/*
 * mdt.c - meta data file for NILFS
 *
 * 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/mpage.h>
#include <linux/mm.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include "nilfs.h"
#include "btnode.h"
#include "segment.h"
#include "page.h"
#include "mdt.h"


#define NILFS_MDT_MAX_RA_BLOCKS         (16 - 1)


static int
nilfs_mdt_insert_new_block(struct inode *inode, unsigned long block,
                           struct buffer_head *bh,
                           void (*init_block)(struct inode *,
                                              struct buffer_head *, void *))
{
        struct nilfs_inode_info *ii = NILFS_I(inode);
        void *kaddr;
        int ret;

        /* Caller exclude read accesses using page lock */

        /* set_buffer_new(bh); */
        bh->b_blocknr = 0;

        ret = nilfs_bmap_insert(ii->i_bmap, block, (unsigned long)bh);
        if (unlikely(ret))
                return ret;

        set_buffer_mapped(bh);

        kaddr = kmap_atomic(bh->b_page);
        memset(kaddr + bh_offset(bh), 0, 1 << inode->i_blkbits);
        if (init_block)
                init_block(inode, bh, kaddr);
        flush_dcache_page(bh->b_page);
        kunmap_atomic(kaddr);

        set_buffer_uptodate(bh);
        mark_buffer_dirty(bh);
        nilfs_mdt_mark_dirty(inode);
        return 0;
}

static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
                                  struct buffer_head **out_bh,
                                  void (*init_block)(struct inode *,
                                                     struct buffer_head *,
                                                     void *))
{
        struct super_block *sb = inode->i_sb;
        struct nilfs_transaction_info ti;
        struct buffer_head *bh;
        int err;

        nilfs_transaction_begin(sb, &ti, 0);

        err = -ENOMEM;
        bh = nilfs_grab_buffer(inode, inode->i_mapping, block, 0);
        if (unlikely(!bh))
                goto failed_unlock;

        err = -EEXIST;
        if (buffer_uptodate(bh))
                goto failed_bh;

        wait_on_buffer(bh);
        if (buffer_uptodate(bh))
                goto failed_bh;

        bh->b_bdev = sb->s_bdev;
        err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
        if (likely(!err)) {
                get_bh(bh);
                *out_bh = bh;
        }

 failed_bh:
        unlock_page(bh->b_page);
        page_cache_release(bh->b_page);
        brelse(bh);

 failed_unlock:
        if (likely(!err))
                err = nilfs_transaction_commit(sb);
        else
                nilfs_transaction_abort(sb);

        return err;
}

static int
nilfs_mdt_submit_block(struct inode *inode, unsigned long blkoff,
                       int mode, struct buffer_head **out_bh)
{
        struct buffer_head *bh;
        __u64 blknum = 0;
        int ret = -ENOMEM;

        bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
        if (unlikely(!bh))
                goto failed;

        ret = -EEXIST; /* internal code */
        if (buffer_uptodate(bh))
                goto out;

        if (mode == READA) {
                if (!trylock_buffer(bh)) {
                        ret = -EBUSY;
                        goto failed_bh;
                }
        } else /* mode == READ */
                lock_buffer(bh);

        if (buffer_uptodate(bh)) {
                unlock_buffer(bh);
                goto out;
        }

        ret = nilfs_bmap_lookup(NILFS_I(inode)->i_bmap, blkoff, &blknum);
        if (unlikely(ret)) {
                unlock_buffer(bh);
                goto failed_bh;
        }
        map_bh(bh, inode->i_sb, (sector_t)blknum);

        bh->b_end_io = end_buffer_read_sync;
        get_bh(bh);
        submit_bh(mode, bh);
        ret = 0;
 out:
        get_bh(bh);
        *out_bh = bh;

 failed_bh:
        unlock_page(bh->b_page);
        page_cache_release(bh->b_page);
        brelse(bh);
 failed:
        return ret;
}

static int nilfs_mdt_read_block(struct inode *inode, unsigned long block,
                                int readahead, struct buffer_head **out_bh)
{
        struct buffer_head *first_bh, *bh;
        unsigned long blkoff;
        int i, nr_ra_blocks = NILFS_MDT_MAX_RA_BLOCKS;
        int err;

        err = nilfs_mdt_submit_block(inode, block, READ, &first_bh);
        if (err == -EEXIST) /* internal code */
                goto out;

        if (unlikely(err))
                goto failed;

        if (readahead) {
                blkoff = block + 1;
                for (i = 0; i < nr_ra_blocks; i++, blkoff++) {
                        err = nilfs_mdt_submit_block(inode, blkoff, READA, &bh);
                        if (likely(!err || err == -EEXIST))
                                brelse(bh);
                        else if (err != -EBUSY)
                                break;
                                /* abort readahead if bmap lookup failed */
                        if (!buffer_locked(first_bh))
                                goto out_no_wait;
                }
        }

