/*
 * alloc.c - NILFS dat/inode allocator
 *
 * Copyright (C) 2006-2008 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
 *
 * Original code was written by Koji Sato <koji@osrg.net>.
 * Two allocators were unified by Ryusuke Konishi <ryusuke@osrg.net>,
 *                                Amagai Yoshiji <amagai@osrg.net>.
 */

#include <linux/types.h>
#include <linux/buffer_head.h>
#include <linux/fs.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include "mdt.h"
#include "alloc.h"


/**
 * nilfs_palloc_groups_per_desc_block - get the number of groups that a group
 *                                      descriptor block can maintain
 * @inode: inode of metadata file using this allocator
 */
static inline unsigned long
nilfs_palloc_groups_per_desc_block(const struct inode *inode)
{
        return (1UL << inode->i_blkbits) /
                sizeof(struct nilfs_palloc_group_desc);
}

/**
 * nilfs_palloc_groups_count - get maximum number of groups
 * @inode: inode of metadata file using this allocator
 */
static inline unsigned long
nilfs_palloc_groups_count(const struct inode *inode)
{
        return 1UL << (BITS_PER_LONG - (inode->i_blkbits + 3 /* log2(8) */));
}

/**
 * nilfs_palloc_init_blockgroup - initialize private variables for allocator
 * @inode: inode of metadata file using this allocator
 * @entry_size: size of the persistent object
 */
int nilfs_palloc_init_blockgroup(struct inode *inode, unsigned entry_size)
{
        struct nilfs_mdt_info *mi = NILFS_MDT(inode);

        mi->mi_bgl = kmalloc(sizeof(*mi->mi_bgl), GFP_NOFS);
        if (!mi->mi_bgl)
                return -ENOMEM;

        bgl_lock_init(mi->mi_bgl);

        nilfs_mdt_set_entry_size(inode, entry_size, 0);

        mi->mi_blocks_per_group =
                DIV_ROUND_UP(nilfs_palloc_entries_per_group(inode),
                             mi->mi_entries_per_block) + 1;
                /* Number of blocks in a group including entry blocks and
                   a bitmap block */
        mi->mi_blocks_per_desc_block =
                nilfs_palloc_groups_per_desc_block(inode) *
                mi->mi_blocks_per_group + 1;
                /* Number of blocks per descriptor including the
                   descriptor block */
        return 0;
}

/**
 * nilfs_palloc_group - get group number and offset from an entry number
 * @inode: inode of metadata file using this allocator
 * @nr: serial number of the entry (e.g. inode number)
 * @offset: pointer to store offset number in the group
 */
static unsigned long nilfs_palloc_group(const struct inode *inode, __u64 nr,
                                        unsigned long *offset)
{
        __u64 group = nr;

        *offset = do_div(group, nilfs_palloc_entries_per_group(inode));
        return group;
}

/**
 * nilfs_palloc_desc_blkoff - get block offset of a group descriptor block
 * @inode: inode of metadata file using this allocator
 * @group: group number
 *
 * nilfs_palloc_desc_blkoff() returns block offset of the descriptor
 * block which contains a descriptor of the specified group.
 */
static unsigned long
nilfs_palloc_desc_blkoff(const struct inode *inode, unsigned long group)
{
        unsigned long desc_block =
                group / nilfs_palloc_groups_per_desc_block(inode);
        return desc_block * NILFS_MDT(inode)->mi_blocks_per_desc_block;
}

/**
 * nilfs_palloc_bitmap_blkoff - get block offset of a bitmap block
 * @inode: inode of metadata file using this allocator
 * @group: group number
 *
 * nilfs_palloc_bitmap_blkoff() returns block offset of the bitmap
 * block used to allocate/deallocate entries in the specified group.
 */
static unsigned long
nilfs_palloc_bitmap_blkoff(const struct inode *inode, unsigned long group)
{
        unsigned long desc_offset =
                group % nilfs_palloc_groups_per_desc_block(inode);
        return nilfs_palloc_desc_blkoff(inode, group) + 1 +
                desc_offset * NILFS_MDT(inode)->mi_blocks_per_group;
}

