userdlm.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * userdlm.c
 *
 * Code which implements the kernel side of a minimal userspace
 * interface to our DLM.
 *
 * Many of the functions here are pared down versions of dlmglue.c
 * functions.
 *
 * Copyright (C) 2003, 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.
 */

#include <linux/signal.h>

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/crc32.h>

#include "ocfs2_lockingver.h"
#include "stackglue.h"
#include "userdlm.h"

#define MLOG_MASK_PREFIX ML_DLMFS
#include "cluster/masklog.h"


static inline struct user_lock_res *user_lksb_to_lock_res(struct ocfs2_dlm_lksb *lksb)
{
    return container_of(lksb, struct user_lock_res, l_lksb);
}

static inline int user_check_wait_flag(struct user_lock_res *lockres,
                       int flag)
{
    int ret;

    spin_lock(&lockres->l_lock);
    ret = lockres->l_flags & flag;
    spin_unlock(&lockres->l_lock);

    return ret;
}

static inline void user_wait_on_busy_lock(struct user_lock_res *lockres)

{
    wait_event(lockres->l_event,
           !user_check_wait_flag(lockres, USER_LOCK_BUSY));
}

static inline void user_wait_on_blocked_lock(struct user_lock_res *lockres)

{
    wait_event(lockres->l_event,
           !user_check_wait_flag(lockres, USER_LOCK_BLOCKED));
}

/* I heart container_of... */
static inline struct ocfs2_cluster_connection *
cluster_connection_from_user_lockres(struct user_lock_res *lockres)
{
    struct dlmfs_inode_private *ip;

    ip = container_of(lockres,
              struct dlmfs_inode_private,
              ip_lockres);
    return ip->ip_conn;
}

static struct inode *
user_dlm_inode_from_user_lockres(struct user_lock_res *lockres)
{
    struct dlmfs_inode_private *ip;

    ip = container_of(lockres,
              struct dlmfs_inode_private,
              ip_lockres);
    return &ip->ip_vfs_inode;
}

static inline void user_recover_from_dlm_error(struct user_lock_res *lockres)
{
    spin_lock(&lockres->l_lock);
    lockres->l_flags &= ~USER_LOCK_BUSY;
    spin_unlock(&lockres->l_lock);
}

#define user_log_dlm_error(_func, _stat, _lockres) do {         \
    mlog(ML_ERROR, "Dlm error %d while calling %s on "      \
        "resource %.*s\n", _stat, _func,            \
        _lockres->l_namelen, _lockres->l_name);         \
} while (0)

/* WARNING: This function lives in a world where the only three lock
 * levels are EX, PR, and NL. It *will* have to be adjusted when more
 * lock types are added. */
static inline int user_highest_compat_lock_level(int level)
{
    int new_level = DLM_LOCK_EX;

    if (level == DLM_LOCK_EX)
        new_level = DLM_LOCK_NL;
    else if (level == DLM_LOCK_PR)
        new_level = DLM_LOCK_PR;
    return new_level;
}

static void user_ast(struct ocfs2_dlm_lksb *lksb)
{
    struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
    int status;

    mlog(ML_BASTS, "AST fired for lockres %.*s, level %d => %d\n",
         lockres->l_namelen, lockres->l_name, lockres->l_level,
         lockres->l_requested);

    spin_lock(&lockres->l_lock);

    status = ocfs2_dlm_lock_status(&lockres->l_lksb);
    if (status) {
        mlog(ML_ERROR, "lksb status value of %u on lockres %.*s\n",
             status, lockres->l_namelen, lockres->l_name);
        spin_unlock(&lockres->l_lock);
        return;
    }

    mlog_bug_on_msg(lockres->l_requested == DLM_LOCK_IV,
            "Lockres %.*s, requested ivmode. flags 0x%x\n",
            lockres->l_namelen, lockres->l_name, lockres->l_flags);

