Re: [PATCH v4 8/9] qemu-img: Add convert --bitmaps option

[Vladimir Sementsov-Ogievskiy]

13.05.2020 04:16, Eric Blake wrote:
> Make it easier to copy all the persistent bitmaps of (the top layer
> of) a source image along with its guest-visible contents, by adding a
> boolean flag for use with qemu-img convert.  This is basically
> shorthand, as the same effect could be accomplished with a series of
> 'qemu-img bitmap --add' and 'qemu-img bitmap --merge -b source'
> commands, or by QMP commands.
>
> Note that this command will fail in the same scenarios where 'qemu-img
> measure --bitmaps' fails, when either the source or the destanation
> lacks persistent bitmap support altogether.
>
> See also https://bugzilla.redhat.com/show_bug.cgi?id=1779893
>
> While touching this, clean up a couple coding issues spotted in the
> same function: an extra blank line, and merging back-to-back 'if
> (!skip_create)' blocks.
>
> Signed-off-by: Eric Blake <address@hidden>
> ---
>   docs/tools/qemu-img.rst |  6 ++-
>   qemu-img.c              | 85 +++++++++++++++++++++++++++++++++++++++--
>   qemu-img-cmds.hx        |  4 +-
>   3 files changed, 89 insertions(+), 6 deletions(-)

[..]

> +static int convert_copy_bitmaps(BlockDriverState *src, BlockDriverState *dst)
> +{
> +    BdrvDirtyBitmap *bm;
> +    Error *err = NULL;
> +    BlockDirtyBitmapMergeSource *merge;
> +    BlockDirtyBitmapMergeSourceList *list;
> +
> +    FOR_EACH_DIRTY_BITMAP(src, bm) {
> +        const char *name;
> +
> +        if (!bdrv_dirty_bitmap_get_persistence(bm)) {
> +            continue;
> +        }
> +        name = bdrv_dirty_bitmap_name(bm);
> +        qmp_block_dirty_bitmap_add(dst->node_name, name,
> +                                   true, bdrv_dirty_bitmap_granularity(bm),
> +                                   true, true,
> +                                   true, !bdrv_dirty_bitmap_enabled(bm),
> +                                   &err);
> +        if (err) {
> +            error_reportf_err(err, "Failed to create bitmap %s: ", name);
> +            return -1;
> +        }
> +
> +        merge = g_new0(BlockDirtyBitmapMergeSource, 1);
> +        merge->type = QTYPE_QDICT;
> +        merge->u.external.node = g_strdup(src->node_name);
> +        merge->u.external.name = g_strdup(name);
> +        list = g_new0(BlockDirtyBitmapMergeSourceList, 1);
> +        list->value = merge;
> +        qmp_block_dirty_bitmap_merge(dst->node_name, name, list, &err);
> +        qapi_free_BlockDirtyBitmapMergeSourceList(list);

^ duplicated code chunk with "case BITMAP_MERGE". Small helper function will 
not hurt.

> +        if (err) {
> +            error_reportf_err(err, "Failed to populate bitmap %s: ", name);
> +            return -1;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
>   #define MAX_BUF_SECTORS 32768
>
>   static int img_convert(int argc, char **argv)
> @@ -2130,6 +2172,8 @@ static int img_convert(int argc, char **argv)
>       int64_t ret = -EINVAL;
>       bool force_share = false;
>       bool explict_min_sparse = false;
> +    bool bitmaps = false;
> +    size_t nbitmaps = 0;
>
>       ImgConvertState s = (ImgConvertState) {
>           /* Need at least 4k of zeros for sparse detection */
> @@ -2149,6 +2193,7 @@ static int img_convert(int argc, char **argv)
>               {"target-image-opts", no_argument, 0, OPTION_TARGET_IMAGE_OPTS},
>               {"salvage", no_argument, 0, OPTION_SALVAGE},
>               {"target-is-zero", no_argument, 0, OPTION_TARGET_IS_ZERO},
> +            {"bitmaps", no_argument, 0, OPTION_BITMAPS},
>               {0, 0, 0, 0}
>           };
>           c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WU",
> @@ -2272,6 +2317,9 @@ static int img_convert(int argc, char **argv)
>                */
>               s.has_zero_init = true;
>               break;
> +        case OPTION_BITMAPS:
> +            bitmaps = true;
> +            break;
>           }
>       }
>
> @@ -2333,7 +2381,6 @@ static int img_convert(int argc, char **argv)
>           goto fail_getopt;
>       }
>
> -
>       /* ret is still -EINVAL until here */
>       ret = bdrv_parse_cache_mode(src_cache, &src_flags, &src_writethrough);
>       if (ret < 0) {
> @@ -2493,6 +2540,27 @@ static int img_convert(int argc, char **argv)
>           }
>       }
>
> +    /* Determine how many bitmaps need copying */
> +    if (bitmaps) {
> +        BdrvDirtyBitmap *bm;
> +
> +        if (s.src_num > 1) {
> +            error_report("Copying bitmaps only possible with single source");
> +            ret = -1;
> +            goto out;
> +        }
> +        if (!bdrv_supports_persistent_dirty_bitmap(blk_bs(s.src[0]))) {
> +            error_report("Source lacks bitmap support");
> +            ret = -1;
> +            goto out;
> +        }
> +        FOR_EACH_DIRTY_BITMAP(blk_bs(s.src[0]), bm) {
> +            if (bdrv_dirty_bitmap_get_persistence(bm)) {

