Merge branch 'upstream' of git://ftp.linux-mips.org/pub/scm/upstream-linus

[pv_ops_mirror.git] / fs / gfs2 / super.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2006 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.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/crc32.h>
#include <linux/gfs2_ondisk.h>
#include <linux/bio.h>
#include <linux/lm_interface.h>

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

static const u32 gfs2_old_fs_formats[] = {
        0
};

static const u32 gfs2_old_multihost_formats[] = {
        0
};

/**
 * gfs2_tune_init - Fill a gfs2_tune structure with default values
 * @gt: tune
 *
 */

void gfs2_tune_init(struct gfs2_tune *gt)
{
        spin_lock_init(&gt->gt_spin);

        gt->gt_ilimit = 100;
        gt->gt_ilimit_tries = 3;
        gt->gt_ilimit_min = 1;
        gt->gt_demote_secs = 300;
        gt->gt_incore_log_blocks = 1024;
        gt->gt_log_flush_secs = 60;
        gt->gt_jindex_refresh_secs = 60;
        gt->gt_recoverd_secs = 60;
        gt->gt_logd_secs = 1;
        gt->gt_quotad_secs = 5;
        gt->gt_quota_simul_sync = 64;
        gt->gt_quota_warn_period = 10;
        gt->gt_quota_scale_num = 1;
        gt->gt_quota_scale_den = 1;
        gt->gt_quota_cache_secs = 300;
        gt->gt_quota_quantum = 60;
        gt->gt_atime_quantum = 3600;
        gt->gt_new_files_jdata = 0;
        gt->gt_new_files_directio = 0;
        gt->gt_max_readahead = 1 << 18;
        gt->gt_lockdump_size = 131072;
        gt->gt_stall_secs = 600;
        gt->gt_complain_secs = 10;
        gt->gt_reclaim_limit = 5000;
        gt->gt_statfs_quantum = 30;
        gt->gt_statfs_slow = 0;
}

/**
 * gfs2_check_sb - Check superblock
 * @sdp: the filesystem
 * @sb: The superblock
 * @silent: Don't print a message if the check fails
 *
 * Checks the version code of the FS is one that we understand how to
 * read and that the sizes of the various on-disk structures have not
 * changed.
 */

int gfs2_check_sb(struct gfs2_sbd *sdp, struct gfs2_sb_host *sb, int silent)
{
        unsigned int x;

        if (sb->sb_magic != GFS2_MAGIC ||
            sb->sb_type != GFS2_METATYPE_SB) {
                if (!silent)
                        printk(KERN_WARNING "GFS2: not a GFS2 filesystem\n");
                return -EINVAL;
        }

        /*  If format numbers match exactly, we're done.  */

        if (sb->sb_fs_format == GFS2_FORMAT_FS &&
            sb->sb_multihost_format == GFS2_FORMAT_MULTI)
                return 0;

        if (sb->sb_fs_format != GFS2_FORMAT_FS) {
                for (x = 0; gfs2_old_fs_formats[x]; x++)
                        if (gfs2_old_fs_formats[x] == sb->sb_fs_format)
                                break;

                if (!gfs2_old_fs_formats[x]) {
                        printk(KERN_WARNING
                               "GFS2: code version (%u, %u) is incompatible "
                               "with ondisk format (%u, %u)\n",
                               GFS2_FORMAT_FS, GFS2_FORMAT_MULTI,
                               sb->sb_fs_format, sb->sb_multihost_format);
                        printk(KERN_WARNING
                               "GFS2: I don't know how to upgrade this FS\n");
                        return -EINVAL;
                }
        }

        if (sb->sb_multihost_format != GFS2_FORMAT_MULTI) {
                for (x = 0; gfs2_old_multihost_formats[x]; x++)
                        if (gfs2_old_multihost_formats[x] ==
                            sb->sb_multihost_format)
                                break;

                if (!gfs2_old_multihost_formats[x]) {
                        printk(KERN_WARNING
                               "GFS2: code version (%u, %u) is incompatible "
                               "with ondisk format (%u, %u)\n",
                               GFS2_FORMAT_FS, GFS2_FORMAT_MULTI,
                               sb->sb_fs_format, sb->sb_multihost_format);
                        printk(KERN_WARNING
                               "GFS2: I don't know how to upgrade this FS\n");
                        return -EINVAL;
                }
        }

