inode.c

Go to the documentation of this file.

/*
 *  linux/fs/ext3/inode.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([email protected])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Goal-directed block allocation by Stephen Tweedie
 *  ([email protected]), 1993, 1998
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 *  64-bit file support on 64-bit platforms by Jakub Jelinek
 *  ([email protected])
 *
 *  Assorted race fixes, rewrite of ext3_get_block() by Al Viro, 2000
 */

#include <linux/highuid.h>
#include <linux/quotaops.h>
#include <linux/writeback.h>
#include <linux/mpage.h>
#include <linux/namei.h>
#include "ext3.h"
#include "xattr.h"
#include "acl.h"

static int ext3_writepage_trans_blocks(struct inode *inode);
static int ext3_block_truncate_page(struct inode *inode, loff_t from);

/*
 * Test whether an inode is a fast symlink.
 */
static int ext3_inode_is_fast_symlink(struct inode *inode)
{
    int ea_blocks = EXT3_I(inode)->i_file_acl ?
        (inode->i_sb->s_blocksize >> 9) : 0;

    return (S_ISLNK(inode->i_mode) && inode->i_blocks - ea_blocks == 0);
}

/*
 * The ext3 forget function must perform a revoke if we are freeing data
 * which has been journaled.  Metadata (eg. indirect blocks) must be
 * revoked in all cases.
 *
 * "bh" may be NULL: a metadata block may have been freed from memory
 * but there may still be a record of it in the journal, and that record
 * still needs to be revoked.
 */
int ext3_forget(handle_t *handle, int is_metadata, struct inode *inode,
            struct buffer_head *bh, ext3_fsblk_t blocknr)
{
    int err;

    might_sleep();

    trace_ext3_forget(inode, is_metadata, blocknr);
    BUFFER_TRACE(bh, "enter");

    jbd_debug(4, "forgetting bh %p: is_metadata = %d, mode %o, "
          "data mode %lx\n",
          bh, is_metadata, inode->i_mode,
          test_opt(inode->i_sb, DATA_FLAGS));

    /* Never use the revoke function if we are doing full data
     * journaling: there is no need to, and a V1 superblock won't
     * support it.  Otherwise, only skip the revoke on un-journaled
     * data blocks. */

    if (test_opt(inode->i_sb, DATA_FLAGS) == EXT3_MOUNT_JOURNAL_DATA ||
        (!is_metadata && !ext3_should_journal_data(inode))) {
        if (bh) {
            BUFFER_TRACE(bh, "call journal_forget");
            return ext3_journal_forget(handle, bh);
        }
        return 0;
    }

    /*
     * data!=journal && (is_metadata || should_journal_data(inode))
     */
    BUFFER_TRACE(bh, "call ext3_journal_revoke");
    err = ext3_journal_revoke(handle, blocknr, bh);
    if (err)
        ext3_abort(inode->i_sb, __func__,
               "error %d when attempting revoke", err);
    BUFFER_TRACE(bh, "exit");
    return err;
}

/*
 * Work out how many blocks we need to proceed with the next chunk of a
 * truncate transaction.
 */
static unsigned long blocks_for_truncate(struct inode *inode)
{
    unsigned long needed;

    needed = inode->i_blocks >> (inode->i_sb->s_blocksize_bits - 9);

    /* Give ourselves just enough room to cope with inodes in which
     * i_blocks is corrupt: we've seen disk corruptions in the past
     * which resulted in random data in an inode which looked enough
     * like a regular file for ext3 to try to delete it.  Things
     * will go a bit crazy if that happens, but at least we should
     * try not to panic the whole kernel. */
    if (needed < 2)
        needed = 2;

    /* But we need to bound the transaction so we don't overflow the
     * journal. */
    if (needed > EXT3_MAX_TRANS_DATA)
        needed = EXT3_MAX_TRANS_DATA;

    return EXT3_DATA_TRANS_BLOCKS(inode->i_sb) + needed;
}

/*
 * Truncate transactions can be complex and absolutely huge.  So we need to
 * be able to restart the transaction at a conventient checkpoint to make
 * sure we don't overflow the journal.
 *
 * start_transaction gets us a new handle for a truncate transaction,
 * and extend_transaction tries to extend the existing one a bit.  If
 * extend fails, we need to propagate the failure up and restart the
 * transaction in the top-level truncate loop. --sct
 */
static handle_t *start_transaction(struct inode *inode)
{
    handle_t *result;

    result = ext3_journal_start(inode, blocks_for_truncate(inode));
    if (!IS_ERR(result))
        return result;

    ext3_std_error(inode->i_sb, PTR_ERR(result));
    return result;
}

/*
 * Try to extend this transaction for the purposes of truncation.
 *
 * Returns 0 if we managed to create more room.  If we can't create more
 * room, and the transaction must be restarted we return 1.
 */
static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
{
    if (handle->h_buffer_credits > EXT3_RESERVE_TRANS_BLOCKS)
        return 0;
    if (!ext3_journal_extend(handle, blocks_for_truncate(inode)))
        return 0;
    return 1;
}

/*
 * Restart the transaction associated with *handle.  This does a commit,
 * so before we call here everything must be consistently dirtied against
 * this transaction.
 */
static int truncate_restart_transaction(handle_t *handle, struct inode *inode)
{
    int ret;

    jbd_debug(2, "restarting handle %p\n", handle);
    /*
     * Drop truncate_mutex to avoid deadlock with ext3_get_blocks_handle
     * At this moment, get_block can be called only for blocks inside
     * i_size since page cache has been already dropped and writes are
     * blocked by i_mutex. So we can safely drop the truncate_mutex.
     */
    mutex_unlock(&EXT3_I(inode)->truncate_mutex);
    ret = ext3_journal_restart(handle, blocks_for_truncate(inode));
    mutex_lock(&EXT3_I(inode)->truncate_mutex);
    return ret;
}

/*
 * Called at inode eviction from icache
 */
void ext3_evict_inode (struct inode *inode)
{
    struct ext3_inode_info *ei = EXT3_I(inode);
    struct ext3_block_alloc_info *rsv;
    handle_t *handle;
    int want_delete = 0;

    trace_ext3_evict_inode(inode);
    if (!inode->i_nlink && !is_bad_inode(inode)) {
        dquot_initialize(inode);
        want_delete = 1;
    }

    /*
     * When journalling data dirty buffers are tracked only in the journal.
     * So although mm thinks everything is clean and ready for reaping the
     * inode might still have some pages to write in the running
     * transaction or waiting to be checkpointed. Thus calling
     * journal_invalidatepage() (via truncate_inode_pages()) to discard
     * these buffers can cause data loss. Also even if we did not discard
     * these buffers, we would have no way to find them after the inode
     * is reaped and thus user could see stale data if he tries to read
     * them before the transaction is checkpointed. So be careful and
     * force everything to disk here... We use ei->i_datasync_tid to
     * store the newest transaction containing inode's data.
     *
     * Note that directories do not have this problem because they don't
     * use page cache.
     *
     * The s_journal check handles the case when ext3_get_journal() fails
     * and puts the journal inode.
     */
    if (inode->i_nlink && ext3_should_journal_data(inode) &&
        EXT3_SB(inode->i_sb)->s_journal &&
        (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode))) {
        tid_t commit_tid = atomic_read(&ei->i_datasync_tid);
        journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;

        log_start_commit(journal, commit_tid);
        log_wait_commit(journal, commit_tid);
        filemap_write_and_wait(&inode->i_data);
    }
    truncate_inode_pages(&inode->i_data, 0);

    ext3_discard_reservation(inode);
    rsv = ei->i_block_alloc_info;
    ei->i_block_alloc_info = NULL;
    if (unlikely(rsv))
        kfree(rsv);

    if (!want_delete)
        goto no_delete;

    handle = start_transaction(inode);
    if (IS_ERR(handle)) {
        /*
         * If we're going to skip the normal cleanup, we still need to
         * make sure that the in-core orphan linked list is properly
         * cleaned up.
         */
        ext3_orphan_del(NULL, inode);
        goto no_delete;
    }

    if (IS_SYNC(inode))
        handle->h_sync = 1;
    inode->i_size = 0;
    if (inode->i_blocks)
        ext3_truncate(inode);
    /*
     * Kill off the orphan record created when the inode lost the last
     * link.  Note that ext3_orphan_del() has to be able to cope with the
     * deletion of a non-existent orphan - ext3_truncate() could
     * have removed the record.
     */
    ext3_orphan_del(handle, inode);
    ei->i_dtime = get_seconds();

    /*
     * One subtle ordering requirement: if anything has gone wrong
     * (transaction abort, IO errors, whatever), then we can still
     * do these next steps (the fs will already have been marked as
     * having errors), but we can't free the inode if the mark_dirty
     * fails.
     */
    if (ext3_mark_inode_dirty(handle, inode)) {
        /* If that failed, just dquot_drop() and be done with that */
        dquot_drop(inode);
        clear_inode(inode);
    } else {
        ext3_xattr_delete_inode(handle, inode);
        dquot_free_inode(inode);
        dquot_drop(inode);
        clear_inode(inode);
        ext3_free_inode(handle, inode);
    }
    ext3_journal_stop(handle);
    return;
no_delete:
    clear_inode(inode);
    dquot_drop(inode);
}

typedef struct {
    __le32  *p;
    __le32  key;
    struct buffer_head *bh;
} Indirect;

static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
{
    p->key = *(p->p = v);
    p->bh = bh;
}

static int verify_chain(Indirect *from, Indirect *to)
{
    while (from <= to && from->key == *from->p)
        from++;
    return (from > to);
}

/*
 * Portability note: the last comparison (check that we fit into triple
 * indirect block) is spelled differently, because otherwise on an
 * architecture with 32-bit longs and 8Kb pages we might get into trouble
 * if our filesystem had 8Kb blocks. We might use long long, but that would
 * kill us on x86. Oh, well, at least the sign propagation does not matter -
 * i_block would have to be negative in the very beginning, so we would not
 * get there at all.
 */

static int ext3_block_to_path(struct inode *inode,
            long i_block, int offsets[4], int *boundary)
{
    int ptrs = EXT3_ADDR_PER_BLOCK(inode->i_sb);
    int ptrs_bits = EXT3_ADDR_PER_BLOCK_BITS(inode->i_sb);
    const long direct_blocks = EXT3_NDIR_BLOCKS,
        indirect_blocks = ptrs,
        double_blocks = (1 << (ptrs_bits * 2));
    int n = 0;
    int final = 0;

    if (i_block < 0) {
        ext3_warning (inode->i_sb, "ext3_block_to_path", "block < 0");
    } else if (i_block < direct_blocks) {
        offsets[n++] = i_block;
        final = direct_blocks;
    } else if ( (i_block -= direct_blocks) < indirect_blocks) {
        offsets[n++] = EXT3_IND_BLOCK;
        offsets[n++] = i_block;
        final = ptrs;
    } else if ((i_block -= indirect_blocks) < double_blocks) {
        offsets[n++] = EXT3_DIND_BLOCK;
        offsets[n++] = i_block >> ptrs_bits;
        offsets[n++] = i_block & (ptrs - 1);
        final = ptrs;
    } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
        offsets[n++] = EXT3_TIND_BLOCK;
        offsets[n++] = i_block >> (ptrs_bits * 2);
        offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
        offsets[n++] = i_block & (ptrs - 1);
        final = ptrs;
    } else {
        ext3_warning(inode->i_sb, "ext3_block_to_path", "block > big");
    }
    if (boundary)
        *boundary = final - 1 - (i_block & (ptrs - 1));
    return n;
}

static Indirect *ext3_get_branch(struct inode *inode, int depth, int *offsets,
                 Indirect chain[4], int *err)
{
    struct super_block *sb = inode->i_sb;
    Indirect *p = chain;
    struct buffer_head *bh;

    *err = 0;
    /* i_data is not going away, no lock needed */
    add_chain (chain, NULL, EXT3_I(inode)->i_data + *offsets);
    if (!p->key)
        goto no_block;
    while (--depth) {
        bh = sb_bread(sb, le32_to_cpu(p->key));
        if (!bh)
            goto failure;
        /* Reader: pointers */
        if (!verify_chain(chain, p))
            goto changed;
        add_chain(++p, bh, (__le32*)bh->b_data + *++offsets);
        /* Reader: end */
        if (!p->key)
            goto no_block;
    }
    return NULL;

changed:
    brelse(bh);
    *err = -EAGAIN;
    goto no_block;
failure:
    *err = -EIO;
no_block:
    return p;
}

static ext3_fsblk_t ext3_find_near(struct inode *inode, Indirect *ind)
{
    struct ext3_inode_info *ei = EXT3_I(inode);
    __le32 *start = ind->bh ? (__le32*) ind->bh->b_data : ei->i_data;
    __le32 *p;
    ext3_fsblk_t bg_start;
    ext3_grpblk_t colour;

    /* Try to find previous block */
    for (p = ind->p - 1; p >= start; p--) {
        if (*p)
            return le32_to_cpu(*p);
    }

    /* No such thing, so let's try location of indirect block */
    if (ind->bh)
        return ind->bh->b_blocknr;

    /*
     * It is going to be referred to from the inode itself? OK, just put it
     * into the same cylinder group then.
     */
    bg_start = ext3_group_first_block_no(inode->i_sb, ei->i_block_group);
    colour = (current->pid % 16) *
            (EXT3_BLOCKS_PER_GROUP(inode->i_sb) / 16);
    return bg_start + colour;
}

static ext3_fsblk_t ext3_find_goal(struct inode *inode, long block,
                   Indirect *partial)
{
    struct ext3_block_alloc_info *block_i;

    block_i =  EXT3_I(inode)->i_block_alloc_info;

