stackglue.h

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * stackglue.h
 *
 * Glue to the underlying cluster stack.
 *
 * Copyright (C) 2007 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, version 2.
 *
 * 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.
 */


#ifndef STACKGLUE_H
#define STACKGLUE_H

#include <linux/types.h>
#include <linux/list.h>
#include <linux/dlmconstants.h>

#include "dlm/dlmapi.h"
#include <linux/dlm.h>

/*
 * dlmconstants.h does not have a LOCAL flag.  We hope to remove it
 * some day, but right now we need it.  Let's fake it.  This value is larger
 * than any flag in dlmconstants.h.
 */
#define DLM_LKF_LOCAL		0x00100000

/*
 * This shadows DLM_LOCKSPACE_LEN in fs/dlm/dlm_internal.h.  That probably
 * wants to be in a public header.
 */
#define GROUP_NAME_MAX		64


/*
 * ocfs2_protocol_version changes when ocfs2 does something different in
 * its inter-node behavior.  See dlmglue.c for more information.
 */
struct ocfs2_protocol_version {
	u8 pv_major;
	u8 pv_minor;
};

/*
 * The ocfs2_locking_protocol defines the handlers called on ocfs2's behalf.
 */
struct ocfs2_locking_protocol {
	struct ocfs2_protocol_version lp_max_version;
	void (*lp_lock_ast)(void *astarg);
	void (*lp_blocking_ast)(void *astarg, int level);
	void (*lp_unlock_ast)(void *astarg, int error);
};


/*
 * The dlm_lockstatus struct includes lvb space, but the dlm_lksb struct only
 * has a pointer to separately allocated lvb space.  This struct exists only to
 * include in the lksb union to make space for a combined dlm_lksb and lvb.
 */
struct fsdlm_lksb_plus_lvb {
	struct dlm_lksb lksb;
	char lvb[DLM_LVB_LEN];
};

/*
 * A union of all lock status structures.  We define it here so that the
 * size of the union is known.  Lock status structures are embedded in
 * ocfs2 inodes.
 */
union ocfs2_dlm_lksb {
	struct dlm_lockstatus lksb_o2dlm;
	struct dlm_lksb lksb_fsdlm;
	struct fsdlm_lksb_plus_lvb padding;
};

/*
 * A cluster connection.  Mostly opaque to ocfs2, the connection holds
 * state for the underlying stack.  ocfs2 does use cc_version to determine
 * locking compatibility.
 */
struct ocfs2_cluster_connection {
	char cc_name[GROUP_NAME_MAX];
	int cc_namelen;
	struct ocfs2_protocol_version cc_version;
	void (*cc_recovery_handler)(int node_num, void *recovery_data);
	void *cc_recovery_data;
	void *cc_lockspace;
	void *cc_private;
};

/*
 * Each cluster stack implements the stack operations structure.  Not used
 * in the ocfs2 code, the stackglue code translates generic cluster calls
 * into stack operations.
 */
struct ocfs2_stack_operations {
	/*
	 * The fs code calls ocfs2_cluster_connect() to attach a new
	 * filesystem to the cluster stack.  The ->connect() op is passed
	 * an ocfs2_cluster_connection with the name and recovery field
	 * filled in.
	 *
	 * The stack must set up any notification mechanisms and create
	 * the filesystem lockspace in the DLM.  The lockspace should be
	 * stored on cc_lockspace.  Any other information can be stored on
	 * cc_private.
	 *
	 * ->connect() must not return until it is guaranteed that
	 *
	 *  - Node down notifications for the filesystem will be recieved
	 *    and passed to conn->cc_recovery_handler().
	 *  - Locking requests for the filesystem will be processed.
	 */
	int (*connect)(struct ocfs2_cluster_connection *conn);

	/*
	 * The fs code calls ocfs2_cluster_disconnect() when a filesystem
	 * no longer needs cluster services.  All DLM locks have been
	 * dropped, and recovery notification is being ignored by the
	 * fs code.  The stack must disengage from the DLM and discontinue
	 * recovery notification.
	 *
	 * Once ->disconnect() has returned, the connection structure will
	 * be freed.  Thus, a stack must not return from ->disconnect()
	 * until it will no longer reference the conn pointer.
	 *
	 * If hangup_pending is zero, ocfs2_cluster_disconnect() will also
	 * be dropping the reference on the module.
	 */
	int (*disconnect)(struct ocfs2_cluster_connection *conn,
			  int hangup_pending);