        if (!sdp->sd_args.ar_upgrade) {
                printk(KERN_WARNING
                       "GFS2: code version (%u, %u) is incompatible "
                       "with ondisk format (%u, %u)\n",
                       GFS2_FORMAT_FS, GFS2_FORMAT_MULTI,
                       sb->sb_fs_format, sb->sb_multihost_format);
                printk(KERN_INFO
                       "GFS2: Use the \"upgrade\" mount option to upgrade "
                       "the FS\n");
                printk(KERN_INFO "GFS2: See the manual for more details\n");
                return -EINVAL;
        }

        return 0;
}


static void end_bio_io_page(struct bio *bio, int error)
{
        struct page *page = bio->bi_private;

        if (!error)
                SetPageUptodate(page);
        else
                printk(KERN_WARNING "gfs2: error %d reading superblock\n", error);
        unlock_page(page);
}

static void gfs2_sb_in(struct gfs2_sb_host *sb, const void *buf)
{
        const struct gfs2_sb *str = buf;

        sb->sb_magic = be32_to_cpu(str->sb_header.mh_magic);
        sb->sb_type = be32_to_cpu(str->sb_header.mh_type);
        sb->sb_format = be32_to_cpu(str->sb_header.mh_format);
        sb->sb_fs_format = be32_to_cpu(str->sb_fs_format);
        sb->sb_multihost_format = be32_to_cpu(str->sb_multihost_format);
        sb->sb_bsize = be32_to_cpu(str->sb_bsize);
        sb->sb_bsize_shift = be32_to_cpu(str->sb_bsize_shift);
        sb->sb_master_dir.no_addr = be64_to_cpu(str->sb_master_dir.no_addr);
        sb->sb_master_dir.no_formal_ino = be64_to_cpu(str->sb_master_dir.no_formal_ino);
        sb->sb_root_dir.no_addr = be64_to_cpu(str->sb_root_dir.no_addr);
        sb->sb_root_dir.no_formal_ino = be64_to_cpu(str->sb_root_dir.no_formal_ino);

        memcpy(sb->sb_lockproto, str->sb_lockproto, GFS2_LOCKNAME_LEN);
        memcpy(sb->sb_locktable, str->sb_locktable, GFS2_LOCKNAME_LEN);
}

/**
 * gfs2_read_super - Read the gfs2 super block from disk
 * @sdp: The GFS2 super block
 * @sector: The location of the super block
 * @error: The error code to return
 *
 * This uses the bio functions to read the super block from disk
 * because we want to be 100% sure that we never read cached data.
 * A super block is read twice only during each GFS2 mount and is
 * never written to by the filesystem. The first time its read no
 * locks are held, and the only details which are looked at are those
 * relating to the locking protocol. Once locking is up and working,
 * the sb is read again under the lock to establish the location of
 * the master directory (contains pointers to journals etc) and the
 * root directory.
 *
 * Returns: 0 on success or error
 */

int gfs2_read_super(struct gfs2_sbd *sdp, sector_t sector)
{
        struct super_block *sb = sdp->sd_vfs;
        struct gfs2_sb *p;
        struct page *page;
        struct bio *bio;

        page = alloc_page(GFP_KERNEL);
        if (unlikely(!page))
                return -ENOBUFS;

        ClearPageUptodate(page);
        ClearPageDirty(page);
        lock_page(page);

        bio = bio_alloc(GFP_KERNEL, 1);
        if (unlikely(!bio)) {
                __free_page(page);
                return -ENOBUFS;
        }

        bio->bi_sector = sector * (sb->s_blocksize >> 9);
        bio->bi_bdev = sb->s_bdev;
        bio_add_page(bio, page, PAGE_SIZE, 0);

        bio->bi_end_io = end_bio_io_page;
        bio->bi_private = page;
        submit_bio(READ_SYNC | (1 << BIO_RW_META), bio);
        wait_on_page_locked(page);
        bio_put(bio);
        if (!PageUptodate(page)) {
                __free_page(page);
                return -EIO;
        }
        p = kmap(page);
        gfs2_sb_in(&sdp->sd_sb, p);
        kunmap(page);
        __free_page(page);
        return 0;
}