/**
 * nilfs_palloc_group_desc_nfrees - get the number of free entries in a group
 * @inode: inode of metadata file using this allocator
 * @group: group number
 * @desc: pointer to descriptor structure for the group
 */
static unsigned long
nilfs_palloc_group_desc_nfrees(struct inode *inode, unsigned long group,
                               const struct nilfs_palloc_group_desc *desc)
{
        unsigned long nfree;

        spin_lock(nilfs_mdt_bgl_lock(inode, group));
        nfree = le32_to_cpu(desc->pg_nfrees);
        spin_unlock(nilfs_mdt_bgl_lock(inode, group));
        return nfree;
}

/**
 * nilfs_palloc_group_desc_add_entries - adjust count of free entries
 * @inode: inode of metadata file using this allocator
 * @group: group number
 * @desc: pointer to descriptor structure for the group
 * @n: delta to be added
 */
static void
nilfs_palloc_group_desc_add_entries(struct inode *inode,
                                    unsigned long group,
                                    struct nilfs_palloc_group_desc *desc,
                                    u32 n)
{
        spin_lock(nilfs_mdt_bgl_lock(inode, group));
        le32_add_cpu(&desc->pg_nfrees, n);
        spin_unlock(nilfs_mdt_bgl_lock(inode, group));
}

/**
 * nilfs_palloc_entry_blkoff - get block offset of an entry block
 * @inode: inode of metadata file using this allocator
 * @nr: serial number of the entry (e.g. inode number)
 */
static unsigned long
nilfs_palloc_entry_blkoff(const struct inode *inode, __u64 nr)
{
        unsigned long group, group_offset;

        group = nilfs_palloc_group(inode, nr, &group_offset);

        return nilfs_palloc_bitmap_blkoff(inode, group) + 1 +
                group_offset / NILFS_MDT(inode)->mi_entries_per_block;
}

/**
 * nilfs_palloc_desc_block_init - initialize buffer of a group descriptor block
 * @inode: inode of metadata file
 * @bh: buffer head of the buffer to be initialized
 * @kaddr: kernel address mapped for the page including the buffer
 */
static void nilfs_palloc_desc_block_init(struct inode *inode,
                                         struct buffer_head *bh, void *kaddr)
{
        struct nilfs_palloc_group_desc *desc = kaddr + bh_offset(bh);
        unsigned long n = nilfs_palloc_groups_per_desc_block(inode);
        __le32 nfrees;

        nfrees = cpu_to_le32(nilfs_palloc_entries_per_group(inode));
        while (n-- > 0) {
                desc->pg_nfrees = nfrees;
                desc++;
        }
}

static int nilfs_palloc_get_block(struct inode *inode, unsigned long blkoff,
                                  int create,
                                  void (*init_block)(struct inode *,
                                                     struct buffer_head *,
                                                     void *),
                                  struct buffer_head **bhp,
                                  struct nilfs_bh_assoc *prev,
                                  spinlock_t *lock)
{
        int ret;

        spin_lock(lock);
        if (prev->bh && blkoff == prev->blkoff) {
                get_bh(prev->bh);
                *bhp = prev->bh;
                spin_unlock(lock);
                return 0;
        }
        spin_unlock(lock);

        ret = nilfs_mdt_get_block(inode, blkoff, create, init_block, bhp);
        if (!ret) {
                spin_lock(lock);
                /*
                 * The following code must be safe for change of the
                 * cache contents during the get block call.
                 */
                brelse(prev->bh);
                get_bh(*bhp);
                prev->bh = *bhp;
                prev->blkoff = blkoff;
                spin_unlock(lock);
        }
        return ret;
}

/**
 * nilfs_palloc_get_desc_block - get buffer head of a group descriptor block
 * @inode: inode of metadata file using this allocator
 * @group: group number
 * @create: create flag
 * @bhp: pointer to store the resultant buffer head
 */
static int nilfs_palloc_get_desc_block(struct inode *inode,
                                       unsigned long group,
                                       int create, struct buffer_head **bhp)
{
        struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;

        return nilfs_palloc_get_block(inode,
                                      nilfs_palloc_desc_blkoff(inode, group),
                                      create, nilfs_palloc_desc_block_init,
                                      bhp, &cache->prev_desc, &cache->lock);
}

