nilfs2: deny write access to inodes in snapshots

[deliverable/linux.git] / fs / nilfs2 / inode.c

/*
 * inode.c - NILFS inode operations.
 *
 * 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/gfp.h>
#include <linux/mpage.h>
#include <linux/writeback.h>
#include <linux/uio.h>
#include "nilfs.h"
#include "btnode.h"
#include "segment.h"
#include "page.h"
#include "mdt.h"
#include "cpfile.h"
#include "ifile.h"

struct nilfs_iget_args {
        u64 ino;
        __u64 cno;
        struct nilfs_root *root;
        int for_gc;
};

/**
 * nilfs_get_block() - get a file block on the filesystem (callback function)
 * @inode - inode struct of the target file
 * @blkoff - file block number
 * @bh_result - buffer head to be mapped on
 * @create - indicate whether allocating the block or not when it has not
 *      been allocated yet.
 *
 * This function does not issue actual read request of the specified data
 * block. It is done by VFS.
 */
int nilfs_get_block(struct inode *inode, sector_t blkoff,
                    struct buffer_head *bh_result, int create)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);
        __u64 blknum = 0;
        int err = 0, ret;
        struct inode *dat = nilfs_dat_inode(NILFS_I_NILFS(inode));
        unsigned maxblocks = bh_result->b_size >> inode->i_blkbits;

        down_read(&NILFS_MDT(dat)->mi_sem);
        ret = nilfs_bmap_lookup_contig(ii->i_bmap, blkoff, &blknum, maxblocks);
        up_read(&NILFS_MDT(dat)->mi_sem);
        if (ret >= 0) { /* found */
                map_bh(bh_result, inode->i_sb, blknum);
                if (ret > 0)
                        bh_result->b_size = (ret << inode->i_blkbits);
                goto out;
        }
        /* data block was not found */
        if (ret == -ENOENT && create) {
                struct nilfs_transaction_info ti;

                bh_result->b_blocknr = 0;
                err = nilfs_transaction_begin(inode->i_sb, &ti, 1);
                if (unlikely(err))
                        goto out;
                err = nilfs_bmap_insert(ii->i_bmap, (unsigned long)blkoff,
                                        (unsigned long)bh_result);
                if (unlikely(err != 0)) {
                        if (err == -EEXIST) {
                                /*
                                 * The get_block() function could be called
                                 * from multiple callers for an inode.
                                 * However, the page having this block must
                                 * be locked in this case.
                                 */
                                printk(KERN_WARNING
                                       "nilfs_get_block: a race condition "
                                       "while inserting a data block. "
                                       "(inode number=%lu, file block "
                                       "offset=%llu)\n",
                                       inode->i_ino,
                                       (unsigned long long)blkoff);
                                err = 0;
                        } else if (err == -EINVAL) {
                                nilfs_error(inode->i_sb, __func__,
                                            "broken bmap (inode=%lu)\n",
                                            inode->i_ino);
                                err = -EIO;
                        }
                        nilfs_transaction_abort(inode->i_sb);
                        goto out;
                }
                nilfs_mark_inode_dirty(inode);
                nilfs_transaction_commit(inode->i_sb); /* never fails */
                /* Error handling should be detailed */
                set_buffer_new(bh_result);
                map_bh(bh_result, inode->i_sb, 0); /* dbn must be changed
                                                      to proper value */
        } else if (ret == -ENOENT) {
                /* not found is not error (e.g. hole); must return without
                   the mapped state flag. */
                ;
        } else {
                err = ret;
        }

 out:
        return err;
}

/**
 * nilfs_readpage() - implement readpage() method of nilfs_aops {}
 * address_space_operations.
 * @file - file struct of the file to be read
 * @page - the page to be read
 */
static int nilfs_readpage(struct file *file, struct page *page)
{
        return mpage_readpage(page, nilfs_get_block);
}

/**
 * nilfs_readpages() - implement readpages() method of nilfs_aops {}
 * address_space_operations.
 * @file - file struct of the file to be read
 * @mapping - address_space struct used for reading multiple pages
 * @pages - the pages to be read
 * @nr_pages - number of pages to be read
 */
static int nilfs_readpages(struct file *file, struct address_space *mapping,
                           struct list_head *pages, unsigned nr_pages)
{
        return mpage_readpages(mapping, pages, nr_pages, nilfs_get_block);
}

static int nilfs_writepages(struct address_space *mapping,
                            struct writeback_control *wbc)
{
        struct inode *inode = mapping->host;
        int err = 0;

        if (wbc->sync_mode == WB_SYNC_ALL)
                err = nilfs_construct_dsync_segment(inode->i_sb, inode,
                                                    wbc->range_start,
                                                    wbc->range_end);
        return err;
}

static int nilfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct inode *inode = page->mapping->host;
        int err;