/**
 * gfs2_read_sb - Read super block
 * @sdp: The GFS2 superblock
 * @gl: the glock for the superblock (assumed to be held)
 * @silent: Don't print message if mount fails
 *
 */

int gfs2_read_sb(struct gfs2_sbd *sdp, struct gfs2_glock *gl, int silent)
{
        u32 hash_blocks, ind_blocks, leaf_blocks;
        u32 tmp_blocks;
        unsigned int x;
        int error;

        error = gfs2_read_super(sdp, GFS2_SB_ADDR >> sdp->sd_fsb2bb_shift);
        if (error) {
                if (!silent)
                        fs_err(sdp, "can't read superblock\n");
                return error;
        }

        error = gfs2_check_sb(sdp, &sdp->sd_sb, silent);
        if (error)
                return error;

        sdp->sd_fsb2bb_shift = sdp->sd_sb.sb_bsize_shift -
                               GFS2_BASIC_BLOCK_SHIFT;
        sdp->sd_fsb2bb = 1 << sdp->sd_fsb2bb_shift;
        sdp->sd_diptrs = (sdp->sd_sb.sb_bsize -
                          sizeof(struct gfs2_dinode)) / sizeof(u64);
        sdp->sd_inptrs = (sdp->sd_sb.sb_bsize -
                          sizeof(struct gfs2_meta_header)) / sizeof(u64);
        sdp->sd_jbsize = sdp->sd_sb.sb_bsize - sizeof(struct gfs2_meta_header);
        sdp->sd_hash_bsize = sdp->sd_sb.sb_bsize / 2;
        sdp->sd_hash_bsize_shift = sdp->sd_sb.sb_bsize_shift - 1;
        sdp->sd_hash_ptrs = sdp->sd_hash_bsize / sizeof(u64);
        sdp->sd_qc_per_block = (sdp->sd_sb.sb_bsize -
                                sizeof(struct gfs2_meta_header)) /
                                sizeof(struct gfs2_quota_change);

        /* Compute maximum reservation required to add a entry to a directory */

        hash_blocks = DIV_ROUND_UP(sizeof(u64) * (1 << GFS2_DIR_MAX_DEPTH),
                             sdp->sd_jbsize);

        ind_blocks = 0;
        for (tmp_blocks = hash_blocks; tmp_blocks > sdp->sd_diptrs;) {
                tmp_blocks = DIV_ROUND_UP(tmp_blocks, sdp->sd_inptrs);
                ind_blocks += tmp_blocks;
        }

        leaf_blocks = 2 + GFS2_DIR_MAX_DEPTH;

        sdp->sd_max_dirres = hash_blocks + ind_blocks + leaf_blocks;

        sdp->sd_heightsize[0] = sdp->sd_sb.sb_bsize -
                                sizeof(struct gfs2_dinode);
        sdp->sd_heightsize[1] = sdp->sd_sb.sb_bsize * sdp->sd_diptrs;
        for (x = 2;; x++) {
                u64 space, d;
                u32 m;

                space = sdp->sd_heightsize[x - 1] * sdp->sd_inptrs;
                d = space;
                m = do_div(d, sdp->sd_inptrs);

                if (d != sdp->sd_heightsize[x - 1] || m)
                        break;
                sdp->sd_heightsize[x] = space;
        }
        sdp->sd_max_height = x;
        gfs2_assert(sdp, sdp->sd_max_height <= GFS2_MAX_META_HEIGHT);

        sdp->sd_jheightsize[0] = sdp->sd_sb.sb_bsize -
                                 sizeof(struct gfs2_dinode);
        sdp->sd_jheightsize[1] = sdp->sd_jbsize * sdp->sd_diptrs;
        for (x = 2;; x++) {
                u64 space, d;
                u32 m;

                space = sdp->sd_jheightsize[x - 1] * sdp->sd_inptrs;
                d = space;
                m = do_div(d, sdp->sd_inptrs);

                if (d != sdp->sd_jheightsize[x - 1] || m)
                        break;
                sdp->sd_jheightsize[x] = space;
        }
        sdp->sd_max_jheight = x;
        gfs2_assert(sdp, sdp->sd_max_jheight <= GFS2_MAX_META_HEIGHT);

