Le Tuesday 29 Oct 2013 à 16:25:52 (+0800), Liu Yuan a écrit :
> Sheepdog support two kinds of redundancy, full replication and erasure coding.
>
> # create a fully replicated vdi with x copies
> -o redundancy=x (1 <= x <= SD_MAX_COPIES)
>
> # create a erasure coded vdi with x data strips and y parity strips
> -o redundancy=x:y (x must be one of {2,4,8,16} and 1 <= y < SD_EC_MAX_STRIP)
>
> E.g, to convert a vdi into sheepdog vdi 'test' with 8:3 erasure coding scheme
>
> $ qemu-img convert -o redundancy=8:3 linux-0.2.img sheepdog:test
>
> Cc: Kevin Wolf
> Cc: Stefan Hajnoczi
> Signed-off-by: Liu Yuan
> ---
> block/sheepdog.c | 78
> -
> include/block/block_int.h |1 +
> 2 files changed, 78 insertions(+), 1 deletion(-)
>
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> index e66d2f8..bd7cfd6 100644
> --- a/block/sheepdog.c
> +++ b/block/sheepdog.c
> @@ -91,6 +91,14 @@
> #define SD_NR_VDIS (1U << 24)
> #define SD_DATA_OBJ_SIZE (UINT64_C(1) << 22)
> #define SD_MAX_VDI_SIZE (SD_DATA_OBJ_SIZE * MAX_DATA_OBJS)
> +/*
> + * For erasure coding, we use at most SD_EC_MAX_STRIP for data strips and
> + * (SD_EC_MAX_STRIP - 1) for parity strips
> + *
> + * SD_MAX_COPIES is sum of number of dats trips and parity strips.
> + */
> +#define SD_EC_MAX_STRIP 16
> +#define SD_MAX_COPIES (SD_EC_MAX_STRIP * 2 - 1)
>
> #define SD_INODE_SIZE (sizeof(SheepdogInode))
> #define CURRENT_VDI_ID 0
> @@ -1446,6 +1454,65 @@ out:
> return ret;
> }
>
> +static int64_t is_numeric(const char *s)
> +{
> +char *end;
> +return strtosz_suffix(s, &end, STRTOSZ_DEFSUFFIX_B);
> +}
> +
> +/*
> + * Sheepdog support two kinds of redundancy, full replication and erasure
> + * coding.
> + *
> + * # create a fully replicated vdi with x copies
> + * -o redundancy=x (1 <= x <= SD_MAX_COPIES)
> + *
> + * # create a erasure coded vdi with x data strips and y parity strips
> + * -o redundancy=x:y (x must be one of {2,4,8,16} and 1 <= y <
> SD_EC_MAX_STRIP)
> + */
> +static int parse_redundancy(BDRVSheepdogState *s, const char *opt)
> +{
> +struct SheepdogInode *inode = &s->inode;
> +const char *n1, *n2;
> +uint8_t copy, parity;
> +char p[10];
> +
> +strncpy(p, opt, sizeof(p));
> +n1 = strtok(p, ":");
> +n2 = strtok(NULL, ":");
> +
> +if ((n1 && !is_numeric(n1)) || (n2 && !is_numeric(n2))) {
> +return -EINVAL;
> +}
> +
> +copy = strtol(n1, NULL, 10);
> +if (copy > SD_MAX_COPIES) {
> +return -EINVAL;
> +}
> +if (!n2) {
> +inode->copy_policy = 0;
> +inode->nr_copies = copy;
> +}
> +
> +if (copy != 2 && copy != 4 && copy != 8 && copy != 16) {
> +return -EINVAL;
> +}
> +
> +parity = strtol(n2, NULL, 10);
> +if (parity >= SD_EC_MAX_STRIP || parity == 0) {
> +return -EINVAL;
> +}
> +
> +/*
> + * 4 bits for parity and 4 bits for data.
> + * We have to compress upper data bits because it can't represent 16
> + */
> +inode->copy_policy = ((copy / 2) << 4) + parity;
> +inode->nr_copies = copy + parity;
> +
> +return 0;
> +}
> +
> static int sd_create(const char *filename, QEMUOptionParameter *options,
> Error **errp)
> {
> @@ -1486,6 +1553,11 @@ static int sd_create(const char *filename,
> QEMUOptionParameter *options,
> ret = -EINVAL;
> goto out;
> }
> +} else if (!strcmp(options->name, BLOCK_OPT_REDUNDANCY)) {
> +ret = parse_redundancy(s, options->value.s);
> +if (ret < 0) {
> +goto out;
> +}
> }
> options++;
> }
> @@ -1528,7 +1600,6 @@ static int sd_create(const char *filename,
> QEMUOptionParameter *options,
> bdrv_unref(bs);
> }
>
> -/* TODO: allow users to specify copy number */
> ret = do_sd_create(s, &vid, 0);
> if (!prealloc || ret) {
> goto out;
> @@ -2332,6 +2403,11 @@ static QEMUOptionParameter sd_create_options[] = {
> .type = OPT_STRING,
> .help = "Preallocation mode (allowed values: off, full)"
> },
> +{
> +.name = BLOCK_OPT_REDUNDANCY,
> +.type = OPT_STRING,
> +.help = "Redundancy of the image"
> +},
> { NULL }
> };
>
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index a48731d..b90862f 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -53,6 +53,7 @@
> #define BLOCK_OPT_COMPAT_LEVEL "compat"
> #define BLOCK_OPT_LAZY_REFCOUNTS"lazy_refcounts"
> #define BLOCK_OPT_ADAPTER_TYPE "adapter_type"
> +#define BLOCK_OPT_REDUNDANCY"redundancy"
>
> typedef struct BdrvTrackedRequest {
> BlockDriverState *bs;
> --
> 1.7.9.5
>
>
Hi,
Perhaps it would be better to implement theses options with the new block driver
options mechanism that Kevin implemented.
>From a user perspective i
