glock.c

linux 内核源代码

	if (gl->gl_state == gl->gl_demote_state ||
	    gl->gl_state == LM_ST_UNLOCKED) {
		gfs2_demote_wake(gl);
		return 0;
	}
	set_bit(GLF_LOCK, &gl->gl_flags);
	if (gl->gl_demote_state == LM_ST_UNLOCKED ||
	    gl->gl_state != LM_ST_EXCLUSIVE) {
		spin_unlock(&gl->gl_spin);
		gfs2_glock_drop_th(gl);
	} else {
		spin_unlock(&gl->gl_spin);
		gfs2_glock_xmote_th(gl, NULL);
	}
	spin_lock(&gl->gl_spin);

	return 0;
}

/**
 * run_queue - process holder structures on a glock
 * @gl: the glock
 *
 */
static void run_queue(struct gfs2_glock *gl)
{
	struct gfs2_holder *gh;
	int blocked = 1;

	for (;;) {
		if (test_bit(GLF_LOCK, &gl->gl_flags))
			break;

		if (!list_empty(&gl->gl_waiters1)) {
			gh = list_entry(gl->gl_waiters1.next,
					struct gfs2_holder, gh_list);

			if (test_bit(HIF_MUTEX, &gh->gh_iflags))
				blocked = rq_mutex(gh);
			else
				gfs2_assert_warn(gl->gl_sbd, 0);

		} else if (test_bit(GLF_DEMOTE, &gl->gl_flags)) {
			blocked = rq_demote(gl);
		} else if (!list_empty(&gl->gl_waiters3)) {
			gh = list_entry(gl->gl_waiters3.next,
					struct gfs2_holder, gh_list);

			if (test_bit(HIF_PROMOTE, &gh->gh_iflags))
				blocked = rq_promote(gh);
			else
				gfs2_assert_warn(gl->gl_sbd, 0);

		} else
			break;

		if (blocked)
			break;
	}
}

/**
 * gfs2_glmutex_lock - acquire a local lock on a glock
 * @gl: the glock
 *
 * Gives caller exclusive access to manipulate a glock structure.
 */

static void gfs2_glmutex_lock(struct gfs2_glock *gl)
{
	struct gfs2_holder gh;

	gfs2_holder_init(gl, 0, 0, &gh);
	set_bit(HIF_MUTEX, &gh.gh_iflags);
	if (test_and_set_bit(HIF_WAIT, &gh.gh_iflags))
		BUG();

	spin_lock(&gl->gl_spin);
	if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
		list_add_tail(&gh.gh_list, &gl->gl_waiters1);
	} else {
		gl->gl_owner_pid = current->pid;
		gl->gl_ip = (unsigned long)__builtin_return_address(0);
		clear_bit(HIF_WAIT, &gh.gh_iflags);
		smp_mb();
		wake_up_bit(&gh.gh_iflags, HIF_WAIT);
	}
	spin_unlock(&gl->gl_spin);

	wait_on_holder(&gh);
	gfs2_holder_uninit(&gh);
}

/**
 * gfs2_glmutex_trylock - try to acquire a local lock on a glock
 * @gl: the glock
 *
 * Returns: 1 if the glock is acquired
 */

static int gfs2_glmutex_trylock(struct gfs2_glock *gl)
{
	int acquired = 1;

	spin_lock(&gl->gl_spin);
	if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
		acquired = 0;
	} else {
		gl->gl_owner_pid = current->pid;
		gl->gl_ip = (unsigned long)__builtin_return_address(0);
	}
	spin_unlock(&gl->gl_spin);

	return acquired;
}

/**
 * gfs2_glmutex_unlock - release a local lock on a glock
 * @gl: the glock
 *
 */

static void gfs2_glmutex_unlock(struct gfs2_glock *gl)
{
	spin_lock(&gl->gl_spin);
	clear_bit(GLF_LOCK, &gl->gl_flags);
	gl->gl_owner_pid = 0;
	gl->gl_ip = 0;
	run_queue(gl);
	BUG_ON(!spin_is_locked(&gl->gl_spin));
	spin_unlock(&gl->gl_spin);
}