        return 0;
}

/**
 * gfs2_jindex_hold - Grab a lock on the jindex
 * @sdp: The GFS2 superblock
 * @ji_gh: the holder for the jindex glock
 *
 * This is very similar to the gfs2_rindex_hold() function, except that
 * in general we hold the jindex lock for longer periods of time and
 * we grab it far less frequently (in general) then the rgrp lock.
 *
 * Returns: errno
 */

int gfs2_jindex_hold(struct gfs2_sbd *sdp, struct gfs2_holder *ji_gh)
{
        struct gfs2_inode *dip = GFS2_I(sdp->sd_jindex);
        struct qstr name;
        char buf[20];
        struct gfs2_jdesc *jd;
        int error;

        name.name = buf;

        mutex_lock(&sdp->sd_jindex_mutex);

        for (;;) {
                error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, ji_gh);
                if (error)
                        break;

                name.len = sprintf(buf, "journal%u", sdp->sd_journals);
                name.hash = gfs2_disk_hash(name.name, name.len);

                error = gfs2_dir_check(sdp->sd_jindex, &name, NULL);
                if (error == -ENOENT) {
                        error = 0;
                        break;
                }

                gfs2_glock_dq_uninit(ji_gh);

                if (error)
                        break;

                error = -ENOMEM;
                jd = kzalloc(sizeof(struct gfs2_jdesc), GFP_KERNEL);
                if (!jd)
                        break;

                jd->jd_inode = gfs2_lookupi(sdp->sd_jindex, &name, 1, NULL);
                if (!jd->jd_inode || IS_ERR(jd->jd_inode)) {
                        if (!jd->jd_inode)
                                error = -ENOENT;
                        else
                                error = PTR_ERR(jd->jd_inode);
                        kfree(jd);
                        break;
                }

                spin_lock(&sdp->sd_jindex_spin);
                jd->jd_jid = sdp->sd_journals++;
                list_add_tail(&jd->jd_list, &sdp->sd_jindex_list);
                spin_unlock(&sdp->sd_jindex_spin);
        }

        mutex_unlock(&sdp->sd_jindex_mutex);

        return error;
}

/**
 * gfs2_jindex_free - Clear all the journal index information
 * @sdp: The GFS2 superblock
 *
 */

void gfs2_jindex_free(struct gfs2_sbd *sdp)
{
        struct list_head list;
        struct gfs2_jdesc *jd;

        spin_lock(&sdp->sd_jindex_spin);
        list_add(&list, &sdp->sd_jindex_list);
        list_del_init(&sdp->sd_jindex_list);
        sdp->sd_journals = 0;
        spin_unlock(&sdp->sd_jindex_spin);

        while (!list_empty(&list)) {
                jd = list_entry(list.next, struct gfs2_jdesc, jd_list);
                list_del(&jd->jd_list);
                iput(jd->jd_inode);
                kfree(jd);
        }
}

static struct gfs2_jdesc *jdesc_find_i(struct list_head *head, unsigned int jid)
{
        struct gfs2_jdesc *jd;
        int found = 0;

        list_for_each_entry(jd, head, jd_list) {
                if (jd->jd_jid == jid) {
                        found = 1;
                        break;
                }
        }

        if (!found)
                jd = NULL;

        return jd;
}

struct gfs2_jdesc *gfs2_jdesc_find(struct gfs2_sbd *sdp, unsigned int jid)
{
        struct gfs2_jdesc *jd;

        spin_lock(&sdp->sd_jindex_spin);
        jd = jdesc_find_i(&sdp->sd_jindex_list, jid);
        spin_unlock(&sdp->sd_jindex_spin);

        return jd;
}

void gfs2_jdesc_make_dirty(struct gfs2_sbd *sdp, unsigned int jid)
{
        struct gfs2_jdesc *jd;

        spin_lock(&sdp->sd_jindex_spin);
        jd = jdesc_find_i(&sdp->sd_jindex_list, jid);
        if (jd)
                jd->jd_dirty = 1;
        spin_unlock(&sdp->sd_jindex_spin);
}

