experimental/cloudsync: Download xlator for archival feature

spec-files:
https://review.gluster.org/#/c/18854/

Overview:
* Cloudsync maintains three file states in it's inode-ctx i.e
  1 - LOCAL,
  2 - REMOTE,
  3 - DOWNLOADING.

* A data modifying fop is allowed only if the state is LOCAL.
  If the state is REMOTE or DOWNLOADING, client will download
  or wait for the download to finish initiated by other client.

* Multiple download and upload from different clients are synchronized
  by inodelk.

* In POSIX a state check is done (part of different commit)before
  allowing the fop to continue. If the state is remote/downloading the
  fop is unwound with EREMOTE. The client will then download the file
  and continue with the fop again.

* Basic Algo for fop (let's say write fop):
  - If LOCAL -> resume fop
  - If REMOTE ->
	- INODELK
	- STAT (this gets state and heal the state if needed)
	- DOWNLOAD
	- resume fop

Note:
* Developers will need to write plugins for download, based on the
remote store they choose. In phase-1, support will be added for
one remote store per volume. In future, more options for multiple
remote stores will be explored.

TODOs:
 - Implement stat/lookup/readdirp to return size info from xattr
 - Make plugins configurable
 - Implement unlink fop
 - Add metrics collection
 - Add sharding support

Design Contributions:
Aravinda V K <avishwan@redhat.com>
Amar Tumballi <amarts@redhat.com>
Ram Ankireddypalle <areddy@commvault.com>
Susant Palai <spalai@redhat.com>

updates: #387
Change-Id: Iddf711ee7ab4e946ae3e472ff62791a7b85e6d4b
Signed-off-by: Susant Palai <spalai@redhat.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/libglusterfs/src/glusterfs.h b/libglusterfs/src/glusterfs.h
index 43e6f48d905..5b9f2a45405 100644
--- a/libglusterfs/src/glusterfs.h
+++ b/libglusterfs/src/glusterfs.h
@@ -358,6 +358,22 @@ enum gf_internal_fop_indicator {
                 }                                               \
         } while (0)                                             \
 
+#define GF_CS_OBJECT_SIZE  "trusted.glusterfs.cs.object_size"
+
+#define GF_CS_OBJECT_UPLOAD_COMPLETE "trusted.glusterfs.csou.complete"
+#define GF_CS_OBJECT_REMOTE "trusted.glusterfs.cs.remote"
+#define GF_CS_OBJECT_DOWNLOADING "trusted.glusterfs.cs.downloading"
+#define GF_CS_OBJECT_DOWNLOADED "trusted.glusterfs.cs.downloaded"
+#define GF_CS_OBJECT_STATUS "trusted.glusterfs.cs.status"
+#define GF_CS_OBJECT_REPAIR "trusted.glusterfs.cs.repair"
+
+typedef enum {
+        GF_CS_LOCAL = 1,
+        GF_CS_REMOTE = 2,
+        GF_CS_REPAIR = 4,
+        GF_CS_DOWNLOADING = 8,
+        GF_CS_ERROR = 16,
+} gf_cs_obj_state;
 
 typedef enum {
         GF_FOP_PRI_UNSPEC = -1,         /* Priority not specified */