bd: posix/multi-brick support to BD xlator

Current BD xlator (block backend) has a few limitations such as
* Creation of directories not supported
* Supports only single brick
* Does not use extended attributes (and client gfid) like posix xlator
* Creation of special files (symbolic links, device nodes etc) not
  supported

Basic limitation of not allowing directory creation is blocking
oVirt/VDSM to consume BD xlator as part of Gluster domain since VDSM
creates multi-level directories when GlusterFS is used as storage
backend for storing VM images.

To overcome these limitations a new BD xlator with following
improvements is suggested.

* New hybrid BD xlator that handles both regular files and block device
  files
* The volume will have both POSIX and BD bricks. Regular files are
  created on POSIX bricks, block devices are created on the BD brick (VG)
* BD xlator leverages exiting POSIX xlator for most POSIX calls and
  hence sits above the POSIX xlator
* Block device file is differentiated from regular file by an extended
  attribute
* The xattr 'user.glusterfs.bd' (BD_XATTR) plays a role in mapping a
  posix file to Logical Volume (LV).
* When a client sends a request to set BD_XATTR on a posix file, a new
  LV is created and mapped to posix file. So every block device will
  have a representative file in POSIX brick with 'user.glusterfs.bd'
  (BD_XATTR) set.
* Here after all operations on this file results in LV related
  operations.

For example opening a file that has BD_XATTR set results in opening
the LV block device, reading results in reading the corresponding LV
block device.

When BD xlator gets request to set BD_XATTR via setxattr call, it
creates a LV and information about this LV is placed in the xattr of the
posix file. xattr "user.glusterfs.bd" used to identify that posix file
is mapped to BD.

Usage:
Server side:
[root@host1 ~]# gluster volume create bdvol host1:/storage/vg1_info?vg1 host2:/storage/vg2_info?vg2
It creates a distributed gluster volume 'bdvol' with Volume Group vg1
using posix brick /storage/vg1_info in host1 and Volume Group vg2 using
/storage/vg2_info in host2.

[root@host1 ~]# gluster volume start bdvol

Client side:
[root@node ~]# mount -t glusterfs host1:/bdvol /media
[root@node ~]# touch /media/posix
It creates regular posix file 'posix' in either host1:/vg1 or host2:/vg2 brick
[root@node ~]# mkdir /media/image
[root@node ~]# touch /media/image/lv1
It also creates regular posix file 'lv1' in either host1:/vg1 or
host2:/vg2 brick
[root@node ~]# setfattr -n "user.glusterfs.bd" -v "lv" /media/image/lv1
[root@node ~]#
Above setxattr results in creating a new LV in corresponding brick's VG
and it sets 'user.glusterfs.bd' with value 'lv:<default-extent-size'
[root@node ~]# truncate -s5G /media/image/lv1
It results in resizig LV 'lv1'to 5G

New BD xlator code is placed in xlators/storage/bd directory.

Also add volume-uuid to the VG so that same VG can't be used for other
bricks/volumes. After deleting a gluster volume, one has to manually
remove the associated tag using vgchange <vg-name> --deltag
<trusted.glusterfs.volume-id:<volume-id>>

Changes from previous version V5:
* Removed support for delayed deleting of LVs

Changes from previous version V4:
* Consolidated the patches
* Removed usage of BD_XATTR_SIZE and consolidated it in BD_XATTR.

Changes from previous version V3:
* Added support in FUSE to support full/linked clone
* Added support to merge snapshots and provide information about origin
* bd_map xlator removed
* iatt structure used in inode_ctx. iatt is cached and updated during
fsync/flush
* aio support
* Type and capabilities of volume are exported through getxattr

Changes from version 2:
* Used inode_context for caching BD size and to check if loc/fd is BD or
  not.
* Added GlusterFS server offloaded copy and snapshot through setfattr
  FOP. As part of this libgfapi is modified.
* BD xlator supports stripe
* During unlinking if a LV file is already opened, its added to delete
  list and bd_del_thread tries to delete from this list when a last
  reference to that file is closed.

Changes from previous version:
* gfid is used as name of LV
* ? is used to specify VG name for creating BD volume in volume
  create, add-brick. gluster volume create volname host:/path?vg
* open-behind issue is fixed
* A replicate brick can be added dynamically and LVs from source brick
  are replicated to destination brick
* A distribute brick can be added dynamically and rebalance operation
  distributes existing LVs/files to the new brick
* Thin provisioning support added.
* bd_map xlator support retained
* setfattr -n user.glusterfs.bd -v "lv" creates a regular LV and
  setfattr -n user.glusterfs.bd -v "thin" creates thin LV
* Capability and backend information added to gluster volume info (and
--xml) so
  that management tools can exploit BD xlator.
* tracing support for bd xlator added

TODO:
* Add support to display snapshots for a given LV
* Display posix filename for list-origin instead of gfid