struct gfs2_jdesc *gfs2_jdesc_find_dirty(struct gfs2_sbd *sdp)
{
        struct gfs2_jdesc *jd;
        int found = 0;

        spin_lock(&sdp->sd_jindex_spin);

        list_for_each_entry(jd, &sdp->sd_jindex_list, jd_list) {
                if (jd->jd_dirty) {
                        jd->jd_dirty = 0;
                        found = 1;
                        break;
                }
        }
        spin_unlock(&sdp->sd_jindex_spin);

        if (!found)
                jd = NULL;

        return jd;
}

int gfs2_jdesc_check(struct gfs2_jdesc *jd)
{
        struct gfs2_inode *ip = GFS2_I(jd->jd_inode);
        struct gfs2_sbd *sdp = GFS2_SB(jd->jd_inode);
        int ar;
        int error;

        if (ip->i_di.di_size < (8 << 20) || ip->i_di.di_size > (1 << 30) ||
            (ip->i_di.di_size & (sdp->sd_sb.sb_bsize - 1))) {
                gfs2_consist_inode(ip);
                return -EIO;
        }
        jd->jd_blocks = ip->i_di.di_size >> sdp->sd_sb.sb_bsize_shift;

        error = gfs2_write_alloc_required(ip, 0, ip->i_di.di_size, &ar);
        if (!error && ar) {
                gfs2_consist_inode(ip);
                error = -EIO;
        }

        return error;
}

/**
 * gfs2_make_fs_rw - Turn a Read-Only FS into a Read-Write one
 * @sdp: the filesystem
 *
 * Returns: errno
 */

int gfs2_make_fs_rw(struct gfs2_sbd *sdp)
{
        struct gfs2_inode *ip = GFS2_I(sdp->sd_jdesc->jd_inode);
        struct gfs2_glock *j_gl = ip->i_gl;
        struct gfs2_holder t_gh;
        struct gfs2_log_header_host head;
        int error;

        error = gfs2_glock_nq_init(sdp->sd_trans_gl, LM_ST_SHARED, 0, &t_gh);
        if (error)
                return error;

        gfs2_meta_cache_flush(ip);
        j_gl->gl_ops->go_inval(j_gl, DIO_METADATA);

        error = gfs2_find_jhead(sdp->sd_jdesc, &head);
        if (error)
                goto fail;

        if (!(head.lh_flags & GFS2_LOG_HEAD_UNMOUNT)) {
                gfs2_consist(sdp);
                error = -EIO;
                goto fail;
        }

        /*  Initialize some head of the log stuff  */
        sdp->sd_log_sequence = head.lh_sequence + 1;
        gfs2_log_pointers_init(sdp, head.lh_blkno);

        error = gfs2_quota_init(sdp);
        if (error)
                goto fail;

        set_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);

        gfs2_glock_dq_uninit(&t_gh);

        return 0;

fail:
        t_gh.gh_flags |= GL_NOCACHE;
        gfs2_glock_dq_uninit(&t_gh);

        return error;
}

/**
 * gfs2_make_fs_ro - Turn a Read-Write FS into a Read-Only one
 * @sdp: the filesystem
 *
 * Returns: errno
 */

int gfs2_make_fs_ro(struct gfs2_sbd *sdp)
{
        struct gfs2_holder t_gh;
        int error;

        gfs2_quota_sync(sdp);
        gfs2_statfs_sync(sdp);

        error = gfs2_glock_nq_init(sdp->sd_trans_gl, LM_ST_SHARED, GL_NOCACHE,
                                   &t_gh);
        if (error && !test_bit(SDF_SHUTDOWN, &sdp->sd_flags))
                return error;

        gfs2_meta_syncfs(sdp);
        gfs2_log_shutdown(sdp);

        clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);

        if (t_gh.gh_gl)
                gfs2_glock_dq_uninit(&t_gh);

        gfs2_quota_cleanup(sdp);

        return error;
}

static void gfs2_statfs_change_in(struct gfs2_statfs_change_host *sc, const void *buf)
{
        const struct gfs2_statfs_change *str = buf;

        sc->sc_total = be64_to_cpu(str->sc_total);
        sc->sc_free = be64_to_cpu(str->sc_free);
        sc->sc_dinodes = be64_to_cpu(str->sc_dinodes);
}