    /*
     * try the heuristic for sequential allocation,
     * failing that at least try to get decent locality.
     */
    if (block_i && (block == block_i->last_alloc_logical_block + 1)
        && (block_i->last_alloc_physical_block != 0)) {
        return block_i->last_alloc_physical_block + 1;
    }

    return ext3_find_near(inode, partial);
}

static int ext3_blks_to_allocate(Indirect *branch, int k, unsigned long blks,
        int blocks_to_boundary)
{
    unsigned long count = 0;

    /*
     * Simple case, [t,d]Indirect block(s) has not allocated yet
     * then it's clear blocks on that path have not allocated
     */
    if (k > 0) {
        /* right now we don't handle cross boundary allocation */
        if (blks < blocks_to_boundary + 1)
            count += blks;
        else
            count += blocks_to_boundary + 1;
        return count;
    }

    count++;
    while (count < blks && count <= blocks_to_boundary &&
        le32_to_cpu(*(branch[0].p + count)) == 0) {
        count++;
    }
    return count;
}

static int ext3_alloc_blocks(handle_t *handle, struct inode *inode,
            ext3_fsblk_t goal, int indirect_blks, int blks,
            ext3_fsblk_t new_blocks[4], int *err)
{
    int target, i;
    unsigned long count = 0;
    int index = 0;
    ext3_fsblk_t current_block = 0;
    int ret = 0;

    /*
     * Here we try to allocate the requested multiple blocks at once,
     * on a best-effort basis.
     * To build a branch, we should allocate blocks for
     * the indirect blocks(if not allocated yet), and at least
     * the first direct block of this branch.  That's the
     * minimum number of blocks need to allocate(required)
     */
    target = blks + indirect_blks;

    while (1) {
        count = target;
        /* allocating blocks for indirect blocks and direct blocks */
        current_block = ext3_new_blocks(handle,inode,goal,&count,err);
        if (*err)
            goto failed_out;

        target -= count;
        /* allocate blocks for indirect blocks */
        while (index < indirect_blks && count) {
            new_blocks[index++] = current_block++;
            count--;
        }

        if (count > 0)
            break;
    }

    /* save the new block number for the first direct block */
    new_blocks[index] = current_block;

    /* total number of blocks allocated for direct blocks */
    ret = count;
    *err = 0;
    return ret;
failed_out:
    for (i = 0; i <index; i++)
        ext3_free_blocks(handle, inode, new_blocks[i], 1);
    return ret;
}

static int ext3_alloc_branch(handle_t *handle, struct inode *inode,
            int indirect_blks, int *blks, ext3_fsblk_t goal,
            int *offsets, Indirect *branch)
{
    int blocksize = inode->i_sb->s_blocksize;
    int i, n = 0;
    int err = 0;
    struct buffer_head *bh;
    int num;
    ext3_fsblk_t new_blocks[4];
    ext3_fsblk_t current_block;

    num = ext3_alloc_blocks(handle, inode, goal, indirect_blks,
                *blks, new_blocks, &err);
    if (err)
        return err;

    branch[0].key = cpu_to_le32(new_blocks[0]);
    /*
     * metadata blocks and data blocks are allocated.
     */
    for (n = 1; n <= indirect_blks;  n++) {
        /*
         * Get buffer_head for parent block, zero it out
         * and set the pointer to new one, then send
         * parent to disk.
         */
        bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
        branch[n].bh = bh;
        lock_buffer(bh);
        BUFFER_TRACE(bh, "call get_create_access");
        err = ext3_journal_get_create_access(handle, bh);
        if (err) {
            unlock_buffer(bh);
            brelse(bh);
            goto failed;
        }

        memset(bh->b_data, 0, blocksize);
        branch[n].p = (__le32 *) bh->b_data + offsets[n];
        branch[n].key = cpu_to_le32(new_blocks[n]);
        *branch[n].p = branch[n].key;
        if ( n == indirect_blks) {
            current_block = new_blocks[n];
            /*
             * End of chain, update the last new metablock of
             * the chain to point to the new allocated
             * data blocks numbers
             */
            for (i=1; i < num; i++)
                *(branch[n].p + i) = cpu_to_le32(++current_block);
        }
        BUFFER_TRACE(bh, "marking uptodate");
        set_buffer_uptodate(bh);
        unlock_buffer(bh);

        BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
        err = ext3_journal_dirty_metadata(handle, bh);
        if (err)
            goto failed;
    }
    *blks = num;
    return err;
failed:
    /* Allocation failed, free what we already allocated */
    for (i = 1; i <= n ; i++) {
        BUFFER_TRACE(branch[i].bh, "call journal_forget");
        ext3_journal_forget(handle, branch[i].bh);
    }
    for (i = 0; i <indirect_blks; i++)
        ext3_free_blocks(handle, inode, new_blocks[i], 1);

    ext3_free_blocks(handle, inode, new_blocks[i], num);

    return err;
}

static int ext3_splice_branch(handle_t *handle, struct inode *inode,
            long block, Indirect *where, int num, int blks)
{
    int i;
    int err = 0;
    struct ext3_block_alloc_info *block_i;
    ext3_fsblk_t current_block;
    struct ext3_inode_info *ei = EXT3_I(inode);
    struct timespec now;

    block_i = ei->i_block_alloc_info;
    /*
     * If we're splicing into a [td]indirect block (as opposed to the
     * inode) then we need to get write access to the [td]indirect block
     * before the splice.
     */
    if (where->bh) {
        BUFFER_TRACE(where->bh, "get_write_access");
        err = ext3_journal_get_write_access(handle, where->bh);
        if (err)
            goto err_out;
    }
    /* That's it */

    *where->p = where->key;

    /*
     * Update the host buffer_head or inode to point to more just allocated
     * direct blocks blocks
     */
    if (num == 0 && blks > 1) {
        current_block = le32_to_cpu(where->key) + 1;
        for (i = 1; i < blks; i++)
            *(where->p + i ) = cpu_to_le32(current_block++);
    }

    /*
     * update the most recently allocated logical & physical block
     * in i_block_alloc_info, to assist find the proper goal block for next
     * allocation
     */
    if (block_i) {
        block_i->last_alloc_logical_block = block + blks - 1;
        block_i->last_alloc_physical_block =
                le32_to_cpu(where[num].key) + blks - 1;
    }

    /* We are done with atomic stuff, now do the rest of housekeeping */
    now = CURRENT_TIME_SEC;
    if (!timespec_equal(&inode->i_ctime, &now) || !where->bh) {
        inode->i_ctime = now;
        ext3_mark_inode_dirty(handle, inode);
    }
    /* ext3_mark_inode_dirty already updated i_sync_tid */
    atomic_set(&ei->i_datasync_tid, handle->h_transaction->t_tid);

    /* had we spliced it onto indirect block? */
    if (where->bh) {
        /*
         * If we spliced it onto an indirect block, we haven't
         * altered the inode.  Note however that if it is being spliced
         * onto an indirect block at the very end of the file (the
         * file is growing) then we *will* alter the inode to reflect
         * the new i_size.  But that is not done here - it is done in
         * generic_commit_write->__mark_inode_dirty->ext3_dirty_inode.
         */
        jbd_debug(5, "splicing indirect only\n");
        BUFFER_TRACE(where->bh, "call ext3_journal_dirty_metadata");
        err = ext3_journal_dirty_metadata(handle, where->bh);
        if (err)
            goto err_out;
    } else {
        /*
         * OK, we spliced it into the inode itself on a direct block.
         * Inode was dirtied above.
         */
        jbd_debug(5, "splicing direct\n");
    }
    return err;

err_out:
    for (i = 1; i <= num; i++) {
        BUFFER_TRACE(where[i].bh, "call journal_forget");
        ext3_journal_forget(handle, where[i].bh);
        ext3_free_blocks(handle,inode,le32_to_cpu(where[i-1].key),1);
    }
    ext3_free_blocks(handle, inode, le32_to_cpu(where[num].key), blks);

    return err;
}

/*
 * Allocation strategy is simple: if we have to allocate something, we will
 * have to go the whole way to leaf. So let's do it before attaching anything
 * to tree, set linkage between the newborn blocks, write them if sync is
 * required, recheck the path, free and repeat if check fails, otherwise
 * set the last missing link (that will protect us from any truncate-generated
 * removals - all blocks on the path are immune now) and possibly force the
 * write on the parent block.
 * That has a nice additional property: no special recovery from the failed
 * allocations is needed - we simply release blocks and do not touch anything
 * reachable from inode.
 *
 * `handle' can be NULL if create == 0.
 *
 * The BKL may not be held on entry here.  Be sure to take it early.
 * return > 0, # of blocks mapped or allocated.
 * return = 0, if plain lookup failed.
 * return < 0, error case.
 */
int ext3_get_blocks_handle(handle_t *handle, struct inode *inode,
        sector_t iblock, unsigned long maxblocks,
        struct buffer_head *bh_result,
        int create)
{
    int err = -EIO;
    int offsets[4];
    Indirect chain[4];
    Indirect *partial;
    ext3_fsblk_t goal;
    int indirect_blks;
    int blocks_to_boundary = 0;
    int depth;
    struct ext3_inode_info *ei = EXT3_I(inode);
    int count = 0;
    ext3_fsblk_t first_block = 0;


    trace_ext3_get_blocks_enter(inode, iblock, maxblocks, create);
    J_ASSERT(handle != NULL || create == 0);
    depth = ext3_block_to_path(inode,iblock,offsets,&blocks_to_boundary);

    if (depth == 0)
        goto out;

    partial = ext3_get_branch(inode, depth, offsets, chain, &err);

    /* Simplest case - block found, no allocation needed */
    if (!partial) {
        first_block = le32_to_cpu(chain[depth - 1].key);
        clear_buffer_new(bh_result);
        count++;
        /*map more blocks*/
        while (count < maxblocks && count <= blocks_to_boundary) {
            ext3_fsblk_t blk;

            if (!verify_chain(chain, chain + depth - 1)) {
                /*
                 * Indirect block might be removed by
                 * truncate while we were reading it.
                 * Handling of that case: forget what we've
                 * got now. Flag the err as EAGAIN, so it
                 * will reread.
                 */
                err = -EAGAIN;
                count = 0;
                break;
            }
            blk = le32_to_cpu(*(chain[depth-1].p + count));

            if (blk == first_block + count)
                count++;
            else
                break;
        }
        if (err != -EAGAIN)
            goto got_it;
    }

    /* Next simple case - plain lookup or failed read of indirect block */
    if (!create || err == -EIO)
        goto cleanup;

    /*
     * Block out ext3_truncate while we alter the tree
     */
    mutex_lock(&ei->truncate_mutex);

    /*
     * If the indirect block is missing while we are reading
     * the chain(ext3_get_branch() returns -EAGAIN err), or
     * if the chain has been changed after we grab the semaphore,
     * (either because another process truncated this branch, or
     * another get_block allocated this branch) re-grab the chain to see if
     * the request block has been allocated or not.
     *
     * Since we already block the truncate/other get_block
     * at this point, we will have the current copy of the chain when we
     * splice the branch into the tree.
     */
    if (err == -EAGAIN || !verify_chain(chain, partial)) {
        while (partial > chain) {
            brelse(partial->bh);
            partial--;
        }
        partial = ext3_get_branch(inode, depth, offsets, chain, &err);
        if (!partial) {
            count++;
            mutex_unlock(&ei->truncate_mutex);
            if (err)
                goto cleanup;
            clear_buffer_new(bh_result);
            goto got_it;
        }
    }

    /*
     * Okay, we need to do block allocation.  Lazily initialize the block
     * allocation info here if necessary
    */
    if (S_ISREG(inode->i_mode) && (!ei->i_block_alloc_info))
        ext3_init_block_alloc_info(inode);

    goal = ext3_find_goal(inode, iblock, partial);

    /* the number of blocks need to allocate for [d,t]indirect blocks */
    indirect_blks = (chain + depth) - partial - 1;

    /*
     * Next look up the indirect map to count the totoal number of
     * direct blocks to allocate for this branch.
     */
    count = ext3_blks_to_allocate(partial, indirect_blks,
                    maxblocks, blocks_to_boundary);
    err = ext3_alloc_branch(handle, inode, indirect_blks, &count, goal,
                offsets + (partial - chain), partial);

    /*
     * The ext3_splice_branch call will free and forget any buffers
     * on the new chain if there is a failure, but that risks using
     * up transaction credits, especially for bitmaps where the
     * credits cannot be returned.  Can we handle this somehow?  We
     * may need to return -EAGAIN upwards in the worst case.  --sct
     */
    if (!err)
        err = ext3_splice_branch(handle, inode, iblock,
                    partial, indirect_blks, count);
    mutex_unlock(&ei->truncate_mutex);
    if (err)
        goto cleanup;

    set_buffer_new(bh_result);
got_it:
    map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
    if (count > blocks_to_boundary)
        set_buffer_boundary(bh_result);
    err = count;
    /* Clean up and exit */
    partial = chain + depth - 1;    /* the whole chain */
cleanup:
    while (partial > chain) {
        BUFFER_TRACE(partial->bh, "call brelse");
        brelse(partial->bh);
        partial--;
    }
    BUFFER_TRACE(bh_result, "returned");
out:
    trace_ext3_get_blocks_exit(inode, iblock,
                   depth ? le32_to_cpu(chain[depth-1].key) : 0,
                   count, err);
    return err;
}

