gfapi: object handle based API extensions

There is an ongoing effort to integrate NFS Ganesha (
https://github.com/nfs-ganesha/nfs-ganesha/wiki ) with GlusterFS as one of
the file system back ends.

Towards this we need extensions to gfapi that can handle object based
operations. Meaning, instead of using full paths or relative paths from
cwd, it is required that we can work with APIs, like the *at POSIX
variants, to be able to create, lookup, open etc. files and directories.
Hence the objects are the files or directories themselves and we give out
handles to these objects that can be used for further operations.

This code drop is an initial implementation of the proposed APIs.

The new APIs are implemented as glfs_h_XXX variants in the file
glfs-handleops.c to mirror glfs-fops.c style. The code leverages holding
onto inode references and doling these out as opaque/cookie type objects to
the callers, to enable them to be used as handles in other operations.

An fd based approach was considered, but due to the extra footprint that
the fd structure and its counterparts would incur, this was dropped to take
the approach of holding inode references themselves.

Tested by extending glfsxmp.c to invoke and exercise the added APIs, and
further tested with a reference integration of the same as an FSAL with NFS
Ganesha.

Change-Id: I23629c99e905b54070fa2e6565147812e5f3fa5d
BUG: 1016000
Signed-off-by: R.Shyamsundar <srangana@redhat.com>
Reviewed-on: http://review.gluster.org/5936
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 143 insertions, 0 deletions

diff --git a/api/src/glfs-handles.h b/api/src/glfs-handles.h
new file mode 100644
index 00000000000..437f2cbc8a5
--- /dev/null
+++ b/api/src/glfs-handles.h
@@ -0,0 +1,143 @@
+/*
+  Copyright (c) 2013 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 _GLFS_HANDLES_H
+#define _GLFS_HANDLES_H
+
+#include "glfs.h"
+
+/* GLFS OBJECT BASED OPERATIONS
+ *
+ * The following APIs are introduced to provide an API framework that can work
+ * with gluster objects (files and directories), instead of absolute paths.
+ *
+ * The following API set can be related to the POSIX *at interfaces (like
+ * openat (2)). The intention of these APIs is to be able to operate based
+ * on parent object and looking up or creating child objects within, OR to be
+ * used on the actual object thus looked up or created, and retrieve information
+ * regarding the same.
+ *
+ * The APIs also provide for generating an opaque invariant handle to the
+ * object, that can later be used to lookup the object, instead of the regular
+ * glfs_h_* variants. The APIs that provide this behaviour are,
+ * glfs_h_extract_handle and glfs_h_create_from_handle.
+ *
+ * The object handles can be transitioned to fd based operations as supported
+ * by glfs.h calls, using the glfs_h_open call. This provides a way to move
+ * from objects to fd's akin to moving from path to fd for required operations.
+ *
+ * NOTE: The opaque invariant handle is the GFID of the object in reality, but
+ * maintained as an opaque data value, for potential internal changes to the
+ * same without impacting the caller.
+ *
+ * NOTE: Currently looking up an object can create multiple object handles to
+ * the same, i.e distinct glfs_object *. Hence each such looked up or received
+ * handle from other calls, would need to be closed. In the future, for a given
+ * object these pointers would be the same, and an ease of use API to forget all
+ * instances of this bject would be provided (instead of a per lookup close).
+ * This should not change the APIs in their current form.
+ *
+ */
+
+/* Values for valid falgs to be used when using XXXsetattr, to set multiple
+ attribute values passed via the related stat structure.
+ */
+#define GFAPI_SET_ATTR_MODE  0x1
+#define GFAPI_SET_ATTR_UID   0x2
+#define GFAPI_SET_ATTR_GID   0x4
+#define GFAPI_SET_ATTR_SIZE  0x8
+#define GFAPI_SET_ATTR_ATIME 0x10
+#define GFAPI_SET_ATTR_MTIME 0x20
+
+/* Handle length for object handles returned from glfs_h_extract_handle or
+ * glfs_h_create_from_handle */
+#define GFAPI_HANDLE_LENGTH 16
+
+__BEGIN_DECLS
+
+/*
+ * Notes:
+ *
+ * The file object handle. One per looked up, created file/directory
+ *
+ * This had been introduced to facilitate gfid/inode based gfapi
+ * - a requirement introduced by nfs-ganesha
+ */
+struct glfs_object;
+typedef struct glfs_object glfs_object_t;
+
+/* Handle based operations */
+/* Operations that generate handles */
+struct glfs_object *glfs_h_lookupat (struct glfs *fs,
+				     struct glfs_object *parent,
+				     const char *path, struct stat *stat);
+
+struct glfs_object *glfs_h_creat (struct glfs *fs, struct glfs_object *parent,
+				  const char *path, int flags, mode_t mode,
+				  struct stat *sb);
+
+struct glfs_object *glfs_h_mkdir (struct glfs *fs, struct glfs_object *parent,
+				  const char *path, mode_t flags,
+				  struct stat *sb);
+
+struct glfs_object *glfs_h_mknod (struct glfs *fs, struct glfs_object *parent,
+				  const char *path, mode_t mode, dev_t dev,
+				  struct stat *sb);
+
+struct glfs_object *glfs_h_symlink (struct glfs *fs, struct glfs_object *parent,
+				    const char *name, const char *data,
+				    struct stat *stat);
+
+/* Operations on the actual objects */
+int glfs_h_unlink (struct glfs *fs, struct glfs_object *parent,
+		   const char *path);
+
+int glfs_h_close (struct glfs_object *object);
+
+int glfs_caller_specific_init (void *uid_caller_key, void *gid_caller_key,
+			       void *future);
+
+int glfs_h_truncate (struct glfs *fs, struct glfs_object *object, off_t offset);
+
+int glfs_h_stat(struct glfs *fs, struct glfs_object *object, struct stat *stat);
+
+int glfs_h_getattrs (struct glfs *fs, struct glfs_object *object,
+		     struct stat *stat);
+
+int glfs_h_setattrs (struct glfs *fs, struct glfs_object *object,
+		     struct stat *sb, int valid);
+
+int glfs_h_readlink (struct glfs *fs, struct glfs_object *object, char *buf,
+		     size_t bufsiz);
+
+int glfs_h_link (struct glfs *fs, struct glfs_object *linktgt,
+		 struct glfs_object *parent, const char *name);
+
+int glfs_h_rename (struct glfs *fs, struct glfs_object *olddir,
+		   const char *oldname, struct glfs_object *newdir,
+		   const char *newname);
+
+/* Operations enabling opaque invariant handle to object transitions */
+ssize_t glfs_h_extract_handle (struct glfs_object *object,
+			       unsigned char *handle, int len);
+
+struct glfs_object *glfs_h_create_from_handle (struct glfs *fs,
+					       unsigned char *handle, int len,
+					       struct stat *stat);
+
+/* Operations enabling object handles to fd transitions */
+struct glfs_fd *glfs_h_opendir (struct glfs *fs, struct glfs_object *object);
+
+struct glfs_fd *glfs_h_open (struct glfs *fs, struct glfs_object *object,
+			     int flags);
+
+__END_DECLS
+
+#endif /* !_GLFS_HANDLES_H */
\ No newline at end of file