static void gfs2_statfs_change_out(const struct gfs2_statfs_change_host *sc, void *buf)
{
        struct gfs2_statfs_change *str = buf;

        str->sc_total = cpu_to_be64(sc->sc_total);
        str->sc_free = cpu_to_be64(sc->sc_free);
        str->sc_dinodes = cpu_to_be64(sc->sc_dinodes);
}

int gfs2_statfs_init(struct gfs2_sbd *sdp)
{
        struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
        struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
        struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
        struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
        struct buffer_head *m_bh, *l_bh;
        struct gfs2_holder gh;
        int error;

        error = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE, GL_NOCACHE,
                                   &gh);
        if (error)
                return error;

        error = gfs2_meta_inode_buffer(m_ip, &m_bh);
        if (error)
                goto out;

        if (sdp->sd_args.ar_spectator) {
                spin_lock(&sdp->sd_statfs_spin);
                gfs2_statfs_change_in(m_sc, m_bh->b_data +
                                      sizeof(struct gfs2_dinode));
                spin_unlock(&sdp->sd_statfs_spin);
        } else {
                error = gfs2_meta_inode_buffer(l_ip, &l_bh);
                if (error)
                        goto out_m_bh;

                spin_lock(&sdp->sd_statfs_spin);
                gfs2_statfs_change_in(m_sc, m_bh->b_data +
                                      sizeof(struct gfs2_dinode));
                gfs2_statfs_change_in(l_sc, l_bh->b_data +
                                      sizeof(struct gfs2_dinode));
                spin_unlock(&sdp->sd_statfs_spin);

                brelse(l_bh);
        }

out_m_bh:
        brelse(m_bh);
out:
        gfs2_glock_dq_uninit(&gh);
        return 0;
}

void gfs2_statfs_change(struct gfs2_sbd *sdp, s64 total, s64 free,
                        s64 dinodes)
{
        struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
        struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
        struct buffer_head *l_bh;
        int error;

        error = gfs2_meta_inode_buffer(l_ip, &l_bh);
        if (error)
                return;

        mutex_lock(&sdp->sd_statfs_mutex);
        gfs2_trans_add_bh(l_ip->i_gl, l_bh, 1);
        mutex_unlock(&sdp->sd_statfs_mutex);

        spin_lock(&sdp->sd_statfs_spin);
        l_sc->sc_total += total;
        l_sc->sc_free += free;
        l_sc->sc_dinodes += dinodes;
        gfs2_statfs_change_out(l_sc, l_bh->b_data + sizeof(struct gfs2_dinode));
        spin_unlock(&sdp->sd_statfs_spin);

        brelse(l_bh);
}

int gfs2_statfs_sync(struct gfs2_sbd *sdp)
{
        struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
        struct gfs2_inode *l_ip = GFS2_I(sdp->sd_sc_inode);
        struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
        struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
        struct gfs2_holder gh;
        struct buffer_head *m_bh, *l_bh;
        int error;

        error = gfs2_glock_nq_init(m_ip->i_gl, LM_ST_EXCLUSIVE, GL_NOCACHE,
                                   &gh);
        if (error)
                return error;

        error = gfs2_meta_inode_buffer(m_ip, &m_bh);
        if (error)
                goto out;

        spin_lock(&sdp->sd_statfs_spin);
        gfs2_statfs_change_in(m_sc, m_bh->b_data +
                              sizeof(struct gfs2_dinode));
        if (!l_sc->sc_total && !l_sc->sc_free && !l_sc->sc_dinodes) {
                spin_unlock(&sdp->sd_statfs_spin);
                goto out_bh;
        }
        spin_unlock(&sdp->sd_statfs_spin);

        error = gfs2_meta_inode_buffer(l_ip, &l_bh);
        if (error)
                goto out_bh;

        error = gfs2_trans_begin(sdp, 2 * RES_DINODE, 0);
        if (error)
                goto out_bh2;

        mutex_lock(&sdp->sd_statfs_mutex);
        gfs2_trans_add_bh(l_ip->i_gl, l_bh, 1);
        mutex_unlock(&sdp->sd_statfs_mutex);