        wait_on_buffer(first_bh);

 out_no_wait:
        err = -EIO;
        if (!buffer_uptodate(first_bh))
                goto failed_bh;
 out:
        *out_bh = first_bh;
        return 0;

 failed_bh:
        brelse(first_bh);
 failed:
        return err;
}

/**
 * nilfs_mdt_get_block - read or create a buffer on meta data file.
 * @inode: inode of the meta data file
 * @blkoff: block offset
 * @create: create flag
 * @init_block: initializer used for newly allocated block
 * @out_bh: output of a pointer to the buffer_head
 *
 * nilfs_mdt_get_block() looks up the specified buffer and tries to create
 * a new buffer if @create is not zero.  On success, the returned buffer is
 * assured to be either existing or formatted using a buffer lock on success.
 * @out_bh is substituted only when zero is returned.
 *
 * Return Value: On success, it returns 0. On error, the following negative
 * error code is returned.
 *
 * %-ENOMEM - Insufficient memory available.
 *
 * %-EIO - I/O error
 *
 * %-ENOENT - the specified block does not exist (hole block)
 *
 * %-EROFS - Read only filesystem (for create mode)
 */
int nilfs_mdt_get_block(struct inode *inode, unsigned long blkoff, int create,
                        void (*init_block)(struct inode *,
                                           struct buffer_head *, void *),
                        struct buffer_head **out_bh)
{
        int ret;

        /* Should be rewritten with merging nilfs_mdt_read_block() */
 retry:
        ret = nilfs_mdt_read_block(inode, blkoff, !create, out_bh);
        if (!create || ret != -ENOENT)
                return ret;

        ret = nilfs_mdt_create_block(inode, blkoff, out_bh, init_block);
        if (unlikely(ret == -EEXIST)) {
                /* create = 0; */  /* limit read-create loop retries */
                goto retry;
        }
        return ret;
}

/**
 * nilfs_mdt_find_block - find and get a buffer on meta data file.
 * @inode: inode of the meta data file
 * @start: start block offset (inclusive)
 * @end: end block offset (inclusive)
 * @blkoff: block offset
 * @out_bh: place to store a pointer to buffer_head struct
 *
 * nilfs_mdt_find_block() looks up an existing block in range of
 * [@start, @end] and stores pointer to a buffer head of the block to
 * @out_bh, and block offset to @blkoff, respectively.  @out_bh and
 * @blkoff are substituted only when zero is returned.
 *
 * Return Value: On success, it returns 0. On error, the following negative
 * error code is returned.
 *
 * %-ENOMEM - Insufficient memory available.
 *
 * %-EIO - I/O error
 *
 * %-ENOENT - no block was found in the range
 */
int nilfs_mdt_find_block(struct inode *inode, unsigned long start,
                         unsigned long end, unsigned long *blkoff,
                         struct buffer_head **out_bh)
{
        __u64 next;
        int ret;

        if (unlikely(start > end))
                return -ENOENT;

        ret = nilfs_mdt_read_block(inode, start, true, out_bh);
        if (!ret) {
                *blkoff = start;
                goto out;
        }
        if (unlikely(ret != -ENOENT || start == ULONG_MAX))
                goto out;

        ret = nilfs_bmap_seek_key(NILFS_I(inode)->i_bmap, start + 1, &next);
        if (!ret) {
                if (next <= end) {
                        ret = nilfs_mdt_read_block(inode, next, true, out_bh);
                        if (!ret)
                                *blkoff = next;
                } else {
                        ret = -ENOENT;
                }
        }
out:
        return ret;
}

/**
 * nilfs_mdt_delete_block - make a hole on the meta data file.
 * @inode: inode of the meta data file
 * @block: block offset
 *
 * Return Value: On success, zero is returned.
 * On error, one of the following negative error code is returned.
 *
 * %-ENOMEM - Insufficient memory available.
 *
 * %-EIO - I/O error
 */
int nilfs_mdt_delete_block(struct inode *inode, unsigned long block)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);
        int err;

        err = nilfs_bmap_delete(ii->i_bmap, block);
        if (!err || err == -ENOENT) {
                nilfs_mdt_mark_dirty(inode);
                nilfs_mdt_forget_block(inode, block);
        }
        return err;
}

