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, 97 insertions, 0 deletions

diff --git a/xlators/features/cloudsync/src/cloudsync-common.h b/xlators/features/cloudsync/src/cloudsync-common.h
new file mode 100644
index 00000000000..3298ab0a6f2
--- /dev/null
+++ b/xlators/features/cloudsync/src/cloudsync-common.h
@@ -0,0 +1,97 @@
+/*
+  Copyright (c) 2018 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  This file is licensed to you under your choice of the GNU Lesser
+  General Public License, version 3 or any later version (LGPLv3 or
+  later), or the GNU General Public License, version 2 (GPLv2), in all
+  cases as published by the Free Software Foundation.
+*/
+#ifndef _CLOUDSYNC_COMMON_H
+#define _CLOUDSYNC_COMMON_H
+
+#include "glusterfs.h"
+#include "call-stub.h"
+#include "xlator.h"
+#include "syncop.h"
+#include "cloudsync-mem-types.h"
+#include "cloudsync-messages.h"
+
+typedef struct cs_local {
+        loc_t           loc;
+        fd_t            *fd;
+        call_stub_t     *stub;
+        call_frame_t    *main_frame;
+        int              op_errno;
+        int              op_ret;
+        fd_t            *dlfd;
+        off_t            dloffset;
+        struct iatt      stbuf;
+        dict_t          *xattr_rsp;
+        dict_t          *xattr_req;
+        glusterfs_fop_t  fop;
+        gf_boolean_t     locked;
+        int              call_cnt;
+        inode_t         *inode;
+        char            *remotepath;
+} cs_local_t;
+
+typedef int (*fop_download_t) (call_frame_t *frame, void *config);
+
+typedef void *(*store_init) (xlator_t *this);
+
+typedef int (*store_reconfigure) (xlator_t *this, dict_t *options);
+
+typedef void (*store_fini) (void *config);
+
+struct cs_remote_stores {
+        char            *name; /* store name */
+        void            *config; /* store related information */
+        fop_download_t   dlfop; /* store specific download function */
+        store_init       init; /* store init to initialize store config */
+        store_reconfigure reconfigure; /* reconfigure store config */
+        store_fini       fini;
+        void            *handle; /* shared library handle*/
+};
+
+typedef struct cs_private {
+        xlator_t *this;
+        struct cs_remote_stores *stores;
+        gf_boolean_t abortdl;
+        pthread_spinlock_t  lock;
+} cs_private_t;
+
+void
+cs_local_wipe (xlator_t *this, cs_local_t *local);
+
+#define CS_STACK_UNWIND(fop, frame, params ...) do {    \
+        cs_local_t *__local  = NULL;                    \
+        xlator_t    *__xl    = NULL;                    \
+        if (frame) {                                    \
+                __xl         = frame->this;             \
+                __local      = frame->local;            \
+                frame->local = NULL;                    \
+        }                                               \
+        STACK_UNWIND_STRICT (fop, frame, params);       \
+        cs_local_wipe (__xl, __local);                 \
+} while (0)
+
+#define CS_STACK_DESTROY(frame) do {                   \
+        cs_local_t *__local  = NULL;            \
+        xlator_t    *__xl    = NULL;            \
+        __xl                 = frame->this;     \
+        __local              = frame->local;    \
+        frame->local         = NULL;            \
+        STACK_DESTROY (frame->root);            \
+        cs_local_wipe (__xl, __local);         \
+} while (0)
+
+typedef struct store_methods {
+        int (*fop_download) (call_frame_t *frame, void *config);
+        /* return type should be the store config */
+        void *(*fop_init) (xlator_t *this);
+        int (*fop_reconfigure) (xlator_t *this, dict_t *options);
+        void (*fop_fini) (void *config);
+} store_methods_t;
+
+#endif /* _CLOUDSYNC_COMMON_H */