        spin_lock(&sdp->sd_statfs_spin);
        m_sc->sc_total += l_sc->sc_total;
        m_sc->sc_free += l_sc->sc_free;
        m_sc->sc_dinodes += l_sc->sc_dinodes;
        memset(l_sc, 0, sizeof(struct gfs2_statfs_change));
        memset(l_bh->b_data + sizeof(struct gfs2_dinode),
               0, sizeof(struct gfs2_statfs_change));
        spin_unlock(&sdp->sd_statfs_spin);

        gfs2_trans_add_bh(m_ip->i_gl, m_bh, 1);
        gfs2_statfs_change_out(m_sc, m_bh->b_data + sizeof(struct gfs2_dinode));

        gfs2_trans_end(sdp);

out_bh2:
        brelse(l_bh);
out_bh:
        brelse(m_bh);
out:
        gfs2_glock_dq_uninit(&gh);
        return error;
}

/**
 * gfs2_statfs_i - Do a statfs
 * @sdp: the filesystem
 * @sg: the sg structure
 *
 * Returns: errno
 */

int gfs2_statfs_i(struct gfs2_sbd *sdp, struct gfs2_statfs_change_host *sc)
{
        struct gfs2_statfs_change_host *m_sc = &sdp->sd_statfs_master;
        struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;

        spin_lock(&sdp->sd_statfs_spin);

        *sc = *m_sc;
        sc->sc_total += l_sc->sc_total;
        sc->sc_free += l_sc->sc_free;
        sc->sc_dinodes += l_sc->sc_dinodes;

        spin_unlock(&sdp->sd_statfs_spin);

        if (sc->sc_free < 0)
                sc->sc_free = 0;
        if (sc->sc_free > sc->sc_total)
                sc->sc_free = sc->sc_total;
        if (sc->sc_dinodes < 0)
                sc->sc_dinodes = 0;

        return 0;
}

/**
 * statfs_fill - fill in the sg for a given RG
 * @rgd: the RG
 * @sc: the sc structure
 *
 * Returns: 0 on success, -ESTALE if the LVB is invalid
 */

static int statfs_slow_fill(struct gfs2_rgrpd *rgd,
                            struct gfs2_statfs_change_host *sc)
{
        gfs2_rgrp_verify(rgd);
        sc->sc_total += rgd->rd_data;
        sc->sc_free += rgd->rd_rg.rg_free;
        sc->sc_dinodes += rgd->rd_rg.rg_dinodes;
        return 0;
}

/**
 * gfs2_statfs_slow - Stat a filesystem using asynchronous locking
 * @sdp: the filesystem
 * @sc: the sc info that will be returned
 *
 * Any error (other than a signal) will cause this routine to fall back
 * to the synchronous version.
 *
 * FIXME: This really shouldn't busy wait like this.
 *
 * Returns: errno
 */

int gfs2_statfs_slow(struct gfs2_sbd *sdp, struct gfs2_statfs_change_host *sc)
{
        struct gfs2_holder ri_gh;
        struct gfs2_rgrpd *rgd_next;
        struct gfs2_holder *gha, *gh;
        unsigned int slots = 64;
        unsigned int x;
        int done;
        int error = 0, err;

        memset(sc, 0, sizeof(struct gfs2_statfs_change_host));
        gha = kcalloc(slots, sizeof(struct gfs2_holder), GFP_KERNEL);
        if (!gha)
                return -ENOMEM;

        error = gfs2_rindex_hold(sdp, &ri_gh);
        if (error)
                goto out;

        rgd_next = gfs2_rgrpd_get_first(sdp);

        for (;;) {
                done = 1;

                for (x = 0; x < slots; x++) {
                        gh = gha + x;

                        if (gh->gh_gl && gfs2_glock_poll(gh)) {
                                err = gfs2_glock_wait(gh);
                                if (err) {
                                        gfs2_holder_uninit(gh);
                                        error = err;
                                } else {
                                        if (!error)
                                                error = statfs_slow_fill(
                                                        gh->gh_gl->gl_object, sc);
                                        gfs2_glock_dq_uninit(gh);
                                }
                        }

