[GFS2] Remove remote lock dropping code

There are several reasons why this is undesirable:

1. It never happens during normal operation anyway
2. If it does happen it causes performance to be very, very poor
3. It isn't likely to solve the original problem (memory shortage
on remote DLM node) it was supposed to solve
4. It uses a bunch of arbitrary constants which are unlikely to be
correct for any particular situation and for which the tuning seems
to be a black art.
5. In an N node cluster, only 1/N of the dropped locked will actually
contribute to solving the problem on average.

So all in all we are better off without it. This also makes merging
the lock_dlm module into GFS2 a bit easier.

Signed-off-by: Steven Whitehouse <[e-mail]>

fs/gfs2/gfs2.h

···
 };
 
 enum {
-	NO_WAIT = 0,
-	WAIT = 1,
-};
-
-enum {
 	NO_FORCE = 0,
 	FORCE = 1,
 };

fs/gfs2/glock.c

···
 			wake_up_process(sdp->sd_recoverd_process);
 		return;
 
-	case LM_CB_DROPLOCKS:
-		gfs2_gl_hash_clear(sdp, NO_WAIT);
-		gfs2_quota_scan(sdp);
-		return;
-
 	default:
 		gfs2_assert_warn(sdp, 0);
 		return;
···
  * @sdp: the filesystem
  * @wait: wait until it's all gone
  *
- * Called when unmounting the filesystem, or when inter-node lock manager
- * requests DROPLOCKS because it is running out of capacity.
+ * Called when unmounting the filesystem.
  */
 
-void gfs2_gl_hash_clear(struct gfs2_sbd *sdp, int wait)
+void gfs2_gl_hash_clear(struct gfs2_sbd *sdp)
 {
 	unsigned long t;
 	unsigned int x;
···
 				cont = 1;
 		}
 
-		if (!wait || !cont)
+		if (!cont)
 			break;
 
 		if (time_after_eq(jiffies,

fs/gfs2/glock.h

···
 void gfs2_glock_cb(void *cb_data, unsigned int type, void *data);
 void gfs2_glock_schedule_for_reclaim(struct gfs2_glock *gl);
 void gfs2_reclaim_glock(struct gfs2_sbd *sdp);
-void gfs2_gl_hash_clear(struct gfs2_sbd *sdp, int wait);
+void gfs2_gl_hash_clear(struct gfs2_sbd *sdp);
 
 int __init gfs2_glock_init(void);
 void gfs2_glock_exit(void);

fs/gfs2/locking/dlm/lock_dlm.h

···
 	wait_queue_head_t	wait_control;
 	struct task_struct	*thread;
 	wait_queue_head_t	thread_wait;
-	unsigned long		drop_time;
-	int			drop_locks_count;
-	int			drop_locks_period;
 };
 
 enum {

fs/gfs2/locking/dlm/mount.c

···
 	if (!ls)
 		return NULL;
 
-	ls->drop_locks_count = GDLM_DROP_COUNT;
-	ls->drop_locks_period = GDLM_DROP_PERIOD;
 	ls->fscb = cb;
 	ls->sdp = sdp;
 	ls->fsflags = flags;
···
 	INIT_LIST_HEAD(&ls->all_locks);
 	init_waitqueue_head(&ls->thread_wait);
 	init_waitqueue_head(&ls->wait_control);
-	ls->drop_time = jiffies;
 	ls->jid = -1;
 
 	strncpy(buf, table_name, 256);

fs/gfs2/locking/dlm/sysfs.c

···
 	return sprintf(buf, "%d\n", ls->recover_jid_status);
 }
 
-static ssize_t drop_count_show(struct gdlm_ls *ls, char *buf)
-{
-	return sprintf(buf, "%d\n", ls->drop_locks_count);
-}
-
-static ssize_t drop_count_store(struct gdlm_ls *ls, const char *buf, size_t len)
-{
-	ls->drop_locks_count = simple_strtol(buf, NULL, 0);
-	return len;
-}
-
 struct gdlm_attr {
 	struct attribute attr;
 	ssize_t (*show)(struct gdlm_ls *, char *);
···
 GDLM_ATTR(recover,        0644, recover_show,        recover_store);
 GDLM_ATTR(recover_done,   0444, recover_done_show,   NULL);
 GDLM_ATTR(recover_status, 0444, recover_status_show, NULL);
-GDLM_ATTR(drop_count,     0644, drop_count_show,     drop_count_store);
 
