/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * 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
 *
 * Authors: Artem Bityutskiy (Битюцкий Артём)
 *          Adrian Hunter
 */

/*
 * This file implements UBIFS journal.
 *
 * The journal consists of 2 parts - the log and bud LEBs. The log has fixed
 * length and position, while a bud logical eraseblock is any LEB in the main
 * area. Buds contain file system data - data nodes, inode nodes, etc. The log
 * contains only references to buds and some other stuff like commit
 * start node. The idea is that when we commit the journal, we do
 * not copy the data, the buds just become indexed. Since after the commit the
 * nodes in bud eraseblocks become leaf nodes of the file system index tree, we
 * use term "bud". Analogy is obvious, bud eraseblocks contain nodes which will
 * become leafs in the future.
 *
 * The journal is multi-headed because we want to write data to the journal as
 * optimally as possible. It is nice to have nodes belonging to the same inode
 * in one LEB, so we may write data owned by different inodes to different
 * journal heads, although at present only one data head is used.
 *
 * For recovery reasons, the base head contains all inode nodes, all directory
 * entry nodes and all truncate nodes. This means that the other heads contain
 * only data nodes.
 *
 * Bud LEBs may be half-indexed. For example, if the bud was not full at the
 * time of commit, the bud is retained to continue to be used in the journal,
 * even though the "front" of the LEB is now indexed. In that case, the log
 * reference contains the offset where the bud starts for the purposes of the
 * journal.
 *
 * The journal size has to be limited, because the larger is the journal, the
 * longer it takes to mount UBIFS (scanning the journal) and the more memory it
 * takes (indexing in the TNC).
 *
 * All the journal write operations like 'ubifs_jnl_update()' here, which write
 * multiple UBIFS nodes to the journal at one go, are atomic with respect to
 * unclean reboots. Should the unclean reboot happen, the recovery code drops
 * all the nodes.
 */

#include "ubifs.h"

/**
 * zero_ino_node_unused - zero out unused fields of an on-flash inode node.
 * @ino: the inode to zero out
 */
static inline void zero_ino_node_unused(struct ubifs_ino_node *ino)
{
        memset(ino->padding1, 0, 4);
        memset(ino->padding2, 0, 26);
}

/**
 * zero_dent_node_unused - zero out unused fields of an on-flash directory
 *                         entry node.
 * @dent: the directory entry to zero out
 */
static inline void zero_dent_node_unused(struct ubifs_dent_node *dent)
{
        dent->padding1 = 0;
        memset(dent->padding2, 0, 4);
}

/**
 * zero_data_node_unused - zero out unused fields of an on-flash data node.
 * @data: the data node to zero out
 */
static inline void zero_data_node_unused(struct ubifs_data_node *data)
{
        memset(data->padding, 0, 2);
}

/**
 * zero_trun_node_unused - zero out unused fields of an on-flash truncation
 *                         node.
 * @trun: the truncation node to zero out
 */
static inline void zero_trun_node_unused(struct ubifs_trun_node *trun)
{
        memset(trun->padding, 0, 12);
}

/**
 * reserve_space - reserve space in the journal.
 * @c: UBIFS file-system description object
 * @jhead: journal head number
 * @len: node length
 *
 * This function reserves space in journal head @head. If the reservation
 * succeeded, the journal head stays locked and later has to be unlocked using
 * 'release_head()'. 'write_node()' and 'write_head()' functions also unlock
 * it. Returns zero in case of success, %-EAGAIN if commit has to be done, and
 * other negative error codes in case of other failures.
 */
static int reserve_space(struct ubifs_info *c, int jhead, int len)
{
        int err = 0, err1, retries = 0, avail, lnum, offs, squeeze;
        struct ubifs_wbuf *wbuf = &c->jheads[jhead].wbuf;

        /*
         * Typically, the base head has smaller nodes written to it, so it is
         * better to try to allocate space at the ends of eraseblocks. This is
         * what the squeeze parameter does.
         */
        ubifs_assert(!c->ro_media && !c->ro_mount);
        squeeze = (jhead == BASEHD);
again:
        mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);

        if (c->ro_error) {
                err = -EROFS;
                goto out_unlock;
        }

        avail = c->leb_size - wbuf->offs - wbuf->used;
        if (wbuf->lnum != -1 && avail >= len)
                return 0;

        /*
         * Write buffer wasn't seek'ed or there is no enough space - look for an
         * LEB with some empty space.
         */
        lnum = ubifs_find_free_space(c, len, &offs, squeeze);
        if (lnum >= 0)
                goto out;

        err = lnum;
        if (err != -ENOSPC)
                goto out_unlock;

        /*
         * No free space, we have to run garbage collector to make
         * some. But the write-buffer mutex has to be unlocked because
         * GC also takes it.
         */
        dbg_jnl("no free space in jhead %s, run GC", dbg_jhead(jhead));
        mutex_unlock(&wbuf->io_mutex);

        lnum = ubifs_garbage_collect(c, 0);
        if (lnum < 0) {
                err = lnum;
                if (err != -ENOSPC)
                        return err;

                /*
                 * GC could not make a free LEB. But someone else may
                 * have allocated new bud for this journal head,
                 * because we dropped @wbuf->io_mutex, so try once
                 * again.
                 */
                dbg_jnl("GC couldn't make a free LEB for jhead %s",
                        dbg_jhead(jhead));
                if (retries++ < 2) {
                        dbg_jnl("retry (%d)", retries);
                        goto again;
                }

                dbg_jnl("return -ENOSPC");
                return err;
        }

        mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
        dbg_jnl("got LEB %d for jhead %s", lnum, dbg_jhead(jhead));
        avail = c->leb_size - wbuf->offs - wbuf->used;

        if (wbuf->lnum != -1 && avail >= len) {
                /*
                 * Someone else has switched the journal head and we have
                 * enough space now. This happens when more than one process is
                 * trying to write to the same journal head at the same time.
                 */
                dbg_jnl("return LEB %d back, already have LEB %d:%d",
                        lnum, wbuf->lnum, wbuf->offs + wbuf->used);
                err = ubifs_return_leb(c, lnum);
                if (err)
                        goto out_unlock;
                return 0;
        }

        offs = 0;

out:
        /*
         * Make sure we synchronize the write-buffer before we add the new bud
         * to the log. Otherwise we may have a power cut after the log
         * reference node for the last bud (@lnum) is written but before the
         * write-buffer data are written to the next-to-last bud
         * (@wbuf->lnum). And the effect would be that the recovery would see
         * that there is corruption in the next-to-last bud.
         */
        err = ubifs_wbuf_sync_nolock(wbuf);
        if (err)
                goto out_return;
        err = ubifs_add_bud_to_log(c, jhead, lnum, offs);
        if (err)
                goto out_return;
        err = ubifs_wbuf_seek_nolock(wbuf, lnum, offs);
        if (err)
                goto out_unlock;

        return 0;

out_unlock:
        mutex_unlock(&wbuf->io_mutex);
        return err;

out_return:
        /* An error occurred and the LEB has to be returned to lprops */
        ubifs_assert(err < 0);
        err1 = ubifs_return_leb(c, lnum);
        if (err1 && err == -EAGAIN)
                /*
                 * Return original error code only if it is not %-EAGAIN,
                 * which is not really an error. Otherwise, return the error
                 * code of 'ubifs_return_leb()'.
                 */
                err = err1;
        mutex_unlock(&wbuf->io_mutex);
        return err;
}

