stackglue.h

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/* -*- 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>

/* Needed for plock-related prototypes */
struct file;
struct file_lock;

/*
 * 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 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.
 */
struct ocfs2_cluster_connection;
struct ocfs2_dlm_lksb {
     union {
         struct dlm_lockstatus lksb_o2dlm;
         struct dlm_lksb lksb_fsdlm;
         struct fsdlm_lksb_plus_lvb padding;
     };
     struct ocfs2_cluster_connection *lksb_conn;
};

/*
 * 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)(struct ocfs2_dlm_lksb *lksb);
    void (*lp_blocking_ast)(struct ocfs2_dlm_lksb *lksb, int level);
    void (*lp_unlock_ast)(struct ocfs2_dlm_lksb *lksb, int error);
};


/*
 * 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;
    struct ocfs2_locking_protocol *cc_proto;
    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 received
     *    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.
     *
     * Once this call returns, the stack glue will be dropping this
     * connection's reference on the module.
     */
    int (*disconnect)(struct ocfs2_cluster_connection *conn);

    /*
     * ->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.  There is no astarg.  The lksb will
     * be passed back to the ast and bast functions.  The caller can
     * use this to find their object.
     */
    int (*dlm_lock)(struct ocfs2_cluster_connection *conn,
            int mode,
            struct ocfs2_dlm_lksb *lksb,
            u32 flags,
            void *name,
            unsigned int namelen);

    /*
     * 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().  There is
     * no astarg.  The lksb will be passed back to the unlock ast
     * function.  The caller can use this to find their object.
     */
    int (*dlm_unlock)(struct ocfs2_cluster_connection *conn,
              struct ocfs2_dlm_lksb *lksb,
              u32 flags);

    /*
     * 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)(struct ocfs2_dlm_lksb *lksb);

    /*
     * Return non-zero if the LVB is valid.
     */
    int (*lvb_valid)(struct ocfs2_dlm_lksb *lksb);

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

    /*
     * Cluster-aware posix locks
     *
     * This is NULL for stacks which do not support posix locks.
     */
    int (*plock)(struct ocfs2_cluster_connection *conn,
             u64 ino,
             struct file *file,
             int cmd,
             struct file_lock *fl);

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


/* Used by the filesystem */
int ocfs2_cluster_connect(const char *stack_name,
              const char *group,
              int grouplen,
              struct ocfs2_locking_protocol *lproto,
              void (*recovery_handler)(int node_num,
                           void *recovery_data),
              void *recovery_data,
              struct ocfs2_cluster_connection **conn);
/*
 * Used by callers that don't store their stack name.  They must ensure
 * all nodes have the same stack.
 */
int ocfs2_cluster_connect_agnostic(const char *group,
                   int grouplen,
                   struct ocfs2_locking_protocol *lproto,
                   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,
           struct ocfs2_dlm_lksb *lksb,
           u32 flags,
           void *name,
           unsigned int namelen);
int ocfs2_dlm_unlock(struct ocfs2_cluster_connection *conn,
             struct ocfs2_dlm_lksb *lksb,
             u32 flags);

int ocfs2_dlm_lock_status(struct ocfs2_dlm_lksb *lksb);
int ocfs2_dlm_lvb_valid(struct ocfs2_dlm_lksb *lksb);
void *ocfs2_dlm_lvb(struct ocfs2_dlm_lksb *lksb);
void ocfs2_dlm_dump_lksb(struct ocfs2_dlm_lksb *lksb);

int ocfs2_stack_supports_plocks(void);
int ocfs2_plock(struct ocfs2_cluster_connection *conn, u64 ino,
        struct file *file, int cmd, struct file_lock *fl);

void ocfs2_stack_glue_set_max_proto_version(struct ocfs2_protocol_version *max_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 */