Just note, that we can't have not persistent bitmaps here.. But the check 
doesn't hurt.

> +                nbitmaps++;
> +            }
> +        }
> +    }
> +
>       /*
>        * The later open call will need any decryption secrets, and
>        * bdrv_create() will purge "opts", so extract them now before
> @@ -2501,9 +2569,7 @@ static int img_convert(int argc, char **argv)
>       if (!skip_create) {
>           open_opts = qdict_new();
>           qemu_opt_foreach(opts, img_add_key_secrets, open_opts, &error_abort);
> -    }
>
> -    if (!skip_create) {
>           /* Create the new image */
>           ret = bdrv_create(drv, out_filename, opts, &local_err);
>           if (ret < 0) {
> @@ -2541,6 +2607,13 @@ static int img_convert(int argc, char **argv)
>       }
>       out_bs = blk_bs(s.target);
>
> +    if (nbitmaps > 0 && !bdrv_supports_persistent_dirty_bitmap(out_bs)) {
> +        error_report("Format driver '%s' does not support bitmaps",
> +                     out_fmt);
> +        ret = -1;
> +        goto out;
> +    }
> +
>       if (s.compressed && !block_driver_can_compress(out_bs->drv)) {
>           error_report("Compression not supported for this file format");
>           ret = -1;
> @@ -2600,6 +2673,12 @@ static int img_convert(int argc, char **argv)
>       }
>
>       ret = convert_do_copy(&s);
> +
> +    /* Now copy the bitmaps */
> +    if (nbitmaps > 0 && ret == 0) {
> +        ret = convert_copy_bitmaps(blk_bs(s.src[0]), out_bs);
> +    }
> +
>   out:
>       if (!ret) {
>           qemu_progress_print(100, 0);
> diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
> index bfcd9f32dddf..2791c4f58ddd 100644
> --- a/qemu-img-cmds.hx
> +++ b/qemu-img-cmds.hx
> @@ -46,9 +46,9 @@ SRST
>   ERST
>
>   DEF("convert", img_convert,
> -    "convert [--object objectdef] [--image-opts] [--target-image-opts] 
> [--target-is-zero] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T src_cache] [-O 
> output_fmt] [-B backing_file] [-o options] [-l snapshot_param] [-S sparse_size] [-m 
> num_coroutines] [-W] [--salvage] filename [filename2 [...]] output_filename")
> +    "convert [--object objectdef] [--image-opts] [--target-image-opts] 
> [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f fmt] [-t cache] [-T 
> src_cache] [-O output_fmt] [-B backing_file] [-o options] [-l snapshot_param] [-S 
> sparse_size] [-m num_coroutines] [-W] [--salvage] filename [filename2 [...]] 
> output_filename")
>   SRST
> -.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] 
> [--target-is-zero] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t CACHE] [-T 
> SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l SNAPSHOT_PARAM] 
> [-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] [--salvage] FILENAME [FILENAME2 
> [...]] OUTPUT_FILENAME
> +.. option:: convert [--object OBJECTDEF] [--image-opts] [--target-image-opts] 
> [--target-is-zero] [--bitmaps] [-U] [-C] [-c] [-p] [-q] [-n] [-f FMT] [-t 
> CACHE] [-T SRC_CACHE] [-O OUTPUT_FMT] [-B BACKING_FILE] [-o OPTIONS] [-l 
> SNAPSHOT_PARAM] [-S SPARSE_SIZE] [-m NUM_COROUTINES] [-W] [--salvage] FILENAME 
> [FILENAME2 [...]] OUTPUT_FILENAME
>   ERST
>
>   DEF("create", img_create,


--
Best regards,
Vladimir