nilfs2: simplify life cycle management of nilfs object

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / nilfs2 / the_nilfs.c

/*
 * the_nilfs.c - the_nilfs shared structure.
 *
 * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Written by Ryusuke Konishi <ryusuke@osrg.net>
 *
 */

#include <linux/buffer_head.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/crc32.h>
#include "nilfs.h"
#include "segment.h"
#include "alloc.h"
#include "cpfile.h"
#include "sufile.h"
#include "dat.h"
#include "segbuf.h"


static int nilfs_valid_sb(struct nilfs_super_block *sbp);

void nilfs_set_last_segment(struct the_nilfs *nilfs,
                            sector_t start_blocknr, u64 seq, __u64 cno)
{
        spin_lock(&nilfs->ns_last_segment_lock);
        nilfs->ns_last_pseg = start_blocknr;
        nilfs->ns_last_seq = seq;
        nilfs->ns_last_cno = cno;

        if (!nilfs_sb_dirty(nilfs)) {
                if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
                        goto stay_cursor;

                set_nilfs_sb_dirty(nilfs);
        }
        nilfs->ns_prev_seq = nilfs->ns_last_seq;

 stay_cursor:
        spin_unlock(&nilfs->ns_last_segment_lock);
}

/**
 * alloc_nilfs - allocate a nilfs object
 * @bdev: block device to which the_nilfs is related
 *
 * Return Value: On success, pointer to the_nilfs is returned.
 * On error, NULL is returned.
 */
struct the_nilfs *alloc_nilfs(struct block_device *bdev)
{
        struct the_nilfs *nilfs;

        nilfs = kzalloc(sizeof(*nilfs), GFP_KERNEL);
        if (!nilfs)
                return NULL;

        nilfs->ns_bdev = bdev;
        atomic_set(&nilfs->ns_ndirtyblks, 0);
        init_rwsem(&nilfs->ns_sem);
        init_rwsem(&nilfs->ns_writer_sem);
        INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
        spin_lock_init(&nilfs->ns_last_segment_lock);
        nilfs->ns_cptree = RB_ROOT;
        spin_lock_init(&nilfs->ns_cptree_lock);
        init_rwsem(&nilfs->ns_segctor_sem);

        return nilfs;
}

/**
 * destroy_nilfs - destroy nilfs object
 * @nilfs: nilfs object to be released
 */
void destroy_nilfs(struct the_nilfs *nilfs)
{
        might_sleep();
        if (nilfs_loaded(nilfs)) {
                nilfs_mdt_destroy(nilfs->ns_sufile);
                nilfs_mdt_destroy(nilfs->ns_cpfile);
                nilfs_mdt_destroy(nilfs->ns_dat);
                nilfs_mdt_destroy(nilfs->ns_gc_dat);
        }
        if (nilfs_init(nilfs)) {
                brelse(nilfs->ns_sbh[0]);
                brelse(nilfs->ns_sbh[1]);
        }
        kfree(nilfs);
}

static int nilfs_load_super_root(struct the_nilfs *nilfs, sector_t sr_block)
{
        struct buffer_head *bh_sr;
        struct nilfs_super_root *raw_sr;
        struct nilfs_super_block **sbp = nilfs->ns_sbp;
        unsigned dat_entry_size, segment_usage_size, checkpoint_size;
        unsigned inode_size;
        int err;

        err = nilfs_read_super_root_block(nilfs, sr_block, &bh_sr, 1);
        if (unlikely(err))
                return err;

        down_read(&nilfs->ns_sem);
        dat_entry_size = le16_to_cpu(sbp[0]->s_dat_entry_size);
        checkpoint_size = le16_to_cpu(sbp[0]->s_checkpoint_size);
        segment_usage_size = le16_to_cpu(sbp[0]->s_segment_usage_size);
        up_read(&nilfs->ns_sem);

        inode_size = nilfs->ns_inode_size;