/* Maximum number of blocks we map for direct IO at once. */
#define DIO_MAX_BLOCKS 4096
/*
 * Number of credits we need for writing DIO_MAX_BLOCKS:
 * We need sb + group descriptor + bitmap + inode -> 4
 * For B blocks with A block pointers per block we need:
 * 1 (triple ind.) + (B/A/A + 2) (doubly ind.) + (B/A + 2) (indirect).
 * If we plug in 4096 for B and 256 for A (for 1KB block size), we get 25.
 */
#define DIO_CREDITS 25

static int ext3_get_block(struct inode *inode, sector_t iblock,
            struct buffer_head *bh_result, int create)
{
    handle_t *handle = ext3_journal_current_handle();
    int ret = 0, started = 0;
    unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;

    if (create && !handle) {    /* Direct IO write... */
        if (max_blocks > DIO_MAX_BLOCKS)
            max_blocks = DIO_MAX_BLOCKS;
        handle = ext3_journal_start(inode, DIO_CREDITS +
                EXT3_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb));
        if (IS_ERR(handle)) {
            ret = PTR_ERR(handle);
            goto out;
        }
        started = 1;
    }

    ret = ext3_get_blocks_handle(handle, inode, iblock,
                    max_blocks, bh_result, create);
    if (ret > 0) {
        bh_result->b_size = (ret << inode->i_blkbits);
        ret = 0;
    }
    if (started)
        ext3_journal_stop(handle);
out:
    return ret;
}

int ext3_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
        u64 start, u64 len)
{
    return generic_block_fiemap(inode, fieinfo, start, len,
                    ext3_get_block);
}

/*
 * `handle' can be NULL if create is zero
 */
struct buffer_head *ext3_getblk(handle_t *handle, struct inode *inode,
                long block, int create, int *errp)
{
    struct buffer_head dummy;
    int fatal = 0, err;

    J_ASSERT(handle != NULL || create == 0);

    dummy.b_state = 0;
    dummy.b_blocknr = -1000;
    buffer_trace_init(&dummy.b_history);
    err = ext3_get_blocks_handle(handle, inode, block, 1,
                    &dummy, create);
    /*
     * ext3_get_blocks_handle() returns number of blocks
     * mapped. 0 in case of a HOLE.
     */
    if (err > 0) {
        if (err > 1)
            WARN_ON(1);
        err = 0;
    }
    *errp = err;
    if (!err && buffer_mapped(&dummy)) {
        struct buffer_head *bh;
        bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
        if (!bh) {
            *errp = -EIO;
            goto err;
        }
        if (buffer_new(&dummy)) {
            J_ASSERT(create != 0);
            J_ASSERT(handle != NULL);

            /*
             * Now that we do not always journal data, we should
             * keep in mind whether this should always journal the
             * new buffer as metadata.  For now, regular file
             * writes use ext3_get_block instead, so it's not a
             * problem.
             */
            lock_buffer(bh);
            BUFFER_TRACE(bh, "call get_create_access");
            fatal = ext3_journal_get_create_access(handle, bh);
            if (!fatal && !buffer_uptodate(bh)) {
                memset(bh->b_data,0,inode->i_sb->s_blocksize);
                set_buffer_uptodate(bh);
            }
            unlock_buffer(bh);
            BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
            err = ext3_journal_dirty_metadata(handle, bh);
            if (!fatal)
                fatal = err;
        } else {
            BUFFER_TRACE(bh, "not a new buffer");
        }
        if (fatal) {
            *errp = fatal;
            brelse(bh);
            bh = NULL;
        }
        return bh;
    }
err:
    return NULL;
}

struct buffer_head *ext3_bread(handle_t *handle, struct inode *inode,
                   int block, int create, int *err)
{
    struct buffer_head * bh;

    bh = ext3_getblk(handle, inode, block, create, err);
    if (!bh)
        return bh;
    if (bh_uptodate_or_lock(bh))
        return bh;
    get_bh(bh);
    bh->b_end_io = end_buffer_read_sync;
    submit_bh(READ | REQ_META | REQ_PRIO, bh);
    wait_on_buffer(bh);
    if (buffer_uptodate(bh))
        return bh;
    put_bh(bh);
    *err = -EIO;
    return NULL;
}

static int walk_page_buffers(   handle_t *handle,
                struct buffer_head *head,
                unsigned from,
                unsigned to,
                int *partial,
                int (*fn)(  handle_t *handle,
                        struct buffer_head *bh))
{
    struct buffer_head *bh;
    unsigned block_start, block_end;
    unsigned blocksize = head->b_size;
    int err, ret = 0;
    struct buffer_head *next;

    for (   bh = head, block_start = 0;
        ret == 0 && (bh != head || !block_start);
        block_start = block_end, bh = next)
    {
        next = bh->b_this_page;
        block_end = block_start + blocksize;
        if (block_end <= from || block_start >= to) {
            if (partial && !buffer_uptodate(bh))
                *partial = 1;
            continue;
        }
        err = (*fn)(handle, bh);
        if (!ret)
            ret = err;
    }
    return ret;
}

/*
 * To preserve ordering, it is essential that the hole instantiation and
 * the data write be encapsulated in a single transaction.  We cannot
 * close off a transaction and start a new one between the ext3_get_block()
 * and the commit_write().  So doing the journal_start at the start of
 * prepare_write() is the right place.
 *
 * Also, this function can nest inside ext3_writepage() ->
 * block_write_full_page(). In that case, we *know* that ext3_writepage()
 * has generated enough buffer credits to do the whole page.  So we won't
 * block on the journal in that case, which is good, because the caller may
 * be PF_MEMALLOC.
 *
 * By accident, ext3 can be reentered when a transaction is open via
 * quota file writes.  If we were to commit the transaction while thus
 * reentered, there can be a deadlock - we would be holding a quota
 * lock, and the commit would never complete if another thread had a
 * transaction open and was blocking on the quota lock - a ranking
 * violation.
 *
 * So what we do is to rely on the fact that journal_stop/journal_start
 * will _not_ run commit under these circumstances because handle->h_ref
 * is elevated.  We'll still have enough credits for the tiny quotafile
 * write.
 */
static int do_journal_get_write_access(handle_t *handle,
                    struct buffer_head *bh)
{
    int dirty = buffer_dirty(bh);
    int ret;

    if (!buffer_mapped(bh) || buffer_freed(bh))
        return 0;
    /*
     * __block_prepare_write() could have dirtied some buffers. Clean
     * the dirty bit as jbd2_journal_get_write_access() could complain
     * otherwise about fs integrity issues. Setting of the dirty bit
     * by __block_prepare_write() isn't a real problem here as we clear
     * the bit before releasing a page lock and thus writeback cannot
     * ever write the buffer.
     */
    if (dirty)
        clear_buffer_dirty(bh);
    ret = ext3_journal_get_write_access(handle, bh);
    if (!ret && dirty)
        ret = ext3_journal_dirty_metadata(handle, bh);
    return ret;
}

/*
 * Truncate blocks that were not used by write. We have to truncate the
 * pagecache as well so that corresponding buffers get properly unmapped.
 */
static void ext3_truncate_failed_write(struct inode *inode)
{
    truncate_inode_pages(inode->i_mapping, inode->i_size);
    ext3_truncate(inode);
}

/*
 * Truncate blocks that were not used by direct IO write. We have to zero out
 * the last file block as well because direct IO might have written to it.
 */
static void ext3_truncate_failed_direct_write(struct inode *inode)
{
    ext3_block_truncate_page(inode, inode->i_size);
    ext3_truncate(inode);
}

static int ext3_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 ret;
    handle_t *handle;
    int retries = 0;
    struct page *page;
    pgoff_t index;
    unsigned from, to;
    /* Reserve one block more for addition to orphan list in case
     * we allocate blocks but write fails for some reason */
    int needed_blocks = ext3_writepage_trans_blocks(inode) + 1;

    trace_ext3_write_begin(inode, pos, len, flags);

    index = pos >> PAGE_CACHE_SHIFT;
    from = pos & (PAGE_CACHE_SIZE - 1);
    to = from + len;

retry:
    page = grab_cache_page_write_begin(mapping, index, flags);
    if (!page)
        return -ENOMEM;
    *pagep = page;

    handle = ext3_journal_start(inode, needed_blocks);
    if (IS_ERR(handle)) {
        unlock_page(page);
        page_cache_release(page);
        ret = PTR_ERR(handle);
        goto out;
    }
    ret = __block_write_begin(page, pos, len, ext3_get_block);
    if (ret)
        goto write_begin_failed;

    if (ext3_should_journal_data(inode)) {
        ret = walk_page_buffers(handle, page_buffers(page),
                from, to, NULL, do_journal_get_write_access);
    }
write_begin_failed:
    if (ret) {
        /*
         * block_write_begin may have instantiated a few blocks
         * outside i_size.  Trim these off again. Don't need
         * i_size_read because we hold i_mutex.
         *
         * Add inode to orphan list in case we crash before truncate
         * finishes. Do this only if ext3_can_truncate() agrees so
         * that orphan processing code is happy.
         */
        if (pos + len > inode->i_size && ext3_can_truncate(inode))
            ext3_orphan_add(handle, inode);
        ext3_journal_stop(handle);
        unlock_page(page);
        page_cache_release(page);
        if (pos + len > inode->i_size)
            ext3_truncate_failed_write(inode);
    }
    if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
        goto retry;
out:
    return ret;
}


int ext3_journal_dirty_data(handle_t *handle, struct buffer_head *bh)
{
    int err = journal_dirty_data(handle, bh);
    if (err)
        ext3_journal_abort_handle(__func__, __func__,
                        bh, handle, err);
    return err;
}

/* For ordered writepage and write_end functions */
static int journal_dirty_data_fn(handle_t *handle, struct buffer_head *bh)
{
    /*
     * Write could have mapped the buffer but it didn't copy the data in
     * yet. So avoid filing such buffer into a transaction.
     */
    if (buffer_mapped(bh) && buffer_uptodate(bh))
        return ext3_journal_dirty_data(handle, bh);
    return 0;
}

/* For write_end() in data=journal mode */
static int write_end_fn(handle_t *handle, struct buffer_head *bh)
{
    if (!buffer_mapped(bh) || buffer_freed(bh))
        return 0;
    set_buffer_uptodate(bh);
    return ext3_journal_dirty_metadata(handle, bh);
}

/*
 * This is nasty and subtle: ext3_write_begin() could have allocated blocks
 * for the whole page but later we failed to copy the data in. Update inode
 * size according to what we managed to copy. The rest is going to be
 * truncated in write_end function.
 */
static void update_file_sizes(struct inode *inode, loff_t pos, unsigned copied)
{
    /* What matters to us is i_disksize. We don't write i_size anywhere */
    if (pos + copied > inode->i_size)
        i_size_write(inode, pos + copied);
    if (pos + copied > EXT3_I(inode)->i_disksize) {
        EXT3_I(inode)->i_disksize = pos + copied;
        mark_inode_dirty(inode);
    }
}

/*
 * We need to pick up the new inode size which generic_commit_write gave us
 * `file' can be NULL - eg, when called from page_symlink().
 *
 * ext3 never places buffers on inode->i_mapping->private_list.  metadata
 * buffers are managed internally.
 */
static int ext3_ordered_write_end(struct file *file,
                struct address_space *mapping,
                loff_t pos, unsigned len, unsigned copied,
                struct page *page, void *fsdata)
{
    handle_t *handle = ext3_journal_current_handle();
    struct inode *inode = file->f_mapping->host;
    unsigned from, to;
    int ret = 0, ret2;

    trace_ext3_ordered_write_end(inode, pos, len, copied);
    copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);

    from = pos & (PAGE_CACHE_SIZE - 1);
    to = from + copied;
    ret = walk_page_buffers(handle, page_buffers(page),
        from, to, NULL, journal_dirty_data_fn);

    if (ret == 0)
        update_file_sizes(inode, pos, copied);
    /*
     * There may be allocated blocks outside of i_size because
     * we failed to copy some data. Prepare for truncate.
     */
    if (pos + len > inode->i_size && ext3_can_truncate(inode))
        ext3_orphan_add(handle, inode);
    ret2 = ext3_journal_stop(handle);
    if (!ret)
        ret = ret2;
    unlock_page(page);
    page_cache_release(page);

    if (pos + len > inode->i_size)
        ext3_truncate_failed_write(inode);
    return ret ? ret : copied;
}

static int ext3_writeback_write_end(struct file *file,
                struct address_space *mapping,
                loff_t pos, unsigned len, unsigned copied,
                struct page *page, void *fsdata)
{
    handle_t *handle = ext3_journal_current_handle();
    struct inode *inode = file->f_mapping->host;
    int ret;

    trace_ext3_writeback_write_end(inode, pos, len, copied);
    copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
    update_file_sizes(inode, pos, copied);
    /*
     * There may be allocated blocks outside of i_size because
     * we failed to copy some data. Prepare for truncate.
     */
    if (pos + len > inode->i_size && ext3_can_truncate(inode))
        ext3_orphan_add(handle, inode);
    ret = ext3_journal_stop(handle);
    unlock_page(page);
    page_cache_release(page);

    if (pos + len > inode->i_size)
        ext3_truncate_failed_write(inode);
    return ret ? ret : copied;
}

static int ext3_journalled_write_end(struct file *file,
                struct address_space *mapping,
                loff_t pos, unsigned len, unsigned copied,
                struct page *page, void *fsdata)
{
    handle_t *handle = ext3_journal_current_handle();
    struct inode *inode = mapping->host;
    struct ext3_inode_info *ei = EXT3_I(inode);
    int ret = 0, ret2;
    int partial = 0;
    unsigned from, to;

    trace_ext3_journalled_write_end(inode, pos, len, copied);
    from = pos & (PAGE_CACHE_SIZE - 1);
    to = from + len;

    if (copied < len) {
        if (!PageUptodate(page))
            copied = 0;
        page_zero_new_buffers(page, from + copied, to);
        to = from + copied;
    }

    ret = walk_page_buffers(handle, page_buffers(page), from,
                to, &partial, write_end_fn);
    if (!partial)
        SetPageUptodate(page);

    if (pos + copied > inode->i_size)
        i_size_write(inode, pos + copied);
    /*
     * There may be allocated blocks outside of i_size because
     * we failed to copy some data. Prepare for truncate.
     */
    if (pos + len > inode->i_size && ext3_can_truncate(inode))
        ext3_orphan_add(handle, inode);
    ext3_set_inode_state(inode, EXT3_STATE_JDATA);
    atomic_set(&ei->i_datasync_tid, handle->h_transaction->t_tid);
    if (inode->i_size > ei->i_disksize) {
        ei->i_disksize = inode->i_size;
        ret2 = ext3_mark_inode_dirty(handle, inode);
        if (!ret)
            ret = ret2;
    }

    ret2 = ext3_journal_stop(handle);
    if (!ret)
        ret = ret2;
    unlock_page(page);
    page_cache_release(page);

    if (pos + len > inode->i_size)
        ext3_truncate_failed_write(inode);
    return ret ? ret : copied;
}

