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, 29 insertions, 0 deletions

diff --git a/xlators/cluster/ec/src/ec-dir-write.c b/xlators/cluster/ec/src/ec-dir-write.c
index a28b7ad1937..92012855087 100644
--- a/xlators/cluster/ec/src/ec-dir-write.c
+++ b/xlators/cluster/ec/src/ec-dir-write.c
@@ -149,6 +149,7 @@ void ec_wind_create(ec_t * ec, ec_fop_data_t * fop, int32_t idx)
 
 int32_t ec_manager_create(ec_fop_data_t * fop, int32_t state)
 {
+    ec_t * ec;
     ec_cbk_data_t * cbk;
     ec_fd_t * ctx;
 
@@ -175,6 +176,34 @@ int32_t ec_manager_create(ec_fop_data_t * fop, int32_t state)
 
             UNLOCK(&fop->fd->lock);
 
+            if (fop->xdata == NULL)
+            {
+                fop->xdata = dict_new();
+                if (fop->xdata == NULL)
+                {
+                    fop->error = EIO;
+
+                    return EC_STATE_REPORT;
+                }
+            }
+
+            ec = fop->xl->private;
+
+            fop->config.version = EC_CONFIG_VERSION;
+            fop->config.algorithm = EC_CONFIG_ALGORITHM;
+            fop->config.gf_word_size = EC_GF_BITS;
+            fop->config.bricks = ec->nodes;
+            fop->config.redundancy = ec->redundancy;
+            fop->config.chunk_size = EC_METHOD_CHUNK_SIZE;
+
+            if (ec_dict_set_config(fop->xdata, EC_XATTR_CONFIG,
+                                   &fop->config) < 0)
+            {
+                fop->error = EIO;
+
+                return EC_STATE_REPORT;
+            }
+
             fop->int32 &= ~O_ACCMODE;
             fop->int32 |= O_RDWR;