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

        if (wbc->sync_mode == WB_SYNC_ALL) {
                err = nilfs_construct_segment(inode->i_sb);
                if (unlikely(err))
                        return err;
        } else if (wbc->for_reclaim)
                nilfs_flush_segment(inode->i_sb, inode->i_ino);

        return 0;
}

static int nilfs_set_page_dirty(struct page *page)
{
        int ret = __set_page_dirty_buffers(page);

        if (ret) {
                struct inode *inode = page->mapping->host;
                struct nilfs_sb_info *sbi = NILFS_SB(inode->i_sb);
                unsigned nr_dirty = 1 << (PAGE_SHIFT - inode->i_blkbits);

                nilfs_set_file_dirty(sbi, inode, nr_dirty);
        }
        return ret;
}

static int nilfs_write_begin(struct file *file, struct address_space *mapping,
                             loff_t pos, unsigned len, unsigned flags,
                             struct page **pagep, void **fsdata)

{
        struct inode *inode = mapping->host;
        int err = nilfs_transaction_begin(inode->i_sb, NULL, 1);

        if (unlikely(err))
                return err;

        err = block_write_begin(mapping, pos, len, flags, pagep,
                                nilfs_get_block);
        if (unlikely(err)) {
                loff_t isize = mapping->host->i_size;
                if (pos + len > isize)
                        vmtruncate(mapping->host, isize);

                nilfs_transaction_abort(inode->i_sb);
        }
        return err;
}

static int nilfs_write_end(struct file *file, struct address_space *mapping,
                           loff_t pos, unsigned len, unsigned copied,
                           struct page *page, void *fsdata)
{
        struct inode *inode = mapping->host;
        unsigned start = pos & (PAGE_CACHE_SIZE - 1);
        unsigned nr_dirty;
        int err;

        nr_dirty = nilfs_page_count_clean_buffers(page, start,
                                                  start + copied);
        copied = generic_write_end(file, mapping, pos, len, copied, page,
                                   fsdata);
        nilfs_set_file_dirty(NILFS_SB(inode->i_sb), inode, nr_dirty);
        err = nilfs_transaction_commit(inode->i_sb);
        return err ? : copied;
}

static ssize_t
nilfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
                loff_t offset, unsigned long nr_segs)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        ssize_t size;

        if (rw == WRITE)
                return 0;

        /* Needs synchronization with the cleaner */
        size = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
                                  offset, nr_segs, nilfs_get_block, NULL);

        /*
         * In case of error extending write may have instantiated a few
         * blocks outside i_size. Trim these off again.
         */
        if (unlikely((rw & WRITE) && size < 0)) {
                loff_t isize = i_size_read(inode);
                loff_t end = offset + iov_length(iov, nr_segs);

                if (end > isize)
                        vmtruncate(inode, isize);
        }

        return size;
}

const struct address_space_operations nilfs_aops = {
        .writepage              = nilfs_writepage,
        .readpage               = nilfs_readpage,
        .sync_page              = block_sync_page,
        .writepages             = nilfs_writepages,
        .set_page_dirty         = nilfs_set_page_dirty,
        .readpages              = nilfs_readpages,
        .write_begin            = nilfs_write_begin,
        .write_end              = nilfs_write_end,
        /* .releasepage         = nilfs_releasepage, */
        .invalidatepage         = block_invalidatepage,
        .direct_IO              = nilfs_direct_IO,
        .is_partially_uptodate  = block_is_partially_uptodate,
};

struct inode *nilfs_new_inode(struct inode *dir, int mode)
{
        struct super_block *sb = dir->i_sb;
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        struct inode *inode;
        struct nilfs_inode_info *ii;
        struct nilfs_root *root;
        int err = -ENOMEM;
        ino_t ino;

        inode = new_inode(sb);
        if (unlikely(!inode))
                goto failed;

        mapping_set_gfp_mask(inode->i_mapping,
                             mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);

