ec: Add config information in an xattr

To simplify backward compatibility of the ec xlator when some
parameter or the implementation itself is changed, a new xattr
is added to each file with the configuration needed to recover
it.

The new attribute is called 'trusted.ec.config', and it's a 64-bit
value containing the following information:

    8 bits: version of the config information (currently always 0)
    8 bits: algorithm used to encode the file (currently always 0)
    8 bits: size of the galois field (currently always 8)
    8 bits: number of bricks
    8 bits: redundancy
   24 bits: chunk size (currently 512)

This new xattr could allow, in a future version, to have different
configurations per file.

Change-Id: I8c12d40ff546cc201fc66caa367484be3d48aeb4
BUG: 1140861
Signed-off-by: Xavier Hernandez <xhernandez@datalab.es>
Reviewed-on: http://review.gluster.org/8770
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Dan Lambright <dlambrig@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/xlators/cluster/ec/src/ec-helpers.c b/xlators/cluster/ec/src/ec-helpers.c
index 181a6f7b41a..534d694cc52 100644
--- a/xlators/cluster/ec/src/ec-helpers.c
+++ b/xlators/cluster/ec/src/ec-helpers.c
@@ -246,6 +246,70 @@ int32_t ec_dict_del_number(dict_t * dict, char * key, uint64_t * value)
     return 0;
 }
 
+int32_t ec_dict_set_config(dict_t * dict, char * key, ec_config_t * config)
+{
+    uint64_t * ptr, data;
+
+    if (config->version > EC_CONFIG_VERSION)
+    {
+        gf_log("ec", GF_LOG_ERROR, "Trying to store an unsupported config "
+                                   "version (%u)", config->version);
+
+        return -1;
+    }
+
+    ptr = GF_MALLOC(sizeof(uint64_t), gf_common_mt_char);
+    if (ptr == NULL)
+    {
+        return -1;
+    }
+
+    data = ((uint64_t)config->version) << 56;
+    data |= ((uint64_t)config->algorithm) << 48;
+    data |= ((uint64_t)config->gf_word_size) << 40;
+    data |= ((uint64_t)config->bricks) << 32;
+    data |= ((uint64_t)config->redundancy) << 24;
+    data |= config->chunk_size;
+
+    *ptr = hton64(data);
+
+    return dict_set_bin(dict, key, ptr, sizeof(uint64_t));
+}
+
+int32_t ec_dict_del_config(dict_t * dict, char * key, ec_config_t * config)
+{
+    void * ptr;
+    uint64_t data;
+    int32_t len;
+
+    if ((dict == NULL) || (dict_get_ptr_and_len(dict, key, &ptr, &len) != 0) ||
+        (len != sizeof(uint64_t)))
+    {
+        return -1;
+    }
+
+    data = ntoh64(*(uint64_t *)ptr);
+
+    config->version = (data >> 56) & 0xff;
+    if (config->version > EC_CONFIG_VERSION)
+    {
+        gf_log("ec", GF_LOG_ERROR, "Found an unsupported config version (%u)",
+               config->version);
+
+        return -1;
+    }
+
+    config->algorithm = (data >> 48) & 0xff;
+    config->gf_word_size = (data >> 40) & 0xff;
+    config->bricks = (data >> 32) & 0xff;
+    config->redundancy = (data >> 24) & 0xff;
+    config->chunk_size = data & 0xffffff;
+
+    dict_del(dict, key);
+
+    return 0;
+}
+
 int32_t ec_loc_gfid_check(xlator_t * xl, uuid_t dst, uuid_t src)
 {
     if (uuid_is_null(src))