/*
 * bmap() is special.  It gets used by applications such as lilo and by
 * the swapper to find the on-disk block of a specific piece of data.
 *
 * Naturally, this is dangerous if the block concerned is still in the
 * journal.  If somebody makes a swapfile on an ext3 data-journaling
 * filesystem and enables swap, then they may get a nasty shock when the
 * data getting swapped to that swapfile suddenly gets overwritten by
 * the original zero's written out previously to the journal and
 * awaiting writeback in the kernel's buffer cache.
 *
 * So, if we see any bmap calls here on a modified, data-journaled file,
 * take extra steps to flush any blocks which might be in the cache.
 */
static sector_t ext3_bmap(struct address_space *mapping, sector_t block)
{
    struct inode *inode = mapping->host;
    journal_t *journal;
    int err;

    if (ext3_test_inode_state(inode, EXT3_STATE_JDATA)) {
        /*
         * This is a REALLY heavyweight approach, but the use of
         * bmap on dirty files is expected to be extremely rare:
         * only if we run lilo or swapon on a freshly made file
         * do we expect this to happen.
         *
         * (bmap requires CAP_SYS_RAWIO so this does not
         * represent an unprivileged user DOS attack --- we'd be
         * in trouble if mortal users could trigger this path at
         * will.)
         *
         * NB. EXT3_STATE_JDATA is not set on files other than
         * regular files.  If somebody wants to bmap a directory
         * or symlink and gets confused because the buffer
         * hasn't yet been flushed to disk, they deserve
         * everything they get.
         */

        ext3_clear_inode_state(inode, EXT3_STATE_JDATA);
        journal = EXT3_JOURNAL(inode);
        journal_lock_updates(journal);
        err = journal_flush(journal);
        journal_unlock_updates(journal);

        if (err)
            return 0;
    }

    return generic_block_bmap(mapping,block,ext3_get_block);
}

static int bget_one(handle_t *handle, struct buffer_head *bh)
{
    get_bh(bh);
    return 0;
}

static int bput_one(handle_t *handle, struct buffer_head *bh)
{
    put_bh(bh);
    return 0;
}

static int buffer_unmapped(handle_t *handle, struct buffer_head *bh)
{
    return !buffer_mapped(bh);
}

/*
 * Note that we always start a transaction even if we're not journalling
 * data.  This is to preserve ordering: any hole instantiation within
 * __block_write_full_page -> ext3_get_block() should be journalled
 * along with the data so we don't crash and then get metadata which
 * refers to old data.
 *
 * In all journalling modes block_write_full_page() will start the I/O.
 *
 * Problem:
 *
 *  ext3_writepage() -> kmalloc() -> __alloc_pages() -> page_launder() ->
 *      ext3_writepage()
 *
 * Similar for:
 *
 *  ext3_file_write() -> generic_file_write() -> __alloc_pages() -> ...
 *
 * Same applies to ext3_get_block().  We will deadlock on various things like
 * lock_journal and i_truncate_mutex.
 *
 * Setting PF_MEMALLOC here doesn't work - too many internal memory
 * allocations fail.
 *
 * 16May01: If we're reentered then journal_current_handle() will be
 *      non-zero. We simply *return*.
 *
 * 1 July 2001: @@@ FIXME:
 *   In journalled data mode, a data buffer may be metadata against the
 *   current transaction.  But the same file is part of a shared mapping
 *   and someone does a writepage() on it.
 *
 *   We will move the buffer onto the async_data list, but *after* it has
 *   been dirtied. So there's a small window where we have dirty data on
 *   BJ_Metadata.
 *
 *   Note that this only applies to the last partial page in the file.  The
 *   bit which block_write_full_page() uses prepare/commit for.  (That's
 *   broken code anyway: it's wrong for msync()).
 *
 *   It's a rare case: affects the final partial page, for journalled data
 *   where the file is subject to bith write() and writepage() in the same
 *   transction.  To fix it we'll need a custom block_write_full_page().
 *   We'll probably need that anyway for journalling writepage() output.
 *
 * We don't honour synchronous mounts for writepage().  That would be
 * disastrous.  Any write() or metadata operation will sync the fs for
 * us.
 *
 * AKPM2: if all the page's buffers are mapped to disk and !data=journal,
 * we don't need to open a transaction here.
 */
static int ext3_ordered_writepage(struct page *page,
                struct writeback_control *wbc)
{
    struct inode *inode = page->mapping->host;
    struct buffer_head *page_bufs;
    handle_t *handle = NULL;
    int ret = 0;
    int err;

    J_ASSERT(PageLocked(page));
    /*
     * We don't want to warn for emergency remount. The condition is
     * ordered to avoid dereferencing inode->i_sb in non-error case to
     * avoid slow-downs.
     */
    WARN_ON_ONCE(IS_RDONLY(inode) &&
             !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS));

    /*
     * We give up here if we're reentered, because it might be for a
     * different filesystem.
     */
    if (ext3_journal_current_handle())
        goto out_fail;

    trace_ext3_ordered_writepage(page);
    if (!page_has_buffers(page)) {
        create_empty_buffers(page, inode->i_sb->s_blocksize,
                (1 << BH_Dirty)|(1 << BH_Uptodate));
        page_bufs = page_buffers(page);
    } else {
        page_bufs = page_buffers(page);
        if (!walk_page_buffers(NULL, page_bufs, 0, PAGE_CACHE_SIZE,
                       NULL, buffer_unmapped)) {
            /* Provide NULL get_block() to catch bugs if buffers
             * weren't really mapped */
            return block_write_full_page(page, NULL, wbc);
        }
    }
    handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));

    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        goto out_fail;
    }

    walk_page_buffers(handle, page_bufs, 0,
            PAGE_CACHE_SIZE, NULL, bget_one);

    ret = block_write_full_page(page, ext3_get_block, wbc);

    /*
     * The page can become unlocked at any point now, and
     * truncate can then come in and change things.  So we
     * can't touch *page from now on.  But *page_bufs is
     * safe due to elevated refcount.
     */

    /*
     * And attach them to the current transaction.  But only if
     * block_write_full_page() succeeded.  Otherwise they are unmapped,
     * and generally junk.
     */
    if (ret == 0) {
        err = walk_page_buffers(handle, page_bufs, 0, PAGE_CACHE_SIZE,
                    NULL, journal_dirty_data_fn);
        if (!ret)
            ret = err;
    }
    walk_page_buffers(handle, page_bufs, 0,
            PAGE_CACHE_SIZE, NULL, bput_one);
    err = ext3_journal_stop(handle);
    if (!ret)
        ret = err;
    return ret;

out_fail:
    redirty_page_for_writepage(wbc, page);
    unlock_page(page);
    return ret;
}

static int ext3_writeback_writepage(struct page *page,
                struct writeback_control *wbc)
{
    struct inode *inode = page->mapping->host;
    handle_t *handle = NULL;
    int ret = 0;
    int err;

    J_ASSERT(PageLocked(page));
    /*
     * We don't want to warn for emergency remount. The condition is
     * ordered to avoid dereferencing inode->i_sb in non-error case to
     * avoid slow-downs.
     */
    WARN_ON_ONCE(IS_RDONLY(inode) &&
             !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS));

    if (ext3_journal_current_handle())
        goto out_fail;

    trace_ext3_writeback_writepage(page);
    if (page_has_buffers(page)) {
        if (!walk_page_buffers(NULL, page_buffers(page), 0,
                      PAGE_CACHE_SIZE, NULL, buffer_unmapped)) {
            /* Provide NULL get_block() to catch bugs if buffers
             * weren't really mapped */
            return block_write_full_page(page, NULL, wbc);
        }
    }

    handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        goto out_fail;
    }

    ret = block_write_full_page(page, ext3_get_block, wbc);

    err = ext3_journal_stop(handle);
    if (!ret)
        ret = err;
    return ret;

out_fail:
    redirty_page_for_writepage(wbc, page);
    unlock_page(page);
    return ret;
}

static int ext3_journalled_writepage(struct page *page,
                struct writeback_control *wbc)
{
    struct inode *inode = page->mapping->host;
    handle_t *handle = NULL;
    int ret = 0;
    int err;

    J_ASSERT(PageLocked(page));
    /*
     * We don't want to warn for emergency remount. The condition is
     * ordered to avoid dereferencing inode->i_sb in non-error case to
     * avoid slow-downs.
     */
    WARN_ON_ONCE(IS_RDONLY(inode) &&
             !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ERROR_FS));

    if (ext3_journal_current_handle())
        goto no_write;

    trace_ext3_journalled_writepage(page);
    handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        goto no_write;
    }

    if (!page_has_buffers(page) || PageChecked(page)) {
        /*
         * It's mmapped pagecache.  Add buffers and journal it.  There
         * doesn't seem much point in redirtying the page here.
         */
        ClearPageChecked(page);
        ret = __block_write_begin(page, 0, PAGE_CACHE_SIZE,
                      ext3_get_block);
        if (ret != 0) {
            ext3_journal_stop(handle);
            goto out_unlock;
        }
        ret = walk_page_buffers(handle, page_buffers(page), 0,
            PAGE_CACHE_SIZE, NULL, do_journal_get_write_access);

        err = walk_page_buffers(handle, page_buffers(page), 0,
                PAGE_CACHE_SIZE, NULL, write_end_fn);
        if (ret == 0)
            ret = err;
        ext3_set_inode_state(inode, EXT3_STATE_JDATA);
        atomic_set(&EXT3_I(inode)->i_datasync_tid,
               handle->h_transaction->t_tid);
        unlock_page(page);
    } else {
        /*
         * It may be a page full of checkpoint-mode buffers.  We don't
         * really know unless we go poke around in the buffer_heads.
         * But block_write_full_page will do the right thing.
         */
        ret = block_write_full_page(page, ext3_get_block, wbc);
    }
    err = ext3_journal_stop(handle);
    if (!ret)
        ret = err;
out:
    return ret;

no_write:
    redirty_page_for_writepage(wbc, page);
out_unlock:
    unlock_page(page);
    goto out;
}

static int ext3_readpage(struct file *file, struct page *page)
{
    trace_ext3_readpage(page);
    return mpage_readpage(page, ext3_get_block);
}

static int
ext3_readpages(struct file *file, struct address_space *mapping,
        struct list_head *pages, unsigned nr_pages)
{
    return mpage_readpages(mapping, pages, nr_pages, ext3_get_block);
}

static void ext3_invalidatepage(struct page *page, unsigned long offset)
{
    journal_t *journal = EXT3_JOURNAL(page->mapping->host);

    trace_ext3_invalidatepage(page, offset);

    /*
     * If it's a full truncate we just forget about the pending dirtying
     */
    if (offset == 0)
        ClearPageChecked(page);

    journal_invalidatepage(journal, page, offset);
}

static int ext3_releasepage(struct page *page, gfp_t wait)
{
    journal_t *journal = EXT3_JOURNAL(page->mapping->host);

    trace_ext3_releasepage(page);
    WARN_ON(PageChecked(page));
    if (!page_has_buffers(page))
        return 0;
    return journal_try_to_free_buffers(journal, page, wait);
}

/*
 * If the O_DIRECT write will extend the file then add this inode to the
 * orphan list.  So recovery will truncate it back to the original size
 * if the machine crashes during the write.
 *
 * If the O_DIRECT write is intantiating holes inside i_size and the machine
 * crashes then stale disk data _may_ be exposed inside the file. But current
 * VFS code falls back into buffered path in that case so we are safe.
 */
static ssize_t ext3_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;
    struct ext3_inode_info *ei = EXT3_I(inode);
    handle_t *handle;
    ssize_t ret;
    int orphan = 0;
    size_t count = iov_length(iov, nr_segs);
    int retries = 0;

    trace_ext3_direct_IO_enter(inode, offset, iov_length(iov, nr_segs), rw);

    if (rw == WRITE) {
        loff_t final_size = offset + count;

        if (final_size > inode->i_size) {
            /* Credits for sb + inode write */
            handle = ext3_journal_start(inode, 2);
            if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                goto out;
            }
            ret = ext3_orphan_add(handle, inode);
            if (ret) {
                ext3_journal_stop(handle);
                goto out;
            }
            orphan = 1;
            ei->i_disksize = inode->i_size;
            ext3_journal_stop(handle);
        }
    }

retry:
    ret = blockdev_direct_IO(rw, iocb, inode, iov, offset, nr_segs,
                 ext3_get_block);
    /*
     * In case of error extending write may have instantiated a few
     * blocks outside i_size. Trim these off again.
     */
    if (unlikely((rw & WRITE) && ret < 0)) {
        loff_t isize = i_size_read(inode);
        loff_t end = offset + iov_length(iov, nr_segs);

        if (end > isize)
            ext3_truncate_failed_direct_write(inode);
    }
    if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
        goto retry;

    if (orphan) {
        int err;

