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Commit 39bf0949 authored by David S. Miller's avatar David S. Miller
Browse files

[AFS]: Eliminate cmpxchg() usage in vlocation code. 



cmpxchg() is not available on every processor so can't
be used in generic code.

Replace with spinlock protection on the ->state changes,
wakeups, and wait loops.

Add what appears to be a missing wakeup on transition
to AFS_VL_VALID state in afs_vlocation_updater().

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 68c708fd

fs/afs/internal.h

+1 −1
Original line number Diff line number Diff line
@@ -219,7 +219,7 @@ struct afs_vlocation { 
	struct afs_volume	*vols[3];	/* volume access record pointer (index by type) */

	wait_queue_head_t	waitq;		/* status change waitqueue */

	time_t			update_at;	/* time at which record should be updated */

	rwlock_t		lock;		/* access lock */

	spinlock_t		lock;		/* access lock */

	afs_vlocation_state_t	state;		/* volume location state */

	unsigned short		upd_rej_cnt;	/* ENOMEDIUM count during update */

	unsigned short		upd_busy_cnt;	/* EBUSY count during update */

fs/afs/vlocation.c

+15 −5
Original line number Diff line number Diff line
@@ -178,7 +178,7 @@ static struct afs_vlocation *afs_vlocation_alloc(struct afs_cell *cell, 
		INIT_LIST_HEAD(&vl->grave);

		INIT_LIST_HEAD(&vl->update);

		init_waitqueue_head(&vl->waitq);

		rwlock_init(&vl->lock);

		spin_lock_init(&vl->lock);

		memcpy(vl->vldb.name, name, namesz);

	}
@@ -414,8 +414,10 @@ struct afs_vlocation *afs_vlocation_lookup(struct afs_cell *cell, 
	ret = afs_vlocation_fill_in_record(vl, key);

	if (ret < 0)

		goto error_abandon;

	spin_lock(&vl->lock);

	vl->state = AFS_VL_VALID;

	wake_up(&vl->waitq);

	spin_unlock(&vl->lock);



	/* schedule for regular updates */

	afs_vlocation_queue_for_updates(vl);
@@ -434,22 +436,23 @@ struct afs_vlocation *afs_vlocation_lookup(struct afs_cell *cell, 
	up_write(&cell->vl_sem);



	/* see if it was an abandoned record that we might try filling in */

	spin_lock(&vl->lock);

	while (vl->state != AFS_VL_VALID) {

		afs_vlocation_state_t state = vl->state;



		_debug("invalid [state %d]", state);



		if ((state == AFS_VL_NEW || state == AFS_VL_NO_VOLUME)) {

			if (cmpxchg(&vl->state, state, AFS_VL_CREATING) ==

			    state)

			vl->state = AFS_VL_CREATING;

			spin_unlock(&vl->lock);

			goto fill_in_record;

			continue;

		}



		/* must now wait for creation or update by someone else to

		 * complete */

		_debug("wait");



		spin_unlock(&vl->lock);

		ret = wait_event_interruptible(

			vl->waitq,

			vl->state == AFS_VL_NEW ||
@@ -457,15 +460,19 @@ struct afs_vlocation *afs_vlocation_lookup(struct afs_cell *cell, 
			vl->state == AFS_VL_NO_VOLUME);

		if (ret < 0)

			goto error;

		spin_lock(&vl->lock);

	}

	spin_unlock(&vl->lock);



success:

	_leave(" = %p",vl);

	return vl;



error_abandon:

	spin_lock(&vl->lock);

	vl->state = AFS_VL_NEW;

	wake_up(&vl->waitq);

	spin_unlock(&vl->lock);

error:

	ASSERT(vl != NULL);

	afs_put_vlocation(vl);
@@ -663,10 +670,12 @@ static void afs_vlocation_updater(struct work_struct *work) 
	vl->upd_busy_cnt = 0;



	ret = afs_vlocation_update_record(vl, NULL, &vldb);

	spin_lock(&vl->lock);

	switch (ret) {

	case 0:

		afs_vlocation_apply_update(vl, &vldb);

		vl->state = AFS_VL_VALID;

		wake_up(&vl->waitq);

		break;

	case -ENOMEDIUM:

		vl->state = AFS_VL_VOLUME_DELETED;
@@ -675,6 +684,7 @@ static void afs_vlocation_updater(struct work_struct *work) 
		vl->state = AFS_VL_UNCERTAIN;

		break;

	}

	spin_unlock(&vl->lock);



	/* and then reschedule */

	_debug("reschedule");