    /* we're downconverting. */
    if (lockres->l_requested < lockres->l_level) {
        if (lockres->l_requested <=
            user_highest_compat_lock_level(lockres->l_blocking)) {
            lockres->l_blocking = DLM_LOCK_NL;
            lockres->l_flags &= ~USER_LOCK_BLOCKED;
        }
    }

    lockres->l_level = lockres->l_requested;
    lockres->l_requested = DLM_LOCK_IV;
    lockres->l_flags |= USER_LOCK_ATTACHED;
    lockres->l_flags &= ~USER_LOCK_BUSY;

    spin_unlock(&lockres->l_lock);

    wake_up(&lockres->l_event);
}

static inline void user_dlm_grab_inode_ref(struct user_lock_res *lockres)
{
    struct inode *inode;
    inode = user_dlm_inode_from_user_lockres(lockres);
    if (!igrab(inode))
        BUG();
}

static void user_dlm_unblock_lock(struct work_struct *work);

static void __user_dlm_queue_lockres(struct user_lock_res *lockres)
{
    if (!(lockres->l_flags & USER_LOCK_QUEUED)) {
        user_dlm_grab_inode_ref(lockres);

        INIT_WORK(&lockres->l_work, user_dlm_unblock_lock);

        queue_work(user_dlm_worker, &lockres->l_work);
        lockres->l_flags |= USER_LOCK_QUEUED;
    }
}

static void __user_dlm_cond_queue_lockres(struct user_lock_res *lockres)
{
    int queue = 0;

    if (!(lockres->l_flags & USER_LOCK_BLOCKED))
        return;

    switch (lockres->l_blocking) {
    case DLM_LOCK_EX:
        if (!lockres->l_ex_holders && !lockres->l_ro_holders)
            queue = 1;
        break;
    case DLM_LOCK_PR:
        if (!lockres->l_ex_holders)
            queue = 1;
        break;
    default:
        BUG();
    }

    if (queue)
        __user_dlm_queue_lockres(lockres);
}

static void user_bast(struct ocfs2_dlm_lksb *lksb, int level)
{
    struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);

    mlog(ML_BASTS, "BAST fired for lockres %.*s, blocking %d, level %d\n",
         lockres->l_namelen, lockres->l_name, level, lockres->l_level);

    spin_lock(&lockres->l_lock);
    lockres->l_flags |= USER_LOCK_BLOCKED;
    if (level > lockres->l_blocking)
        lockres->l_blocking = level;

    __user_dlm_queue_lockres(lockres);
    spin_unlock(&lockres->l_lock);

    wake_up(&lockres->l_event);
}

static void user_unlock_ast(struct ocfs2_dlm_lksb *lksb, int status)
{
    struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);

    mlog(ML_BASTS, "UNLOCK AST fired for lockres %.*s, flags 0x%x\n",
         lockres->l_namelen, lockres->l_name, lockres->l_flags);

    if (status)
        mlog(ML_ERROR, "dlm returns status %d\n", status);

    spin_lock(&lockres->l_lock);
    /* The teardown flag gets set early during the unlock process,
     * so test the cancel flag to make sure that this ast isn't
     * for a concurrent cancel. */
    if (lockres->l_flags & USER_LOCK_IN_TEARDOWN
        && !(lockres->l_flags & USER_LOCK_IN_CANCEL)) {
        lockres->l_level = DLM_LOCK_IV;
    } else if (status == DLM_CANCELGRANT) {
        /* We tried to cancel a convert request, but it was
         * already granted. Don't clear the busy flag - the
         * ast should've done this already. */
        BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
        lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
        goto out_noclear;
    } else {
        BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
        /* Cancel succeeded, we want to re-queue */
        lockres->l_requested = DLM_LOCK_IV; /* cancel an
                            * upconvert
                            * request. */
        lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
        /* we want the unblock thread to look at it again
         * now. */
        if (lockres->l_flags & USER_LOCK_BLOCKED)
            __user_dlm_queue_lockres(lockres);
    }

    lockres->l_flags &= ~USER_LOCK_BUSY;
out_noclear:
    spin_unlock(&lockres->l_lock);

    wake_up(&lockres->l_event);
}

/*
 * This is the userdlmfs locking protocol version.
 *
 * See fs/ocfs2/dlmglue.c for more details on locking versions.
 */
static struct ocfs2_locking_protocol user_dlm_lproto = {
    .lp_max_version = {
        .pv_major = OCFS2_LOCKING_PROTOCOL_MAJOR,
        .pv_minor = OCFS2_LOCKING_PROTOCOL_MINOR,
    },
    .lp_lock_ast        = user_ast,
    .lp_blocking_ast    = user_bast,
    .lp_unlock_ast      = user_unlock_ast,
};