        /* Credits for sb + inode write */
        handle = ext3_journal_start(inode, 2);
        if (IS_ERR(handle)) {
            /* This is really bad luck. We've written the data
             * but cannot extend i_size. Truncate allocated blocks
             * and pretend the write failed... */
            ext3_truncate_failed_direct_write(inode);
            ret = PTR_ERR(handle);
            goto out;
        }
        if (inode->i_nlink)
            ext3_orphan_del(handle, inode);
        if (ret > 0) {
            loff_t end = offset + ret;
            if (end > inode->i_size) {
                ei->i_disksize = end;
                i_size_write(inode, end);
                /*
                 * We're going to return a positive `ret'
                 * here due to non-zero-length I/O, so there's
                 * no way of reporting error returns from
                 * ext3_mark_inode_dirty() to userspace.  So
                 * ignore it.
                 */
                ext3_mark_inode_dirty(handle, inode);
            }
        }
        err = ext3_journal_stop(handle);
        if (ret == 0)
            ret = err;
    }
out:
    trace_ext3_direct_IO_exit(inode, offset,
                iov_length(iov, nr_segs), rw, ret);
    return ret;
}

/*
 * Pages can be marked dirty completely asynchronously from ext3's journalling
 * activity.  By filemap_sync_pte(), try_to_unmap_one(), etc.  We cannot do
 * much here because ->set_page_dirty is called under VFS locks.  The page is
 * not necessarily locked.
 *
 * We cannot just dirty the page and leave attached buffers clean, because the
 * buffers' dirty state is "definitive".  We cannot just set the buffers dirty
 * or jbddirty because all the journalling code will explode.
 *
 * So what we do is to mark the page "pending dirty" and next time writepage
 * is called, propagate that into the buffers appropriately.
 */
static int ext3_journalled_set_page_dirty(struct page *page)
{
    SetPageChecked(page);
    return __set_page_dirty_nobuffers(page);
}

static const struct address_space_operations ext3_ordered_aops = {
    .readpage       = ext3_readpage,
    .readpages      = ext3_readpages,
    .writepage      = ext3_ordered_writepage,
    .write_begin        = ext3_write_begin,
    .write_end      = ext3_ordered_write_end,
    .bmap           = ext3_bmap,
    .invalidatepage     = ext3_invalidatepage,
    .releasepage        = ext3_releasepage,
    .direct_IO      = ext3_direct_IO,
    .migratepage        = buffer_migrate_page,
    .is_partially_uptodate  = block_is_partially_uptodate,
    .error_remove_page  = generic_error_remove_page,
};

static const struct address_space_operations ext3_writeback_aops = {
    .readpage       = ext3_readpage,
    .readpages      = ext3_readpages,
    .writepage      = ext3_writeback_writepage,
    .write_begin        = ext3_write_begin,
    .write_end      = ext3_writeback_write_end,
    .bmap           = ext3_bmap,
    .invalidatepage     = ext3_invalidatepage,
    .releasepage        = ext3_releasepage,
    .direct_IO      = ext3_direct_IO,
    .migratepage        = buffer_migrate_page,
    .is_partially_uptodate  = block_is_partially_uptodate,
    .error_remove_page  = generic_error_remove_page,
};

static const struct address_space_operations ext3_journalled_aops = {
    .readpage       = ext3_readpage,
    .readpages      = ext3_readpages,
    .writepage      = ext3_journalled_writepage,
    .write_begin        = ext3_write_begin,
    .write_end      = ext3_journalled_write_end,
    .set_page_dirty     = ext3_journalled_set_page_dirty,
    .bmap           = ext3_bmap,
    .invalidatepage     = ext3_invalidatepage,
    .releasepage        = ext3_releasepage,
    .is_partially_uptodate  = block_is_partially_uptodate,
    .error_remove_page  = generic_error_remove_page,
};

void ext3_set_aops(struct inode *inode)
{
    if (ext3_should_order_data(inode))
        inode->i_mapping->a_ops = &ext3_ordered_aops;
    else if (ext3_should_writeback_data(inode))
        inode->i_mapping->a_ops = &ext3_writeback_aops;
    else
        inode->i_mapping->a_ops = &ext3_journalled_aops;
}

/*
 * ext3_block_truncate_page() zeroes out a mapping from file offset `from'
 * up to the end of the block which corresponds to `from'.
 * This required during truncate. We need to physically zero the tail end
 * of that block so it doesn't yield old data if the file is later grown.
 */
static int ext3_block_truncate_page(struct inode *inode, loff_t from)
{
    ext3_fsblk_t index = from >> PAGE_CACHE_SHIFT;
    unsigned offset = from & (PAGE_CACHE_SIZE - 1);
    unsigned blocksize, iblock, length, pos;
    struct page *page;
    handle_t *handle = NULL;
    struct buffer_head *bh;
    int err = 0;

    /* Truncated on block boundary - nothing to do */
    blocksize = inode->i_sb->s_blocksize;
    if ((from & (blocksize - 1)) == 0)
        return 0;

    page = grab_cache_page(inode->i_mapping, index);
    if (!page)
        return -ENOMEM;
    length = blocksize - (offset & (blocksize - 1));
    iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);

    if (!page_has_buffers(page))
        create_empty_buffers(page, blocksize, 0);

    /* Find the buffer that contains "offset" */
    bh = page_buffers(page);
    pos = blocksize;
    while (offset >= pos) {
        bh = bh->b_this_page;
        iblock++;
        pos += blocksize;
    }

    err = 0;
    if (buffer_freed(bh)) {
        BUFFER_TRACE(bh, "freed: skip");
        goto unlock;
    }

    if (!buffer_mapped(bh)) {
        BUFFER_TRACE(bh, "unmapped");
        ext3_get_block(inode, iblock, bh, 0);
        /* unmapped? It's a hole - nothing to do */
        if (!buffer_mapped(bh)) {
            BUFFER_TRACE(bh, "still unmapped");
            goto unlock;
        }
    }

    /* Ok, it's mapped. Make sure it's up-to-date */
    if (PageUptodate(page))
        set_buffer_uptodate(bh);

    if (!bh_uptodate_or_lock(bh)) {
        err = bh_submit_read(bh);
        /* Uhhuh. Read error. Complain and punt. */
        if (err)
            goto unlock;
    }

    /* data=writeback mode doesn't need transaction to zero-out data */
    if (!ext3_should_writeback_data(inode)) {
        /* We journal at most one block */
        handle = ext3_journal_start(inode, 1);
        if (IS_ERR(handle)) {
            clear_highpage(page);
            flush_dcache_page(page);
            err = PTR_ERR(handle);
            goto unlock;
        }
    }

    if (ext3_should_journal_data(inode)) {
        BUFFER_TRACE(bh, "get write access");
        err = ext3_journal_get_write_access(handle, bh);
        if (err)
            goto stop;
    }

    zero_user(page, offset, length);
    BUFFER_TRACE(bh, "zeroed end of block");

    err = 0;
    if (ext3_should_journal_data(inode)) {
        err = ext3_journal_dirty_metadata(handle, bh);
    } else {
        if (ext3_should_order_data(inode))
            err = ext3_journal_dirty_data(handle, bh);
        mark_buffer_dirty(bh);
    }
stop:
    if (handle)
        ext3_journal_stop(handle);

unlock:
    unlock_page(page);
    page_cache_release(page);
    return err;
}

/*
 * Probably it should be a library function... search for first non-zero word
 * or memcmp with zero_page, whatever is better for particular architecture.
 * Linus?
 */
static inline int all_zeroes(__le32 *p, __le32 *q)
{
    while (p < q)
        if (*p++)
            return 0;
    return 1;
}

static Indirect *ext3_find_shared(struct inode *inode, int depth,
            int offsets[4], Indirect chain[4], __le32 *top)
{
    Indirect *partial, *p;
    int k, err;

    *top = 0;
    /* Make k index the deepest non-null offset + 1 */
    for (k = depth; k > 1 && !offsets[k-1]; k--)
        ;
    partial = ext3_get_branch(inode, k, offsets, chain, &err);
    /* Writer: pointers */
    if (!partial)
        partial = chain + k-1;
    /*
     * If the branch acquired continuation since we've looked at it -
     * fine, it should all survive and (new) top doesn't belong to us.
     */
    if (!partial->key && *partial->p)
        /* Writer: end */
        goto no_top;
    for (p=partial; p>chain && all_zeroes((__le32*)p->bh->b_data,p->p); p--)
        ;
    /*
     * OK, we've found the last block that must survive. The rest of our
     * branch should be detached before unlocking. However, if that rest
     * of branch is all ours and does not grow immediately from the inode
     * it's easier to cheat and just decrement partial->p.
     */
    if (p == chain + k - 1 && p > chain) {
        p->p--;
    } else {
        *top = *p->p;
        /* Nope, don't do this in ext3.  Must leave the tree intact */
#if 0
        *p->p = 0;
#endif
    }
    /* Writer: end */

    while(partial > p) {
        brelse(partial->bh);
        partial--;
    }
no_top:
    return partial;
}

/*
 * Zero a number of block pointers in either an inode or an indirect block.
 * If we restart the transaction we must again get write access to the
 * indirect block for further modification.
 *
 * We release `count' blocks on disk, but (last - first) may be greater
 * than `count' because there can be holes in there.
 */
static void ext3_clear_blocks(handle_t *handle, struct inode *inode,
        struct buffer_head *bh, ext3_fsblk_t block_to_free,
        unsigned long count, __le32 *first, __le32 *last)
{
    __le32 *p;
    if (try_to_extend_transaction(handle, inode)) {
        if (bh) {
            BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
            if (ext3_journal_dirty_metadata(handle, bh))
                return;
        }
        ext3_mark_inode_dirty(handle, inode);
        truncate_restart_transaction(handle, inode);
        if (bh) {
            BUFFER_TRACE(bh, "retaking write access");
            if (ext3_journal_get_write_access(handle, bh))
                return;
        }
    }

    /*
     * Any buffers which are on the journal will be in memory. We find
     * them on the hash table so journal_revoke() will run journal_forget()
     * on them.  We've already detached each block from the file, so
     * bforget() in journal_forget() should be safe.
     *
     * AKPM: turn on bforget in journal_forget()!!!
     */
    for (p = first; p < last; p++) {
        u32 nr = le32_to_cpu(*p);
        if (nr) {
            struct buffer_head *bh;

            *p = 0;
            bh = sb_find_get_block(inode->i_sb, nr);
            ext3_forget(handle, 0, inode, bh, nr);
        }
    }

    ext3_free_blocks(handle, inode, block_to_free, count);
}

static void ext3_free_data(handle_t *handle, struct inode *inode,
               struct buffer_head *this_bh,
               __le32 *first, __le32 *last)
{
    ext3_fsblk_t block_to_free = 0;    /* Starting block # of a run */
    unsigned long count = 0;        /* Number of blocks in the run */
    __le32 *block_to_free_p = NULL;     /* Pointer into inode/ind
                           corresponding to
                           block_to_free */
    ext3_fsblk_t nr;            /* Current block # */
    __le32 *p;              /* Pointer into inode/ind
                           for current block */
    int err;

    if (this_bh) {              /* For indirect block */
        BUFFER_TRACE(this_bh, "get_write_access");
        err = ext3_journal_get_write_access(handle, this_bh);
        /* Important: if we can't update the indirect pointers
         * to the blocks, we can't free them. */
        if (err)
            return;
    }

    for (p = first; p < last; p++) {
        nr = le32_to_cpu(*p);
        if (nr) {
            /* accumulate blocks to free if they're contiguous */
            if (count == 0) {
                block_to_free = nr;
                block_to_free_p = p;
                count = 1;
            } else if (nr == block_to_free + count) {
                count++;
            } else {
                ext3_clear_blocks(handle, inode, this_bh,
                          block_to_free,
                          count, block_to_free_p, p);
                block_to_free = nr;
                block_to_free_p = p;
                count = 1;
            }
        }
    }

    if (count > 0)
        ext3_clear_blocks(handle, inode, this_bh, block_to_free,
                  count, block_to_free_p, p);

    if (this_bh) {
        BUFFER_TRACE(this_bh, "call ext3_journal_dirty_metadata");

        /*
         * The buffer head should have an attached journal head at this
         * point. However, if the data is corrupted and an indirect
         * block pointed to itself, it would have been detached when
         * the block was cleared. Check for this instead of OOPSing.
         */
        if (bh2jh(this_bh))
            ext3_journal_dirty_metadata(handle, this_bh);
        else
            ext3_error(inode->i_sb, "ext3_free_data",
                   "circular indirect block detected, "
                   "inode=%lu, block=%llu",
                   inode->i_ino,
                   (unsigned long long)this_bh->b_blocknr);
    }
}

static void ext3_free_branches(handle_t *handle, struct inode *inode,
                   struct buffer_head *parent_bh,
                   __le32 *first, __le32 *last, int depth)
{
    ext3_fsblk_t nr;
    __le32 *p;

    if (is_handle_aborted(handle))
        return;

    if (depth--) {
        struct buffer_head *bh;
        int addr_per_block = EXT3_ADDR_PER_BLOCK(inode->i_sb);
        p = last;
        while (--p >= first) {
            nr = le32_to_cpu(*p);
            if (!nr)
                continue;       /* A hole */

            /* Go read the buffer for the next level down */
            bh = sb_bread(inode->i_sb, nr);

            /*
             * A read failure? Report error and clear slot
             * (should be rare).
             */
            if (!bh) {
                ext3_error(inode->i_sb, "ext3_free_branches",
                       "Read failure, inode=%lu, block="E3FSBLK,
                       inode->i_ino, nr);
                continue;
            }

            /* This zaps the entire block.  Bottom up. */
            BUFFER_TRACE(bh, "free child branches");
            ext3_free_branches(handle, inode, bh,
                       (__le32*)bh->b_data,
                       (__le32*)bh->b_data + addr_per_block,
                       depth);