/**
 * nilfs_palloc_get_bitmap_block - get buffer head of a bitmap block
 * @inode: inode of metadata file using this allocator
 * @group: group number
 * @create: create flag
 * @bhp: pointer to store the resultant buffer head
 */
static int nilfs_palloc_get_bitmap_block(struct inode *inode,
                                         unsigned long group,
                                         int create, struct buffer_head **bhp)
{
        struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;

        return nilfs_palloc_get_block(inode,
                                      nilfs_palloc_bitmap_blkoff(inode, group),
                                      create, NULL, bhp,
                                      &cache->prev_bitmap, &cache->lock);
}

/**
 * nilfs_palloc_get_entry_block - get buffer head of an entry block
 * @inode: inode of metadata file using this allocator
 * @nr: serial number of the entry (e.g. inode number)
 * @create: create flag
 * @bhp: pointer to store the resultant buffer head
 */
int nilfs_palloc_get_entry_block(struct inode *inode, __u64 nr,
                                 int create, struct buffer_head **bhp)
{
        struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;

        return nilfs_palloc_get_block(inode,
                                      nilfs_palloc_entry_blkoff(inode, nr),
                                      create, NULL, bhp,
                                      &cache->prev_entry, &cache->lock);
}

/**
 * nilfs_palloc_block_get_group_desc - get kernel address of a group descriptor
 * @inode: inode of metadata file using this allocator
 * @group: group number
 * @bh: buffer head of the buffer storing the group descriptor block
 * @kaddr: kernel address mapped for the page including the buffer
 */
static struct nilfs_palloc_group_desc *
nilfs_palloc_block_get_group_desc(const struct inode *inode,
                                  unsigned long group,
                                  const struct buffer_head *bh, void *kaddr)
{
        return (struct nilfs_palloc_group_desc *)(kaddr + bh_offset(bh)) +
                group % nilfs_palloc_groups_per_desc_block(inode);
}

/**
 * nilfs_palloc_block_get_entry - get kernel address of an entry
 * @inode: inode of metadata file using this allocator
 * @nr: serial number of the entry (e.g. inode number)
 * @bh: buffer head of the buffer storing the entry block
 * @kaddr: kernel address mapped for the page including the buffer
 */
void *nilfs_palloc_block_get_entry(const struct inode *inode, __u64 nr,
                                   const struct buffer_head *bh, void *kaddr)
{
        unsigned long entry_offset, group_offset;

        nilfs_palloc_group(inode, nr, &group_offset);
        entry_offset = group_offset % NILFS_MDT(inode)->mi_entries_per_block;

        return kaddr + bh_offset(bh) +
                entry_offset * NILFS_MDT(inode)->mi_entry_size;
}

/**
 * nilfs_palloc_find_available_slot - find available slot in a group
 * @inode: inode of metadata file using this allocator
 * @group: group number
 * @target: offset number of an entry in the group (start point)
 * @bitmap: bitmap of the group
 * @bsize: size in bits
 */
static int nilfs_palloc_find_available_slot(struct inode *inode,
                                            unsigned long group,
                                            unsigned long target,
                                            unsigned char *bitmap,
                                            int bsize)
{
        int curr, pos, end, i;

        if (target > 0) {
                end = (target + BITS_PER_LONG - 1) & ~(BITS_PER_LONG - 1);
                if (end > bsize)
                        end = bsize;
                pos = nilfs_find_next_zero_bit(bitmap, end, target);
                if (pos < end &&
                    !nilfs_set_bit_atomic(
                            nilfs_mdt_bgl_lock(inode, group), pos, bitmap))
                        return pos;
        } else
                end = 0;

        for (i = 0, curr = end;
             i < bsize;
             i += BITS_PER_LONG, curr += BITS_PER_LONG) {
                /* wrap around */
                if (curr >= bsize)
                        curr = 0;
                while (*((unsigned long *)bitmap + curr / BITS_PER_LONG)
                       != ~0UL) {
                        end = curr + BITS_PER_LONG;
                        if (end > bsize)
                                end = bsize;
                        pos = nilfs_find_next_zero_bit(bitmap, end, curr);
                        if ((pos < end) &&
                            !nilfs_set_bit_atomic(
                                    nilfs_mdt_bgl_lock(inode, group), pos,
                                    bitmap))
                                return pos;
                }
        }
        return -ENOSPC;
}

