Commit 8df08c89 authored by Mark Fasheh's avatar Mark Fasheh Committed by Joel Becker

[PATCH] OCFS2: The Second Oracle Cluster Filesystem

dlmfs: A minimal dlm userspace interface implemented via a virtual
file system.
Most of the OCFS2 tools make use of this to take cluster locks when
doing operations on the file system.
Signed-off-by: default avatarMark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: default avatarKurt Hackel <kurt.hackel@oracle.com>
parent 6714d8e8
......@@ -18,6 +18,8 @@ cramfs.txt
- info on the cram filesystem for small storage (ROMs etc)
devfs/
- directory containing devfs documentation.
dlmfs.txt
- info on the userspace interface to the OCFS2 DLM.
ext2.txt
- info, mount options and specifications for the Ext2 filesystem.
fat_cvf.txt
......
dlmfs
==================
A minimal DLM userspace interface implemented via a virtual file
system.
dlmfs is built with OCFS2 as it requires most of its infrastructure.
Project web page: http://oss.oracle.com/projects/ocfs2
Tools web page: http://oss.oracle.com/projects/ocfs2-tools
OCFS2 mailing lists: http://oss.oracle.com/projects/ocfs2/mailman/
All code copyright 2005 Oracle except when otherwise noted.
CREDITS
=======
Some code taken from ramfs which is Copyright (C) 2000 Linus Torvalds
and Transmeta Corp.
Mark Fasheh <mark.fasheh@oracle.com>
Caveats
=======
- Right now it only works with the OCFS2 DLM, though support for other
DLM implementations should not be a major issue.
Mount options
=============
None
Usage
=====
If you're just interested in OCFS2, then please see ocfs2.txt. The
rest of this document will be geared towards those who want to use
dlmfs for easy to setup and easy to use clustered locking in
userspace.
Setup
=====
dlmfs requires that the OCFS2 cluster infrastructure be in
place. Please download ocfs2-tools from the above url and configure a
cluster.
You'll want to start heartbeating on a volume which all the nodes in
your lockspace can access. The easiest way to do this is via
ocfs2_hb_ctl (distributed with ocfs2-tools). Right now it requires
that an OCFS2 file system be in place so that it can automatically
find it's heartbeat area, though it will eventually support heartbeat
against raw disks.
Please see the ocfs2_hb_ctl and mkfs.ocfs2 manual pages distributed
with ocfs2-tools.
Once you're heartbeating, DLM lock 'domains' can be easily created /
destroyed and locks within them accessed.
Locking
=======
Users may access dlmfs via standard file system calls, or they can use
'libo2dlm' (distributed with ocfs2-tools) which abstracts the file
system calls and presents a more traditional locking api.
dlmfs handles lock caching automatically for the user, so a lock
request for an already acquired lock will not generate another DLM
call. Userspace programs are assumed to handle their own local
locking.
Two levels of locks are supported - Shared Read, and Exlcusive.
Also supported is a Trylock operation.
For information on the libo2dlm interface, please see o2dlm.h,
distributed with ocfs2-tools.
Lock value blocks can be read and written to a resource via read(2)
and write(2) against the fd obtained via your open(2) call. The
maximum currently supported LVB length is 64 bytes (though that is an
OCFS2 DLM limitation). Through this mechanism, users of dlmfs can share
small amounts of data amongst their nodes.
mkdir(2) signals dlmfs to join a domain (which will have the same name
as the resulting directory)
rmdir(2) signals dlmfs to leave the domain
Locks for a given domain are represented by regular inodes inside the
domain directory. Locking against them is done via the open(2) system
call.
The open(2) call will not return until your lock has been granted or
an error has occurred, unless it has been instructed to do a trylock
operation. If the lock succeeds, you'll get an fd.
open(2) with O_CREAT to ensure the resource inode is created - dlmfs does
not automatically create inodes for existing lock resources.
Open Flag Lock Request Type
--------- -----------------
O_RDONLY Shared Read
O_RDWR Exclusive
Open Flag Resulting Locking Behavior
--------- --------------------------
O_NONBLOCK Trylock operation
You must provide exactly one of O_RDONLY or O_RDWR.
If O_NONBLOCK is also provided and the trylock operation was valid but
could not lock the resource then open(2) will return ETXTBUSY.
close(2) drops the lock associated with your fd.
Modes passed to mkdir(2) or open(2) are adhered to locally. Chown is
supported locally as well. This means you can use them to restrict
access to the resources via dlmfs on your local node only.
