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, 101 insertions, 0 deletions

diff --git a/xlators/features/metadisp/src/metadisp-create.c b/xlators/features/metadisp/src/metadisp-create.c
new file mode 100644
index 00000000000..f8c9798dd59
--- /dev/null
+++ b/xlators/features/metadisp/src/metadisp-create.c
@@ -0,0 +1,101 @@
+#include "metadisp.h"
+#include <glusterfs/call-stub.h>
+
+/**
+ * Create, like stat, is a two-step process. We send a create
+ * to the METADATA_CHILD, then send another create to the DATA_CHILD.
+ *
+ * We do the metadata child first to ensure that the ACLs are enforced.
+ */
+
+int32_t
+metadisp_create_dentry_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
+                           int32_t op_ret, int32_t op_errno, fd_t *fd,
+                           inode_t *inode, struct iatt *buf,
+                           struct iatt *preparent, struct iatt *postparent,
+                           dict_t *xdata)
+{
+    STACK_UNWIND_STRICT(create, frame, op_ret, op_errno, fd, inode, buf,
+                        preparent, postparent, xdata);
+    return 0;
+}
+
+int32_t
+metadisp_create_resume(call_frame_t *frame, xlator_t *this, loc_t *loc,
+                       int32_t flags, mode_t mode, mode_t umask, fd_t *fd,
+                       dict_t *xdata)
+{
+    // create the backend data inode
+    STACK_WIND(frame, metadisp_create_dentry_cbk, DATA_CHILD(this),
+               DATA_CHILD(this)->fops->create, loc, flags, mode, umask, fd,
+               xdata);
+    return 0;
+}
+
+int32_t
+metadisp_create_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
+                    int32_t op_ret, int32_t op_errno, fd_t *fd, inode_t *inode,
+                    struct iatt *buf, struct iatt *preparent,
+                    struct iatt *postparent, dict_t *xdata)
+{
+    METADISP_TRACE("%d %d", op_ret, op_errno);
+    call_stub_t *stub = cookie;
+    if (op_ret != 0) {
+        STACK_UNWIND_STRICT(create, frame, op_ret, op_errno, fd, inode, buf,
+                            preparent, postparent, xdata);
+        return 0;
+    }
+
+    if (stub == NULL) {
+        goto unwind;
+    }
+
+    if (stub->poison) {
+        call_stub_destroy(stub);
+        return 0;
+    }
+
+    call_resume(stub);
+    return 0;
+
+unwind:
+    STACK_UNWIND_STRICT(create, frame, -1, EINVAL, NULL, NULL, NULL, NULL, NULL,
+                        NULL);
+    return 0;
+}
+
+int32_t
+metadisp_create(call_frame_t *frame, xlator_t *this, loc_t *loc, int32_t flags,
+                mode_t mode, mode_t umask, fd_t *fd, dict_t *xdata)
+{
+    METADISP_TRACE(".");
+
+    loc_t backend_loc = {
+        0,
+    };
+    call_stub_t *stub = NULL;
+    uuid_t *gfid_req = NULL;
+
+    RESOLVE_GFID_REQ(xdata, gfid_req, out);
+
+    if (build_backend_loc(*gfid_req, loc, &backend_loc)) {
+        goto unwind;
+    }
+
+    frame->local = loc;
+
+    stub = fop_create_stub(frame, metadisp_create_resume, &backend_loc, flags,
+                           mode, umask, fd, xdata);
+
+    STACK_WIND_COOKIE(frame, metadisp_create_cbk, stub, METADATA_CHILD(this),
+                      METADATA_CHILD(this)->fops->create, loc, flags, mode,
+                      umask, fd, xdata);
+    return 0;
+
+unwind:
+    STACK_UNWIND_STRICT(create, frame, -1, EINVAL, NULL, NULL, NULL, NULL, NULL,
+                        NULL);
+    return 0;
+out:
+    return -1;
+}