static inline void user_dlm_drop_inode_ref(struct user_lock_res *lockres)
{
    struct inode *inode;
    inode = user_dlm_inode_from_user_lockres(lockres);
    iput(inode);
}

static void user_dlm_unblock_lock(struct work_struct *work)
{
    int new_level, status;
    struct user_lock_res *lockres =
        container_of(work, struct user_lock_res, l_work);
    struct ocfs2_cluster_connection *conn =
        cluster_connection_from_user_lockres(lockres);

    mlog(0, "lockres %.*s\n", lockres->l_namelen, lockres->l_name);

    spin_lock(&lockres->l_lock);

    mlog_bug_on_msg(!(lockres->l_flags & USER_LOCK_QUEUED),
            "Lockres %.*s, flags 0x%x\n",
            lockres->l_namelen, lockres->l_name, lockres->l_flags);

    /* notice that we don't clear USER_LOCK_BLOCKED here. If it's
     * set, we want user_ast clear it. */
    lockres->l_flags &= ~USER_LOCK_QUEUED;

    /* It's valid to get here and no longer be blocked - if we get
     * several basts in a row, we might be queued by the first
     * one, the unblock thread might run and clear the queued
     * flag, and finally we might get another bast which re-queues
     * us before our ast for the downconvert is called. */
    if (!(lockres->l_flags & USER_LOCK_BLOCKED)) {
        mlog(ML_BASTS, "lockres %.*s USER_LOCK_BLOCKED\n",
             lockres->l_namelen, lockres->l_name);
        spin_unlock(&lockres->l_lock);
        goto drop_ref;
    }

    if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
        mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_TEARDOWN\n",
             lockres->l_namelen, lockres->l_name);
        spin_unlock(&lockres->l_lock);
        goto drop_ref;
    }

    if (lockres->l_flags & USER_LOCK_BUSY) {
        if (lockres->l_flags & USER_LOCK_IN_CANCEL) {
            mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_CANCEL\n",
                 lockres->l_namelen, lockres->l_name);
            spin_unlock(&lockres->l_lock);
            goto drop_ref;
        }

        lockres->l_flags |= USER_LOCK_IN_CANCEL;
        spin_unlock(&lockres->l_lock);

        status = ocfs2_dlm_unlock(conn, &lockres->l_lksb,
                      DLM_LKF_CANCEL);
        if (status)
            user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
        goto drop_ref;
    }

    /* If there are still incompat holders, we can exit safely
     * without worrying about re-queueing this lock as that will
     * happen on the last call to user_cluster_unlock. */
    if ((lockres->l_blocking == DLM_LOCK_EX)
        && (lockres->l_ex_holders || lockres->l_ro_holders)) {
        spin_unlock(&lockres->l_lock);
        mlog(ML_BASTS, "lockres %.*s, EX/PR Holders %u,%u\n",
             lockres->l_namelen, lockres->l_name,
             lockres->l_ex_holders, lockres->l_ro_holders);
        goto drop_ref;
    }

    if ((lockres->l_blocking == DLM_LOCK_PR)
        && lockres->l_ex_holders) {
        spin_unlock(&lockres->l_lock);
        mlog(ML_BASTS, "lockres %.*s, EX Holders %u\n",
             lockres->l_namelen, lockres->l_name,
             lockres->l_ex_holders);
        goto drop_ref;
    }

    /* yay, we can downconvert now. */
    new_level = user_highest_compat_lock_level(lockres->l_blocking);
    lockres->l_requested = new_level;
    lockres->l_flags |= USER_LOCK_BUSY;
    mlog(ML_BASTS, "lockres %.*s, downconvert %d => %d\n",
         lockres->l_namelen, lockres->l_name, lockres->l_level, new_level);
    spin_unlock(&lockres->l_lock);

    /* need lock downconvert request now... */
    status = ocfs2_dlm_lock(conn, new_level, &lockres->l_lksb,
                DLM_LKF_CONVERT|DLM_LKF_VALBLK,
                lockres->l_name,
                lockres->l_namelen);
    if (status) {
        user_log_dlm_error("ocfs2_dlm_lock", status, lockres);
        user_recover_from_dlm_error(lockres);
    }

drop_ref:
    user_dlm_drop_inode_ref(lockres);
}

static inline void user_dlm_inc_holders(struct user_lock_res *lockres,
                    int level)
{
    switch(level) {
    case DLM_LOCK_EX:
        lockres->l_ex_holders++;
        break;
    case DLM_LOCK_PR:
        lockres->l_ro_holders++;
        break;
    default:
        BUG();
    }
}