/**
 * handle_callback - process a demote request
 * @gl: the glock
 * @state: the state the caller wants us to change to
 *
 * There are only two requests that we are going to see in actual
 * practise: LM_ST_SHARED and LM_ST_UNLOCKED
 */

static void handle_callback(struct gfs2_glock *gl, unsigned int state,
			    int remote, unsigned long delay)
{
	int bit = delay ? GLF_PENDING_DEMOTE : GLF_DEMOTE;

	spin_lock(&gl->gl_spin);
	set_bit(bit, &gl->gl_flags);
	if (gl->gl_demote_state == LM_ST_EXCLUSIVE) {
		gl->gl_demote_state = state;
		gl->gl_demote_time = jiffies;
		if (remote && gl->gl_ops->go_type == LM_TYPE_IOPEN &&
		    gl->gl_object) {
			gfs2_glock_schedule_for_reclaim(gl);
			spin_unlock(&gl->gl_spin);
			return;
		}
	} else if (gl->gl_demote_state != LM_ST_UNLOCKED &&
			gl->gl_demote_state != state) {
		gl->gl_demote_state = LM_ST_UNLOCKED;
	}
	spin_unlock(&gl->gl_spin);
}

/**
 * state_change - record that the glock is now in a different state
 * @gl: the glock
 * @new_state the new state
 *
 */

static void state_change(struct gfs2_glock *gl, unsigned int new_state)
{
	int held1, held2;

	held1 = (gl->gl_state != LM_ST_UNLOCKED);
	held2 = (new_state != LM_ST_UNLOCKED);

	if (held1 != held2) {
		if (held2)
			gfs2_glock_hold(gl);
		else
			gfs2_glock_put(gl);
	}

	gl->gl_state = new_state;
	gl->gl_tchange = jiffies;
}

/**
 * xmote_bh - Called after the lock module is done acquiring a lock
 * @gl: The glock in question
 * @ret: the int returned from the lock module
 *
 */

static void xmote_bh(struct gfs2_glock *gl, unsigned int ret)
{
	struct gfs2_sbd *sdp = gl->gl_sbd;
	const struct gfs2_glock_operations *glops = gl->gl_ops;
	struct gfs2_holder *gh = gl->gl_req_gh;
	int prev_state = gl->gl_state;
	int op_done = 1;

	gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
	gfs2_assert_warn(sdp, list_empty(&gl->gl_holders));
	gfs2_assert_warn(sdp, !(ret & LM_OUT_ASYNC));

	state_change(gl, ret & LM_OUT_ST_MASK);

	if (prev_state != LM_ST_UNLOCKED && !(ret & LM_OUT_CACHEABLE)) {
		if (glops->go_inval)
			glops->go_inval(gl, DIO_METADATA);
	} else if (gl->gl_state == LM_ST_DEFERRED) {
		/* We might not want to do this here.
		   Look at moving to the inode glops. */
		if (glops->go_inval)
			glops->go_inval(gl, 0);
	}

	/*  Deal with each possible exit condition  */

	if (!gh) {
		gl->gl_stamp = jiffies;
		if (ret & LM_OUT_CANCELED) {
			op_done = 0;
		} else {
			spin_lock(&gl->gl_spin);
			if (gl->gl_state != gl->gl_demote_state) {
				gl->gl_req_bh = NULL;
				spin_unlock(&gl->gl_spin);
				gfs2_glock_drop_th(gl);
				gfs2_glock_put(gl);
				return;
			}
			gfs2_demote_wake(gl);
			spin_unlock(&gl->gl_spin);
		}
	} else {
		spin_lock(&gl->gl_spin);
		list_del_init(&gh->gh_list);
		gh->gh_error = -EIO;
		if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) 
			goto out;
		gh->gh_error = GLR_CANCELED;
		if (ret & LM_OUT_CANCELED) 
			goto out;
		if (relaxed_state_ok(gl->gl_state, gh->gh_state, gh->gh_flags)) {
			list_add_tail(&gh->gh_list, &gl->gl_holders);
			gh->gh_error = 0;
			set_bit(HIF_HOLDER, &gh->gh_iflags);
			set_bit(HIF_FIRST, &gh->gh_iflags);
			op_done = 0;
			goto out;
		}
		gh->gh_error = GLR_TRYFAILED;
		if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))
			goto out;
		gh->gh_error = -EINVAL;
		if (gfs2_assert_withdraw(sdp, 0) == -1)
			fs_err(sdp, "ret = 0x%.8X\n", ret);
out:
		spin_unlock(&gl->gl_spin);
	}

	if (glops->go_xmote_bh)
		glops->go_xmote_bh(gl);

	if (op_done) {
		spin_lock(&gl->gl_spin);
		gl->gl_req_gh = NULL;
		gl->gl_req_bh = NULL;
		clear_bit(GLF_LOCK, &gl->gl_flags);
		spin_unlock(&gl->gl_spin);
	}

	gfs2_glock_put(gl);

	if (gh)
		gfs2_holder_wake(gh);
}

/**
 * gfs2_glock_xmote_th - Call into the lock module to acquire or change a glock
 * @gl: The glock in question
 * @state: the requested state
 * @flags: modifier flags to the lock call
 *
 */

