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> index 5d6d8cd634..7b177686b4 100644
> --- a/tests/qtest/migration-test.c
> +++ b/tests/qtest/migration-test.c
> @@ -2081,6 +2081,63 @@ static void test_precopy_file(void)
>      test_file_common(&args, true);
>  }
>  
> +#ifndef _WIN32
> +static void file_dirty_offset_region(void)
> +{
> +#if defined(__linux__)

Hmm, what's the case to cover when !_WIN32 && __linux__?  Can we remove one
layer of ifdef?

I'm also wondering why it can't work on win32?  I thought win32 has all
these stuff we used here, but I may miss something.

> +    g_autofree char *path = g_strdup_printf("%s/%s", tmpfs, FILE_TEST_FILENAME);
> +    size_t size = FILE_TEST_OFFSET;
> +    uintptr_t *addr, *p;
> +    int fd;
> +
> +    fd = open(path, O_CREAT | O_RDWR, 0660);
> +    g_assert(fd != -1);
> +
> +    g_assert(!ftruncate(fd, size));
> +
> +    addr = mmap(NULL, size, PROT_WRITE, MAP_SHARED, fd, 0);
> +    g_assert(addr != MAP_FAILED);
> +
> +    /* ensure the skipped offset contains some data */
> +    p = addr;
> +    while (p < addr + FILE_TEST_OFFSET / sizeof(uintptr_t)) {
> +        *p = (unsigned long) FILE_TEST_FILENAME;

This is fine, but not as clear what is assigned..  I think here we assigned
is the pointer pointing to the binary's RO section (rather than the chars).
Maybe using some random numbers would be more straightforward, but no
strong opinions.

> +        p++;
> +    }
> +
> +    munmap(addr, size);
> +    fsync(fd);
> +    close(fd);
> +#endif
> +}
> +
> +static void *file_offset_start_hook(QTestState *from, QTestState *to)
> +{
> +    g_autofree char *file = g_strdup_printf("%s/%s", tmpfs, FILE_TEST_FILENAME);
> +    int src_flags = O_WRONLY;
> +    int dst_flags = O_RDONLY;
> +    int fds[2];
> +
> +    file_dirty_offset_region();
> +
> +    fds[0] = open(file, src_flags, 0660);
> +    assert(fds[0] != -1);
> +
> +    fds[1] = open(file, dst_flags, 0660);
> +    assert(fds[1] != -1);
> +
> +    qtest_qmp_fds_assert_success(from, &fds[0], 1, "{'execute': 'add-fd', "
> +                                 "'arguments': {'fdset-id': 1}}");
> +
> +    qtest_qmp_fds_assert_success(to, &fds[1], 1, "{'execute': 'add-fd', "
> +                                 "'arguments': {'fdset-id': 1}}");
> +
> +    close(fds[0]);
> +    close(fds[1]);
> +
> +    return NULL;
> +}
> +
>  static void file_offset_finish_hook(QTestState *from, QTestState *to,
>                                      void *opaque)
>  {
> @@ -2096,12 +2153,12 @@ static void file_offset_finish_hook(QTestState *from, QTestState *to,
>      g_assert(addr != MAP_FAILED);
>  
>      /*
> -     * Ensure the skipped offset contains zeros and the migration
> -     * stream starts at the right place.
> +     * Ensure the skipped offset region's data has not been touched
> +     * and the migration stream starts at the right place.
>       */
>      p = addr;
>      while (p < addr + FILE_TEST_OFFSET / sizeof(uintptr_t)) {
> -        g_assert(*p == 0);
> +        g_assert_cmpstr((char *) *p, ==, FILE_TEST_FILENAME);
>          p++;
>      }
>      g_assert_cmpint(cpu_to_be64(*p) >> 32, ==, QEMU_VM_FILE_MAGIC);
> @@ -2113,17 +2170,18 @@ static void file_offset_finish_hook(QTestState *from, QTestState *to,
>  
>  static void test_precopy_file_offset(void)
>  {
> -    g_autofree char *uri = g_strdup_printf("file:%s/%s,offset=%d", tmpfs,
> -                                           FILE_TEST_FILENAME,
> +    g_autofree char *uri = g_strdup_printf("file:/dev/fdset/1,offset=%d",
>                                             FILE_TEST_OFFSET);

Do we want to keep both tests to cover both normal file and fdsets?

>      MigrateCommon args = {
>          .connect_uri = uri,
>          .listen_uri = "defer",
> +        .start_hook = file_offset_start_hook,
>          .finish_hook = file_offset_finish_hook,
>      };
>  
>      test_file_common(&args, false);
>  }
> +#endif
>  
>  static void test_precopy_file_offset_bad(void)
>  {
> @@ -3636,8 +3694,10 @@ int main(int argc, char **argv)
>  
>      migration_test_add("/migration/precopy/file",
>                         test_precopy_file);
> +#ifndef _WIN32
>      migration_test_add("/migration/precopy/file/offset",
>                         test_precopy_file_offset);
> +#endif
>      migration_test_add("/migration/precopy/file/offset/bad",
>                         test_precopy_file_offset_bad);
>  
> -- 
> 2.35.3
> 

-- 
Peter Xu