        err = -ENOMEM;
        nilfs->ns_dat = nilfs_dat_new(nilfs, dat_entry_size);
        if (unlikely(!nilfs->ns_dat))
                goto failed;

        nilfs->ns_gc_dat = nilfs_dat_new(nilfs, dat_entry_size);
        if (unlikely(!nilfs->ns_gc_dat))
                goto failed_dat;

        nilfs->ns_cpfile = nilfs_cpfile_new(nilfs, checkpoint_size);
        if (unlikely(!nilfs->ns_cpfile))
                goto failed_gc_dat;

        nilfs->ns_sufile = nilfs_sufile_new(nilfs, segment_usage_size);
        if (unlikely(!nilfs->ns_sufile))
                goto failed_cpfile;

        nilfs_mdt_set_shadow(nilfs->ns_dat, nilfs->ns_gc_dat);

        err = nilfs_dat_read(nilfs->ns_dat, (void *)bh_sr->b_data +
                             NILFS_SR_DAT_OFFSET(inode_size));
        if (unlikely(err))
                goto failed_sufile;

        err = nilfs_cpfile_read(nilfs->ns_cpfile, (void *)bh_sr->b_data +
                                NILFS_SR_CPFILE_OFFSET(inode_size));
        if (unlikely(err))
                goto failed_sufile;

        err = nilfs_sufile_read(nilfs->ns_sufile, (void *)bh_sr->b_data +
                                NILFS_SR_SUFILE_OFFSET(inode_size));
        if (unlikely(err))
                goto failed_sufile;

        raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
        nilfs->ns_nongc_ctime = le64_to_cpu(raw_sr->sr_nongc_ctime);

 failed:
        brelse(bh_sr);
        return err;

 failed_sufile:
        nilfs_mdt_destroy(nilfs->ns_sufile);

 failed_cpfile:
        nilfs_mdt_destroy(nilfs->ns_cpfile);

 failed_gc_dat:
        nilfs_mdt_destroy(nilfs->ns_gc_dat);

 failed_dat:
        nilfs_mdt_destroy(nilfs->ns_dat);
        goto failed;
}

static void nilfs_init_recovery_info(struct nilfs_recovery_info *ri)
{
        memset(ri, 0, sizeof(*ri));
        INIT_LIST_HEAD(&ri->ri_used_segments);
}

static void nilfs_clear_recovery_info(struct nilfs_recovery_info *ri)
{
        nilfs_dispose_segment_list(&ri->ri_used_segments);
}

/**
 * nilfs_store_log_cursor - load log cursor from a super block
 * @nilfs: nilfs object
 * @sbp: buffer storing super block to be read
 *
 * nilfs_store_log_cursor() reads the last position of the log
 * containing a super root from a given super block, and initializes
 * relevant information on the nilfs object preparatory for log
 * scanning and recovery.
 */
static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
                                  struct nilfs_super_block *sbp)
{
        int ret = 0;

        nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
        nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
        nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);

        nilfs->ns_prev_seq = nilfs->ns_last_seq;
        nilfs->ns_seg_seq = nilfs->ns_last_seq;
        nilfs->ns_segnum =
                nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
        nilfs->ns_cno = nilfs->ns_last_cno + 1;
        if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
                printk(KERN_ERR "NILFS invalid last segment number.\n");
                ret = -EINVAL;
        }
        return ret;
}

