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, 14 insertions, 0 deletions

diff --git a/xlators/cluster/ec/src/ec-data.h b/xlators/cluster/ec/src/ec-data.h
index 71f047a9aba..49090933ade 100644
--- a/xlators/cluster/ec/src/ec-data.h
+++ b/xlators/cluster/ec/src/ec-data.h
@@ -25,6 +25,9 @@
 
 #include "ec.h"
 
+struct _ec_config;
+typedef struct _ec_config ec_config_t;
+
 struct _ec_fd;
 typedef struct _ec_fd ec_fd_t;
 
@@ -53,6 +56,16 @@ typedef void (* ec_wind_f)(ec_t *, ec_fop_data_t *, int32_t);
 typedef int32_t (* ec_handler_f)(ec_fop_data_t *, int32_t);
 typedef void (* ec_resume_f)(ec_fop_data_t *, int32_t);
 
+struct _ec_config
+{
+    uint32_t version;
+    uint8_t  algorithm;
+    uint8_t  gf_word_size;
+    uint8_t  bricks;
+    uint8_t  redundancy;
+    uint32_t chunk_size;
+};
+
 struct _ec_fd
 {
     uintptr_t bad;
@@ -184,6 +197,7 @@ struct _ec_fop_data
     uint64_t           pre_size;
     uint64_t           post_size;
     gf_lock_t          lock;
+    ec_config_t        config;
 
     uint32_t           flags;
     uint32_t           first;