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 <kw...@redhat.com>
Cc: Stefan Hajnoczi <stefa...@redhat.com>
Signed-off-by: Liu Yuan <namei.u...@gmail.com>
---
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