/**
 * load_nilfs - load and recover the nilfs
 * @nilfs: the_nilfs structure to be released
 * @sbi: nilfs_sb_info used to recover past segment
 *
 * load_nilfs() searches and load the latest super root,
 * attaches the last segment, and does recovery if needed.
 * The caller must call this exclusively for simultaneous mounts.
 */
int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
{
        struct nilfs_recovery_info ri;
        unsigned int s_flags = sbi->s_super->s_flags;
        int really_read_only = bdev_read_only(nilfs->ns_bdev);
        int valid_fs = nilfs_valid_fs(nilfs);
        int err;

        if (!valid_fs) {
                printk(KERN_WARNING "NILFS warning: mounting unchecked fs\n");
                if (s_flags & MS_RDONLY) {
                        printk(KERN_INFO "NILFS: INFO: recovery "
                               "required for readonly filesystem.\n");
                        printk(KERN_INFO "NILFS: write access will "
                               "be enabled during recovery.\n");
                }
        }

        nilfs_init_recovery_info(&ri);

        err = nilfs_search_super_root(nilfs, &ri);
        if (unlikely(err)) {
                struct nilfs_super_block **sbp = nilfs->ns_sbp;
                int blocksize;

                if (err != -EINVAL)
                        goto scan_error;

                if (!nilfs_valid_sb(sbp[1])) {
                        printk(KERN_WARNING
                               "NILFS warning: unable to fall back to spare"
                               "super block\n");
                        goto scan_error;
                }
                printk(KERN_INFO
                       "NILFS: try rollback from an earlier position\n");

                /*
                 * restore super block with its spare and reconfigure
                 * relevant states of the nilfs object.
                 */
                memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
                nilfs->ns_crc_seed = le32_to_cpu(sbp[0]->s_crc_seed);
                nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);

                /* verify consistency between two super blocks */
                blocksize = BLOCK_SIZE << le32_to_cpu(sbp[0]->s_log_block_size);
                if (blocksize != nilfs->ns_blocksize) {
                        printk(KERN_WARNING
                               "NILFS warning: blocksize differs between "
                               "two super blocks (%d != %d)\n",
                               blocksize, nilfs->ns_blocksize);
                        goto scan_error;
                }

                err = nilfs_store_log_cursor(nilfs, sbp[0]);
                if (err)
                        goto scan_error;

                /* drop clean flag to allow roll-forward and recovery */
                nilfs->ns_mount_state &= ~NILFS_VALID_FS;
                valid_fs = 0;

                err = nilfs_search_super_root(nilfs, &ri);
                if (err)
                        goto scan_error;
        }

        err = nilfs_load_super_root(nilfs, ri.ri_super_root);
        if (unlikely(err)) {
                printk(KERN_ERR "NILFS: error loading super root.\n");
                goto failed;
        }

        if (valid_fs)
                goto skip_recovery;

        if (s_flags & MS_RDONLY) {
                __u64 features;

                if (nilfs_test_opt(sbi, NORECOVERY)) {
                        printk(KERN_INFO "NILFS: norecovery option specified. "
                               "skipping roll-forward recovery\n");
                        goto skip_recovery;
                }
                features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
                        ~NILFS_FEATURE_COMPAT_RO_SUPP;
                if (features) {
                        printk(KERN_ERR "NILFS: couldn't proceed with "
                               "recovery because of unsupported optional "
                               "features (%llx)\n",
                               (unsigned long long)features);
                        err = -EROFS;
                        goto failed_unload;
                }
                if (really_read_only) {
                        printk(KERN_ERR "NILFS: write access "
                               "unavailable, cannot proceed.\n");
                        err = -EROFS;
                        goto failed_unload;
                }
                sbi->s_super->s_flags &= ~MS_RDONLY;
        } else if (nilfs_test_opt(sbi, NORECOVERY)) {
                printk(KERN_ERR "NILFS: recovery cancelled because norecovery "
                       "option was specified for a read/write mount\n");
                err = -EINVAL;
                goto failed_unload;
        }

        err = nilfs_salvage_orphan_logs(nilfs, sbi, &ri);
        if (err)
                goto failed_unload;

        down_write(&nilfs->ns_sem);
        nilfs->ns_mount_state |= NILFS_VALID_FS; /* set "clean" flag */
        err = nilfs_cleanup_super(sbi);
        up_write(&nilfs->ns_sem);