/**
 * nilfs_mdt_forget_block - discard dirty state and try to remove the page
 * @inode: inode of the meta data file
 * @block: block offset
 *
 * nilfs_mdt_forget_block() clears a dirty flag of the specified buffer, and
 * tries to release the page including the buffer from a page cache.
 *
 * Return Value: On success, 0 is returned. On error, one of the following
 * negative error code is returned.
 *
 * %-EBUSY - page has an active buffer.
 *
 * %-ENOENT - page cache has no page addressed by the offset.
 */
int nilfs_mdt_forget_block(struct inode *inode, unsigned long block)
{
        pgoff_t index = (pgoff_t)block >>
                (PAGE_CACHE_SHIFT - inode->i_blkbits);
        struct page *page;
        unsigned long first_block;
        int ret = 0;
        int still_dirty;

        page = find_lock_page(inode->i_mapping, index);
        if (!page)
                return -ENOENT;

        wait_on_page_writeback(page);

        first_block = (unsigned long)index <<
                (PAGE_CACHE_SHIFT - inode->i_blkbits);
        if (page_has_buffers(page)) {
                struct buffer_head *bh;

                bh = nilfs_page_get_nth_block(page, block - first_block);
                nilfs_forget_buffer(bh);
        }
        still_dirty = PageDirty(page);
        unlock_page(page);
        page_cache_release(page);

        if (still_dirty ||
            invalidate_inode_pages2_range(inode->i_mapping, index, index) != 0)
                ret = -EBUSY;
        return ret;
}

/**
 * nilfs_mdt_mark_block_dirty - mark a block on the meta data file dirty.
 * @inode: inode of the meta data file
 * @block: block offset
 *
 * Return Value: On success, it returns 0. On error, the following negative
 * error code is returned.
 *
 * %-ENOMEM - Insufficient memory available.
 *
 * %-EIO - I/O error
 *
 * %-ENOENT - the specified block does not exist (hole block)
 */
int nilfs_mdt_mark_block_dirty(struct inode *inode, unsigned long block)
{
        struct buffer_head *bh;
        int err;

        err = nilfs_mdt_read_block(inode, block, 0, &bh);
        if (unlikely(err))
                return err;
        mark_buffer_dirty(bh);
        nilfs_mdt_mark_dirty(inode);
        brelse(bh);
        return 0;
}

int nilfs_mdt_fetch_dirty(struct inode *inode)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);

        if (nilfs_bmap_test_and_clear_dirty(ii->i_bmap)) {
                set_bit(NILFS_I_DIRTY, &ii->i_state);
                return 1;
        }
        return test_bit(NILFS_I_DIRTY, &ii->i_state);
}

static int
nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
{
        struct inode *inode = page->mapping->host;
        struct super_block *sb;
        int err = 0;

        if (inode && (inode->i_sb->s_flags & MS_RDONLY)) {
                /*
                 * It means that filesystem was remounted in read-only
                 * mode because of error or metadata corruption. But we
                 * have dirty pages that try to be flushed in background.
                 * So, here we simply discard this dirty page.
                 */
                nilfs_clear_dirty_page(page, false);
                unlock_page(page);
                return -EROFS;
        }

        redirty_page_for_writepage(wbc, page);
        unlock_page(page);

        if (!inode)
                return 0;

        sb = inode->i_sb;

        if (wbc->sync_mode == WB_SYNC_ALL)
                err = nilfs_construct_segment(sb);
        else if (wbc->for_reclaim)
                nilfs_flush_segment(sb, inode->i_ino);

        return err;
}


static const struct address_space_operations def_mdt_aops = {
        .writepage              = nilfs_mdt_write_page,
};

static const struct inode_operations def_mdt_iops;
static const struct file_operations def_mdt_fops;


int nilfs_mdt_init(struct inode *inode, gfp_t gfp_mask, size_t objsz)
{
        struct nilfs_mdt_info *mi;

        mi = kzalloc(max(sizeof(*mi), objsz), GFP_NOFS);
        if (!mi)
                return -ENOMEM;

        init_rwsem(&mi->mi_sem);
        inode->i_private = mi;

        inode->i_mode = S_IFREG;
        mapping_set_gfp_mask(inode->i_mapping, gfp_mask);

        inode->i_op = &def_mdt_iops;
        inode->i_fop = &def_mdt_fops;
        inode->i_mapping->a_ops = &def_mdt_aops;

        return 0;
}

void nilfs_mdt_set_entry_size(struct inode *inode, unsigned entry_size,
                              unsigned header_size)
{
        struct nilfs_mdt_info *mi = NILFS_MDT(inode);

        mi->mi_entry_size = entry_size;
        mi->mi_entries_per_block = (1 << inode->i_blkbits) / entry_size;
        mi->mi_first_entry_offset = DIV_ROUND_UP(header_size, entry_size);
}

/**
 * nilfs_mdt_setup_shadow_map - setup shadow map and bind it to metadata file
 * @inode: inode of the metadata file
 * @shadow: shadow mapping
 */
int nilfs_mdt_setup_shadow_map(struct inode *inode,
                               struct nilfs_shadow_map *shadow)
{
        struct nilfs_mdt_info *mi = NILFS_MDT(inode);

