Re: [Qemu-devel] [PATCH v4 1/1] qga: minimal support for fstrim for Windows guests

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Denis V. Lunev (2016-10-05 06:13:12)
> On 10/04/2016 04:43 PM, Marc-André Lureau wrote:
> > Hi
> >
> > On Mon, Oct 3, 2016 at 6:01 PM Denis V. Lunev <den@openvz.org
> > <mailto:den@openvz.org>> 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.
> >
> >     Signed-off-by: Denis V. Lunev <den@openvz.org <mailto:den@openvz.org>>
> >     Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com
> >     <mailto:dplotnikov@virtuozzo.com>>
> >     CC: Michael Roth <mdroth@linux.vnet.ibm.com
> >     <mailto:mdroth@linux.vnet.ibm.com>>
> >     CC: Stefan Weil <sw@weilnetz.de <mailto:sw@weilnetz.de>>
> >     CC: Marc-André Lureau <marcandre.lureau@gmail.com
> >     <mailto:marcandre.lureau@gmail.com>>
> >
> >
> > overall looks good to me, few remarks below:
> >  
> >
> >     ---
> >      qga/commands-win32.c | 97
> >     ++++++++++++++++++++++++++++++++++++++++++++++++++--
> >      1 file changed, 94 insertions(+), 3 deletions(-)
> >
> >     Changes from v3:
> >     - fixed memory leak on error path for FindFirstVolumeW
> >     - replaced g_malloc0 with g_malloc for uc_path. g_malloc is better
> >     as we are
> >       allocating string, not an object
> >
> >     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..cebf4cc 100644
> >     --- a/qga/commands-win32.c
> >     +++ b/qga/commands-win32.c
> >     @@ -840,8 +840,99 @@ 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;
> >     +    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;
> >     +    }
> >     +
> >     +    resp = g_new0(GuestFilesystemTrimResponse, 1);
> >     +
> >     +    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);
> >     +
> >
> >
> > It assumes GetVolumePathNamesForVolumeNameW() == 0, perhaps better be
> > explicit about it with an assert() or a warning()?
> original assumption was that in this case we'll call
> GetVolumePathNamesForVolumeNameW()
> with the exactly the same parameter set and fail there.
> 
> 
> >
> >     +        if (GetLastError() != ERROR_MORE_DATA) {
> >
> >
> > Would it be useful to log the error in this case?
> >  
> >
> >     +            continue;
> >     +        }
> >     +        if (GetDriveTypeW(guid) != DRIVE_FIXED) {
> >     +            continue;
> >     +        }
> >     +
> >     +        uc_path = g_malloc(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 */
> >
> >
> > What size?
> >  
> with char_count == 2
> 
> > Same remark regarding logging error.
> >
> >     +            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) {
> >
> >
> > Why check gerr->code? To be consistent with error checking code, I
> > would check if path == NULL instead, which by glib doc says that gerr
> > will be set in this case.
> >  
> ok

Thanks, applied to qga tree with the above suggestion squashed in:

  https://github.com/mdroth/qemu/commits/qga

> 
> >     +            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);
> >
> >
> > It could use continue; here, like the other error code paths, to avoid
> > the else indent?
> I need indent for local variable
> 
> >  
> >
> >     +        } 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 +1507,7 @@ 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
> 
>