/**
 * write_node - write node to a journal head.
 * @c: UBIFS file-system description object
 * @jhead: journal head
 * @node: node to write
 * @len: node length
 * @lnum: LEB number written is returned here
 * @offs: offset written is returned here
 *
 * This function writes a node to reserved space of journal head @jhead.
 * Returns zero in case of success and a negative error code in case of
 * failure.
 */
static int write_node(struct ubifs_info *c, int jhead, void *node, int len,
                      int *lnum, int *offs)
{
        struct ubifs_wbuf *wbuf = &c->jheads[jhead].wbuf;

        ubifs_assert(jhead != GCHD);

        *lnum = c->jheads[jhead].wbuf.lnum;
        *offs = c->jheads[jhead].wbuf.offs + c->jheads[jhead].wbuf.used;

        dbg_jnl("jhead %s, LEB %d:%d, len %d",
                dbg_jhead(jhead), *lnum, *offs, len);
        ubifs_prepare_node(c, node, len, 0);

        return ubifs_wbuf_write_nolock(wbuf, node, len);
}

/**
 * write_head - write data to a journal head.
 * @c: UBIFS file-system description object
 * @jhead: journal head
 * @buf: buffer to write
 * @len: length to write
 * @lnum: LEB number written is returned here
 * @offs: offset written is returned here
 * @sync: non-zero if the write-buffer has to by synchronized
 *
 * This function is the same as 'write_node()' but it does not assume the
 * buffer it is writing is a node, so it does not prepare it (which means
 * initializing common header and calculating CRC).
 */
static int write_head(struct ubifs_info *c, int jhead, void *buf, int len,
                      int *lnum, int *offs, int sync)
{
        int err;
        struct ubifs_wbuf *wbuf = &c->jheads[jhead].wbuf;

        ubifs_assert(jhead != GCHD);

        *lnum = c->jheads[jhead].wbuf.lnum;
        *offs = c->jheads[jhead].wbuf.offs + c->jheads[jhead].wbuf.used;
        dbg_jnl("jhead %s, LEB %d:%d, len %d",
                dbg_jhead(jhead), *lnum, *offs, len);

        err = ubifs_wbuf_write_nolock(wbuf, buf, len);
        if (err)
                return err;
        if (sync)
                err = ubifs_wbuf_sync_nolock(wbuf);
        return err;
}

/**
 * make_reservation - reserve journal space.
 * @c: UBIFS file-system description object
 * @jhead: journal head
 * @len: how many bytes to reserve
 *
 * This function makes space reservation in journal head @jhead. The function
 * takes the commit lock and locks the journal head, and the caller has to
 * unlock the head and finish the reservation with 'finish_reservation()'.
 * Returns zero in case of success and a negative error code in case of
 * failure.
 *
 * Note, the journal head may be unlocked as soon as the data is written, while
 * the commit lock has to be released after the data has been added to the
 * TNC.
 */
static int make_reservation(struct ubifs_info *c, int jhead, int len)
{
        int err, cmt_retries = 0, nospc_retries = 0;

again:
        down_read(&c->commit_sem);
        err = reserve_space(c, jhead, len);
        if (!err)
                return 0;
        up_read(&c->commit_sem);

        if (err == -ENOSPC) {
                /*
                 * GC could not make any progress. We should try to commit
                 * once because it could make some dirty space and GC would
                 * make progress, so make the error -EAGAIN so that the below
                 * will commit and re-try.
                 */
                if (nospc_retries++ < 2) {
                        dbg_jnl("no space, retry");
                        err = -EAGAIN;
                }

                /*
                 * This means that the budgeting is incorrect. We always have
                 * to be able to write to the media, because all operations are
                 * budgeted. Deletions are not budgeted, though, but we reserve
                 * an extra LEB for them.
                 */
        }

        if (err != -EAGAIN)
                goto out;

        /*
         * -EAGAIN means that the journal is full or too large, or the above
         * code wants to do one commit. Do this and re-try.
         */
        if (cmt_retries > 128) {
                /*
                 * This should not happen unless the journal size limitations
                 * are too tough.
                 */
                ubifs_err("stuck in space allocation");
                err = -ENOSPC;
                goto out;
        } else if (cmt_retries > 32)
                ubifs_warn("too many space allocation re-tries (%d)",
                           cmt_retries);

        dbg_jnl("-EAGAIN, commit and retry (retried %d times)",
                cmt_retries);
        cmt_retries += 1;

        err = ubifs_run_commit(c);
        if (err)
                return err;
        goto again;

out:
        ubifs_err("cannot reserve %d bytes in jhead %d, error %d",
                  len, jhead, err);
        if (err == -ENOSPC) {
                /* This are some budgeting problems, print useful information */
                down_write(&c->commit_sem);
                dump_stack();
                ubifs_dump_budg(c, &c->bi);
                ubifs_dump_lprops(c);
                cmt_retries = dbg_check_lprops(c);
                up_write(&c->commit_sem);
        }
        return err;
}

/**
 * release_head - release a journal head.
 * @c: UBIFS file-system description object
 * @jhead: journal head
 *
 * This function releases journal head @jhead which was locked by
 * the 'make_reservation()' function. It has to be called after each successful
 * 'make_reservation()' invocation.
 */
static inline void release_head(struct ubifs_info *c, int jhead)
{
        mutex_unlock(&c->jheads[jhead].wbuf.io_mutex);
}

/**
 * finish_reservation - finish a reservation.
 * @c: UBIFS file-system description object
 *
 * This function finishes journal space reservation. It must be called after
 * 'make_reservation()'.
 */
static void finish_reservation(struct ubifs_info *c)
{
        up_read(&c->commit_sem);
}

