Re: [Qemu-devel] [PATCH v3 1/1] qga: minimal support for fstrim for Windows guests

[Denis V. Lunev]

On 10/03/2016 03:22 PM, Marc-André Lureau wrote:
> Hi Denis
>
> On Mon, Oct 3, 2016 at 4:08 PM Denis V. Lunev <address@hidden> wrote:
>
>> Unfortunately, there is no public Windows API to start trimming the
>> filesystem. The only viable way here is to call 'defrag.exe /L' for
>> each volume.
>>
>> This is working since Win8 and Win2k12.
>>
> Could you describe the changes the made between the versions and why? (btw
> I didn't receive reply to my previous review comments)
>
> thanks
>
>

The only change with this patch is error code for FindFirstVolumeW,
which is now generated exactly like in the case inside
qmp_guest_get_fsinfo()

I do not want to reuse this code as this will result in 2 line helper.
I do not see much benefit with that. On the other hand,
qmp_guest_get_fsinfo() should be rewritten to use unicode. I have
started doing that but this work is not completed. These
patches have revealed serious problems inside get_fsinfo(),
which is completely broken now.

But I have missed the fact, that this exact patch is rotten,
I have missed de-allocation on the error path, pls disregard.

Thank you for a prompt reply.

Den

>> Signed-off-by: Denis V. Lunev <address@hidden>
>> Signed-off-by: Denis Plotnikov <address@hidden>
>> CC: Michael Roth <address@hidden>
>> CC: Stefan Weil <address@hidden>
>> CC: Marc-André Lureau <address@hidden>
>> ---
>>  qga/commands-win32.c | 95
>> ++++++++++++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 92 insertions(+), 3 deletions(-)
>>
>> Changes from v1, v2:
>> - next attempt to fix error handling on error in FindFirstVolumeW
>>
>> diff --git a/qga/commands-win32.c b/qga/commands-win32.c
>> index 9c9be12..57436b9 100644
>> --- a/qga/commands-win32.c
>> +++ b/qga/commands-win32.c
>> @@ -840,8 +840,97 @@ static void guest_fsfreeze_cleanup(void)
>>  GuestFilesystemTrimResponse *
>>  qmp_guest_fstrim(bool has_minimum, int64_t minimum, Error **errp)
>>  {
>> -    error_setg(errp, QERR_UNSUPPORTED);
>> -    return NULL;
>> +    GuestFilesystemTrimResponse *resp =
>> g_new0(GuestFilesystemTrimResponse, 1);
>> +    HANDLE handle;
>> +    WCHAR guid[MAX_PATH] = L"";
>> +
>> +    handle = FindFirstVolumeW(guid, ARRAYSIZE(guid));
>> +    if (handle == INVALID_HANDLE_VALUE) {
>> +        error_setg_win32(errp, GetLastError(), "failed to find any
>> volume");
>> +        return NULL;
>> +    }
>> +
>> +    do {
>> +        GuestFilesystemTrimResult *res;
>> +        GuestFilesystemTrimResultList *list;
>> +        PWCHAR uc_path;
>> +        DWORD char_count = 0;
>> +        char *path, *out;
>> +        GError *gerr = NULL;
>> +        gchar * argv[4];
>> +
>> +        GetVolumePathNamesForVolumeNameW(guid, NULL, 0, &char_count);
>> +
>> +        if (GetLastError() != ERROR_MORE_DATA) {
>> +            continue;
>> +        }
>> +        if (GetDriveTypeW(guid) != DRIVE_FIXED) {
>> +            continue;
>> +        }
>> +
>> +        uc_path = g_malloc0(sizeof(WCHAR) * char_count);
>> +        if (!GetVolumePathNamesForVolumeNameW(guid, uc_path, char_count,
>> +                                              &char_count) || !*uc_path) {
>> +            /* strange, but this condition could be faced even with size
>> == 2 */
>> +            g_free(uc_path);
>> +            continue;
>> +        }
>> +
>> +        res = g_new0(GuestFilesystemTrimResult, 1);
>> +
>> +        path = g_utf16_to_utf8(uc_path, char_count, NULL, NULL, &gerr);
>> +
>> +        g_free(uc_path);
>> +
>> +        if (gerr != NULL && gerr->code) {
>> +            res->has_error = true;
>> +            res->error = g_strdup(gerr->message);
>> +            g_error_free(gerr);
>> +            break;
>> +        }
>> +
>> +        res->path = path;
>> +
>> +        list = g_new0(GuestFilesystemTrimResultList, 1);
>> +        list->value = res;
>> +        list->next = resp->paths;
>> +
>> +        resp->paths = list;
>> +
>> +        memset(argv, 0, sizeof(argv));
>> +        argv[0] = (gchar *)"defrag.exe";
>> +        argv[1] = (gchar *)"/L";
>> +        argv[2] = path;
>> +
>> +        if (!g_spawn_sync(NULL, argv, NULL, G_SPAWN_SEARCH_PATH, NULL,
>> NULL,
>> +                          &out /* stdout */, NULL /* stdin */,
>> +                          NULL, &gerr)) {
>> +            res->has_error = true;
>> +            res->error = g_strdup(gerr->message);
>> +            g_error_free(gerr);
>> +        } else {
>> +            /* defrag.exe is UGLY. Exit code is ALWAYS zero.
>> +               Error is reported in the output with something like
>> +               (x89000020) etc code in the stdout */
>> +
>> +            int i;
>> +            gchar **lines = g_strsplit(out, "\r\n", 0);
>> +            g_free(out);
>> +
>> +            for (i = 0; lines[i] != NULL; i++) {
>> +                if (g_strstr_len(lines[i], -1, "(0x") == NULL) {
>> +                    continue;
>> +                }
>> +                res->has_error = true;
>> +                res->error = g_strdup(lines[i]);
>> +                break;
>> +            }
>> +            g_strfreev(lines);
>> +        }
>> +    } while (FindNextVolumeW(handle, guid, ARRAYSIZE(guid)));
>> +
>> +    FindVolumeClose(handle);
>> +    return resp;
>>  }
>>
>>  typedef enum {
>> @@ -1416,7 +1505,7 @@ GList *ga_command_blacklist_init(GList *blacklist)
>>          "guest-get-memory-blocks", "guest-set-memory-blocks",
>>          "guest-get-memory-block-size",
>>          "guest-fsfreeze-freeze-list",
>> -        "guest-fstrim", NULL};
>> +        NULL};
>>      char **p = (char **)list_unsupported;
>>
>>      while (*p) {
>> --
>> 2.7.4
>>
>> --
> Marc-André Lureau