/**
 * nilfs_palloc_rest_groups_in_desc_block - get the remaining number of groups
 *                                          in a group descriptor block
 * @inode: inode of metadata file using this allocator
 * @curr: current group number
 * @max: maximum number of groups
 */
static unsigned long
nilfs_palloc_rest_groups_in_desc_block(const struct inode *inode,
                                       unsigned long curr, unsigned long max)
{
        return min_t(unsigned long,
                     nilfs_palloc_groups_per_desc_block(inode) -
                     curr % nilfs_palloc_groups_per_desc_block(inode),
                     max - curr + 1);
}

/**
 * nilfs_palloc_prepare_alloc_entry - prepare to allocate a persistent object
 * @inode: inode of metadata file using this allocator
 * @req: nilfs_palloc_req structure exchanged for the allocation
 */
int nilfs_palloc_prepare_alloc_entry(struct inode *inode,
                                     struct nilfs_palloc_req *req)
{
        struct buffer_head *desc_bh, *bitmap_bh;
        struct nilfs_palloc_group_desc *desc;
        unsigned char *bitmap;
        void *desc_kaddr, *bitmap_kaddr;
        unsigned long group, maxgroup, ngroups;
        unsigned long group_offset, maxgroup_offset;
        unsigned long n, entries_per_group, groups_per_desc_block;
        unsigned long i, j;
        int pos, ret;

        ngroups = nilfs_palloc_groups_count(inode);
        maxgroup = ngroups - 1;
        group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
        entries_per_group = nilfs_palloc_entries_per_group(inode);
        groups_per_desc_block = nilfs_palloc_groups_per_desc_block(inode);

        for (i = 0; i < ngroups; i += n) {
                if (group >= ngroups) {
                        /* wrap around */
                        group = 0;
                        maxgroup = nilfs_palloc_group(inode, req->pr_entry_nr,
                                                      &maxgroup_offset) - 1;
                }
                ret = nilfs_palloc_get_desc_block(inode, group, 1, &desc_bh);
                if (ret < 0)
                        return ret;
                desc_kaddr = kmap(desc_bh->b_page);
                desc = nilfs_palloc_block_get_group_desc(
                        inode, group, desc_bh, desc_kaddr);
                n = nilfs_palloc_rest_groups_in_desc_block(inode, group,
                                                           maxgroup);
                for (j = 0; j < n; j++, desc++, group++) {
                        if (nilfs_palloc_group_desc_nfrees(inode, group, desc)
                            > 0) {
                                ret = nilfs_palloc_get_bitmap_block(
                                        inode, group, 1, &bitmap_bh);
                                if (ret < 0)
                                        goto out_desc;
                                bitmap_kaddr = kmap(bitmap_bh->b_page);
                                bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
                                pos = nilfs_palloc_find_available_slot(
                                        inode, group, group_offset, bitmap,
                                        entries_per_group);
                                if (pos >= 0) {
                                        /* found a free entry */
                                        nilfs_palloc_group_desc_add_entries(
                                                inode, group, desc, -1);
                                        req->pr_entry_nr =
                                                entries_per_group * group + pos;
                                        kunmap(desc_bh->b_page);
                                        kunmap(bitmap_bh->b_page);

                                        req->pr_desc_bh = desc_bh;
                                        req->pr_bitmap_bh = bitmap_bh;
                                        return 0;
                                }
                                kunmap(bitmap_bh->b_page);
                                brelse(bitmap_bh);
                        }

                        group_offset = 0;
                }

                kunmap(desc_bh->b_page);
                brelse(desc_bh);
        }

        /* no entries left */
        return -ENOSPC;

 out_desc:
        kunmap(desc_bh->b_page);
        brelse(desc_bh);
        return ret;
}