static void gfs2_glock_xmote_th(struct gfs2_glock *gl, struct gfs2_holder *gh)
{
	struct gfs2_sbd *sdp = gl->gl_sbd;
	int flags = gh ? gh->gh_flags : 0;
	unsigned state = gh ? gh->gh_state : gl->gl_demote_state;
	const struct gfs2_glock_operations *glops = gl->gl_ops;
	int lck_flags = flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB |
				 LM_FLAG_NOEXP | LM_FLAG_ANY |
				 LM_FLAG_PRIORITY);
	unsigned int lck_ret;

	if (glops->go_xmote_th)
		glops->go_xmote_th(gl);

	gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
	gfs2_assert_warn(sdp, list_empty(&gl->gl_holders));
	gfs2_assert_warn(sdp, state != LM_ST_UNLOCKED);
	gfs2_assert_warn(sdp, state != gl->gl_state);

	gfs2_glock_hold(gl);
	gl->gl_req_bh = xmote_bh;

	lck_ret = gfs2_lm_lock(sdp, gl->gl_lock, gl->gl_state, state, lck_flags);

	if (gfs2_assert_withdraw(sdp, !(lck_ret & LM_OUT_ERROR)))
		return;

	if (lck_ret & LM_OUT_ASYNC)
		gfs2_assert_warn(sdp, lck_ret == LM_OUT_ASYNC);
	else
		xmote_bh(gl, lck_ret);
}

/**
 * drop_bh - Called after a lock module unlock completes
 * @gl: the glock
 * @ret: the return status
 *
 * Doesn't wake up the process waiting on the struct gfs2_holder (if any)
 * Doesn't drop the reference on the glock the top half took out
 *
 */

static void drop_bh(struct gfs2_glock *gl, unsigned int ret)
{
	struct gfs2_sbd *sdp = gl->gl_sbd;
	const struct gfs2_glock_operations *glops = gl->gl_ops;
	struct gfs2_holder *gh = gl->gl_req_gh;

	gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
	gfs2_assert_warn(sdp, list_empty(&gl->gl_holders));
	gfs2_assert_warn(sdp, !ret);

	state_change(gl, LM_ST_UNLOCKED);

	if (glops->go_inval)
		glops->go_inval(gl, DIO_METADATA);

	if (gh) {
		spin_lock(&gl->gl_spin);
		list_del_init(&gh->gh_list);
		gh->gh_error = 0;
		spin_unlock(&gl->gl_spin);
	}

	spin_lock(&gl->gl_spin);
	gfs2_demote_wake(gl);
	gl->gl_req_gh = NULL;
	gl->gl_req_bh = NULL;
	clear_bit(GLF_LOCK, &gl->gl_flags);
	spin_unlock(&gl->gl_spin);

	gfs2_glock_put(gl);

	if (gh)
		gfs2_holder_wake(gh);
}

/**
 * gfs2_glock_drop_th - call into the lock module to unlock a lock
 * @gl: the glock
 *
 */

static void gfs2_glock_drop_th(struct gfs2_glock *gl)
{
	struct gfs2_sbd *sdp = gl->gl_sbd;
	const struct gfs2_glock_operations *glops = gl->gl_ops;
	unsigned int ret;

	if (glops->go_drop_th)
		glops->go_drop_th(gl);

	gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
	gfs2_assert_warn(sdp, list_empty(&gl->gl_holders));
	gfs2_assert_warn(sdp, gl->gl_state != LM_ST_UNLOCKED);

	gfs2_glock_hold(gl);
	gl->gl_req_bh = drop_bh;

	ret = gfs2_lm_unlock(sdp, gl->gl_lock, gl->gl_state);

	if (gfs2_assert_withdraw(sdp, !(ret & LM_OUT_ERROR)))
		return;

	if (!ret)
		drop_bh(gl, ret);
	else
		gfs2_assert_warn(sdp, ret == LM_OUT_ASYNC);
}

