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, 7 insertions, 0 deletions

diff --git a/xlators/cluster/ec/src/ec-helpers.h b/xlators/cluster/ec/src/ec-helpers.h
index 3010ea856de..044e6239e8b 100644
--- a/xlators/cluster/ec/src/ec-helpers.h
+++ b/xlators/cluster/ec/src/ec-helpers.h
@@ -36,6 +36,8 @@ size_t ec_iov_copy_to(void * dst, struct iovec * vector, int32_t count,
 
 int32_t ec_dict_set_number(dict_t * dict, char * key, uint64_t value);
 int32_t ec_dict_del_number(dict_t * dict, char * key, uint64_t * value);
+int32_t ec_dict_set_config(dict_t * dict, char * key, ec_config_t * config);
+int32_t ec_dict_del_config(dict_t * dict, char * key, ec_config_t * config);
 
 int32_t ec_loc_parent(xlator_t * xl, loc_t * loc, loc_t * parent,
                       char ** name);
@@ -56,4 +58,9 @@ ec_fd_t * ec_fd_get(fd_t * fd, xlator_t * xl);
 uint32_t ec_adjust_offset(ec_t * ec, off_t * offset, int32_t scale);
 uint64_t ec_adjust_size(ec_t * ec, uint64_t size, int32_t scale);
 
+static inline int32_t ec_is_power_of_2(uint32_t value)
+{
+    return (value != 0) && ((value & (value - 1)) == 0);
+}
+
 #endif /* __EC_HELPERS_H__ */