 static struct attribute *gdlm_attrs[] = {
 	&gdlm_attr_proto_name.attr,
···
 	&gdlm_attr_recover.attr,
 	&gdlm_attr_recover_done.attr,
 	&gdlm_attr_recover_status.attr,
-	&gdlm_attr_drop_count.attr,
 	NULL,
 };
 

fs/gfs2/locking/dlm/thread.c

···
 	return ret;
 }
 
-static inline int check_drop(struct gdlm_ls *ls)
-{
-	if (!ls->drop_locks_count)
-		return 0;
-
-	if (time_after(jiffies, ls->drop_time + ls->drop_locks_period * HZ)) {
-		ls->drop_time = jiffies;
-		if (ls->all_locks_count >= ls->drop_locks_count)
-			return 1;
-	}
-	return 0;
-}
-
 static int gdlm_thread(void *data)
 {
 	struct gdlm_ls *ls = (struct gdlm_ls *) data;
···
 			list_del_init(&lp->delay_list);
 			spin_unlock(&ls->async_lock);
 			gdlm_do_lock(lp);
-			spin_lock(&ls->async_lock);
-		}
-		/* Does this ever happen these days? I hope not anyway */
-		if (check_drop(ls)) {
-			spin_unlock(&ls->async_lock);
-			ls->fscb(ls->sdp, LM_CB_DROPLOCKS, NULL);
 			spin_lock(&ls->async_lock);
 		}
 		spin_unlock(&ls->async_lock);

fs/gfs2/ops_fstype.c

···
 fail_locking:
 	init_locking(sdp, &mount_gh, UNDO);
 fail_lm:
-	gfs2_gl_hash_clear(sdp, WAIT);
+	gfs2_gl_hash_clear(sdp);
 	gfs2_lm_unmount(sdp);
 	while (invalidate_inodes(sb))
 		yield();

fs/gfs2/ops_super.c

···
 	gfs2_clear_rgrpd(sdp);
 	gfs2_jindex_free(sdp);
 	/*  Take apart glock structures and buffer lists  */
-	gfs2_gl_hash_clear(sdp, WAIT);
+	gfs2_gl_hash_clear(sdp);
 	/*  Unmount the locking protocol  */
 	gfs2_lm_unmount(sdp);
 

fs/gfs2/sys.c

···
 	return len;
 }
 
-static ssize_t shrink_store(struct gfs2_sbd *sdp, const char *buf, size_t len)
-{
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
-
-	if (simple_strtol(buf, NULL, 0) != 1)
-		return -EINVAL;
-
-	gfs2_gl_hash_clear(sdp, NO_WAIT);
-	return len;
-}
-
 static ssize_t quota_sync_store(struct gfs2_sbd *sdp, const char *buf,
 				size_t len)
 {
···
 GFS2_ATTR(id,                  0444, id_show,       NULL);
 GFS2_ATTR(fsname,              0444, fsname_show,   NULL);
 GFS2_ATTR(freeze,              0644, freeze_show,   freeze_store);
-GFS2_ATTR(shrink,              0200, NULL,          shrink_store);
 GFS2_ATTR(withdraw,            0644, withdraw_show, withdraw_store);
 GFS2_ATTR(statfs_sync,         0200, NULL,          statfs_sync_store);
 GFS2_ATTR(quota_sync,          0200, NULL,          quota_sync_store);
···
 	&gfs2_attr_id.attr,
 	&gfs2_attr_fsname.attr,
 	&gfs2_attr_freeze.attr,
-	&gfs2_attr_shrink.attr,
 	&gfs2_attr_withdraw.attr,
 	&gfs2_attr_statfs_sync.attr,
 	&gfs2_attr_quota_sync.attr,

include/linux/lm_interface.h

···
  * LM_CB_NEED_RECOVERY
  * The given journal needs to be recovered.
  *
- * LM_CB_DROPLOCKS
- * Reduce the number of cached locks.
- *
  * LM_CB_ASYNC
  * The given lock has been granted.
  */
···
 #define LM_CB_NEED_D		258
 #define LM_CB_NEED_S		259
 #define LM_CB_NEED_RECOVERY	260
-#define LM_CB_DROPLOCKS		261
 #define LM_CB_ASYNC		262
 
 /*