        root = NILFS_I(dir)->i_root;
        ii = NILFS_I(inode);
        ii->i_state = 1 << NILFS_I_NEW;
        ii->i_root = root;

        err = nilfs_ifile_create_inode(root->ifile, &ino, &ii->i_bh);
        if (unlikely(err))
                goto failed_ifile_create_inode;
        /* reference count of i_bh inherits from nilfs_mdt_read_block() */

        atomic_inc(&root->inodes_count);
        inode_init_owner(inode, dir, mode);
        inode->i_ino = ino;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

        if (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)) {
                err = nilfs_bmap_read(ii->i_bmap, NULL);
                if (err < 0)
                        goto failed_bmap;

                set_bit(NILFS_I_BMAP, &ii->i_state);
                /* No lock is needed; iget() ensures it. */
        }

        ii->i_flags = NILFS_I(dir)->i_flags;
        if (S_ISLNK(mode))
                ii->i_flags &= ~(NILFS_IMMUTABLE_FL | NILFS_APPEND_FL);
        if (!S_ISDIR(mode))
                ii->i_flags &= ~NILFS_DIRSYNC_FL;

        /* ii->i_file_acl = 0; */
        /* ii->i_dir_acl = 0; */
        ii->i_dir_start_lookup = 0;
        nilfs_set_inode_flags(inode);
        spin_lock(&sbi->s_next_gen_lock);
        inode->i_generation = sbi->s_next_generation++;
        spin_unlock(&sbi->s_next_gen_lock);
        insert_inode_hash(inode);

        err = nilfs_init_acl(inode, dir);
        if (unlikely(err))
                goto failed_acl; /* never occur. When supporting
                                    nilfs_init_acl(), proper cancellation of
                                    above jobs should be considered */

        return inode;

 failed_acl:
 failed_bmap:
        inode->i_nlink = 0;
        iput(inode);  /* raw_inode will be deleted through
                         generic_delete_inode() */
        goto failed;

 failed_ifile_create_inode:
        make_bad_inode(inode);
        iput(inode);  /* if i_nlink == 1, generic_forget_inode() will be
                         called */
 failed:
        return ERR_PTR(err);
}

void nilfs_set_inode_flags(struct inode *inode)
{
        unsigned int flags = NILFS_I(inode)->i_flags;

        inode->i_flags &= ~(S_SYNC | S_APPEND | S_IMMUTABLE | S_NOATIME |
                            S_DIRSYNC);
        if (flags & NILFS_SYNC_FL)
                inode->i_flags |= S_SYNC;
        if (flags & NILFS_APPEND_FL)
                inode->i_flags |= S_APPEND;
        if (flags & NILFS_IMMUTABLE_FL)
                inode->i_flags |= S_IMMUTABLE;
#ifndef NILFS_ATIME_DISABLE
        if (flags & NILFS_NOATIME_FL)
#endif
                inode->i_flags |= S_NOATIME;
        if (flags & NILFS_DIRSYNC_FL)
                inode->i_flags |= S_DIRSYNC;
        mapping_set_gfp_mask(inode->i_mapping,
                             mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
}

int nilfs_read_inode_common(struct inode *inode,
                            struct nilfs_inode *raw_inode)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);
        int err;

        inode->i_mode = le16_to_cpu(raw_inode->i_mode);
        inode->i_uid = (uid_t)le32_to_cpu(raw_inode->i_uid);
        inode->i_gid = (gid_t)le32_to_cpu(raw_inode->i_gid);
        inode->i_nlink = le16_to_cpu(raw_inode->i_links_count);
        inode->i_size = le64_to_cpu(raw_inode->i_size);
        inode->i_atime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
        inode->i_ctime.tv_sec = le64_to_cpu(raw_inode->i_ctime);
        inode->i_mtime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
        inode->i_atime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
        inode->i_ctime.tv_nsec = le32_to_cpu(raw_inode->i_ctime_nsec);
        inode->i_mtime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
        if (inode->i_nlink == 0 && inode->i_mode == 0)
                return -EINVAL; /* this inode is deleted */

        inode->i_blocks = le64_to_cpu(raw_inode->i_blocks);
        ii->i_flags = le32_to_cpu(raw_inode->i_flags);
#if 0
        ii->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
        ii->i_dir_acl = S_ISREG(inode->i_mode) ?
                0 : le32_to_cpu(raw_inode->i_dir_acl);
#endif
        ii->i_dir_start_lookup = 0;
        inode->i_generation = le32_to_cpu(raw_inode->i_generation);