/**
 * get_dent_type - translate VFS inode mode to UBIFS directory entry type.
 * @mode: inode mode
 */
static int get_dent_type(int mode)
{
        switch (mode & S_IFMT) {
        case S_IFREG:
                return UBIFS_ITYPE_REG;
        case S_IFDIR:
                return UBIFS_ITYPE_DIR;
        case S_IFLNK:
                return UBIFS_ITYPE_LNK;
        case S_IFBLK:
                return UBIFS_ITYPE_BLK;
        case S_IFCHR:
                return UBIFS_ITYPE_CHR;
        case S_IFIFO:
                return UBIFS_ITYPE_FIFO;
        case S_IFSOCK:
                return UBIFS_ITYPE_SOCK;
        default:
                BUG();
        }
        return 0;
}

/**
 * pack_inode - pack an inode node.
 * @c: UBIFS file-system description object
 * @ino: buffer in which to pack inode node
 * @inode: inode to pack
 * @last: indicates the last node of the group
 */
static void pack_inode(struct ubifs_info *c, struct ubifs_ino_node *ino,
                       const struct inode *inode, int last)
{
        int data_len = 0, last_reference = !inode->i_nlink;
        struct ubifs_inode *ui = ubifs_inode(inode);

        ino->ch.node_type = UBIFS_INO_NODE;
        ino_key_init_flash(c, &ino->key, inode->i_ino);
        ino->creat_sqnum = cpu_to_le64(ui->creat_sqnum);
        ino->atime_sec  = cpu_to_le64(inode->i_atime.tv_sec);
        ino->atime_nsec = cpu_to_le32(inode->i_atime.tv_nsec);
        ino->ctime_sec  = cpu_to_le64(inode->i_ctime.tv_sec);
        ino->ctime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);
        ino->mtime_sec  = cpu_to_le64(inode->i_mtime.tv_sec);
        ino->mtime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
        ino->uid   = cpu_to_le32(inode->i_uid);
        ino->gid   = cpu_to_le32(inode->i_gid);
        ino->mode  = cpu_to_le32(inode->i_mode);
        ino->flags = cpu_to_le32(ui->flags);
        ino->size  = cpu_to_le64(ui->ui_size);
        ino->nlink = cpu_to_le32(inode->i_nlink);
        ino->compr_type  = cpu_to_le16(ui->compr_type);
        ino->data_len    = cpu_to_le32(ui->data_len);
        ino->xattr_cnt   = cpu_to_le32(ui->xattr_cnt);
        ino->xattr_size  = cpu_to_le32(ui->xattr_size);
        ino->xattr_names = cpu_to_le32(ui->xattr_names);
        zero_ino_node_unused(ino);

        /*
         * Drop the attached data if this is a deletion inode, the data is not
         * needed anymore.
         */
        if (!last_reference) {
                memcpy(ino->data, ui->data, ui->data_len);
                data_len = ui->data_len;
        }

        ubifs_prep_grp_node(c, ino, UBIFS_INO_NODE_SZ + data_len, last);
}

/**
 * mark_inode_clean - mark UBIFS inode as clean.
 * @c: UBIFS file-system description object
 * @ui: UBIFS inode to mark as clean
 *
 * This helper function marks UBIFS inode @ui as clean by cleaning the
 * @ui->dirty flag and releasing its budget. Note, VFS may still treat the
 * inode as dirty and try to write it back, but 'ubifs_write_inode()' would
 * just do nothing.
 */
static void mark_inode_clean(struct ubifs_info *c, struct ubifs_inode *ui)
{
        if (ui->dirty)
                ubifs_release_dirty_inode_budget(c, ui);
        ui->dirty = 0;
}

/**
 * ubifs_jnl_update - update inode.
 * @c: UBIFS file-system description object
 * @dir: parent inode or host inode in case of extended attributes
 * @nm: directory entry name
 * @inode: inode to update
 * @deletion: indicates a directory entry deletion i.e unlink or rmdir
 * @xent: non-zero if the directory entry is an extended attribute entry
 *
 * This function updates an inode by writing a directory entry (or extended
 * attribute entry), the inode itself, and the parent directory inode (or the
 * host inode) to the journal.
 *
 * The function writes the host inode @dir last, which is important in case of
 * extended attributes. Indeed, then we guarantee that if the host inode gets
 * synchronized (with 'fsync()'), and the write-buffer it sits in gets flushed,
 * the extended attribute inode gets flushed too. And this is exactly what the
 * user expects - synchronizing the host inode synchronizes its extended
 * attributes. Similarly, this guarantees that if @dir is synchronized, its
 * directory entry corresponding to @nm gets synchronized too.
 *
 * If the inode (@inode) or the parent directory (@dir) are synchronous, this
 * function synchronizes the write-buffer.
 *
 * This function marks the @dir and @inode inodes as clean and returns zero on
 * success. In case of failure, a negative error code is returned.
 */
int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
                     const struct qstr *nm, const struct inode *inode,
                     int deletion, int xent)
{
        int err, dlen, ilen, len, lnum, ino_offs, dent_offs;
        int aligned_dlen, aligned_ilen, sync = IS_DIRSYNC(dir);
        int last_reference = !!(deletion && inode->i_nlink == 0);
        struct ubifs_inode *ui = ubifs_inode(inode);
        struct ubifs_inode *dir_ui = ubifs_inode(dir);
        struct ubifs_dent_node *dent;
        struct ubifs_ino_node *ino;
        union ubifs_key dent_key, ino_key;

        dbg_jnl("ino %lu, dent '%.*s', data len %d in dir ino %lu",
                inode->i_ino, nm->len, nm->name, ui->data_len, dir->i_ino);
        ubifs_assert(dir_ui->data_len == 0);
        ubifs_assert(mutex_is_locked(&dir_ui->ui_mutex));

        dlen = UBIFS_DENT_NODE_SZ + nm->len + 1;
        ilen = UBIFS_INO_NODE_SZ;

        /*
         * If the last reference to the inode is being deleted, then there is
         * no need to attach and write inode data, it is being deleted anyway.
         * And if the inode is being deleted, no need to synchronize
         * write-buffer even if the inode is synchronous.
         */
        if (!last_reference) {
                ilen += ui->data_len;
                sync |= IS_SYNC(inode);
        }

        aligned_dlen = ALIGN(dlen, 8);
        aligned_ilen = ALIGN(ilen, 8);
        len = aligned_dlen + aligned_ilen + UBIFS_INO_NODE_SZ;
        dent = kmalloc(len, GFP_NOFS);
        if (!dent)
                return -ENOMEM;

