metadisp: new translator for data and metadata separation

Summary:

feature/metadisp is an xlator for performing "metadata dispersal" across
multiple children. it does this by flattening the complex
POSIX paths into /$GFID style paths, then forwarding the
metadata operations to its first child and forwarding the
data operations to its second child.

The purpose of this xlator is to allow separation of data and metadata,
in cases where metadata might be stored in another format (embedded kv?),
on another disk (ssd), on another host (dht2).

Change-Id: I392c8bd0c867a3237d144aea327323f700a2728d
Updates: #816
Signed-Off-By: Sheena Artrip <sheenobu@fb.com>
Tested-By: Amar Tumballi <amar@kadalu.io>

1 files changed, 45 insertions, 0 deletions

diff --git a/xlators/features/metadisp/src/backend.c b/xlators/features/metadisp/src/backend.c
new file mode 100644
index 00000000000..ee2c25bfaa7
--- /dev/null
+++ b/xlators/features/metadisp/src/backend.c
@@ -0,0 +1,45 @@
+#define GFID_STR_LEN 37
+
+#include "metadisp.h"
+
+/*
+ * backend.c
+ *
+ * functions responsible for converting user-facing paths to backend-style
+ * "/$GFID" paths.
+ */
+
+int32_t
+build_backend_loc(uuid_t gfid, loc_t *src_loc, loc_t *dst_loc)
+{
+    static uuid_t root = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
+    char gfid_buf[GFID_STR_LEN + 1] = {
+        0,
+    };
+    char *path = NULL;
+
+    GF_VALIDATE_OR_GOTO("metadisp", src_loc, out);
+    GF_VALIDATE_OR_GOTO("metadisp", dst_loc, out);
+
+    loc_copy(dst_loc, src_loc);
+    memcpy(dst_loc->pargfid, root, sizeof(root));
+    GF_FREE((char *)dst_loc->path);  // we are overwriting path so nuke
+                                     // whatever loc_copy gave us
+
+    uuid_utoa_r(gfid, gfid_buf);
+
+    path = GF_CALLOC(GFID_STR_LEN + 1, sizeof(char),
+                     gf_common_mt_char);  // freed via loc_wipe
+
+    path[0] = '/';
+    strncpy(path + 1, gfid_buf, GFID_STR_LEN);
+    path[GFID_STR_LEN] = 0;
+    dst_loc->path = path;
+    if (src_loc->name)
+        dst_loc->name = strrchr(dst_loc->path, '/');
+    if (dst_loc->name)
+        dst_loc->name++;
+    return 0;
+out:
+    return -1;
+}