        if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
            S_ISLNK(inode->i_mode)) {
                err = nilfs_bmap_read(ii->i_bmap, raw_inode);
                if (err < 0)
                        return err;
                set_bit(NILFS_I_BMAP, &ii->i_state);
                /* No lock is needed; iget() ensures it. */
        }
        return 0;
}

static int __nilfs_read_inode(struct super_block *sb,
                              struct nilfs_root *root, unsigned long ino,
                              struct inode *inode)
{
        struct nilfs_sb_info *sbi = NILFS_SB(sb);
        struct inode *dat = nilfs_dat_inode(sbi->s_nilfs);
        struct buffer_head *bh;
        struct nilfs_inode *raw_inode;
        int err;

        down_read(&NILFS_MDT(dat)->mi_sem);     /* XXX */
        err = nilfs_ifile_get_inode_block(root->ifile, ino, &bh);
        if (unlikely(err))
                goto bad_inode;

        raw_inode = nilfs_ifile_map_inode(root->ifile, ino, bh);

        err = nilfs_read_inode_common(inode, raw_inode);
        if (err)
                goto failed_unmap;

        if (S_ISREG(inode->i_mode)) {
                inode->i_op = &nilfs_file_inode_operations;
                inode->i_fop = &nilfs_file_operations;
                inode->i_mapping->a_ops = &nilfs_aops;
        } else if (S_ISDIR(inode->i_mode)) {
                inode->i_op = &nilfs_dir_inode_operations;
                inode->i_fop = &nilfs_dir_operations;
                inode->i_mapping->a_ops = &nilfs_aops;
        } else if (S_ISLNK(inode->i_mode)) {
                inode->i_op = &nilfs_symlink_inode_operations;
                inode->i_mapping->a_ops = &nilfs_aops;
        } else {
                inode->i_op = &nilfs_special_inode_operations;
                init_special_inode(
                        inode, inode->i_mode,
                        huge_decode_dev(le64_to_cpu(raw_inode->i_device_code)));
        }
        nilfs_ifile_unmap_inode(root->ifile, ino, bh);
        brelse(bh);
        up_read(&NILFS_MDT(dat)->mi_sem);       /* XXX */
        nilfs_set_inode_flags(inode);
        return 0;

 failed_unmap:
        nilfs_ifile_unmap_inode(root->ifile, ino, bh);
        brelse(bh);

 bad_inode:
        up_read(&NILFS_MDT(dat)->mi_sem);       /* XXX */
        return err;
}

static int nilfs_iget_test(struct inode *inode, void *opaque)
{
        struct nilfs_iget_args *args = opaque;
        struct nilfs_inode_info *ii;

        if (args->ino != inode->i_ino || args->root != NILFS_I(inode)->i_root)
                return 0;

        ii = NILFS_I(inode);
        if (!test_bit(NILFS_I_GCINODE, &ii->i_state))
                return !args->for_gc;

        return args->for_gc && args->cno == ii->i_cno;
}

static int nilfs_iget_set(struct inode *inode, void *opaque)
{
        struct nilfs_iget_args *args = opaque;

        inode->i_ino = args->ino;
        if (args->for_gc) {
                NILFS_I(inode)->i_state = 1 << NILFS_I_GCINODE;
                NILFS_I(inode)->i_cno = args->cno;
                NILFS_I(inode)->i_root = NULL;
        } else {
                if (args->root && args->ino == NILFS_ROOT_INO)
                        nilfs_get_root(args->root);
                NILFS_I(inode)->i_root = args->root;
        }
        return 0;
}

struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
                         unsigned long ino)
{
        struct nilfs_iget_args args = {
                .ino = ino, .root = root, .cno = 0, .for_gc = 0
        };
        struct inode *inode;
        int err;

        inode = iget5_locked(sb, ino, nilfs_iget_test, nilfs_iget_set, &args);
        if (unlikely(!inode))
                return ERR_PTR(-ENOMEM);
        if (!(inode->i_state & I_NEW))
                return inode;

        err = __nilfs_read_inode(sb, root, ino, inode);
        if (unlikely(err)) {
                iget_failed(inode);
                return ERR_PTR(err);
        }
        unlock_new_inode(inode);
        return inode;
}