                        if (gh->gh_gl)
                                done = 0;
                        else if (rgd_next && !error) {
                                error = gfs2_glock_nq_init(rgd_next->rd_gl,
                                                           LM_ST_SHARED,
                                                           GL_ASYNC,
                                                           gh);
                                rgd_next = gfs2_rgrpd_get_next(rgd_next);
                                done = 0;
                        }

                        if (signal_pending(current))
                                error = -ERESTARTSYS;
                }

                if (done)
                        break;

                yield();
        }

        gfs2_glock_dq_uninit(&ri_gh);

out:
        kfree(gha);
        return error;
}

struct lfcc {
        struct list_head list;
        struct gfs2_holder gh;
};

/**
 * gfs2_lock_fs_check_clean - Stop all writes to the FS and check that all
 *                            journals are clean
 * @sdp: the file system
 * @state: the state to put the transaction lock into
 * @t_gh: the hold on the transaction lock
 *
 * Returns: errno
 */

static int gfs2_lock_fs_check_clean(struct gfs2_sbd *sdp,
                                    struct gfs2_holder *t_gh)
{
        struct gfs2_inode *ip;
        struct gfs2_holder ji_gh;
        struct gfs2_jdesc *jd;
        struct lfcc *lfcc;
        LIST_HEAD(list);
        struct gfs2_log_header_host lh;
        int error;

        error = gfs2_jindex_hold(sdp, &ji_gh);
        if (error)
                return error;

        list_for_each_entry(jd, &sdp->sd_jindex_list, jd_list) {
                lfcc = kmalloc(sizeof(struct lfcc), GFP_KERNEL);
                if (!lfcc) {
                        error = -ENOMEM;
                        goto out;
                }
                ip = GFS2_I(jd->jd_inode);
                error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &lfcc->gh);
                if (error) {
                        kfree(lfcc);
                        goto out;
                }
                list_add(&lfcc->list, &list);
        }

        error = gfs2_glock_nq_init(sdp->sd_trans_gl, LM_ST_DEFERRED,
                               LM_FLAG_PRIORITY | GL_NOCACHE,
                               t_gh);

        list_for_each_entry(jd, &sdp->sd_jindex_list, jd_list) {
                error = gfs2_jdesc_check(jd);
                if (error)
                        break;
                error = gfs2_find_jhead(jd, &lh);
                if (error)
                        break;
                if (!(lh.lh_flags & GFS2_LOG_HEAD_UNMOUNT)) {
                        error = -EBUSY;
                        break;
                }
        }

        if (error)
                gfs2_glock_dq_uninit(t_gh);

out:
        while (!list_empty(&list)) {
                lfcc = list_entry(list.next, struct lfcc, list);
                list_del(&lfcc->list);
                gfs2_glock_dq_uninit(&lfcc->gh);
                kfree(lfcc);
        }
        gfs2_glock_dq_uninit(&ji_gh);
        return error;
}

/**
 * gfs2_freeze_fs - freezes the file system
 * @sdp: the file system
 *
 * This function flushes data and meta data for all machines by
 * aquiring the transaction log exclusively.  All journals are
 * ensured to be in a clean state as well.
 *
 * Returns: errno
 */

int gfs2_freeze_fs(struct gfs2_sbd *sdp)
{
        int error = 0;

        mutex_lock(&sdp->sd_freeze_lock);

        if (!sdp->sd_freeze_count++) {
                error = gfs2_lock_fs_check_clean(sdp, &sdp->sd_freeze_gh);
                if (error)
                        sdp->sd_freeze_count--;
        }

        mutex_unlock(&sdp->sd_freeze_lock);

        return error;
}

/**
 * gfs2_unfreeze_fs - unfreezes the file system
 * @sdp: the file system
 *
 * This function allows the file system to proceed by unlocking
 * the exclusively held transaction lock.  Other GFS2 nodes are
 * now free to acquire the lock shared and go on with their lives.
 *
 */

void gfs2_unfreeze_fs(struct gfs2_sbd *sdp)
{
        mutex_lock(&sdp->sd_freeze_lock);

        if (sdp->sd_freeze_count && !--sdp->sd_freeze_count)
                gfs2_glock_dq_uninit(&sdp->sd_freeze_gh);

        mutex_unlock(&sdp->sd_freeze_lock);
}