        if (err) {
                printk(KERN_ERR "NILFS: failed to update super block. "
                       "recovery unfinished.\n");
                goto failed_unload;
        }
        printk(KERN_INFO "NILFS: recovery complete.\n");

 skip_recovery:
        set_nilfs_loaded(nilfs);
        nilfs_clear_recovery_info(&ri);
        sbi->s_super->s_flags = s_flags;
        return 0;

 scan_error:
        printk(KERN_ERR "NILFS: error searching super root.\n");
        goto failed;

 failed_unload:
        nilfs_mdt_destroy(nilfs->ns_cpfile);
        nilfs_mdt_destroy(nilfs->ns_sufile);
        nilfs_mdt_destroy(nilfs->ns_dat);
        nilfs_mdt_destroy(nilfs->ns_gc_dat);

 failed:
        nilfs_clear_recovery_info(&ri);
        sbi->s_super->s_flags = s_flags;
        return err;
}

static unsigned long long nilfs_max_size(unsigned int blkbits)
{
        unsigned int max_bits;
        unsigned long long res = MAX_LFS_FILESIZE; /* page cache limit */

        max_bits = blkbits + NILFS_BMAP_KEY_BIT; /* bmap size limit */
        if (max_bits < 64)
                res = min_t(unsigned long long, res, (1ULL << max_bits) - 1);
        return res;
}

static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
                                   struct nilfs_super_block *sbp)
{
        if (le32_to_cpu(sbp->s_rev_level) < NILFS_MIN_SUPP_REV) {
                printk(KERN_ERR "NILFS: unsupported revision "
                       "(superblock rev.=%d.%d, current rev.=%d.%d). "
                       "Please check the version of mkfs.nilfs.\n",
                       le32_to_cpu(sbp->s_rev_level),
                       le16_to_cpu(sbp->s_minor_rev_level),
                       NILFS_CURRENT_REV, NILFS_MINOR_REV);
                return -EINVAL;
        }
        nilfs->ns_sbsize = le16_to_cpu(sbp->s_bytes);
        if (nilfs->ns_sbsize > BLOCK_SIZE)
                return -EINVAL;

        nilfs->ns_inode_size = le16_to_cpu(sbp->s_inode_size);
        nilfs->ns_first_ino = le32_to_cpu(sbp->s_first_ino);

        nilfs->ns_blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
        if (nilfs->ns_blocks_per_segment < NILFS_SEG_MIN_BLOCKS) {
                printk(KERN_ERR "NILFS: too short segment.\n");
                return -EINVAL;
        }

        nilfs->ns_first_data_block = le64_to_cpu(sbp->s_first_data_block);
        nilfs->ns_nsegments = le64_to_cpu(sbp->s_nsegments);
        nilfs->ns_r_segments_percentage =
                le32_to_cpu(sbp->s_r_segments_percentage);
        nilfs->ns_nrsvsegs =
                max_t(unsigned long, NILFS_MIN_NRSVSEGS,
                      DIV_ROUND_UP(nilfs->ns_nsegments *
                                   nilfs->ns_r_segments_percentage, 100));
        nilfs->ns_crc_seed = le32_to_cpu(sbp->s_crc_seed);
        return 0;
}

static int nilfs_valid_sb(struct nilfs_super_block *sbp)
{
        static unsigned char sum[4];
        const int sumoff = offsetof(struct nilfs_super_block, s_sum);
        size_t bytes;
        u32 crc;

        if (!sbp || le16_to_cpu(sbp->s_magic) != NILFS_SUPER_MAGIC)
                return 0;
        bytes = le16_to_cpu(sbp->s_bytes);
        if (bytes > BLOCK_SIZE)
                return 0;
        crc = crc32_le(le32_to_cpu(sbp->s_crc_seed), (unsigned char *)sbp,
                       sumoff);
        crc = crc32_le(crc, sum, 4);
        crc = crc32_le(crc, (unsigned char *)sbp + sumoff + 4,
                       bytes - sumoff - 4);
        return crc == le32_to_cpu(sbp->s_sum);
}