struct inode *nilfs_iget_for_gc(struct super_block *sb, unsigned long ino,
                                __u64 cno)
{
        struct nilfs_iget_args args = {
                .ino = ino, .root = NULL, .cno = cno, .for_gc = 1
        };
        struct inode *inode;
        int err;

        inode = iget5_locked(sb, ino, nilfs_iget_test, nilfs_iget_set, &args);
        if (unlikely(!inode))
                return ERR_PTR(-ENOMEM);
        if (!(inode->i_state & I_NEW))
                return inode;

        err = nilfs_init_gcinode(inode);
        if (unlikely(err)) {
                iget_failed(inode);
                return ERR_PTR(err);
        }
        unlock_new_inode(inode);
        return inode;
}

void nilfs_write_inode_common(struct inode *inode,
                              struct nilfs_inode *raw_inode, int has_bmap)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);

        raw_inode->i_mode = cpu_to_le16(inode->i_mode);
        raw_inode->i_uid = cpu_to_le32(inode->i_uid);
        raw_inode->i_gid = cpu_to_le32(inode->i_gid);
        raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
        raw_inode->i_size = cpu_to_le64(inode->i_size);
        raw_inode->i_ctime = cpu_to_le64(inode->i_ctime.tv_sec);
        raw_inode->i_mtime = cpu_to_le64(inode->i_mtime.tv_sec);
        raw_inode->i_ctime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);
        raw_inode->i_mtime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
        raw_inode->i_blocks = cpu_to_le64(inode->i_blocks);

        raw_inode->i_flags = cpu_to_le32(ii->i_flags);
        raw_inode->i_generation = cpu_to_le32(inode->i_generation);

        if (has_bmap)
                nilfs_bmap_write(ii->i_bmap, raw_inode);
        else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode))
                raw_inode->i_device_code =
                        cpu_to_le64(huge_encode_dev(inode->i_rdev));
        /* When extending inode, nilfs->ns_inode_size should be checked
           for substitutions of appended fields */
}

void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh)
{
        ino_t ino = inode->i_ino;
        struct nilfs_inode_info *ii = NILFS_I(inode);
        struct inode *ifile = ii->i_root->ifile;
        struct nilfs_inode *raw_inode;

        raw_inode = nilfs_ifile_map_inode(ifile, ino, ibh);

        if (test_and_clear_bit(NILFS_I_NEW, &ii->i_state))
                memset(raw_inode, 0, NILFS_MDT(ifile)->mi_entry_size);
        set_bit(NILFS_I_INODE_DIRTY, &ii->i_state);

        nilfs_write_inode_common(inode, raw_inode, 0);
                /* XXX: call with has_bmap = 0 is a workaround to avoid
                   deadlock of bmap. This delays update of i_bmap to just
                   before writing */
        nilfs_ifile_unmap_inode(ifile, ino, ibh);
}

#define NILFS_MAX_TRUNCATE_BLOCKS       16384  /* 64MB for 4KB block */

static void nilfs_truncate_bmap(struct nilfs_inode_info *ii,
                                unsigned long from)
{
        unsigned long b;
        int ret;

        if (!test_bit(NILFS_I_BMAP, &ii->i_state))
                return;
 repeat:
        ret = nilfs_bmap_last_key(ii->i_bmap, &b);
        if (ret == -ENOENT)
                return;
        else if (ret < 0)
                goto failed;

        if (b < from)
                return;

        b -= min_t(unsigned long, NILFS_MAX_TRUNCATE_BLOCKS, b - from);
        ret = nilfs_bmap_truncate(ii->i_bmap, b);
        nilfs_relax_pressure_in_lock(ii->vfs_inode.i_sb);
        if (!ret || (ret == -ENOMEM &&
                     nilfs_bmap_truncate(ii->i_bmap, b) == 0))
                goto repeat;

 failed:
        if (ret == -EINVAL)
                nilfs_error(ii->vfs_inode.i_sb, __func__,
                            "bmap is broken (ino=%lu)", ii->vfs_inode.i_ino);
        else
                nilfs_warning(ii->vfs_inode.i_sb, __func__,
                              "failed to truncate bmap (ino=%lu, err=%d)",
                              ii->vfs_inode.i_ino, ret);
}