/* predict what lock level we'll be dropping down to on behalf
 * of another node, and return true if the currently wanted
 * level will be compatible with it. */
static inline int
user_may_continue_on_blocked_lock(struct user_lock_res *lockres,
                  int wanted)
{
    BUG_ON(!(lockres->l_flags & USER_LOCK_BLOCKED));

    return wanted <= user_highest_compat_lock_level(lockres->l_blocking);
}

int user_dlm_cluster_lock(struct user_lock_res *lockres,
              int level,
              int lkm_flags)
{
    int status, local_flags;
    struct ocfs2_cluster_connection *conn =
        cluster_connection_from_user_lockres(lockres);

    if (level != DLM_LOCK_EX &&
        level != DLM_LOCK_PR) {
        mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
             lockres->l_namelen, lockres->l_name);
        status = -EINVAL;
        goto bail;
    }

    mlog(ML_BASTS, "lockres %.*s, level %d, flags = 0x%x\n",
         lockres->l_namelen, lockres->l_name, level, lkm_flags);

again:
    if (signal_pending(current)) {
        status = -ERESTARTSYS;
        goto bail;
    }

    spin_lock(&lockres->l_lock);

    /* We only compare against the currently granted level
     * here. If the lock is blocked waiting on a downconvert,
     * we'll get caught below. */
    if ((lockres->l_flags & USER_LOCK_BUSY) &&
        (level > lockres->l_level)) {
        /* is someone sitting in dlm_lock? If so, wait on
         * them. */
        spin_unlock(&lockres->l_lock);

        user_wait_on_busy_lock(lockres);
        goto again;
    }

    if ((lockres->l_flags & USER_LOCK_BLOCKED) &&
        (!user_may_continue_on_blocked_lock(lockres, level))) {
        /* is the lock is currently blocked on behalf of
         * another node */
        spin_unlock(&lockres->l_lock);

        user_wait_on_blocked_lock(lockres);
        goto again;
    }

    if (level > lockres->l_level) {
        local_flags = lkm_flags | DLM_LKF_VALBLK;
        if (lockres->l_level != DLM_LOCK_IV)
            local_flags |= DLM_LKF_CONVERT;

        lockres->l_requested = level;
        lockres->l_flags |= USER_LOCK_BUSY;
        spin_unlock(&lockres->l_lock);

        BUG_ON(level == DLM_LOCK_IV);
        BUG_ON(level == DLM_LOCK_NL);

        /* call dlm_lock to upgrade lock now */
        status = ocfs2_dlm_lock(conn, level, &lockres->l_lksb,
                    local_flags, lockres->l_name,
                    lockres->l_namelen);
        if (status) {
            if ((lkm_flags & DLM_LKF_NOQUEUE) &&
                (status != -EAGAIN))
                user_log_dlm_error("ocfs2_dlm_lock",
                           status, lockres);
            user_recover_from_dlm_error(lockres);
            goto bail;
        }

        user_wait_on_busy_lock(lockres);
        goto again;
    }

    user_dlm_inc_holders(lockres, level);
    spin_unlock(&lockres->l_lock);

    status = 0;
bail:
    return status;
}

static inline void user_dlm_dec_holders(struct user_lock_res *lockres,
                    int level)
{
    switch(level) {
    case DLM_LOCK_EX:
        BUG_ON(!lockres->l_ex_holders);
        lockres->l_ex_holders--;
        break;
    case DLM_LOCK_PR:
        BUG_ON(!lockres->l_ro_holders);
        lockres->l_ro_holders--;
        break;
    default:
        BUG();
    }
}

void user_dlm_cluster_unlock(struct user_lock_res *lockres,
                 int level)
{
    if (level != DLM_LOCK_EX &&
        level != DLM_LOCK_PR) {
        mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
             lockres->l_namelen, lockres->l_name);
        return;
    }

    spin_lock(&lockres->l_lock);
    user_dlm_dec_holders(lockres, level);
    __user_dlm_cond_queue_lockres(lockres);
    spin_unlock(&lockres->l_lock);
}

void user_dlm_write_lvb(struct inode *inode,
            const char *val,
            unsigned int len)
{
    struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
    char *lvb;