            /*
             * Everything below this this pointer has been
             * released.  Now let this top-of-subtree go.
             *
             * We want the freeing of this indirect block to be
             * atomic in the journal with the updating of the
             * bitmap block which owns it.  So make some room in
             * the journal.
             *
             * We zero the parent pointer *after* freeing its
             * pointee in the bitmaps, so if extend_transaction()
             * for some reason fails to put the bitmap changes and
             * the release into the same transaction, recovery
             * will merely complain about releasing a free block,
             * rather than leaking blocks.
             */
            if (is_handle_aborted(handle))
                return;
            if (try_to_extend_transaction(handle, inode)) {
                ext3_mark_inode_dirty(handle, inode);
                truncate_restart_transaction(handle, inode);
            }

            /*
             * We've probably journalled the indirect block several
             * times during the truncate.  But it's no longer
             * needed and we now drop it from the transaction via
             * journal_revoke().
             *
             * That's easy if it's exclusively part of this
             * transaction.  But if it's part of the committing
             * transaction then journal_forget() will simply
             * brelse() it.  That means that if the underlying
             * block is reallocated in ext3_get_block(),
             * unmap_underlying_metadata() will find this block
             * and will try to get rid of it.  damn, damn. Thus
             * we don't allow a block to be reallocated until
             * a transaction freeing it has fully committed.
             *
             * We also have to make sure journal replay after a
             * crash does not overwrite non-journaled data blocks
             * with old metadata when the block got reallocated for
             * data.  Thus we have to store a revoke record for a
             * block in the same transaction in which we free the
             * block.
             */
            ext3_forget(handle, 1, inode, bh, bh->b_blocknr);

            ext3_free_blocks(handle, inode, nr, 1);

            if (parent_bh) {
                /*
                 * The block which we have just freed is
                 * pointed to by an indirect block: journal it
                 */
                BUFFER_TRACE(parent_bh, "get_write_access");
                if (!ext3_journal_get_write_access(handle,
                                   parent_bh)){
                    *p = 0;
                    BUFFER_TRACE(parent_bh,
                    "call ext3_journal_dirty_metadata");
                    ext3_journal_dirty_metadata(handle,
                                    parent_bh);
                }
            }
        }
    } else {
        /* We have reached the bottom of the tree. */
        BUFFER_TRACE(parent_bh, "free data blocks");
        ext3_free_data(handle, inode, parent_bh, first, last);
    }
}

int ext3_can_truncate(struct inode *inode)
{
    if (S_ISREG(inode->i_mode))
        return 1;
    if (S_ISDIR(inode->i_mode))
        return 1;
    if (S_ISLNK(inode->i_mode))
        return !ext3_inode_is_fast_symlink(inode);
    return 0;
}

/*
 * ext3_truncate()
 *
 * We block out ext3_get_block() block instantiations across the entire
 * transaction, and VFS/VM ensures that ext3_truncate() cannot run
 * simultaneously on behalf of the same inode.
 *
 * As we work through the truncate and commit bits of it to the journal there
 * is one core, guiding principle: the file's tree must always be consistent on
 * disk.  We must be able to restart the truncate after a crash.
 *
 * The file's tree may be transiently inconsistent in memory (although it
 * probably isn't), but whenever we close off and commit a journal transaction,
 * the contents of (the filesystem + the journal) must be consistent and
 * restartable.  It's pretty simple, really: bottom up, right to left (although
 * left-to-right works OK too).
 *
 * Note that at recovery time, journal replay occurs *before* the restart of
 * truncate against the orphan inode list.
 *
 * The committed inode has the new, desired i_size (which is the same as
 * i_disksize in this case).  After a crash, ext3_orphan_cleanup() will see
 * that this inode's truncate did not complete and it will again call
 * ext3_truncate() to have another go.  So there will be instantiated blocks
 * to the right of the truncation point in a crashed ext3 filesystem.  But
 * that's fine - as long as they are linked from the inode, the post-crash
 * ext3_truncate() run will find them and release them.
 */
void ext3_truncate(struct inode *inode)
{
    handle_t *handle;
    struct ext3_inode_info *ei = EXT3_I(inode);
    __le32 *i_data = ei->i_data;
    int addr_per_block = EXT3_ADDR_PER_BLOCK(inode->i_sb);
    int offsets[4];
    Indirect chain[4];
    Indirect *partial;
    __le32 nr = 0;
    int n;
    long last_block;
    unsigned blocksize = inode->i_sb->s_blocksize;

    trace_ext3_truncate_enter(inode);

    if (!ext3_can_truncate(inode))
        goto out_notrans;

    if (inode->i_size == 0 && ext3_should_writeback_data(inode))
        ext3_set_inode_state(inode, EXT3_STATE_FLUSH_ON_CLOSE);

    handle = start_transaction(inode);
    if (IS_ERR(handle))
        goto out_notrans;

    last_block = (inode->i_size + blocksize-1)
                    >> EXT3_BLOCK_SIZE_BITS(inode->i_sb);
    n = ext3_block_to_path(inode, last_block, offsets, NULL);
    if (n == 0)
        goto out_stop;  /* error */

    /*
     * OK.  This truncate is going to happen.  We add the inode to the
     * orphan list, so that if this truncate spans multiple transactions,
     * and we crash, we will resume the truncate when the filesystem
     * recovers.  It also marks the inode dirty, to catch the new size.
     *
     * Implication: the file must always be in a sane, consistent
     * truncatable state while each transaction commits.
     */
    if (ext3_orphan_add(handle, inode))
        goto out_stop;

    /*
     * The orphan list entry will now protect us from any crash which
     * occurs before the truncate completes, so it is now safe to propagate
     * the new, shorter inode size (held for now in i_size) into the
     * on-disk inode. We do this via i_disksize, which is the value which
     * ext3 *really* writes onto the disk inode.
     */
    ei->i_disksize = inode->i_size;

    /*
     * From here we block out all ext3_get_block() callers who want to
     * modify the block allocation tree.
     */
    mutex_lock(&ei->truncate_mutex);

    if (n == 1) {       /* direct blocks */
        ext3_free_data(handle, inode, NULL, i_data+offsets[0],
                   i_data + EXT3_NDIR_BLOCKS);
        goto do_indirects;
    }

    partial = ext3_find_shared(inode, n, offsets, chain, &nr);
    /* Kill the top of shared branch (not detached) */
    if (nr) {
        if (partial == chain) {
            /* Shared branch grows from the inode */
            ext3_free_branches(handle, inode, NULL,
                       &nr, &nr+1, (chain+n-1) - partial);
            *partial->p = 0;
            /*
             * We mark the inode dirty prior to restart,
             * and prior to stop.  No need for it here.
             */
        } else {
            /* Shared branch grows from an indirect block */
            ext3_free_branches(handle, inode, partial->bh,
                    partial->p,
                    partial->p+1, (chain+n-1) - partial);
        }
    }
    /* Clear the ends of indirect blocks on the shared branch */
    while (partial > chain) {
        ext3_free_branches(handle, inode, partial->bh, partial->p + 1,
                   (__le32*)partial->bh->b_data+addr_per_block,
                   (chain+n-1) - partial);
        BUFFER_TRACE(partial->bh, "call brelse");
        brelse (partial->bh);
        partial--;
    }
do_indirects:
    /* Kill the remaining (whole) subtrees */
    switch (offsets[0]) {
    default:
        nr = i_data[EXT3_IND_BLOCK];
        if (nr) {
            ext3_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
            i_data[EXT3_IND_BLOCK] = 0;
        }
    case EXT3_IND_BLOCK:
        nr = i_data[EXT3_DIND_BLOCK];
        if (nr) {
            ext3_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
            i_data[EXT3_DIND_BLOCK] = 0;
        }
    case EXT3_DIND_BLOCK:
        nr = i_data[EXT3_TIND_BLOCK];
        if (nr) {
            ext3_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
            i_data[EXT3_TIND_BLOCK] = 0;
        }
    case EXT3_TIND_BLOCK:
        ;
    }

    ext3_discard_reservation(inode);

    mutex_unlock(&ei->truncate_mutex);
    inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
    ext3_mark_inode_dirty(handle, inode);

    /*
     * In a multi-transaction truncate, we only make the final transaction
     * synchronous
     */
    if (IS_SYNC(inode))
        handle->h_sync = 1;
out_stop:
    /*
     * If this was a simple ftruncate(), and the file will remain alive
     * then we need to clear up the orphan record which we created above.
     * However, if this was a real unlink then we were called by
     * ext3_evict_inode(), and we allow that function to clean up the
     * orphan info for us.
     */
    if (inode->i_nlink)
        ext3_orphan_del(handle, inode);

    ext3_journal_stop(handle);
    trace_ext3_truncate_exit(inode);
    return;
out_notrans:
    /*
     * Delete the inode from orphan list so that it doesn't stay there
     * forever and trigger assertion on umount.
     */
    if (inode->i_nlink)
        ext3_orphan_del(NULL, inode);
    trace_ext3_truncate_exit(inode);
}

static ext3_fsblk_t ext3_get_inode_block(struct super_block *sb,
        unsigned long ino, struct ext3_iloc *iloc)
{
    unsigned long block_group;
    unsigned long offset;
    ext3_fsblk_t block;
    struct ext3_group_desc *gdp;

    if (!ext3_valid_inum(sb, ino)) {
        /*
         * This error is already checked for in namei.c unless we are
         * looking at an NFS filehandle, in which case no error
         * report is needed
         */
        return 0;
    }

    block_group = (ino - 1) / EXT3_INODES_PER_GROUP(sb);
    gdp = ext3_get_group_desc(sb, block_group, NULL);
    if (!gdp)
        return 0;
    /*
     * Figure out the offset within the block group inode table
     */
    offset = ((ino - 1) % EXT3_INODES_PER_GROUP(sb)) *
        EXT3_INODE_SIZE(sb);
    block = le32_to_cpu(gdp->bg_inode_table) +
        (offset >> EXT3_BLOCK_SIZE_BITS(sb));

    iloc->block_group = block_group;
    iloc->offset = offset & (EXT3_BLOCK_SIZE(sb) - 1);
    return block;
}

/*
 * ext3_get_inode_loc returns with an extra refcount against the inode's
 * underlying buffer_head on success. If 'in_mem' is true, we have all
 * data in memory that is needed to recreate the on-disk version of this
 * inode.
 */
static int __ext3_get_inode_loc(struct inode *inode,
                struct ext3_iloc *iloc, int in_mem)
{
    ext3_fsblk_t block;
    struct buffer_head *bh;

    block = ext3_get_inode_block(inode->i_sb, inode->i_ino, iloc);
    if (!block)
        return -EIO;

    bh = sb_getblk(inode->i_sb, block);
    if (!bh) {
        ext3_error (inode->i_sb, "ext3_get_inode_loc",
                "unable to read inode block - "
                "inode=%lu, block="E3FSBLK,
                 inode->i_ino, block);
        return -EIO;
    }
    if (!buffer_uptodate(bh)) {
        lock_buffer(bh);

        /*
         * If the buffer has the write error flag, we have failed
         * to write out another inode in the same block.  In this
         * case, we don't have to read the block because we may
         * read the old inode data successfully.
         */
        if (buffer_write_io_error(bh) && !buffer_uptodate(bh))
            set_buffer_uptodate(bh);

        if (buffer_uptodate(bh)) {
            /* someone brought it uptodate while we waited */
            unlock_buffer(bh);
            goto has_buffer;
        }

        /*
         * If we have all information of the inode in memory and this
         * is the only valid inode in the block, we need not read the
         * block.
         */
        if (in_mem) {
            struct buffer_head *bitmap_bh;
            struct ext3_group_desc *desc;
            int inodes_per_buffer;
            int inode_offset, i;
            int block_group;
            int start;

            block_group = (inode->i_ino - 1) /
                    EXT3_INODES_PER_GROUP(inode->i_sb);
            inodes_per_buffer = bh->b_size /
                EXT3_INODE_SIZE(inode->i_sb);
            inode_offset = ((inode->i_ino - 1) %
                    EXT3_INODES_PER_GROUP(inode->i_sb));
            start = inode_offset & ~(inodes_per_buffer - 1);

            /* Is the inode bitmap in cache? */
            desc = ext3_get_group_desc(inode->i_sb,
                        block_group, NULL);
            if (!desc)
                goto make_io;

            bitmap_bh = sb_getblk(inode->i_sb,
                    le32_to_cpu(desc->bg_inode_bitmap));
            if (!bitmap_bh)
                goto make_io;