void nilfs_truncate(struct inode *inode)
{
        unsigned long blkoff;
        unsigned int blocksize;
        struct nilfs_transaction_info ti;
        struct super_block *sb = inode->i_sb;
        struct nilfs_inode_info *ii = NILFS_I(inode);

        if (!test_bit(NILFS_I_BMAP, &ii->i_state))
                return;
        if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
                return;

        blocksize = sb->s_blocksize;
        blkoff = (inode->i_size + blocksize - 1) >> sb->s_blocksize_bits;
        nilfs_transaction_begin(sb, &ti, 0); /* never fails */

        block_truncate_page(inode->i_mapping, inode->i_size, nilfs_get_block);

        nilfs_truncate_bmap(ii, blkoff);

        inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        if (IS_SYNC(inode))
                nilfs_set_transaction_flag(NILFS_TI_SYNC);

        nilfs_mark_inode_dirty(inode);
        nilfs_set_file_dirty(NILFS_SB(sb), inode, 0);
        nilfs_transaction_commit(sb);
        /* May construct a logical segment and may fail in sync mode.
           But truncate has no return value. */
}

static void nilfs_clear_inode(struct inode *inode)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);

        /*
         * Free resources allocated in nilfs_read_inode(), here.
         */
        BUG_ON(!list_empty(&ii->i_dirty));
        brelse(ii->i_bh);
        ii->i_bh = NULL;

        if (test_bit(NILFS_I_BMAP, &ii->i_state))
                nilfs_bmap_clear(ii->i_bmap);

        nilfs_btnode_cache_clear(&ii->i_btnode_cache);

        if (ii->i_root && inode->i_ino == NILFS_ROOT_INO)
                nilfs_put_root(ii->i_root);
}

void nilfs_evict_inode(struct inode *inode)
{
        struct nilfs_transaction_info ti;
        struct super_block *sb = inode->i_sb;
        struct nilfs_inode_info *ii = NILFS_I(inode);

        if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
                if (inode->i_data.nrpages)
                        truncate_inode_pages(&inode->i_data, 0);
                end_writeback(inode);
                nilfs_clear_inode(inode);
                return;
        }
        nilfs_transaction_begin(sb, &ti, 0); /* never fails */

        if (inode->i_data.nrpages)
                truncate_inode_pages(&inode->i_data, 0);

        /* TODO: some of the following operations may fail.  */
        nilfs_truncate_bmap(ii, 0);
        nilfs_mark_inode_dirty(inode);
        end_writeback(inode);

        nilfs_ifile_delete_inode(ii->i_root->ifile, inode->i_ino);
        atomic_dec(&ii->i_root->inodes_count);

        nilfs_clear_inode(inode);

        if (IS_SYNC(inode))
                nilfs_set_transaction_flag(NILFS_TI_SYNC);
        nilfs_transaction_commit(sb);
        /* May construct a logical segment and may fail in sync mode.
           But delete_inode has no return value. */
}

int nilfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
        struct nilfs_transaction_info ti;
        struct inode *inode = dentry->d_inode;
        struct super_block *sb = inode->i_sb;
        int err;

        err = inode_change_ok(inode, iattr);
        if (err)
                return err;

        err = nilfs_transaction_begin(sb, &ti, 0);
        if (unlikely(err))
                return err;

        if ((iattr->ia_valid & ATTR_SIZE) &&
            iattr->ia_size != i_size_read(inode)) {
                err = vmtruncate(inode, iattr->ia_size);
                if (unlikely(err))
                        goto out_err;
        }

        setattr_copy(inode, iattr);
        mark_inode_dirty(inode);

        if (iattr->ia_valid & ATTR_MODE) {
                err = nilfs_acl_chmod(inode);
                if (unlikely(err))
                        goto out_err;
        }

        return nilfs_transaction_commit(sb);

out_err:
        nilfs_transaction_abort(sb);
        return err;
}

int nilfs_permission(struct inode *inode, int mask)
{
        struct nilfs_root *root = NILFS_I(inode)->i_root;

        if ((mask & MAY_WRITE) && root &&
            root->cno != NILFS_CPTREE_CURRENT_CNO)
                return -EROFS; /* snapshot is not writable */

        return generic_permission(inode, mask, NULL);
}

int nilfs_load_inode_block(struct nilfs_sb_info *sbi, struct inode *inode,
                           struct buffer_head **pbh)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);
        int err;