/**
 * nilfs_palloc_commit_alloc_entry - finish allocation of a persistent object
 * @inode: inode of metadata file using this allocator
 * @req: nilfs_palloc_req structure exchanged for the allocation
 */
void nilfs_palloc_commit_alloc_entry(struct inode *inode,
                                     struct nilfs_palloc_req *req)
{
        mark_buffer_dirty(req->pr_bitmap_bh);
        mark_buffer_dirty(req->pr_desc_bh);
        nilfs_mdt_mark_dirty(inode);

        brelse(req->pr_bitmap_bh);
        brelse(req->pr_desc_bh);
}

/**
 * nilfs_palloc_commit_free_entry - finish deallocating a persistent object
 * @inode: inode of metadata file using this allocator
 * @req: nilfs_palloc_req structure exchanged for the removal
 */
void nilfs_palloc_commit_free_entry(struct inode *inode,
                                    struct nilfs_palloc_req *req)
{
        struct nilfs_palloc_group_desc *desc;
        unsigned long group, group_offset;
        unsigned char *bitmap;
        void *desc_kaddr, *bitmap_kaddr;

        group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
        desc_kaddr = kmap(req->pr_desc_bh->b_page);
        desc = nilfs_palloc_block_get_group_desc(inode, group,
                                                 req->pr_desc_bh, desc_kaddr);
        bitmap_kaddr = kmap(req->pr_bitmap_bh->b_page);
        bitmap = bitmap_kaddr + bh_offset(req->pr_bitmap_bh);

        if (!nilfs_clear_bit_atomic(nilfs_mdt_bgl_lock(inode, group),
                                    group_offset, bitmap))
                printk(KERN_WARNING "%s: entry number %llu already freed\n",
                       __func__, (unsigned long long)req->pr_entry_nr);
        else
                nilfs_palloc_group_desc_add_entries(inode, group, desc, 1);

        kunmap(req->pr_bitmap_bh->b_page);
        kunmap(req->pr_desc_bh->b_page);

        mark_buffer_dirty(req->pr_desc_bh);
        mark_buffer_dirty(req->pr_bitmap_bh);
        nilfs_mdt_mark_dirty(inode);

        brelse(req->pr_bitmap_bh);
        brelse(req->pr_desc_bh);
}

/**
 * nilfs_palloc_abort_alloc_entry - cancel allocation of a persistent object
 * @inode: inode of metadata file using this allocator
 * @req: nilfs_palloc_req structure exchanged for the allocation
 */
void nilfs_palloc_abort_alloc_entry(struct inode *inode,
                                    struct nilfs_palloc_req *req)
{
        struct nilfs_palloc_group_desc *desc;
        void *desc_kaddr, *bitmap_kaddr;
        unsigned char *bitmap;
        unsigned long group, group_offset;

        group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
        desc_kaddr = kmap(req->pr_desc_bh->b_page);
        desc = nilfs_palloc_block_get_group_desc(inode, group,
                                                 req->pr_desc_bh, desc_kaddr);
        bitmap_kaddr = kmap(req->pr_bitmap_bh->b_page);
        bitmap = bitmap_kaddr + bh_offset(req->pr_bitmap_bh);
        if (!nilfs_clear_bit_atomic(nilfs_mdt_bgl_lock(inode, group),
                                    group_offset, bitmap))
                printk(KERN_WARNING "%s: entry number %llu already freed\n",
                       __func__, (unsigned long long)req->pr_entry_nr);
        else
                nilfs_palloc_group_desc_add_entries(inode, group, desc, 1);

        kunmap(req->pr_bitmap_bh->b_page);
        kunmap(req->pr_desc_bh->b_page);

        brelse(req->pr_bitmap_bh);
        brelse(req->pr_desc_bh);

        req->pr_entry_nr = 0;
        req->pr_bitmap_bh = NULL;
        req->pr_desc_bh = NULL;
}

/**
 * nilfs_palloc_prepare_free_entry - prepare to deallocate a persistent object
 * @inode: inode of metadata file using this allocator
 * @req: nilfs_palloc_req structure exchanged for the removal
 */
int nilfs_palloc_prepare_free_entry(struct inode *inode,
                                    struct nilfs_palloc_req *req)
{
        struct buffer_head *desc_bh, *bitmap_bh;
        unsigned long group, group_offset;
        int ret;

        group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
        ret = nilfs_palloc_get_desc_block(inode, group, 1, &desc_bh);
        if (ret < 0)
                return ret;
        ret = nilfs_palloc_get_bitmap_block(inode, group, 1, &bitmap_bh);
        if (ret < 0) {
                brelse(desc_bh);
                return ret;
        }

        req->pr_desc_bh = desc_bh;
        req->pr_bitmap_bh = bitmap_bh;
        return 0;
}