	/*
	 * ocfs2_cluster_hangup() exists for compatibility with older
	 * ocfs2 tools.  Only the classic stack really needs it.  As such
	 * ->hangup() is not required of all stacks.  See the comment by
	 * ocfs2_cluster_hangup() for more details.
	 *
	 * Note that ocfs2_cluster_hangup() can only be called if
	 * hangup_pending was passed to ocfs2_cluster_disconnect().
	 */
	void (*hangup)(const char *group, int grouplen);

	/*
	 * ->this_node() returns the cluster's unique identifier for the
	 * local node.
	 */
	int (*this_node)(unsigned int *node);

	/*
	 * Call the underlying dlm lock function.  The ->dlm_lock()
	 * callback should convert the flags and mode as appropriate.
	 *
	 * ast and bast functions are not part of the call because the
	 * stack will likely want to wrap ast and bast calls before passing
	 * them to stack->sp_proto.
	 */
	int (*dlm_lock)(struct ocfs2_cluster_connection *conn,
			int mode,
			union ocfs2_dlm_lksb *lksb,
			u32 flags,
			void *name,
			unsigned int namelen,
			void *astarg);

	/*
	 * Call the underlying dlm unlock function.  The ->dlm_unlock()
	 * function should convert the flags as appropriate.
	 *
	 * The unlock ast is not passed, as the stack will want to wrap
	 * it before calling stack->sp_proto->lp_unlock_ast().
	 */
	int (*dlm_unlock)(struct ocfs2_cluster_connection *conn,
			  union ocfs2_dlm_lksb *lksb,
			  u32 flags,
			  void *astarg);

	/*
	 * Return the status of the current lock status block.  The fs
	 * code should never dereference the union.  The ->lock_status()
	 * callback pulls out the stack-specific lksb, converts the status
	 * to a proper errno, and returns it.
	 */
	int (*lock_status)(union ocfs2_dlm_lksb *lksb);

	/*
	 * Pull the lvb pointer off of the stack-specific lksb.
	 */
	void *(*lock_lvb)(union ocfs2_dlm_lksb *lksb);

	/*
	 * This is an optoinal debugging hook.  If provided, the
	 * stack can dump debugging information about this lock.
	 */
	void (*dump_lksb)(union ocfs2_dlm_lksb *lksb);
};

/*
 * Each stack plugin must describe itself by registering a
 * ocfs2_stack_plugin structure.  This is only seen by stackglue and the
 * stack driver.
 */
struct ocfs2_stack_plugin {
	char *sp_name;
	struct ocfs2_stack_operations *sp_ops;
	struct module *sp_owner;

	/* These are managed by the stackglue code. */
	struct list_head sp_list;
	unsigned int sp_count;
	struct ocfs2_locking_protocol *sp_proto;
};


/* Used by the filesystem */
int ocfs2_cluster_connect(const char *stack_name,
			  const char *group,
			  int grouplen,
			  void (*recovery_handler)(int node_num,
						   void *recovery_data),
			  void *recovery_data,
			  struct ocfs2_cluster_connection **conn);
int ocfs2_cluster_disconnect(struct ocfs2_cluster_connection *conn,
			     int hangup_pending);
void ocfs2_cluster_hangup(const char *group, int grouplen);
int ocfs2_cluster_this_node(unsigned int *node);

struct ocfs2_lock_res;
int ocfs2_dlm_lock(struct ocfs2_cluster_connection *conn,
		   int mode,
		   union ocfs2_dlm_lksb *lksb,
		   u32 flags,
		   void *name,
		   unsigned int namelen,
		   struct ocfs2_lock_res *astarg);
int ocfs2_dlm_unlock(struct ocfs2_cluster_connection *conn,
		     union ocfs2_dlm_lksb *lksb,
		     u32 flags,
		     struct ocfs2_lock_res *astarg);

int ocfs2_dlm_lock_status(union ocfs2_dlm_lksb *lksb);
void *ocfs2_dlm_lvb(union ocfs2_dlm_lksb *lksb);
void ocfs2_dlm_dump_lksb(union ocfs2_dlm_lksb *lksb);

void ocfs2_stack_glue_set_locking_protocol(struct ocfs2_locking_protocol *proto);


/* Used by stack plugins */
int ocfs2_stack_glue_register(struct ocfs2_stack_plugin *plugin);
void ocfs2_stack_glue_unregister(struct ocfs2_stack_plugin *plugin);

#endif  /* STACKGLUE_H */