static int nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
{
        return offset < ((le64_to_cpu(sbp->s_nsegments) *
                          le32_to_cpu(sbp->s_blocks_per_segment)) <<
                         (le32_to_cpu(sbp->s_log_block_size) + 10));
}

static void nilfs_release_super_block(struct the_nilfs *nilfs)
{
        int i;

        for (i = 0; i < 2; i++) {
                if (nilfs->ns_sbp[i]) {
                        brelse(nilfs->ns_sbh[i]);
                        nilfs->ns_sbh[i] = NULL;
                        nilfs->ns_sbp[i] = NULL;
                }
        }
}

void nilfs_fall_back_super_block(struct the_nilfs *nilfs)
{
        brelse(nilfs->ns_sbh[0]);
        nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
        nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
        nilfs->ns_sbh[1] = NULL;
        nilfs->ns_sbp[1] = NULL;
}

void nilfs_swap_super_block(struct the_nilfs *nilfs)
{
        struct buffer_head *tsbh = nilfs->ns_sbh[0];
        struct nilfs_super_block *tsbp = nilfs->ns_sbp[0];

        nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
        nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
        nilfs->ns_sbh[1] = tsbh;
        nilfs->ns_sbp[1] = tsbp;
}

static int nilfs_load_super_block(struct the_nilfs *nilfs,
                                  struct super_block *sb, int blocksize,
                                  struct nilfs_super_block **sbpp)
{
        struct nilfs_super_block **sbp = nilfs->ns_sbp;
        struct buffer_head **sbh = nilfs->ns_sbh;
        u64 sb2off = NILFS_SB2_OFFSET_BYTES(nilfs->ns_bdev->bd_inode->i_size);
        int valid[2], swp = 0;

        sbp[0] = nilfs_read_super_block(sb, NILFS_SB_OFFSET_BYTES, blocksize,
                                        &sbh[0]);
        sbp[1] = nilfs_read_super_block(sb, sb2off, blocksize, &sbh[1]);

        if (!sbp[0]) {
                if (!sbp[1]) {
                        printk(KERN_ERR "NILFS: unable to read superblock\n");
                        return -EIO;
                }
                printk(KERN_WARNING
                       "NILFS warning: unable to read primary superblock\n");
        } else if (!sbp[1])
                printk(KERN_WARNING
                       "NILFS warning: unable to read secondary superblock\n");

        /*
         * Compare two super blocks and set 1 in swp if the secondary
         * super block is valid and newer.  Otherwise, set 0 in swp.
         */
        valid[0] = nilfs_valid_sb(sbp[0]);
        valid[1] = nilfs_valid_sb(sbp[1]);
        swp = valid[1] && (!valid[0] ||
                           le64_to_cpu(sbp[1]->s_last_cno) >
                           le64_to_cpu(sbp[0]->s_last_cno));

        if (valid[swp] && nilfs_sb2_bad_offset(sbp[swp], sb2off)) {
                brelse(sbh[1]);
                sbh[1] = NULL;
                sbp[1] = NULL;
                swp = 0;
        }
        if (!valid[swp]) {
                nilfs_release_super_block(nilfs);
                printk(KERN_ERR "NILFS: Can't find nilfs on dev %s.\n",
                       sb->s_id);
                return -EINVAL;
        }

        if (!valid[!swp])
                printk(KERN_WARNING "NILFS warning: broken superblock. "
                       "using spare superblock.\n");
        if (swp)
                nilfs_swap_super_block(nilfs);

        nilfs->ns_sbwcount = 0;
        nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
        nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
        *sbpp = sbp[0];
        return 0;
}