        /* Make reservation before allocating sequence numbers */
        err = make_reservation(c, BASEHD, len);
        if (err)
                goto out_free;

        if (!xent) {
                dent->ch.node_type = UBIFS_DENT_NODE;
                dent_key_init(c, &dent_key, dir->i_ino, nm);
        } else {
                dent->ch.node_type = UBIFS_XENT_NODE;
                xent_key_init(c, &dent_key, dir->i_ino, nm);
        }

        key_write(c, &dent_key, dent->key);
        dent->inum = deletion ? 0 : cpu_to_le64(inode->i_ino);
        dent->type = get_dent_type(inode->i_mode);
        dent->nlen = cpu_to_le16(nm->len);
        memcpy(dent->name, nm->name, nm->len);
        dent->name[nm->len] = '\0';
        zero_dent_node_unused(dent);
        ubifs_prep_grp_node(c, dent, dlen, 0);

        ino = (void *)dent + aligned_dlen;
        pack_inode(c, ino, inode, 0);
        ino = (void *)ino + aligned_ilen;
        pack_inode(c, ino, dir, 1);

        if (last_reference) {
                err = ubifs_add_orphan(c, inode->i_ino);
                if (err) {
                        release_head(c, BASEHD);
                        goto out_finish;
                }
                ui->del_cmtno = c->cmt_no;
        }

        err = write_head(c, BASEHD, dent, len, &lnum, &dent_offs, sync);
        if (err)
                goto out_release;
        if (!sync) {
                struct ubifs_wbuf *wbuf = &c->jheads[BASEHD].wbuf;

                ubifs_wbuf_add_ino_nolock(wbuf, inode->i_ino);
                ubifs_wbuf_add_ino_nolock(wbuf, dir->i_ino);
        }
        release_head(c, BASEHD);
        kfree(dent);

        if (deletion) {
                err = ubifs_tnc_remove_nm(c, &dent_key, nm);
                if (err)
                        goto out_ro;
                err = ubifs_add_dirt(c, lnum, dlen);
        } else
                err = ubifs_tnc_add_nm(c, &dent_key, lnum, dent_offs, dlen, nm);
        if (err)
                goto out_ro;

        /*
         * Note, we do not remove the inode from TNC even if the last reference
         * to it has just been deleted, because the inode may still be opened.
         * Instead, the inode has been added to orphan lists and the orphan
         * subsystem will take further care about it.
         */
        ino_key_init(c, &ino_key, inode->i_ino);
        ino_offs = dent_offs + aligned_dlen;
        err = ubifs_tnc_add(c, &ino_key, lnum, ino_offs, ilen);
        if (err)
                goto out_ro;

        ino_key_init(c, &ino_key, dir->i_ino);
        ino_offs += aligned_ilen;
        err = ubifs_tnc_add(c, &ino_key, lnum, ino_offs, UBIFS_INO_NODE_SZ);
        if (err)
                goto out_ro;

        finish_reservation(c);
        spin_lock(&ui->ui_lock);
        ui->synced_i_size = ui->ui_size;
        spin_unlock(&ui->ui_lock);
        mark_inode_clean(c, ui);
        mark_inode_clean(c, dir_ui);
        return 0;

out_finish:
        finish_reservation(c);
out_free:
        kfree(dent);
        return err;

out_release:
        release_head(c, BASEHD);
        kfree(dent);
out_ro:
        ubifs_ro_mode(c, err);
        if (last_reference)
                ubifs_delete_orphan(c, inode->i_ino);
        finish_reservation(c);
        return err;
}

/**
 * ubifs_jnl_write_data - write a data node to the journal.
 * @c: UBIFS file-system description object
 * @inode: inode the data node belongs to
 * @key: node key
 * @buf: buffer to write
 * @len: data length (must not exceed %UBIFS_BLOCK_SIZE)
 *
 * This function writes a data node to the journal. Returns %0 if the data node
 * was successfully written, and a negative error code in case of failure.
 */
int ubifs_jnl_write_data(struct ubifs_info *c, const struct inode *inode,
                         const union ubifs_key *key, const void *buf, int len)
{
        struct ubifs_data_node *data;
        int err, lnum, offs, compr_type, out_len;
        int dlen = COMPRESSED_DATA_NODE_BUF_SZ, allocated = 1;
        struct ubifs_inode *ui = ubifs_inode(inode);

        dbg_jnlk(key, "ino %lu, blk %u, len %d, key ",
                (unsigned long)key_inum(c, key), key_block(c, key), len);
        ubifs_assert(len <= UBIFS_BLOCK_SIZE);

        data = kmalloc(dlen, GFP_NOFS | __GFP_NOWARN);
        if (!data) {
                /*
                 * Fall-back to the write reserve buffer. Note, we might be
                 * currently on the memory reclaim path, when the kernel is
                 * trying to free some memory by writing out dirty pages. The
                 * write reserve buffer helps us to guarantee that we are
                 * always able to write the data.
                 */
                allocated = 0;
                mutex_lock(&c->write_reserve_mutex);
                data = c->write_reserve_buf;
        }

        data->ch.node_type = UBIFS_DATA_NODE;
        key_write(c, key, &data->key);
        data->size = cpu_to_le32(len);
        zero_data_node_unused(data);

        if (!(ui->flags & UBIFS_COMPR_FL))
                /* Compression is disabled for this inode */
                compr_type = UBIFS_COMPR_NONE;
        else
                compr_type = ui->compr_type;

        out_len = dlen - UBIFS_DATA_NODE_SZ;
        ubifs_compress(buf, len, &data->data, &out_len, &compr_type);
        ubifs_assert(out_len <= UBIFS_BLOCK_SIZE);

        dlen = UBIFS_DATA_NODE_SZ + out_len;
        data->compr_type = cpu_to_le16(compr_type);

        /* Make reservation before allocating sequence numbers */
        err = make_reservation(c, DATAHD, dlen);
        if (err)
                goto out_free;

        err = write_node(c, DATAHD, data, dlen, &lnum, &offs);
        if (err)
                goto out_release;
        ubifs_wbuf_add_ino_nolock(&c->jheads[DATAHD].wbuf, key_inum(c, key));
        release_head(c, DATAHD);

        err = ubifs_tnc_add(c, key, lnum, offs, dlen);
        if (err)
                goto out_ro;

        finish_reservation(c);
        if (!allocated)
                mutex_unlock(&c->write_reserve_mutex);
        else
                kfree(data);
        return 0;

out_release:
        release_head(c, DATAHD);
out_ro:
        ubifs_ro_mode(c, err);
        finish_reservation(c);
out_free:
        if (!allocated)
                mutex_unlock(&c->write_reserve_mutex);
        else
                kfree(data);
        return err;
}

