path: root/fs/gfs2/quota.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

/*
 * Quota change tags are associated with each transaction that allocates or
 * deallocates space.  Those changes are accumulated locally to each node (in a
 * per-node file) and then are periodically synced to the quota file.  This
 * avoids the bottleneck of constantly touching the quota file, but introduces
 * fuzziness in the current usage value of IDs that are being used on different
 * nodes in the cluster simultaneously.  So, it is possible for a user on
 * multiple nodes to overrun their quota, but that overrun is controlable.
 * Since quota tags are part of transactions, there is no need to a quota check
 * program to be run on node crashes or anything like that.
 *
 * There are couple of knobs that let the administrator manage the quota
 * fuzziness.  "quota_quantum" sets the maximum time a quota change can be
 * sitting on one node before being synced to the quota file.  (The default is
 * 60 seconds.)  Another knob, "quota_scale" controls how quickly the frequency
 * of quota file syncs increases as the user moves closer to their limit.  The
 * more frequent the syncs, the more accurate the quota enforcement, but that
 * means that there is more contention between the nodes for the quota file.
 * The default value is one.  This sets the maximum theoretical quota overrun
 * (with infinite node with infinite bandwidth) to twice the user's limit.  (In
 * practice, the maximum overrun you see should be much less.)  A "quota_scale"
 * number greater than one makes quota syncs more frequent and reduces the
 * maximum overrun.  Numbers less than one (but greater than zero) make quota
 * syncs less frequent.
 *
 * GFS quotas also use per-ID Lock Value Blocks (LVBs) to cache the contents of
 * the quota file, so it is not being constantly read.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/sort.h>
#include <linux/fs.h>
#include <linux/bio.h>
#include <linux/gfs2_ondisk.h>
#include <linux/kthread.h>
#include <linux/freezer.h>

#include "gfs2.h"
#include "incore.h"
#include "bmap.h"
#include "glock.h"
#include "glops.h"
#include "log.h"
#include "meta_io.h"
#include "quota.h"
#include "rgrp.h"
#include "super.h"
#include "trans.h"
#include "inode.h"
#include "ops_address.h"
#include "util.h"

#define QUOTA_USER 1
#define QUOTA_GROUP 0

struct gfs2_quota_host {
	u64 qu_limit;
	u64 qu_warn;
	s64 qu_value;
	u32 qu_ll_next;
};

struct gfs2_quota_change_host {
	u64 qc_change;
	u32 qc_flags; /* GFS2_QCF_... */
	u32 qc_id;
};

static LIST_HEAD(qd_lru_list);
static atomic_t qd_lru_count = ATOMIC_INIT(0);
static DEFINE_SPINLOCK(qd_lru_lock);

int gfs2_shrink_qd_memory(int nr, gfp_t gfp_mask)
{
	struct gfs2_quota_data *qd;
	struct gfs2_sbd *sdp;

	if (nr == 0)
		goto out;

	if (!(gfp_mask & __GFP_FS))
		return -1;