Change-Id: I00d32dfbab3b7c806e0841515c86c3aa519332f2
BUG: 1028672
Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Reviewed-on: http://review.gluster.org/4809
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 140 insertions, 0 deletions

diff --git a/xlators/storage/bd/src/bd.h b/xlators/storage/bd/src/bd.h
new file mode 100644
index 000000000..4d8b89545
--- /dev/null
+++ b/xlators/storage/bd/src/bd.h
@@ -0,0 +1,140 @@
+/*
+  BD translator - Exports Block devices on server side as regular
+  files to client
+
+  Copyright IBM, Corp. 2012
+
+  This file is part of GlusterFS.
+
+  Author:
+  M. Mohan Kumar <mohan@in.ibm.com>
+
+  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 _BD_H
+#define _BD_H
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include "xlator.h"
+#include "mem-types.h"
+
+#define BD_XLATOR "block device mapper xlator"
+#define BACKEND_VG "vg"
+#define GF_XATTR "user.glusterfs"
+#define BD_XATTR GF_XATTR ".bd"
+
+#define BD_LV "lv"
+#define BD_THIN "thin"
+
+#define LVM_RESIZE "/sbin/lvresize"
+#define LVM_CREATE "/sbin/lvcreate"
+
+#define VOL_TYPE "volume.type"
+#define VOL_CAPS "volume.caps"
+
+#define ALIGN_SIZE 4096
+
+#define BD_CAPS_BD               0x01
+#define BD_CAPS_THIN             0x02
+
+#define BD_VALIDATE_MEM_ALLOC(buff, op_errno, label)                \
+        if (!buff) {                                                \
+                op_errno = ENOMEM;                                  \
+                gf_log (this->name, GF_LOG_ERROR, "out of memory"); \
+                goto label;                                         \
+        }
+
+#define BD_VALIDATE_LOCAL_OR_GOTO(local, op_errno, label) \
+        if (!local) {                                     \
+                op_errno = EINVAL;                        \
+                goto label;                               \
+        }
+
+#define BD_STACK_UNWIND(typ, frame, args ...) do {      \
+        bd_local_t *__local = frame->local;             \
+        xlator_t   *__this = frame->this;               \
+                                                        \
+        frame->local = NULL;                            \
+        STACK_UNWIND_STRICT (typ, frame, args);         \
+        if (__local)                                    \
+                bd_local_free (__this, __local);        \
+        } while (0)
+
+typedef char bd_gfid_t[GF_UUID_BUF_SIZE];
+
+enum gf_bd_mem_types_ {
+        gf_bd_private  = gf_common_mt_end + 1,
+        gf_bd_attr,
+        gf_bd_fd,
+        gf_bd_mt_end
+};
+
+/**
+ * bd_fd - internal structure
+ */
+typedef struct bd_fd {
+        int             fd;
+        int32_t         flag;
+} bd_fd_t;
+
+typedef struct bd_priv {
+        lvm_t             handle;
+        char              *vg;
+        char              *pool;
+        int                caps;
+} bd_priv_t;
+
+
+typedef enum bd_type {
+        BD_TYPE_NONE,
+        BD_TYPE_LV,
+} bd_type_t;
+
+typedef struct {
+        struct iatt  iatt;
+        char        *type;
+} bd_attr_t;
+
+typedef struct {
+        dict_t      *dict;
+        bd_attr_t   *bdatt;
+        inode_t     *inode;
+        loc_t        loc;
+        fd_t        *fd;
+        data_t      *data; /* for setxattr */
+} bd_local_t;
+
+typedef struct {
+        char            *lv;
+        struct list_head list;
+} bd_del_entry;
+
+/* Prototypes */
+int bd_inode_ctx_set (inode_t *inode, xlator_t *this, bd_attr_t *ctx);
+int bd_inode_ctx_get (inode_t *inode, xlator_t *this, bd_attr_t **ctx);
+int bd_scan_vg (xlator_t *this, bd_priv_t *priv);
+bd_local_t *bd_local_init (call_frame_t *frame, xlator_t *this);
+void bd_local_free (xlator_t *this, bd_local_t *local);
+int bd_fd_ctx_get (xlator_t *this, fd_t *fd, bd_fd_t **bdfd);
+char *page_aligned_alloc (size_t size, char **aligned_buf);
+int bd_validate_bd_xattr (xlator_t *this, char *bd, char **type,
+                          uint64_t *lv_size, uuid_t uuid);
+uint64_t bd_get_default_extent (bd_priv_t *priv);
+uint64_t bd_adjust_size (bd_priv_t *priv, uint64_t size);
+int bd_create (uuid_t uuid, uint64_t size, char *type, bd_priv_t *priv);
+int bd_resize (bd_priv_t *priv, uuid_t uuid, off_t size);
+int bd_delete_lv (bd_priv_t *priv, const char *lv_name, int *op_errno);
+int bd_snapshot_create (bd_local_t *local, bd_priv_t *priv);
+int bd_clone (bd_local_t *local, bd_priv_t *priv);
+
+int bd_merge (bd_priv_t *priv, uuid_t gfid);
+int bd_get_origin (bd_priv_t *priv, loc_t *loc, fd_t *fd, dict_t *dict);
+#endif