    BUG_ON(len > DLM_LVB_LEN);

    spin_lock(&lockres->l_lock);

    BUG_ON(lockres->l_level < DLM_LOCK_EX);
    lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
    memcpy(lvb, val, len);

    spin_unlock(&lockres->l_lock);
}

ssize_t user_dlm_read_lvb(struct inode *inode,
              char *val,
              unsigned int len)
{
    struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
    char *lvb;
    ssize_t ret = len;

    BUG_ON(len > DLM_LVB_LEN);

    spin_lock(&lockres->l_lock);

    BUG_ON(lockres->l_level < DLM_LOCK_PR);
    if (ocfs2_dlm_lvb_valid(&lockres->l_lksb)) {
        lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
        memcpy(val, lvb, len);
    } else
        ret = 0;

    spin_unlock(&lockres->l_lock);
    return ret;
}

void user_dlm_lock_res_init(struct user_lock_res *lockres,
                struct dentry *dentry)
{
    memset(lockres, 0, sizeof(*lockres));

    spin_lock_init(&lockres->l_lock);
    init_waitqueue_head(&lockres->l_event);
    lockres->l_level = DLM_LOCK_IV;
    lockres->l_requested = DLM_LOCK_IV;
    lockres->l_blocking = DLM_LOCK_IV;

    /* should have been checked before getting here. */
    BUG_ON(dentry->d_name.len >= USER_DLM_LOCK_ID_MAX_LEN);

    memcpy(lockres->l_name,
           dentry->d_name.name,
           dentry->d_name.len);
    lockres->l_namelen = dentry->d_name.len;
}

int user_dlm_destroy_lock(struct user_lock_res *lockres)
{
    int status = -EBUSY;
    struct ocfs2_cluster_connection *conn =
        cluster_connection_from_user_lockres(lockres);

    mlog(ML_BASTS, "lockres %.*s\n", lockres->l_namelen, lockres->l_name);

    spin_lock(&lockres->l_lock);
    if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
        spin_unlock(&lockres->l_lock);
        return 0;
    }

    lockres->l_flags |= USER_LOCK_IN_TEARDOWN;

    while (lockres->l_flags & USER_LOCK_BUSY) {
        spin_unlock(&lockres->l_lock);

        user_wait_on_busy_lock(lockres);

        spin_lock(&lockres->l_lock);
    }

    if (lockres->l_ro_holders || lockres->l_ex_holders) {
        spin_unlock(&lockres->l_lock);
        goto bail;
    }

    status = 0;
    if (!(lockres->l_flags & USER_LOCK_ATTACHED)) {
        spin_unlock(&lockres->l_lock);
        goto bail;
    }

    lockres->l_flags &= ~USER_LOCK_ATTACHED;
    lockres->l_flags |= USER_LOCK_BUSY;
    spin_unlock(&lockres->l_lock);

    status = ocfs2_dlm_unlock(conn, &lockres->l_lksb, DLM_LKF_VALBLK);
    if (status) {
        user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
        goto bail;
    }

    user_wait_on_busy_lock(lockres);

    status = 0;
bail:
    return status;
}

static void user_dlm_recovery_handler_noop(int node_num,
                       void *recovery_data)
{
    /* We ignore recovery events */
    return;
}

void user_dlm_set_locking_protocol(void)
{
    ocfs2_stack_glue_set_max_proto_version(&user_dlm_lproto.lp_max_version);
}

struct ocfs2_cluster_connection *user_dlm_register(struct qstr *name)
{
    int rc;
    struct ocfs2_cluster_connection *conn;

    rc = ocfs2_cluster_connect_agnostic(name->name, name->len,
                        &user_dlm_lproto,
                        user_dlm_recovery_handler_noop,
                        NULL, &conn);
    if (rc)
        mlog_errno(rc);

    return rc ? ERR_PTR(rc) : conn;
}

void user_dlm_unregister(struct ocfs2_cluster_connection *conn)
{
    ocfs2_cluster_disconnect(conn, 0);
}