Re: [Qemu-devel] [PATCH V5 04/13] block: add snapshot info query function bdrv_query_snapshot_infolist()

[Kevin Wolf]

Am 24.01.2013 03:57, schrieb Wenchao Xia:
>   This patch add function bdrv_query_snapshot_infolist(), which will
> return snapshot info of an image in qmp object format. The implementation
> code are mostly copied from qemu-img.c with modification to fit more
> for qmp based block layer API.
>   To help filter out snapshot info not needed, a call back function is
> added in bdrv_query_snapshot_infolist().
>   bdrv_can_read_snapshot() should be called before call this function,
> to avoid got *errp set unexpectedly.
> 
> Signed-off-by: Wenchao Xia <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> ---
>  block.c               |   60 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/block/block.h |    7 +++++
>  2 files changed, 67 insertions(+), 0 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 934bb3f..7cdb6c6 100644
> --- a/block.c
> +++ b/block.c
> @@ -2842,6 +2842,66 @@ int coroutine_fn 
> bdrv_co_is_allocated_above(BlockDriverState *top,
>      return 0;
>  }
>  
> +SnapshotInfoList *bdrv_query_snapshot_infolist(BlockDriverState *bs,
> +                                               SnapshotFilterFunc filter,

This filter things looks overengineered to me, and no patch in this
series really uses it. Do we really need it?


> +                                               void *opaque,
> +                                               Error **errp)
> +{
> +    int i, sn_count;
> +    QEMUSnapshotInfo *sn_tab = NULL;
> +    SnapshotInfoList *info_list, *cur_item = NULL, *head = NULL;
> +
> +    sn_count = bdrv_snapshot_list(bs, &sn_tab);
> +    if (sn_count < 0) {
> +        /* Now bdrv_snapshot_list() use negative value to tip error, so a 
> check
> +         * of it was done here. In future errp can be set by that function
> +         * itself, by changing the call back functions in c files in ./block.
> +         */
> +        const char *dev = bdrv_get_device_name(bs);
> +        if (sn_count == -ENOMEDIUM) {
> +            error_setg(errp, "Device '%s' is not inserted.", dev);
> +        } else if (sn_count == -ENOTSUP) {
> +            error_setg(errp,
> +                       "Device '%s' does not support internal snapshot.",
> +                       dev);
> +        } else {
> +            error_setg(errp,
> +                       "Device '%s' got %d for bdrv_snapshot_list().",
> +                       dev, sn_count);

strerror(-sn_count) would make the error message more useful.

You could also consider using switch instead of an if/else if chain.

> +        }
> +        return NULL;
> +    }
> +
> +    for (i = 0; i < sn_count; i++) {
> +        if (filter && filter(&sn_tab[i], opaque) != 0) {
> +            continue;
> +        }
> +
> +        info_list = g_new0(SnapshotInfoList, 1);
> +
> +        info_list->value                = g_new0(SnapshotInfo, 1);
> +        info_list->value->id            = g_strdup(sn_tab[i].id_str);
> +        info_list->value->name          = g_strdup(sn_tab[i].name);
> +        info_list->value->vm_state_size = sn_tab[i].vm_state_size;
> +        info_list->value->date_sec      = sn_tab[i].date_sec;
> +        info_list->value->date_nsec     = sn_tab[i].date_nsec;
> +        info_list->value->vm_clock_sec  = sn_tab[i].vm_clock_nsec / 
> 1000000000;
> +        info_list->value->vm_clock_nsec = sn_tab[i].vm_clock_nsec % 
> 1000000000;

Did I already mention somewhere that I'm a fan of compound literals?
Looks so much nicer than repeating info_list->value-> in each line. ;-)

Kevin