mdt.c

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/*
 * 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 <[email protected]>
 */

#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;
}

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;
}

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;
}

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;
}

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;
    struct super_block *sb;
    int err = 0;

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

    inode = page->mapping->host;
    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_mapping->backing_dev_info = inode->i_sb->s_bdi;

    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);
}

int nilfs_mdt_setup_shadow_map(struct inode *inode,
                   struct nilfs_shadow_map *shadow)
{
    struct nilfs_mdt_info *mi = NILFS_MDT(inode);
    struct backing_dev_info *bdi = inode->i_sb->s_bdi;

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

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 */
    }
}

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

    nilfs_clear_dirty_pages(&ii->i_btnode_cache);
    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);
}

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);
}