/**
 * do_cancels - cancel requests for locks stuck waiting on an expire flag
 * @gh: the LM_FLAG_PRIORITY holder waiting to acquire the lock
 *
 * Don't cancel GL_NOCANCEL requests.
 */

static void do_cancels(struct gfs2_holder *gh)
{
	struct gfs2_glock *gl = gh->gh_gl;

	spin_lock(&gl->gl_spin);

	while (gl->gl_req_gh != gh &&
	       !test_bit(HIF_HOLDER, &gh->gh_iflags) &&
	       !list_empty(&gh->gh_list)) {
		if (gl->gl_req_bh && !(gl->gl_req_gh &&
				     (gl->gl_req_gh->gh_flags & GL_NOCANCEL))) {
			spin_unlock(&gl->gl_spin);
			gfs2_lm_cancel(gl->gl_sbd, gl->gl_lock);
			msleep(100);
			spin_lock(&gl->gl_spin);
		} else {
			spin_unlock(&gl->gl_spin);
			msleep(100);
			spin_lock(&gl->gl_spin);
		}
	}

	spin_unlock(&gl->gl_spin);
}

/**
 * glock_wait_internal - wait on a glock acquisition
 * @gh: the glock holder
 *
 * Returns: 0 on success
 */

static int glock_wait_internal(struct gfs2_holder *gh)
{
	struct gfs2_glock *gl = gh->gh_gl;
	struct gfs2_sbd *sdp = gl->gl_sbd;
	const struct gfs2_glock_operations *glops = gl->gl_ops;

	if (test_bit(HIF_ABORTED, &gh->gh_iflags))
		return -EIO;

	if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) {
		spin_lock(&gl->gl_spin);
		if (gl->gl_req_gh != gh &&
		    !test_bit(HIF_HOLDER, &gh->gh_iflags) &&
		    !list_empty(&gh->gh_list)) {
			list_del_init(&gh->gh_list);
			gh->gh_error = GLR_TRYFAILED;
			run_queue(gl);
			spin_unlock(&gl->gl_spin);
			return gh->gh_error;
		}
		spin_unlock(&gl->gl_spin);
	}

	if (gh->gh_flags & LM_FLAG_PRIORITY)
		do_cancels(gh);

	wait_on_holder(gh);
	if (gh->gh_error)
		return gh->gh_error;

	gfs2_assert_withdraw(sdp, test_bit(HIF_HOLDER, &gh->gh_iflags));
	gfs2_assert_withdraw(sdp, relaxed_state_ok(gl->gl_state, gh->gh_state,
						   gh->gh_flags));

	if (test_bit(HIF_FIRST, &gh->gh_iflags)) {
		gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));

		if (glops->go_lock) {
			gh->gh_error = glops->go_lock(gh);
			if (gh->gh_error) {
				spin_lock(&gl->gl_spin);
				list_del_init(&gh->gh_list);
				spin_unlock(&gl->gl_spin);
			}
		}

		spin_lock(&gl->gl_spin);
		gl->gl_req_gh = NULL;
		gl->gl_req_bh = NULL;
		clear_bit(GLF_LOCK, &gl->gl_flags);
		run_queue(gl);
		spin_unlock(&gl->gl_spin);
	}

	return gh->gh_error;
}

static inline struct gfs2_holder *
find_holder_by_owner(struct list_head *head, pid_t pid)
{
	struct gfs2_holder *gh;

	list_for_each_entry(gh, head, gh_list) {
		if (gh->gh_owner_pid == pid)
			return gh;
	}

	return NULL;
}

static void print_dbg(struct glock_iter *gi, const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	if (gi) {
		vsprintf(gi->string, fmt, args);
		seq_printf(gi->seq, gi->string);
	}
	else
		vprintk(fmt, args);
	va_end(args);
}

/**
 * add_to_queue - Add a holder to the wait queue (but look for recursion)
 * @gh: the holder structure to add
 *
 */

static void add_to_queue(struct gfs2_holder *gh)
{
	struct gfs2_glock *gl = gh->gh_gl;
	struct gfs2_holder *existing;

	BUG_ON(!gh->gh_owner_pid);
	if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags))
		BUG();

	if (!(gh->gh_flags & GL_FLOCK)) {
		existing = find_holder_by_owner(&gl->gl_holders, 
						gh->gh_owner_pid);
		if (existing) {
			print_symbol(KERN_WARNING "original: %s\n", 
				     existing->gh_ip);
			printk(KERN_INFO "pid : %d\n", existing->gh_owner_pid);
			printk(KERN_INFO "lock type : %d lock state : %d\n",
			       existing->gh_gl->gl_name.ln_type, 
			       existing->gh_gl->gl_state);
			print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip);
			printk(KERN_INFO "pid : %d\n", gh->gh_owner_pid);
			printk(KERN_INFO "lock type : %d lock state : %d\n",
			       gl->gl_name.ln_type, gl->gl_state);
			BUG();
		}
		
		existing = find_holder_by_owner(&gl->gl_waiters3, 
						gh->gh_owner_pid);
		if (existing) {
			print_symbol(KERN_WARNING "original: %s\n", 
				     existing->gh_ip);
			print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip);
			BUG();