/**
 * init_nilfs - initialize a NILFS instance.
 * @nilfs: the_nilfs structure
 * @sbi: nilfs_sb_info
 * @sb: super block
 * @data: mount options
 *
 * init_nilfs() performs common initialization per block device (e.g.
 * reading the super block, getting disk layout information, initializing
 * shared fields in the_nilfs).
 *
 * Return Value: On success, 0 is returned. On error, a negative error
 * code is returned.
 */
int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
{
        struct super_block *sb = sbi->s_super;
        struct nilfs_super_block *sbp;
        struct backing_dev_info *bdi;
        int blocksize;
        int err;

        down_write(&nilfs->ns_sem);

        blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
        if (!blocksize) {
                printk(KERN_ERR "NILFS: unable to set blocksize\n");
                err = -EINVAL;
                goto out;
        }
        err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
        if (err)
                goto out;

        err = nilfs_store_magic_and_option(sb, sbp, data);
        if (err)
                goto failed_sbh;

        err = nilfs_check_feature_compatibility(sb, sbp);
        if (err)
                goto failed_sbh;

        blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
        if (blocksize < NILFS_MIN_BLOCK_SIZE ||
            blocksize > NILFS_MAX_BLOCK_SIZE) {
                printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
                       "filesystem blocksize %d\n", blocksize);
                err = -EINVAL;
                goto failed_sbh;
        }
        if (sb->s_blocksize != blocksize) {
                int hw_blocksize = bdev_logical_block_size(sb->s_bdev);

                if (blocksize < hw_blocksize) {
                        printk(KERN_ERR
                               "NILFS: blocksize %d too small for device "
                               "(sector-size = %d).\n",
                               blocksize, hw_blocksize);
                        err = -EINVAL;
                        goto failed_sbh;
                }
                nilfs_release_super_block(nilfs);
                sb_set_blocksize(sb, blocksize);

                err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
                if (err)
                        goto out;
                        /* not failed_sbh; sbh is released automatically
                           when reloading fails. */
        }
        nilfs->ns_blocksize_bits = sb->s_blocksize_bits;
        nilfs->ns_blocksize = blocksize;

        err = nilfs_store_disk_layout(nilfs, sbp);
        if (err)
                goto failed_sbh;

        sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);

        nilfs->ns_mount_state = le16_to_cpu(sbp->s_state);

        bdi = nilfs->ns_bdev->bd_inode->i_mapping->backing_dev_info;
        nilfs->ns_bdi = bdi ? : &default_backing_dev_info;

        err = nilfs_store_log_cursor(nilfs, sbp);
        if (err)
                goto failed_sbh;

        set_nilfs_init(nilfs);
        err = 0;
 out:
        up_write(&nilfs->ns_sem);
        return err;

 failed_sbh:
        nilfs_release_super_block(nilfs);
        goto out;
}

int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
                            size_t nsegs)
{
        sector_t seg_start, seg_end;
        sector_t start = 0, nblocks = 0;
        unsigned int sects_per_block;
        __u64 *sn;
        int ret = 0;

        sects_per_block = (1 << nilfs->ns_blocksize_bits) /
                bdev_logical_block_size(nilfs->ns_bdev);
        for (sn = segnump; sn < segnump + nsegs; sn++) {
                nilfs_get_segment_range(nilfs, *sn, &seg_start, &seg_end);

                if (!nblocks) {
                        start = seg_start;
                        nblocks = seg_end - seg_start + 1;
                } else if (start + nblocks == seg_start) {
                        nblocks += seg_end - seg_start + 1;
                } else {
                        ret = blkdev_issue_discard(nilfs->ns_bdev,
                                                   start * sects_per_block,
                                                   nblocks * sects_per_block,
                                                   GFP_NOFS,
                                                   BLKDEV_IFL_WAIT |
                                                   BLKDEV_IFL_BARRIER);
                        if (ret < 0)
                                return ret;
                        nblocks = 0;
                }
        }
        if (nblocks)
                ret = blkdev_issue_discard(nilfs->ns_bdev,
                                           start * sects_per_block,
                                           nblocks * sects_per_block,
                                           GFP_NOFS,
                                          BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
        return ret;
}