/**
 * nilfs_palloc_abort_free_entry - cancel deallocating a persistent object
 * @inode: inode of metadata file using this allocator
 * @req: nilfs_palloc_req structure exchanged for the removal
 */
void nilfs_palloc_abort_free_entry(struct inode *inode,
                                   struct nilfs_palloc_req *req)
{
        brelse(req->pr_bitmap_bh);
        brelse(req->pr_desc_bh);

        req->pr_entry_nr = 0;
        req->pr_bitmap_bh = NULL;
        req->pr_desc_bh = NULL;
}

/**
 * nilfs_palloc_group_is_in - judge if an entry is in a group
 * @inode: inode of metadata file using this allocator
 * @group: group number
 * @nr: serial number of the entry (e.g. inode number)
 */
static int
nilfs_palloc_group_is_in(struct inode *inode, unsigned long group, __u64 nr)
{
        __u64 first, last;

        first = group * nilfs_palloc_entries_per_group(inode);
        last = first + nilfs_palloc_entries_per_group(inode) - 1;
        return (nr >= first) && (nr <= last);
}

/**
 * nilfs_palloc_freev - deallocate a set of persistent objects
 * @inode: inode of metadata file using this allocator
 * @entry_nrs: array of entry numbers to be deallocated
 * @nitems: number of entries stored in @entry_nrs
 */
int nilfs_palloc_freev(struct inode *inode, __u64 *entry_nrs, size_t nitems)
{
        struct buffer_head *desc_bh, *bitmap_bh;
        struct nilfs_palloc_group_desc *desc;
        unsigned char *bitmap;
        void *desc_kaddr, *bitmap_kaddr;
        unsigned long group, group_offset;
        int i, j, n, ret;

        for (i = 0; i < nitems; i = j) {
                group = nilfs_palloc_group(inode, entry_nrs[i], &group_offset);
                ret = nilfs_palloc_get_desc_block(inode, group, 0, &desc_bh);
                if (ret < 0)
                        return ret;
                ret = nilfs_palloc_get_bitmap_block(inode, group, 0,
                                                    &bitmap_bh);
                if (ret < 0) {
                        brelse(desc_bh);
                        return ret;
                }
                desc_kaddr = kmap(desc_bh->b_page);
                desc = nilfs_palloc_block_get_group_desc(
                        inode, group, desc_bh, desc_kaddr);
                bitmap_kaddr = kmap(bitmap_bh->b_page);
                bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
                for (j = i, n = 0;
                     (j < nitems) && nilfs_palloc_group_is_in(inode, group,
                                                              entry_nrs[j]);
                     j++) {
                        nilfs_palloc_group(inode, entry_nrs[j], &group_offset);
                        if (!nilfs_clear_bit_atomic(
                                    nilfs_mdt_bgl_lock(inode, group),
                                    group_offset, bitmap)) {
                                printk(KERN_WARNING
                                       "%s: entry number %llu already freed\n",
                                       __func__,
                                       (unsigned long long)entry_nrs[j]);
                        } else {
                                n++;
                        }
                }
                nilfs_palloc_group_desc_add_entries(inode, group, desc, n);

                kunmap(bitmap_bh->b_page);
                kunmap(desc_bh->b_page);

                mark_buffer_dirty(desc_bh);
                mark_buffer_dirty(bitmap_bh);
                nilfs_mdt_mark_dirty(inode);

                brelse(bitmap_bh);
                brelse(desc_bh);
        }
        return 0;
}

void nilfs_palloc_setup_cache(struct inode *inode,
                              struct nilfs_palloc_cache *cache)
{
        NILFS_MDT(inode)->mi_palloc_cache = cache;
        spin_lock_init(&cache->lock);
}

void nilfs_palloc_clear_cache(struct inode *inode)
{
        struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;

        spin_lock(&cache->lock);
        brelse(cache->prev_desc.bh);
        brelse(cache->prev_bitmap.bh);
        brelse(cache->prev_entry.bh);
        cache->prev_desc.bh = NULL;
        cache->prev_bitmap.bh = NULL;
        cache->prev_entry.bh = NULL;
        spin_unlock(&cache->lock);
}

void nilfs_palloc_destroy_cache(struct inode *inode)
{
        nilfs_palloc_clear_cache(inode);
        NILFS_MDT(inode)->mi_palloc_cache = NULL;
}