        INIT_LIST_HEAD(&shadow->frozen_buffers);
        address_space_init_once(&shadow->frozen_data);
        nilfs_mapping_init(&shadow->frozen_data, inode);
        address_space_init_once(&shadow->frozen_btnodes);
        nilfs_mapping_init(&shadow->frozen_btnodes, inode);
        mi->mi_shadow = shadow;
        return 0;
}

/**
 * nilfs_mdt_save_to_shadow_map - copy bmap and dirty pages to shadow map
 * @inode: inode of the metadata file
 */
int nilfs_mdt_save_to_shadow_map(struct inode *inode)
{
        struct nilfs_mdt_info *mi = NILFS_MDT(inode);
        struct nilfs_inode_info *ii = NILFS_I(inode);
        struct nilfs_shadow_map *shadow = mi->mi_shadow;
        int ret;

        ret = nilfs_copy_dirty_pages(&shadow->frozen_data, inode->i_mapping);
        if (ret)
                goto out;

        ret = nilfs_copy_dirty_pages(&shadow->frozen_btnodes,
                                     &ii->i_btnode_cache);
        if (ret)
                goto out;

        nilfs_bmap_save(ii->i_bmap, &shadow->bmap_store);
 out:
        return ret;
}

int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh)
{
        struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
        struct buffer_head *bh_frozen;
        struct page *page;
        int blkbits = inode->i_blkbits;

        page = grab_cache_page(&shadow->frozen_data, bh->b_page->index);
        if (!page)
                return -ENOMEM;

        if (!page_has_buffers(page))
                create_empty_buffers(page, 1 << blkbits, 0);

        bh_frozen = nilfs_page_get_nth_block(page, bh_offset(bh) >> blkbits);

        if (!buffer_uptodate(bh_frozen))
                nilfs_copy_buffer(bh_frozen, bh);
        if (list_empty(&bh_frozen->b_assoc_buffers)) {
                list_add_tail(&bh_frozen->b_assoc_buffers,
                              &shadow->frozen_buffers);
                set_buffer_nilfs_redirected(bh);
        } else {
                brelse(bh_frozen); /* already frozen */
        }

        unlock_page(page);
        page_cache_release(page);
        return 0;
}

struct buffer_head *
nilfs_mdt_get_frozen_buffer(struct inode *inode, struct buffer_head *bh)
{
        struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
        struct buffer_head *bh_frozen = NULL;
        struct page *page;
        int n;

        page = find_lock_page(&shadow->frozen_data, bh->b_page->index);
        if (page) {
                if (page_has_buffers(page)) {
                        n = bh_offset(bh) >> inode->i_blkbits;
                        bh_frozen = nilfs_page_get_nth_block(page, n);
                }
                unlock_page(page);
                page_cache_release(page);
        }
        return bh_frozen;
}

static void nilfs_release_frozen_buffers(struct nilfs_shadow_map *shadow)
{
        struct list_head *head = &shadow->frozen_buffers;
        struct buffer_head *bh;

        while (!list_empty(head)) {
                bh = list_first_entry(head, struct buffer_head,
                                      b_assoc_buffers);
                list_del_init(&bh->b_assoc_buffers);
                brelse(bh); /* drop ref-count to make it releasable */
        }
}

/**
 * nilfs_mdt_restore_from_shadow_map - restore dirty pages and bmap state
 * @inode: inode of the metadata file
 */
void nilfs_mdt_restore_from_shadow_map(struct inode *inode)
{
        struct nilfs_mdt_info *mi = NILFS_MDT(inode);
        struct nilfs_inode_info *ii = NILFS_I(inode);
        struct nilfs_shadow_map *shadow = mi->mi_shadow;

        down_write(&mi->mi_sem);

        if (mi->mi_palloc_cache)
                nilfs_palloc_clear_cache(inode);

        nilfs_clear_dirty_pages(inode->i_mapping, true);
        nilfs_copy_back_pages(inode->i_mapping, &shadow->frozen_data);

        nilfs_clear_dirty_pages(&ii->i_btnode_cache, true);
        nilfs_copy_back_pages(&ii->i_btnode_cache, &shadow->frozen_btnodes);

        nilfs_bmap_restore(ii->i_bmap, &shadow->bmap_store);

        up_write(&mi->mi_sem);
}

/**
 * nilfs_mdt_clear_shadow_map - truncate pages in shadow map caches
 * @inode: inode of the metadata file
 */
void nilfs_mdt_clear_shadow_map(struct inode *inode)
{
        struct nilfs_mdt_info *mi = NILFS_MDT(inode);
        struct nilfs_shadow_map *shadow = mi->mi_shadow;

        down_write(&mi->mi_sem);
        nilfs_release_frozen_buffers(shadow);
        truncate_inode_pages(&shadow->frozen_data, 0);
        truncate_inode_pages(&shadow->frozen_btnodes, 0);
        up_write(&mi->mi_sem);
}