The resource LVB may be read from the fd in either Shared Read or
Exclusive modes via the read(2) system call. It can be written via
write(2) only when open in Exclusive mode.
Once written, an LVB will be visible to other nodes who obtain Read
Only or higher level locks on the resource.
See Also
========
http://opendlm.sourceforge.net/cvsmirror/opendlm/docs/dlmbook_final.pdf
For more information on the VMS distributed locking API.
EXTRA_CFLAGS += -Ifs/ocfs2
obj-$(CONFIG_OCFS2_FS) += ocfs2_dlm.o
obj-$(CONFIG_OCFS2_FS) += ocfs2_dlm.o ocfs2_dlmfs.o
ocfs2_dlm-objs := dlmdomain.o dlmdebug.o dlmthread.o dlmrecovery.o \
dlmmaster.o dlmast.o dlmconvert.o dlmlock.o dlmunlock.o dlmver.o
ocfs2_dlmfs-objs := userdlm.o dlmfs.o dlmfsver.o
This diff is collapsed.
/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* dlmfsver.c
*
* version string
*
* Copyright (C) 2002, 2005 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include "dlmfsver.h"
#define DLM_BUILD_VERSION "1.3.3"
#define VERSION_STR "OCFS2 DLMFS " DLM_BUILD_VERSION
void dlmfs_print_version(void)
{
printk(KERN_INFO "%s\n", VERSION_STR);
}
MODULE_DESCRIPTION(VERSION_STR);
MODULE_VERSION(DLM_BUILD_VERSION);
/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* dlmver.h
*
* Function prototypes
*
* Copyright (C) 2005 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#ifndef DLMFS_VER_H
#define DLMFS_VER_H
void dlmfs_print_version(void);
#endif /* DLMFS_VER_H */
This diff is collapsed.
/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* userdlm.h
*
* Userspace dlm defines
*
* Copyright (C) 2002, 2004 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#ifndef USERDLM_H
#define USERDLM_H
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/workqueue.h>
/* user_lock_res->l_flags flags. */
#define USER_LOCK_ATTACHED (0x00000001) /* have we initialized
* the lvb */
#define USER_LOCK_BUSY (0x00000002) /* we are currently in
* dlm_lock */
#define USER_LOCK_BLOCKED (0x00000004) /* blocked waiting to
* downconvert*/
#define USER_LOCK_IN_TEARDOWN (0x00000008) /* we're currently
* destroying this
* lock. */
#define USER_LOCK_QUEUED (0x00000010) /* lock is on the
* workqueue */
#define USER_LOCK_IN_CANCEL (0x00000020)
struct user_lock_res {
spinlock_t l_lock;
int l_flags;
#define USER_DLM_LOCK_ID_MAX_LEN 32
char l_name[USER_DLM_LOCK_ID_MAX_LEN];
int l_level;
unsigned int l_ro_holders;
unsigned int l_ex_holders;
struct dlm_lockstatus l_lksb;
int l_requested;
int l_blocking;
wait_queue_head_t l_event;
struct work_struct l_work;
};
extern struct workqueue_struct *user_dlm_worker;
void user_dlm_lock_res_init(struct user_lock_res *lockres,
struct dentry *dentry);
int user_dlm_destroy_lock(struct user_lock_res *lockres);
int user_dlm_cluster_lock(struct user_lock_res *lockres,
int level,
int lkm_flags);
void user_dlm_cluster_unlock(struct user_lock_res *lockres,
int level);
void user_dlm_write_lvb(struct inode *inode,
const char *val,
unsigned int len);
void user_dlm_read_lvb(struct inode *inode,
char *val,
unsigned int len);
struct dlm_ctxt *user_dlm_register_context(struct qstr *name);
void user_dlm_unregister_context(struct dlm_ctxt *dlm);
struct dlmfs_inode_private {
struct dlm_ctxt *ip_dlm;
struct user_lock_res ip_lockres; /* unused for directories. */
struct inode *ip_parent;
struct inode ip_vfs_inode;
};
static inline struct dlmfs_inode_private *
DLMFS_I(struct inode *inode)
{
return container_of(inode,
struct dlmfs_inode_private,
ip_vfs_inode);
}
struct dlmfs_filp_private {
int fp_lock_level;
};
#define DLMFS_MAGIC 0x76a9f425
#endif /* USERDLM_H */
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