/**
 * ubifs_jnl_write_inode - flush inode to the journal.
 * @c: UBIFS file-system description object
 * @inode: inode to flush
 *
 * This function writes inode @inode to the journal. If the inode is
 * synchronous, it also synchronizes the write-buffer. Returns zero in case of
 * success and a negative error code in case of failure.
 */
int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode)
{
        int err, lnum, offs;
        struct ubifs_ino_node *ino;
        struct ubifs_inode *ui = ubifs_inode(inode);
        int sync = 0, len = UBIFS_INO_NODE_SZ, last_reference = !inode->i_nlink;

        dbg_jnl("ino %lu, nlink %u", inode->i_ino, inode->i_nlink);

        /*
         * If the inode is being deleted, do not write the attached data. No
         * need to synchronize the write-buffer either.
         */
        if (!last_reference) {
                len += ui->data_len;
                sync = IS_SYNC(inode);
        }
        ino = kmalloc(len, GFP_NOFS);
        if (!ino)
                return -ENOMEM;

        /* Make reservation before allocating sequence numbers */
        err = make_reservation(c, BASEHD, len);
        if (err)
                goto out_free;

        pack_inode(c, ino, inode, 1);
        err = write_head(c, BASEHD, ino, len, &lnum, &offs, sync);
        if (err)
                goto out_release;
        if (!sync)
                ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf,
                                          inode->i_ino);
        release_head(c, BASEHD);

        if (last_reference) {
                err = ubifs_tnc_remove_ino(c, inode->i_ino);
                if (err)
                        goto out_ro;
                ubifs_delete_orphan(c, inode->i_ino);
                err = ubifs_add_dirt(c, lnum, len);
        } else {
                union ubifs_key key;

                ino_key_init(c, &key, inode->i_ino);
                err = ubifs_tnc_add(c, &key, lnum, offs, len);
        }
        if (err)
                goto out_ro;

        finish_reservation(c);
        spin_lock(&ui->ui_lock);
        ui->synced_i_size = ui->ui_size;
        spin_unlock(&ui->ui_lock);
        kfree(ino);
        return 0;

out_release:
        release_head(c, BASEHD);
out_ro:
        ubifs_ro_mode(c, err);
        finish_reservation(c);
out_free:
        kfree(ino);
        return err;
}

/**
 * ubifs_jnl_delete_inode - delete an inode.
 * @c: UBIFS file-system description object
 * @inode: inode to delete
 *
 * This function deletes inode @inode which includes removing it from orphans,
 * deleting it from TNC and, in some cases, writing a deletion inode to the
 * journal.
 *
 * When regular file inodes are unlinked or a directory inode is removed, the
 * 'ubifs_jnl_update()' function writes a corresponding deletion inode and
 * direntry to the media, and adds the inode to orphans. After this, when the
 * last reference to this inode has been dropped, this function is called. In
 * general, it has to write one more deletion inode to the media, because if
 * a commit happened between 'ubifs_jnl_update()' and
 * 'ubifs_jnl_delete_inode()', the deletion inode is not in the journal
 * anymore, and in fact it might not be on the flash anymore, because it might
 * have been garbage-collected already. And for optimization reasons UBIFS does
 * not read the orphan area if it has been unmounted cleanly, so it would have
 * no indication in the journal that there is a deleted inode which has to be
 * removed from TNC.
 *
 * However, if there was no commit between 'ubifs_jnl_update()' and
 * 'ubifs_jnl_delete_inode()', then there is no need to write the deletion
 * inode to the media for the second time. And this is quite a typical case.
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
int ubifs_jnl_delete_inode(struct ubifs_info *c, const struct inode *inode)
{
        int err;
        struct ubifs_inode *ui = ubifs_inode(inode);

        ubifs_assert(inode->i_nlink == 0);

        if (ui->del_cmtno != c->cmt_no)
                /* A commit happened for sure */
                return ubifs_jnl_write_inode(c, inode);

        down_read(&c->commit_sem);
        /*
         * Check commit number again, because the first test has been done
         * without @c->commit_sem, so a commit might have happened.
         */
        if (ui->del_cmtno != c->cmt_no) {
                up_read(&c->commit_sem);
                return ubifs_jnl_write_inode(c, inode);
        }

        err = ubifs_tnc_remove_ino(c, inode->i_ino);
        if (err)
                ubifs_ro_mode(c, err);
        else
                ubifs_delete_orphan(c, inode->i_ino);
        up_read(&c->commit_sem);
        return err;
}

/**
 * ubifs_jnl_rename - rename a directory entry.
 * @c: UBIFS file-system description object
 * @old_dir: parent inode of directory entry to rename
 * @old_dentry: directory entry to rename
 * @new_dir: parent inode of directory entry to rename
 * @new_dentry: new directory entry (or directory entry to replace)
 * @sync: non-zero if the write-buffer has to be synchronized
 *
 * This function implements the re-name operation which may involve writing up
 * to 3 inodes and 2 directory entries. It marks the written inodes as clean
 * and returns zero on success. In case of failure, a negative error code is
 * returned.
 */
int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
                     const struct dentry *old_dentry,
                     const struct inode *new_dir,
                     const struct dentry *new_dentry, int sync)
{
        void *p;
        union ubifs_key key;
        struct ubifs_dent_node *dent, *dent2;
        int err, dlen1, dlen2, ilen, lnum, offs, len;
        const struct inode *old_inode = old_dentry->d_inode;
        const struct inode *new_inode = new_dentry->d_inode;
        int aligned_dlen1, aligned_dlen2, plen = UBIFS_INO_NODE_SZ;
        int last_reference = !!(new_inode && new_inode->i_nlink == 0);
        int move = (old_dir != new_dir);
        struct ubifs_inode *uninitialized_var(new_ui);

        dbg_jnl("dent '%.*s' in dir ino %lu to dent '%.*s' in dir ino %lu",
                old_dentry->d_name.len, old_dentry->d_name.name,
                old_dir->i_ino, new_dentry->d_name.len,
                new_dentry->d_name.name, new_dir->i_ino);
        ubifs_assert(ubifs_inode(old_dir)->data_len == 0);
        ubifs_assert(ubifs_inode(new_dir)->data_len == 0);
        ubifs_assert(mutex_is_locked(&ubifs_inode(old_dir)->ui_mutex));
        ubifs_assert(mutex_is_locked(&ubifs_inode(new_dir)->ui_mutex));