        spin_lock(&sbi->s_inode_lock);
        if (ii->i_bh == NULL) {
                spin_unlock(&sbi->s_inode_lock);
                err = nilfs_ifile_get_inode_block(ii->i_root->ifile,
                                                  inode->i_ino, pbh);
                if (unlikely(err))
                        return err;
                spin_lock(&sbi->s_inode_lock);
                if (ii->i_bh == NULL)
                        ii->i_bh = *pbh;
                else {
                        brelse(*pbh);
                        *pbh = ii->i_bh;
                }
        } else
                *pbh = ii->i_bh;

        get_bh(*pbh);
        spin_unlock(&sbi->s_inode_lock);
        return 0;
}

int nilfs_inode_dirty(struct inode *inode)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);
        struct nilfs_sb_info *sbi = NILFS_SB(inode->i_sb);
        int ret = 0;

        if (!list_empty(&ii->i_dirty)) {
                spin_lock(&sbi->s_inode_lock);
                ret = test_bit(NILFS_I_DIRTY, &ii->i_state) ||
                        test_bit(NILFS_I_BUSY, &ii->i_state);
                spin_unlock(&sbi->s_inode_lock);
        }
        return ret;
}

int nilfs_set_file_dirty(struct nilfs_sb_info *sbi, struct inode *inode,
                         unsigned nr_dirty)
{
        struct nilfs_inode_info *ii = NILFS_I(inode);

        atomic_add(nr_dirty, &sbi->s_nilfs->ns_ndirtyblks);

        if (test_and_set_bit(NILFS_I_DIRTY, &ii->i_state))
                return 0;

        spin_lock(&sbi->s_inode_lock);
        if (!test_bit(NILFS_I_QUEUED, &ii->i_state) &&
            !test_bit(NILFS_I_BUSY, &ii->i_state)) {
                /* Because this routine may race with nilfs_dispose_list(),
                   we have to check NILFS_I_QUEUED here, too. */
                if (list_empty(&ii->i_dirty) && igrab(inode) == NULL) {
                        /* This will happen when somebody is freeing
                           this inode. */
                        nilfs_warning(sbi->s_super, __func__,
                                      "cannot get inode (ino=%lu)\n",
                                      inode->i_ino);
                        spin_unlock(&sbi->s_inode_lock);
                        return -EINVAL; /* NILFS_I_DIRTY may remain for
                                           freeing inode */
                }
                list_del(&ii->i_dirty);
                list_add_tail(&ii->i_dirty, &sbi->s_dirty_files);
                set_bit(NILFS_I_QUEUED, &ii->i_state);
        }
        spin_unlock(&sbi->s_inode_lock);
        return 0;
}

int nilfs_mark_inode_dirty(struct inode *inode)
{
        struct nilfs_sb_info *sbi = NILFS_SB(inode->i_sb);
        struct buffer_head *ibh;
        int err;

        err = nilfs_load_inode_block(sbi, inode, &ibh);
        if (unlikely(err)) {
                nilfs_warning(inode->i_sb, __func__,
                              "failed to reget inode block.\n");
                return err;
        }
        nilfs_update_inode(inode, ibh);
        nilfs_mdt_mark_buffer_dirty(ibh);
        nilfs_mdt_mark_dirty(NILFS_I(inode)->i_root->ifile);
        brelse(ibh);
        return 0;
}

/**
 * nilfs_dirty_inode - reflect changes on given inode to an inode block.
 * @inode: inode of the file to be registered.
 *
 * nilfs_dirty_inode() loads a inode block containing the specified
 * @inode and copies data from a nilfs_inode to a corresponding inode
 * entry in the inode block. This operation is excluded from the segment
 * construction. This function can be called both as a single operation
 * and as a part of indivisible file operations.
 */
void nilfs_dirty_inode(struct inode *inode)
{
        struct nilfs_transaction_info ti;
        struct nilfs_mdt_info *mdi = NILFS_MDT(inode);

        if (is_bad_inode(inode)) {
                nilfs_warning(inode->i_sb, __func__,
                              "tried to mark bad_inode dirty. ignored.\n");
                dump_stack();
                return;
        }
        if (mdi) {
                nilfs_mdt_mark_dirty(inode);
                return;
        }
        nilfs_transaction_begin(inode->i_sb, &ti, 0);
        nilfs_mark_inode_dirty(inode);
        nilfs_transaction_commit(inode->i_sb); /* never fails */
}