int nilfs_count_free_blocks(struct the_nilfs *nilfs, sector_t *nblocks)
{
        struct inode *dat = nilfs_dat_inode(nilfs);
        unsigned long ncleansegs;

        down_read(&NILFS_MDT(dat)->mi_sem);     /* XXX */
        ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
        up_read(&NILFS_MDT(dat)->mi_sem);       /* XXX */
        *nblocks = (sector_t)ncleansegs * nilfs->ns_blocks_per_segment;
        return 0;
}

int nilfs_near_disk_full(struct the_nilfs *nilfs)
{
        unsigned long ncleansegs, nincsegs;

        ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
        nincsegs = atomic_read(&nilfs->ns_ndirtyblks) /
                nilfs->ns_blocks_per_segment + 1;

        return ncleansegs <= nilfs->ns_nrsvsegs + nincsegs;
}

struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno)
{
        struct rb_node *n;
        struct nilfs_root *root;

        spin_lock(&nilfs->ns_cptree_lock);
        n = nilfs->ns_cptree.rb_node;
        while (n) {
                root = rb_entry(n, struct nilfs_root, rb_node);

                if (cno < root->cno) {
                        n = n->rb_left;
                } else if (cno > root->cno) {
                        n = n->rb_right;
                } else {
                        atomic_inc(&root->count);
                        spin_unlock(&nilfs->ns_cptree_lock);
                        return root;
                }
        }
        spin_unlock(&nilfs->ns_cptree_lock);

        return NULL;
}

struct nilfs_root *
nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
{
        struct rb_node **p, *parent;
        struct nilfs_root *root, *new;

        root = nilfs_lookup_root(nilfs, cno);
        if (root)
                return root;

        new = kmalloc(sizeof(*root), GFP_KERNEL);
        if (!new)
                return NULL;

        spin_lock(&nilfs->ns_cptree_lock);

        p = &nilfs->ns_cptree.rb_node;
        parent = NULL;

        while (*p) {
                parent = *p;
                root = rb_entry(parent, struct nilfs_root, rb_node);

                if (cno < root->cno) {
                        p = &(*p)->rb_left;
                } else if (cno > root->cno) {
                        p = &(*p)->rb_right;
                } else {
                        atomic_inc(&root->count);
                        spin_unlock(&nilfs->ns_cptree_lock);
                        kfree(new);
                        return root;
                }
        }

        new->cno = cno;
        new->ifile = NULL;
        new->nilfs = nilfs;
        atomic_set(&new->count, 1);
        atomic_set(&new->inodes_count, 0);
        atomic_set(&new->blocks_count, 0);

        rb_link_node(&new->rb_node, parent, p);
        rb_insert_color(&new->rb_node, &nilfs->ns_cptree);

        spin_unlock(&nilfs->ns_cptree_lock);

        return new;
}

void nilfs_put_root(struct nilfs_root *root)
{
        if (atomic_dec_and_test(&root->count)) {
                struct the_nilfs *nilfs = root->nilfs;

                spin_lock(&nilfs->ns_cptree_lock);
                rb_erase(&root->rb_node, &nilfs->ns_cptree);
                spin_unlock(&nilfs->ns_cptree_lock);
                if (root->ifile)
                        nilfs_mdt_destroy(root->ifile);

                kfree(root);
        }
}

int nilfs_checkpoint_is_mounted(struct the_nilfs *nilfs, __u64 cno,
                                int snapshot_mount)
{
        struct nilfs_root *root;
        int ret;

        if (cno < 0 || cno > nilfs->ns_cno)
                return false;

        if (cno >= nilfs_last_cno(nilfs))
                return true;    /* protect recent checkpoints */

        ret = false;
        root = nilfs_lookup_root(nilfs, cno);
        if (root) {
                ret = true;
                nilfs_put_root(root);
        }
        return ret;
}