        dlen1 = UBIFS_DENT_NODE_SZ + new_dentry->d_name.len + 1;
        dlen2 = UBIFS_DENT_NODE_SZ + old_dentry->d_name.len + 1;
        if (new_inode) {
                new_ui = ubifs_inode(new_inode);
                ubifs_assert(mutex_is_locked(&new_ui->ui_mutex));
                ilen = UBIFS_INO_NODE_SZ;
                if (!last_reference)
                        ilen += new_ui->data_len;
        } else
                ilen = 0;

        aligned_dlen1 = ALIGN(dlen1, 8);
        aligned_dlen2 = ALIGN(dlen2, 8);
        len = aligned_dlen1 + aligned_dlen2 + ALIGN(ilen, 8) + ALIGN(plen, 8);
        if (old_dir != new_dir)
                len += plen;
        dent = kmalloc(len, GFP_NOFS);
        if (!dent)
                return -ENOMEM;

        /* Make reservation before allocating sequence numbers */
        err = make_reservation(c, BASEHD, len);
        if (err)
                goto out_free;

        /* Make new dent */
        dent->ch.node_type = UBIFS_DENT_NODE;
        dent_key_init_flash(c, &dent->key, new_dir->i_ino, &new_dentry->d_name);
        dent->inum = cpu_to_le64(old_inode->i_ino);
        dent->type = get_dent_type(old_inode->i_mode);
        dent->nlen = cpu_to_le16(new_dentry->d_name.len);
        memcpy(dent->name, new_dentry->d_name.name, new_dentry->d_name.len);
        dent->name[new_dentry->d_name.len] = '\0';
        zero_dent_node_unused(dent);
        ubifs_prep_grp_node(c, dent, dlen1, 0);

        /* Make deletion dent */
        dent2 = (void *)dent + aligned_dlen1;
        dent2->ch.node_type = UBIFS_DENT_NODE;
        dent_key_init_flash(c, &dent2->key, old_dir->i_ino,
                            &old_dentry->d_name);
        dent2->inum = 0;
        dent2->type = DT_UNKNOWN;
        dent2->nlen = cpu_to_le16(old_dentry->d_name.len);
        memcpy(dent2->name, old_dentry->d_name.name, old_dentry->d_name.len);
        dent2->name[old_dentry->d_name.len] = '\0';
        zero_dent_node_unused(dent2);
        ubifs_prep_grp_node(c, dent2, dlen2, 0);

        p = (void *)dent2 + aligned_dlen2;
        if (new_inode) {
                pack_inode(c, p, new_inode, 0);
                p += ALIGN(ilen, 8);
        }

        if (!move)

                pack_inode(c, p, old_dir, 1);
        else {
                pack_inode(c, p, old_dir, 0);
                p += ALIGN(plen, 8);
                pack_inode(c, p, new_dir, 1);
        }

        if (last_reference) {
                err = ubifs_add_orphan(c, new_inode->i_ino);
                if (err) {
                        release_head(c, BASEHD);
                        goto out_finish;
                }
                new_ui->del_cmtno = c->cmt_no;
        }

        err = write_head(c, BASEHD, dent, len, &lnum, &offs, sync);
        if (err)
                goto out_release;
        if (!sync) {
                struct ubifs_wbuf *wbuf = &c->jheads[BASEHD].wbuf;

                ubifs_wbuf_add_ino_nolock(wbuf, new_dir->i_ino);
                ubifs_wbuf_add_ino_nolock(wbuf, old_dir->i_ino);
                if (new_inode)
                        ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf,
                                                  new_inode->i_ino);
        }
        release_head(c, BASEHD);

        dent_key_init(c, &key, new_dir->i_ino, &new_dentry->d_name);
        err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen1, &new_dentry->d_name);
        if (err)
                goto out_ro;

        err = ubifs_add_dirt(c, lnum, dlen2);
        if (err)
                goto out_ro;

        dent_key_init(c, &key, old_dir->i_ino, &old_dentry->d_name);
        err = ubifs_tnc_remove_nm(c, &key, &old_dentry->d_name);
        if (err)
                goto out_ro;

        offs += aligned_dlen1 + aligned_dlen2;
        if (new_inode) {
                ino_key_init(c, &key, new_inode->i_ino);
                err = ubifs_tnc_add(c, &key, lnum, offs, ilen);
                if (err)
                        goto out_ro;
                offs += ALIGN(ilen, 8);
        }

        ino_key_init(c, &key, old_dir->i_ino);
        err = ubifs_tnc_add(c, &key, lnum, offs, plen);
        if (err)
                goto out_ro;

        if (old_dir != new_dir) {
                offs += ALIGN(plen, 8);
                ino_key_init(c, &key, new_dir->i_ino);
                err = ubifs_tnc_add(c, &key, lnum, offs, plen);
                if (err)
                        goto out_ro;
        }

        finish_reservation(c);
        if (new_inode) {
                mark_inode_clean(c, new_ui);
                spin_lock(&new_ui->ui_lock);
                new_ui->synced_i_size = new_ui->ui_size;
                spin_unlock(&new_ui->ui_lock);
        }
        mark_inode_clean(c, ubifs_inode(old_dir));
        if (move)
                mark_inode_clean(c, ubifs_inode(new_dir));
        kfree(dent);
        return 0;

out_release:
        release_head(c, BASEHD);
out_ro:
        ubifs_ro_mode(c, err);
        if (last_reference)
                ubifs_delete_orphan(c, new_inode->i_ino);
out_finish:
        finish_reservation(c);
out_free:
        kfree(dent);
        return err;
}

/**
 * recomp_data_node - re-compress a truncated data node.
 * @dn: data node to re-compress
 * @new_len: new length
 *
 * This function is used when an inode is truncated and the last data node of
 * the inode has to be re-compressed and re-written.
 */
static int recomp_data_node(struct ubifs_data_node *dn, int *new_len)
{
        void *buf;
        int err, len, compr_type, out_len;

        out_len = le32_to_cpu(dn->size);
        buf = kmalloc(out_len * WORST_COMPR_FACTOR, GFP_NOFS);
        if (!buf)
                return -ENOMEM;

        len = le32_to_cpu(dn->ch.len) - UBIFS_DATA_NODE_SZ;
        compr_type = le16_to_cpu(dn->compr_type);
        err = ubifs_decompress(&dn->data, len, buf, &out_len, compr_type);
        if (err)
                goto out;

        ubifs_compress(buf, *new_len, &dn->data, &out_len, &compr_type);
        ubifs_assert(out_len <= UBIFS_BLOCK_SIZE);
        dn->compr_type = cpu_to_le16(compr_type);
        dn->size = cpu_to_le32(*new_len);
        *new_len = UBIFS_DATA_NODE_SZ + out_len;
out:
        kfree(buf);
        return err;
}