            /*
             * If the inode bitmap isn't in cache then the
             * optimisation may end up performing two reads instead
             * of one, so skip it.
             */
            if (!buffer_uptodate(bitmap_bh)) {
                brelse(bitmap_bh);
                goto make_io;
            }
            for (i = start; i < start + inodes_per_buffer; i++) {
                if (i == inode_offset)
                    continue;
                if (ext3_test_bit(i, bitmap_bh->b_data))
                    break;
            }
            brelse(bitmap_bh);
            if (i == start + inodes_per_buffer) {
                /* all other inodes are free, so skip I/O */
                memset(bh->b_data, 0, bh->b_size);
                set_buffer_uptodate(bh);
                unlock_buffer(bh);
                goto has_buffer;
            }
        }

make_io:
        /*
         * There are other valid inodes in the buffer, this inode
         * has in-inode xattrs, or we don't have this inode in memory.
         * Read the block from disk.
         */
        trace_ext3_load_inode(inode);
        get_bh(bh);
        bh->b_end_io = end_buffer_read_sync;
        submit_bh(READ | REQ_META | REQ_PRIO, bh);
        wait_on_buffer(bh);
        if (!buffer_uptodate(bh)) {
            ext3_error(inode->i_sb, "ext3_get_inode_loc",
                    "unable to read inode block - "
                    "inode=%lu, block="E3FSBLK,
                    inode->i_ino, block);
            brelse(bh);
            return -EIO;
        }
    }
has_buffer:
    iloc->bh = bh;
    return 0;
}

int ext3_get_inode_loc(struct inode *inode, struct ext3_iloc *iloc)
{
    /* We have all inode data except xattrs in memory here. */
    return __ext3_get_inode_loc(inode, iloc,
        !ext3_test_inode_state(inode, EXT3_STATE_XATTR));
}

void ext3_set_inode_flags(struct inode *inode)
{
    unsigned int flags = EXT3_I(inode)->i_flags;

    inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
    if (flags & EXT3_SYNC_FL)
        inode->i_flags |= S_SYNC;
    if (flags & EXT3_APPEND_FL)
        inode->i_flags |= S_APPEND;
    if (flags & EXT3_IMMUTABLE_FL)
        inode->i_flags |= S_IMMUTABLE;
    if (flags & EXT3_NOATIME_FL)
        inode->i_flags |= S_NOATIME;
    if (flags & EXT3_DIRSYNC_FL)
        inode->i_flags |= S_DIRSYNC;
}

/* Propagate flags from i_flags to EXT3_I(inode)->i_flags */
void ext3_get_inode_flags(struct ext3_inode_info *ei)
{
    unsigned int flags = ei->vfs_inode.i_flags;

    ei->i_flags &= ~(EXT3_SYNC_FL|EXT3_APPEND_FL|
            EXT3_IMMUTABLE_FL|EXT3_NOATIME_FL|EXT3_DIRSYNC_FL);
    if (flags & S_SYNC)
        ei->i_flags |= EXT3_SYNC_FL;
    if (flags & S_APPEND)
        ei->i_flags |= EXT3_APPEND_FL;
    if (flags & S_IMMUTABLE)
        ei->i_flags |= EXT3_IMMUTABLE_FL;
    if (flags & S_NOATIME)
        ei->i_flags |= EXT3_NOATIME_FL;
    if (flags & S_DIRSYNC)
        ei->i_flags |= EXT3_DIRSYNC_FL;
}

struct inode *ext3_iget(struct super_block *sb, unsigned long ino)
{
    struct ext3_iloc iloc;
    struct ext3_inode *raw_inode;
    struct ext3_inode_info *ei;
    struct buffer_head *bh;
    struct inode *inode;
    journal_t *journal = EXT3_SB(sb)->s_journal;
    transaction_t *transaction;
    long ret;
    int block;
    uid_t i_uid;
    gid_t i_gid;

    inode = iget_locked(sb, ino);
    if (!inode)
        return ERR_PTR(-ENOMEM);
    if (!(inode->i_state & I_NEW))
        return inode;

    ei = EXT3_I(inode);
    ei->i_block_alloc_info = NULL;

    ret = __ext3_get_inode_loc(inode, &iloc, 0);
    if (ret < 0)
        goto bad_inode;
    bh = iloc.bh;
    raw_inode = ext3_raw_inode(&iloc);
    inode->i_mode = le16_to_cpu(raw_inode->i_mode);
    i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
    i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
    if(!(test_opt (inode->i_sb, NO_UID32))) {
        i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
        i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
    }
    i_uid_write(inode, i_uid);
    i_gid_write(inode, i_gid);
    set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));
    inode->i_size = le32_to_cpu(raw_inode->i_size);
    inode->i_atime.tv_sec = (signed)le32_to_cpu(raw_inode->i_atime);
    inode->i_ctime.tv_sec = (signed)le32_to_cpu(raw_inode->i_ctime);
    inode->i_mtime.tv_sec = (signed)le32_to_cpu(raw_inode->i_mtime);
    inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec = inode->i_mtime.tv_nsec = 0;

    ei->i_state_flags = 0;
    ei->i_dir_start_lookup = 0;
    ei->i_dtime = le32_to_cpu(raw_inode->i_dtime);
    /* We now have enough fields to check if the inode was active or not.
     * This is needed because nfsd might try to access dead inodes
     * the test is that same one that e2fsck uses
     * NeilBrown 1999oct15
     */
    if (inode->i_nlink == 0) {
        if (inode->i_mode == 0 ||
            !(EXT3_SB(inode->i_sb)->s_mount_state & EXT3_ORPHAN_FS)) {
            /* this inode is deleted */
            brelse (bh);
            ret = -ESTALE;
            goto bad_inode;
        }
        /* The only unlinked inodes we let through here have
         * valid i_mode and are being read by the orphan
         * recovery code: that's fine, we're about to complete
         * the process of deleting those. */
    }
    inode->i_blocks = le32_to_cpu(raw_inode->i_blocks);
    ei->i_flags = le32_to_cpu(raw_inode->i_flags);
#ifdef EXT3_FRAGMENTS
    ei->i_faddr = le32_to_cpu(raw_inode->i_faddr);
    ei->i_frag_no = raw_inode->i_frag;
    ei->i_frag_size = raw_inode->i_fsize;
#endif
    ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
    if (!S_ISREG(inode->i_mode)) {
        ei->i_dir_acl = le32_to_cpu(raw_inode->i_dir_acl);
    } else {
        inode->i_size |=
            ((__u64)le32_to_cpu(raw_inode->i_size_high)) << 32;
    }
    ei->i_disksize = inode->i_size;
    inode->i_generation = le32_to_cpu(raw_inode->i_generation);
    ei->i_block_group = iloc.block_group;
    /*
     * NOTE! The in-memory inode i_data array is in little-endian order
     * even on big-endian machines: we do NOT byteswap the block numbers!
     */
    for (block = 0; block < EXT3_N_BLOCKS; block++)
        ei->i_data[block] = raw_inode->i_block[block];
    INIT_LIST_HEAD(&ei->i_orphan);

    /*
     * Set transaction id's of transactions that have to be committed
     * to finish f[data]sync. We set them to currently running transaction
     * as we cannot be sure that the inode or some of its metadata isn't
     * part of the transaction - the inode could have been reclaimed and
     * now it is reread from disk.
     */
    if (journal) {
        tid_t tid;

        spin_lock(&journal->j_state_lock);
        if (journal->j_running_transaction)
            transaction = journal->j_running_transaction;
        else
            transaction = journal->j_committing_transaction;
        if (transaction)
            tid = transaction->t_tid;
        else
            tid = journal->j_commit_sequence;
        spin_unlock(&journal->j_state_lock);
        atomic_set(&ei->i_sync_tid, tid);
        atomic_set(&ei->i_datasync_tid, tid);
    }

    if (inode->i_ino >= EXT3_FIRST_INO(inode->i_sb) + 1 &&
        EXT3_INODE_SIZE(inode->i_sb) > EXT3_GOOD_OLD_INODE_SIZE) {
        /*
         * When mke2fs creates big inodes it does not zero out
         * the unused bytes above EXT3_GOOD_OLD_INODE_SIZE,
         * so ignore those first few inodes.
         */
        ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
        if (EXT3_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
            EXT3_INODE_SIZE(inode->i_sb)) {
            brelse (bh);
            ret = -EIO;
            goto bad_inode;
        }
        if (ei->i_extra_isize == 0) {
            /* The extra space is currently unused. Use it. */
            ei->i_extra_isize = sizeof(struct ext3_inode) -
                        EXT3_GOOD_OLD_INODE_SIZE;
        } else {
            __le32 *magic = (void *)raw_inode +
                    EXT3_GOOD_OLD_INODE_SIZE +
                    ei->i_extra_isize;
            if (*magic == cpu_to_le32(EXT3_XATTR_MAGIC))
                 ext3_set_inode_state(inode, EXT3_STATE_XATTR);
        }
    } else
        ei->i_extra_isize = 0;

    if (S_ISREG(inode->i_mode)) {
        inode->i_op = &ext3_file_inode_operations;
        inode->i_fop = &ext3_file_operations;
        ext3_set_aops(inode);
    } else if (S_ISDIR(inode->i_mode)) {
        inode->i_op = &ext3_dir_inode_operations;
        inode->i_fop = &ext3_dir_operations;
    } else if (S_ISLNK(inode->i_mode)) {
        if (ext3_inode_is_fast_symlink(inode)) {
            inode->i_op = &ext3_fast_symlink_inode_operations;
            nd_terminate_link(ei->i_data, inode->i_size,
                sizeof(ei->i_data) - 1);
        } else {
            inode->i_op = &ext3_symlink_inode_operations;
            ext3_set_aops(inode);
        }
    } else {
        inode->i_op = &ext3_special_inode_operations;
        if (raw_inode->i_block[0])
            init_special_inode(inode, inode->i_mode,
               old_decode_dev(le32_to_cpu(raw_inode->i_block[0])));
        else
            init_special_inode(inode, inode->i_mode,
               new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
    }
    brelse (iloc.bh);
    ext3_set_inode_flags(inode);
    unlock_new_inode(inode);
    return inode;

bad_inode:
    iget_failed(inode);
    return ERR_PTR(ret);
}

/*
 * Post the struct inode info into an on-disk inode location in the
 * buffer-cache.  This gobbles the caller's reference to the
 * buffer_head in the inode location struct.
 *
 * The caller must have write access to iloc->bh.
 */
static int ext3_do_update_inode(handle_t *handle,
                struct inode *inode,
                struct ext3_iloc *iloc)
{
    struct ext3_inode *raw_inode = ext3_raw_inode(iloc);
    struct ext3_inode_info *ei = EXT3_I(inode);
    struct buffer_head *bh = iloc->bh;
    int err = 0, rc, block;
    int need_datasync = 0;
    __le32 disksize;
    uid_t i_uid;
    gid_t i_gid;

again:
    /* we can't allow multiple procs in here at once, its a bit racey */
    lock_buffer(bh);

    /* For fields not not tracking in the in-memory inode,
     * initialise them to zero for new inodes. */
    if (ext3_test_inode_state(inode, EXT3_STATE_NEW))
        memset(raw_inode, 0, EXT3_SB(inode->i_sb)->s_inode_size);

    ext3_get_inode_flags(ei);
    raw_inode->i_mode = cpu_to_le16(inode->i_mode);
    i_uid = i_uid_read(inode);
    i_gid = i_gid_read(inode);
    if(!(test_opt(inode->i_sb, NO_UID32))) {
        raw_inode->i_uid_low = cpu_to_le16(low_16_bits(i_uid));
        raw_inode->i_gid_low = cpu_to_le16(low_16_bits(i_gid));
/*
 * Fix up interoperability with old kernels. Otherwise, old inodes get
 * re-used with the upper 16 bits of the uid/gid intact
 */
        if(!ei->i_dtime) {
            raw_inode->i_uid_high =
                cpu_to_le16(high_16_bits(i_uid));
            raw_inode->i_gid_high =
                cpu_to_le16(high_16_bits(i_gid));
        } else {
            raw_inode->i_uid_high = 0;
            raw_inode->i_gid_high = 0;
        }
    } else {
        raw_inode->i_uid_low =
            cpu_to_le16(fs_high2lowuid(i_uid));
        raw_inode->i_gid_low =
            cpu_to_le16(fs_high2lowgid(i_gid));
        raw_inode->i_uid_high = 0;
        raw_inode->i_gid_high = 0;
    }
    raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
    disksize = cpu_to_le32(ei->i_disksize);
    if (disksize != raw_inode->i_size) {
        need_datasync = 1;
        raw_inode->i_size = disksize;
    }
    raw_inode->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
    raw_inode->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
    raw_inode->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
    raw_inode->i_blocks = cpu_to_le32(inode->i_blocks);
    raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
    raw_inode->i_flags = cpu_to_le32(ei->i_flags);
#ifdef EXT3_FRAGMENTS
    raw_inode->i_faddr = cpu_to_le32(ei->i_faddr);
    raw_inode->i_frag = ei->i_frag_no;
    raw_inode->i_fsize = ei->i_frag_size;
#endif
    raw_inode->i_file_acl = cpu_to_le32(ei->i_file_acl);
    if (!S_ISREG(inode->i_mode)) {
        raw_inode->i_dir_acl = cpu_to_le32(ei->i_dir_acl);
    } else {
        disksize = cpu_to_le32(ei->i_disksize >> 32);
        if (disksize != raw_inode->i_size_high) {
            raw_inode->i_size_high = disksize;
            need_datasync = 1;
        }
        if (ei->i_disksize > 0x7fffffffULL) {
            struct super_block *sb = inode->i_sb;
            if (!EXT3_HAS_RO_COMPAT_FEATURE(sb,
                    EXT3_FEATURE_RO_COMPAT_LARGE_FILE) ||
                EXT3_SB(sb)->s_es->s_rev_level ==
                    cpu_to_le32(EXT3_GOOD_OLD_REV)) {
                   /* If this is the first large file
                * created, add a flag to the superblock.
                */
                unlock_buffer(bh);
                err = ext3_journal_get_write_access(handle,
                        EXT3_SB(sb)->s_sbh);
                if (err)
                    goto out_brelse;

                ext3_update_dynamic_rev(sb);
                EXT3_SET_RO_COMPAT_FEATURE(sb,
                    EXT3_FEATURE_RO_COMPAT_LARGE_FILE);
                handle->h_sync = 1;
                err = ext3_journal_dirty_metadata(handle,
                        EXT3_SB(sb)->s_sbh);
                /* get our lock and start over */
                goto again;
            }
        }
    }
    raw_inode->i_generation = cpu_to_le32(inode->i_generation);
    if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
        if (old_valid_dev(inode->i_rdev)) {
            raw_inode->i_block[0] =
                cpu_to_le32(old_encode_dev(inode->i_rdev));
            raw_inode->i_block[1] = 0;
        } else {
            raw_inode->i_block[0] = 0;
            raw_inode->i_block[1] =
                cpu_to_le32(new_encode_dev(inode->i_rdev));
            raw_inode->i_block[2] = 0;
        }
    } else for (block = 0; block < EXT3_N_BLOCKS; block++)
        raw_inode->i_block[block] = ei->i_data[block];

    if (ei->i_extra_isize)
        raw_inode->i_extra_isize = cpu_to_le16(ei->i_extra_isize);

    BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
    unlock_buffer(bh);
    rc = ext3_journal_dirty_metadata(handle, bh);
    if (!err)
        err = rc;
    ext3_clear_inode_state(inode, EXT3_STATE_NEW);

    atomic_set(&ei->i_sync_tid, handle->h_transaction->t_tid);
    if (need_datasync)
        atomic_set(&ei->i_datasync_tid, handle->h_transaction->t_tid);
out_brelse:
    brelse (bh);
    ext3_std_error(inode->i_sb, err);
    return err;
}

/*
 * ext3_write_inode()
 *
 * We are called from a few places:
 *
 * - Within generic_file_write() for O_SYNC files.
 *   Here, there will be no transaction running. We wait for any running
 *   transaction to commit.
 *
 * - Within sys_sync(), kupdate and such.
 *   We wait on commit, if tol to.
 *
 * - Within prune_icache() (PF_MEMALLOC == true)
 *   Here we simply return.  We can't afford to block kswapd on the
 *   journal commit.
 *
 * In all cases it is actually safe for us to return without doing anything,
 * because the inode has been copied into a raw inode buffer in
 * ext3_mark_inode_dirty().  This is a correctness thing for O_SYNC and for
 * knfsd.
 *
 * Note that we are absolutely dependent upon all inode dirtiers doing the
 * right thing: they *must* call mark_inode_dirty() after dirtying info in
 * which we are interested.
 *
 * It would be a bug for them to not do this.  The code:
 *
 *  mark_inode_dirty(inode)
 *  stuff();
 *  inode->i_size = expr;
 *
 * is in error because a kswapd-driven write_inode() could occur while
 * `stuff()' is running, and the new i_size will be lost.  Plus the inode
 * will no longer be on the superblock's dirty inode list.
 */
int ext3_write_inode(struct inode *inode, struct writeback_control *wbc)
{
    if (current->flags & PF_MEMALLOC)
        return 0;

    if (ext3_journal_current_handle()) {
        jbd_debug(1, "called recursively, non-PF_MEMALLOC!\n");
        dump_stack();
        return -EIO;
    }

    if (wbc->sync_mode != WB_SYNC_ALL)
        return 0;

    return ext3_force_commit(inode->i_sb);
}

/*
 * ext3_setattr()
 *
 * Called from notify_change.
 *
 * We want to trap VFS attempts to truncate the file as soon as
 * possible.  In particular, we want to make sure that when the VFS
 * shrinks i_size, we put the inode on the orphan list and modify
 * i_disksize immediately, so that during the subsequent flushing of
 * dirty pages and freeing of disk blocks, we can guarantee that any
 * commit will leave the blocks being flushed in an unused state on
 * disk.  (On recovery, the inode will get truncated and the blocks will
 * be freed, so we have a strong guarantee that no future commit will
 * leave these blocks visible to the user.)
 *
 * Called with inode->sem down.
 */
int ext3_setattr(struct dentry *dentry, struct iattr *attr)
{
    struct inode *inode = dentry->d_inode;
    int error, rc = 0;
    const unsigned int ia_valid = attr->ia_valid;

    error = inode_change_ok(inode, attr);
    if (error)
        return error;

    if (is_quota_modification(inode, attr))
        dquot_initialize(inode);
    if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, inode->i_uid)) ||
        (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, inode->i_gid))) {
        handle_t *handle;

        /* (user+group)*(old+new) structure, inode write (sb,
         * inode block, ? - but truncate inode update has it) */
        handle = ext3_journal_start(inode, EXT3_MAXQUOTAS_INIT_BLOCKS(inode->i_sb)+
                    EXT3_MAXQUOTAS_DEL_BLOCKS(inode->i_sb)+3);
        if (IS_ERR(handle)) {
            error = PTR_ERR(handle);
            goto err_out;
        }
        error = dquot_transfer(inode, attr);
        if (error) {
            ext3_journal_stop(handle);
            return error;
        }
        /* Update corresponding info in inode so that everything is in
         * one transaction */
        if (attr->ia_valid & ATTR_UID)
            inode->i_uid = attr->ia_uid;
        if (attr->ia_valid & ATTR_GID)
            inode->i_gid = attr->ia_gid;
        error = ext3_mark_inode_dirty(handle, inode);
        ext3_journal_stop(handle);
    }

    if (attr->ia_valid & ATTR_SIZE)
        inode_dio_wait(inode);

    if (S_ISREG(inode->i_mode) &&
        attr->ia_valid & ATTR_SIZE && attr->ia_size < inode->i_size) {
        handle_t *handle;

        handle = ext3_journal_start(inode, 3);
        if (IS_ERR(handle)) {
            error = PTR_ERR(handle);
            goto err_out;
        }

        error = ext3_orphan_add(handle, inode);
        if (error) {
            ext3_journal_stop(handle);
            goto err_out;
        }
        EXT3_I(inode)->i_disksize = attr->ia_size;
        error = ext3_mark_inode_dirty(handle, inode);
        ext3_journal_stop(handle);
        if (error) {
            /* Some hard fs error must have happened. Bail out. */
            ext3_orphan_del(NULL, inode);
            goto err_out;
        }
        rc = ext3_block_truncate_page(inode, attr->ia_size);
        if (rc) {
            /* Cleanup orphan list and exit */
            handle = ext3_journal_start(inode, 3);
            if (IS_ERR(handle)) {
                ext3_orphan_del(NULL, inode);
                goto err_out;
            }
            ext3_orphan_del(handle, inode);
            ext3_journal_stop(handle);
            goto err_out;
        }
    }

    if ((attr->ia_valid & ATTR_SIZE) &&
        attr->ia_size != i_size_read(inode)) {
        truncate_setsize(inode, attr->ia_size);
        ext3_truncate(inode);
    }

    setattr_copy(inode, attr);
    mark_inode_dirty(inode);

    if (ia_valid & ATTR_MODE)
        rc = ext3_acl_chmod(inode);

err_out:
    ext3_std_error(inode->i_sb, error);
    if (!error)
        error = rc;
    return error;
}


/*
 * How many blocks doth make a writepage()?
 *
 * With N blocks per page, it may be:
 * N data blocks
 * 2 indirect block
 * 2 dindirect
 * 1 tindirect
 * N+5 bitmap blocks (from the above)
 * N+5 group descriptor summary blocks
 * 1 inode block
 * 1 superblock.
 * 2 * EXT3_SINGLEDATA_TRANS_BLOCKS for the quote files
 *
 * 3 * (N + 5) + 2 + 2 * EXT3_SINGLEDATA_TRANS_BLOCKS
 *
 * With ordered or writeback data it's the same, less the N data blocks.
 *
 * If the inode's direct blocks can hold an integral number of pages then a
 * page cannot straddle two indirect blocks, and we can only touch one indirect
 * and dindirect block, and the "5" above becomes "3".
 *
 * This still overestimates under most circumstances.  If we were to pass the
 * start and end offsets in here as well we could do block_to_path() on each
 * block and work out the exact number of indirects which are touched.  Pah.
 */

static int ext3_writepage_trans_blocks(struct inode *inode)
{
    int bpp = ext3_journal_blocks_per_page(inode);
    int indirects = (EXT3_NDIR_BLOCKS % bpp) ? 5 : 3;
    int ret;

    if (ext3_should_journal_data(inode))
        ret = 3 * (bpp + indirects) + 2;
    else
        ret = 2 * (bpp + indirects) + indirects + 2;

#ifdef CONFIG_QUOTA
    /* We know that structure was already allocated during dquot_initialize so
     * we will be updating only the data blocks + inodes */
    ret += EXT3_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb);
#endif

    return ret;
}

/*
 * The caller must have previously called ext3_reserve_inode_write().
 * Give this, we know that the caller already has write access to iloc->bh.
 */
int ext3_mark_iloc_dirty(handle_t *handle,
        struct inode *inode, struct ext3_iloc *iloc)
{
    int err = 0;

    /* the do_update_inode consumes one bh->b_count */
    get_bh(iloc->bh);

    /* ext3_do_update_inode() does journal_dirty_metadata */
    err = ext3_do_update_inode(handle, inode, iloc);
    put_bh(iloc->bh);
    return err;
}

/*
 * On success, We end up with an outstanding reference count against
 * iloc->bh.  This _must_ be cleaned up later.
 */

int
ext3_reserve_inode_write(handle_t *handle, struct inode *inode,
             struct ext3_iloc *iloc)
{
    int err = 0;
    if (handle) {
        err = ext3_get_inode_loc(inode, iloc);
        if (!err) {
            BUFFER_TRACE(iloc->bh, "get_write_access");
            err = ext3_journal_get_write_access(handle, iloc->bh);
            if (err) {
                brelse(iloc->bh);
                iloc->bh = NULL;
            }
        }
    }
    ext3_std_error(inode->i_sb, err);
    return err;
}

/*
 * What we do here is to mark the in-core inode as clean with respect to inode
 * dirtiness (it may still be data-dirty).
 * This means that the in-core inode may be reaped by prune_icache
 * without having to perform any I/O.  This is a very good thing,
 * because *any* task may call prune_icache - even ones which
 * have a transaction open against a different journal.
 *
 * Is this cheating?  Not really.  Sure, we haven't written the
 * inode out, but prune_icache isn't a user-visible syncing function.
 * Whenever the user wants stuff synced (sys_sync, sys_msync, sys_fsync)
 * we start and wait on commits.
 */
int ext3_mark_inode_dirty(handle_t *handle, struct inode *inode)
{
    struct ext3_iloc iloc;
    int err;

    might_sleep();
    trace_ext3_mark_inode_dirty(inode, _RET_IP_);
    err = ext3_reserve_inode_write(handle, inode, &iloc);
    if (!err)
        err = ext3_mark_iloc_dirty(handle, inode, &iloc);
    return err;
}

/*
 * ext3_dirty_inode() is called from __mark_inode_dirty()
 *
 * We're really interested in the case where a file is being extended.
 * i_size has been changed by generic_commit_write() and we thus need
 * to include the updated inode in the current transaction.
 *
 * Also, dquot_alloc_space() will always dirty the inode when blocks
 * are allocated to the file.
 *
 * If the inode is marked synchronous, we don't honour that here - doing
 * so would cause a commit on atime updates, which we don't bother doing.
 * We handle synchronous inodes at the highest possible level.
 */
void ext3_dirty_inode(struct inode *inode, int flags)
{
    handle_t *current_handle = ext3_journal_current_handle();
    handle_t *handle;

    handle = ext3_journal_start(inode, 2);
    if (IS_ERR(handle))
        goto out;
    if (current_handle &&
        current_handle->h_transaction != handle->h_transaction) {
        /* This task has a transaction open against a different fs */
        printk(KERN_EMERG "%s: transactions do not match!\n",
               __func__);
    } else {
        jbd_debug(5, "marking dirty.  outer handle=%p\n",
                current_handle);
        ext3_mark_inode_dirty(handle, inode);
    }
    ext3_journal_stop(handle);
out:
    return;
}

#if 0
/*
 * Bind an inode's backing buffer_head into this transaction, to prevent
 * it from being flushed to disk early.  Unlike
 * ext3_reserve_inode_write, this leaves behind no bh reference and
 * returns no iloc structure, so the caller needs to repeat the iloc
 * lookup to mark the inode dirty later.
 */
static int ext3_pin_inode(handle_t *handle, struct inode *inode)
{
    struct ext3_iloc iloc;

    int err = 0;
    if (handle) {
        err = ext3_get_inode_loc(inode, &iloc);
        if (!err) {
            BUFFER_TRACE(iloc.bh, "get_write_access");
            err = journal_get_write_access(handle, iloc.bh);
            if (!err)
                err = ext3_journal_dirty_metadata(handle,
                                  iloc.bh);
            brelse(iloc.bh);
        }
    }
    ext3_std_error(inode->i_sb, err);
    return err;
}
#endif

int ext3_change_inode_journal_flag(struct inode *inode, int val)
{
    journal_t *journal;
    handle_t *handle;
    int err;

    /*
     * We have to be very careful here: changing a data block's
     * journaling status dynamically is dangerous.  If we write a
     * data block to the journal, change the status and then delete
     * that block, we risk forgetting to revoke the old log record
     * from the journal and so a subsequent replay can corrupt data.
     * So, first we make sure that the journal is empty and that
     * nobody is changing anything.
     */

    journal = EXT3_JOURNAL(inode);
    if (is_journal_aborted(journal))
        return -EROFS;

    journal_lock_updates(journal);
    journal_flush(journal);

    /*
     * OK, there are no updates running now, and all cached data is
     * synced to disk.  We are now in a completely consistent state
     * which doesn't have anything in the journal, and we know that
     * no filesystem updates are running, so it is safe to modify
     * the inode's in-core data-journaling state flag now.
     */

    if (val)
        EXT3_I(inode)->i_flags |= EXT3_JOURNAL_DATA_FL;
    else
        EXT3_I(inode)->i_flags &= ~EXT3_JOURNAL_DATA_FL;
    ext3_set_aops(inode);

    journal_unlock_updates(journal);

    /* Finally we can mark the inode as dirty. */

    handle = ext3_journal_start(inode, 1);
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    err = ext3_mark_inode_dirty(handle, inode);
    handle->h_sync = 1;
    ext3_journal_stop(handle);
    ext3_std_error(inode->i_sb, err);

    return err;
}