/**
 * ubifs_jnl_truncate - update the journal for a truncation.
 * @c: UBIFS file-system description object
 * @inode: inode to truncate
 * @old_size: old size
 * @new_size: new size
 *
 * When the size of a file decreases due to truncation, a truncation node is
 * written, the journal tree is updated, and the last data block is re-written
 * if it has been affected. The inode is also updated in order to synchronize
 * the new inode size.
 *
 * This function marks the inode as clean and returns zero on success. In case
 * of failure, a negative error code is returned.
 */
int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
                       loff_t old_size, loff_t new_size)
{
        union ubifs_key key, to_key;
        struct ubifs_ino_node *ino;
        struct ubifs_trun_node *trun;
        struct ubifs_data_node *uninitialized_var(dn);
        int err, dlen, len, lnum, offs, bit, sz, sync = IS_SYNC(inode);
        struct ubifs_inode *ui = ubifs_inode(inode);
        ino_t inum = inode->i_ino;
        unsigned int blk;

        dbg_jnl("ino %lu, size %lld -> %lld",
                (unsigned long)inum, old_size, new_size);
        ubifs_assert(!ui->data_len);
        ubifs_assert(S_ISREG(inode->i_mode));
        ubifs_assert(mutex_is_locked(&ui->ui_mutex));

        sz = UBIFS_TRUN_NODE_SZ + UBIFS_INO_NODE_SZ +
             UBIFS_MAX_DATA_NODE_SZ * WORST_COMPR_FACTOR;
        ino = kmalloc(sz, GFP_NOFS);
        if (!ino)
                return -ENOMEM;

        trun = (void *)ino + UBIFS_INO_NODE_SZ;
        trun->ch.node_type = UBIFS_TRUN_NODE;
        trun->inum = cpu_to_le32(inum);
        trun->old_size = cpu_to_le64(old_size);
        trun->new_size = cpu_to_le64(new_size);
        zero_trun_node_unused(trun);

        dlen = new_size & (UBIFS_BLOCK_SIZE - 1);
        if (dlen) {
                /* Get last data block so it can be truncated */
                dn = (void *)trun + UBIFS_TRUN_NODE_SZ;
                blk = new_size >> UBIFS_BLOCK_SHIFT;
                data_key_init(c, &key, inum, blk);
                dbg_jnlk(&key, "last block key ");
                err = ubifs_tnc_lookup(c, &key, dn);
                if (err == -ENOENT)
                        dlen = 0; /* Not found (so it is a hole) */
                else if (err)
                        goto out_free;
                else {
                        if (le32_to_cpu(dn->size) <= dlen)
                                dlen = 0; /* Nothing to do */
                        else {
                                int compr_type = le16_to_cpu(dn->compr_type);

                                if (compr_type != UBIFS_COMPR_NONE) {
                                        err = recomp_data_node(dn, &dlen);
                                        if (err)
                                                goto out_free;
                                } else {
                                        dn->size = cpu_to_le32(dlen);
                                        dlen += UBIFS_DATA_NODE_SZ;
                                }
                                zero_data_node_unused(dn);
                        }
                }
        }

        /* Must make reservation before allocating sequence numbers */
        len = UBIFS_TRUN_NODE_SZ + UBIFS_INO_NODE_SZ;
        if (dlen)
                len += dlen;
        err = make_reservation(c, BASEHD, len);
        if (err)
                goto out_free;

        pack_inode(c, ino, inode, 0);
        ubifs_prep_grp_node(c, trun, UBIFS_TRUN_NODE_SZ, dlen ? 0 : 1);
        if (dlen)
                ubifs_prep_grp_node(c, dn, dlen, 1);

        err = write_head(c, BASEHD, ino, len, &lnum, &offs, sync);
        if (err)
                goto out_release;
        if (!sync)
                ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf, inum);
        release_head(c, BASEHD);

        if (dlen) {
                sz = offs + UBIFS_INO_NODE_SZ + UBIFS_TRUN_NODE_SZ;
                err = ubifs_tnc_add(c, &key, lnum, sz, dlen);
                if (err)
                        goto out_ro;
        }

        ino_key_init(c, &key, inum);
        err = ubifs_tnc_add(c, &key, lnum, offs, UBIFS_INO_NODE_SZ);
        if (err)
                goto out_ro;

        err = ubifs_add_dirt(c, lnum, UBIFS_TRUN_NODE_SZ);
        if (err)
                goto out_ro;

        bit = new_size & (UBIFS_BLOCK_SIZE - 1);
        blk = (new_size >> UBIFS_BLOCK_SHIFT) + (bit ? 1 : 0);
        data_key_init(c, &key, inum, blk);

        bit = old_size & (UBIFS_BLOCK_SIZE - 1);
        blk = (old_size >> UBIFS_BLOCK_SHIFT) - (bit ? 0 : 1);
        data_key_init(c, &to_key, inum, blk);

        err = ubifs_tnc_remove_range(c, &key, &to_key);
        if (err)
                goto out_ro;

        finish_reservation(c);
        spin_lock(&ui->ui_lock);
        ui->synced_i_size = ui->ui_size;
        spin_unlock(&ui->ui_lock);
        mark_inode_clean(c, ui);
        kfree(ino);
        return 0;

out_release:
        release_head(c, BASEHD);
out_ro:
        ubifs_ro_mode(c, err);
        finish_reservation(c);
out_free:
        kfree(ino);
        return err;
}


/**
 * ubifs_jnl_delete_xattr - delete an extended attribute.
 * @c: UBIFS file-system description object
 * @host: host inode
 * @inode: extended attribute inode
 * @nm: extended attribute entry name
 *
 * This function delete an extended attribute which is very similar to
 * un-linking regular files - it writes a deletion xentry, a deletion inode and
 * updates the target inode. Returns zero in case of success and a negative
 * error code in case of failure.
 */
int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
                           const struct inode *inode, const struct qstr *nm)
{
        int err, xlen, hlen, len, lnum, xent_offs, aligned_xlen;
        struct ubifs_dent_node *xent;
        struct ubifs_ino_node *ino;
        union ubifs_key xent_key, key1, key2;
        int sync = IS_DIRSYNC(host);
        struct ubifs_inode *host_ui = ubifs_inode(host);

        dbg_jnl("host %lu, xattr ino %lu, name '%s', data len %d",
                host->i_ino, inode->i_ino, nm->name,
                ubifs_inode(inode)->data_len);
        ubifs_assert(inode->i_nlink == 0);
        ubifs_assert(mutex_is_locked(&host_ui->ui_mutex));

        /*
         * Since we are deleting the inode, we do not bother to attach any data
         * to it and assume its length is %UBIFS_INO_NODE_SZ.
         */
        xlen = UBIFS_DENT_NODE_SZ + nm->len + 1;
        aligned_xlen = ALIGN(xlen, 8);
        hlen = host_ui->data_len + UBIFS_INO_NODE_SZ;
        len = aligned_xlen + UBIFS_INO_NODE_SZ + ALIGN(hlen, 8);

        xent = kmalloc(len, GFP_NOFS);
        if (!xent)
                return -ENOMEM;

        /* Make reservation before allocating sequence numbers */
        err = make_reservation(c, BASEHD, len);
        if (err) {
                kfree(xent);
                return err;
        }

        xent->ch.node_type = UBIFS_XENT_NODE;
        xent_key_init(c, &xent_key, host->i_ino, nm);
        key_write(c, &xent_key, xent->key);
        xent->inum = 0;
        xent->type = get_dent_type(inode->i_mode);
        xent->nlen = cpu_to_le16(nm->len);
        memcpy(xent->name, nm->name, nm->len);
        xent->name[nm->len] = '\0';
        zero_dent_node_unused(xent);
        ubifs_prep_grp_node(c, xent, xlen, 0);

        ino = (void *)xent + aligned_xlen;
        pack_inode(c, ino, inode, 0);
        ino = (void *)ino + UBIFS_INO_NODE_SZ;
        pack_inode(c, ino, host, 1);

        err = write_head(c, BASEHD, xent, len, &lnum, &xent_offs, sync);
        if (!sync && !err)
                ubifs_wbuf_add_ino_nolock(&c->jheads[BASEHD].wbuf, host->i_ino);
        release_head(c, BASEHD);
        kfree(xent);
        if (err)
                goto out_ro;

        /* Remove the extended attribute entry from TNC */
        err = ubifs_tnc_remove_nm(c, &xent_key, nm);
        if (err)
                goto out_ro;
        err = ubifs_add_dirt(c, lnum, xlen);
        if (err)
                goto out_ro;

        /*
         * Remove all nodes belonging to the extended attribute inode from TNC.
         * Well, there actually must be only one node - the inode itself.
         */
        lowest_ino_key(c, &key1, inode->i_ino);
        highest_ino_key(c, &key2, inode->i_ino);
        err = ubifs_tnc_remove_range(c, &key1, &key2);
        if (err)
                goto out_ro;
        err = ubifs_add_dirt(c, lnum, UBIFS_INO_NODE_SZ);
        if (err)
                goto out_ro;

        /* And update TNC with the new host inode position */
        ino_key_init(c, &key1, host->i_ino);
        err = ubifs_tnc_add(c, &key1, lnum, xent_offs + len - hlen, hlen);
        if (err)
                goto out_ro;

        finish_reservation(c);
        spin_lock(&host_ui->ui_lock);
        host_ui->synced_i_size = host_ui->ui_size;
        spin_unlock(&host_ui->ui_lock);
        mark_inode_clean(c, host_ui);
        return 0;

out_ro:
        ubifs_ro_mode(c, err);
        finish_reservation(c);
        return err;
}

/**
 * ubifs_jnl_change_xattr - change an extended attribute.
 * @c: UBIFS file-system description object
 * @inode: extended attribute inode
 * @host: host inode
 *
 * This function writes the updated version of an extended attribute inode and
 * the host inode to the journal (to the base head). The host inode is written
 * after the extended attribute inode in order to guarantee that the extended
 * attribute will be flushed when the inode is synchronized by 'fsync()' and
 * consequently, the write-buffer is synchronized. This function returns zero
 * in case of success and a negative error code in case of failure.
 */
int ubifs_jnl_change_xattr(struct ubifs_info *c, const struct inode *inode,
                           const struct inode *host)
{
        int err, len1, len2, aligned_len, aligned_len1, lnum, offs;
        struct ubifs_inode *host_ui = ubifs_inode(host);
        struct ubifs_ino_node *ino;
        union ubifs_key key;
        int sync = IS_DIRSYNC(host);

        dbg_jnl("ino %lu, ino %lu", host->i_ino, inode->i_ino);
        ubifs_assert(host->i_nlink > 0);
        ubifs_assert(inode->i_nlink > 0);
        ubifs_assert(mutex_is_locked(&host_ui->ui_mutex));

        len1 = UBIFS_INO_NODE_SZ + host_ui->data_len;
        len2 = UBIFS_INO_NODE_SZ + ubifs_inode(inode)->data_len;
        aligned_len1 = ALIGN(len1, 8);
        aligned_len = aligned_len1 + ALIGN(len2, 8);

        ino = kmalloc(aligned_len, GFP_NOFS);
        if (!ino)
                return -ENOMEM;

        /* Make reservation before allocating sequence numbers */
        err = make_reservation(c, BASEHD, aligned_len);
        if (err)
                goto out_free;

        pack_inode(c, ino, host, 0);
        pack_inode(c, (void *)ino + aligned_len1, inode, 1);

        err = write_head(c, BASEHD, ino, aligned_len, &lnum, &offs, 0);
        if (!sync && !err) {
                struct ubifs_wbuf *wbuf = &c->jheads[BASEHD].wbuf;

                ubifs_wbuf_add_ino_nolock(wbuf, host->i_ino);
                ubifs_wbuf_add_ino_nolock(wbuf, inode->i_ino);
        }
        release_head(c, BASEHD);
        if (err)
                goto out_ro;

        ino_key_init(c, &key, host->i_ino);
        err = ubifs_tnc_add(c, &key, lnum, offs, len1);
        if (err)
                goto out_ro;

        ino_key_init(c, &key, inode->i_ino);
        err = ubifs_tnc_add(c, &key, lnum, offs + aligned_len1, len2);
        if (err)
                goto out_ro;

        finish_reservation(c);
        spin_lock(&host_ui->ui_lock);
        host_ui->synced_i_size = host_ui->ui_size;
        spin_unlock(&host_ui->ui_lock);
        mark_inode_clean(c, host_ui);
        kfree(ino);
        return 0;

out_ro:
        ubifs_ro_mode(c, err);
        finish_reservation(c);
out_free:
        kfree(ino);
        return err;
}