added a lot of printk output to ease writing of emulator

[linux-2.4.21-pre4.git] / fs / ext3 / inode.c

/*
 *  linux/fs/ext3/inode.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * 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
 *      (sct@redhat.com), 1993, 1998
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 *  64-bit file support on 64-bit platforms by Jakub Jelinek
 *      (jj@sunsite.ms.mff.cuni.cz)
 *
 *  Assorted race fixes, rewrite of ext3_get_block() by Al Viro, 2000
 */

#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/ext3_jbd.h>
#include <linux/jbd.h>
#include <linux/locks.h>
#include <linux/smp_lock.h>
#include <linux/highuid.h>
#include <linux/quotaops.h>
#include <linux/module.h>

/*
 * SEARCH_FROM_ZERO forces each block allocation to search from the start
 * of the filesystem.  This is to force rapid reallocation of recently-freed
 * blocks.  The file fragmentation is horrendous.
 */
#undef SEARCH_FROM_ZERO

/* 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.
 */

static int ext3_forget(handle_t *handle, int is_metadata,
                       struct inode *inode, struct buffer_head *bh,
                       int blocknr)
{
        int err;

        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");
                        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, __FUNCTION__,
                           "error %d when attempting revoke", err);
        BUFFER_TRACE(bh, "exit");
        return err;
}

/* 
 * 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) 
{
        long needed;
        handle_t *result;
        
        needed = inode->i_blocks;
        if (needed > EXT3_MAX_TRANS_DATA) 
                needed = EXT3_MAX_TRANS_DATA;
        
        result = ext3_journal_start(inode, EXT3_DATA_TRANS_BLOCKS + needed);
        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)
{
        long needed;
        
        if (handle->h_buffer_credits > EXT3_RESERVE_TRANS_BLOCKS)
                return 0;
        needed = inode->i_blocks;
        if (needed > EXT3_MAX_TRANS_DATA) 
                needed = EXT3_MAX_TRANS_DATA;
        if (!ext3_journal_extend(handle, EXT3_RESERVE_TRANS_BLOCKS + needed))
                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 ext3_journal_test_restart(handle_t *handle, struct inode *inode)
{
        long needed = inode->i_blocks;
        if (needed > EXT3_MAX_TRANS_DATA) 
                needed = EXT3_MAX_TRANS_DATA;
        jbd_debug(2, "restarting handle %p\n", handle);
        return ext3_journal_restart(handle, EXT3_DATA_TRANS_BLOCKS + needed);
}

/*
 * Called at each iput()
 */
void ext3_put_inode (struct inode * inode)
{
        ext3_discard_prealloc (inode);
}

/*
 * Called at the last iput() if i_nlink is zero.
 */
void ext3_delete_inode (struct inode * inode)
{
        handle_t *handle;
        
        if (is_bad_inode(inode) ||
            inode->i_ino == EXT3_ACL_IDX_INO ||
            inode->i_ino == EXT3_ACL_DATA_INO)
                goto no_delete;

        lock_kernel();
        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);

                ext3_std_error(inode->i_sb, PTR_ERR(handle));
                unlock_kernel();
                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 which ext3_truncate created.
         * AKPM: I think this can be inside the above `if'.
         * Note that ext3_orphan_del() has to be able to cope with the
         * deletion of a non-existent orphan - this is because we don't
         * know if ext3_truncate() actually created an orphan record.
         * (Well, we could do this if we need to, but heck - it works)
         */
        ext3_orphan_del(handle, inode);
        inode->u.ext3_i.i_dtime = CURRENT_TIME;

        /* 
         * 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 do the required in-core inode clear. */
                clear_inode(inode);
        else
                ext3_free_inode(handle, inode);
        ext3_journal_stop(handle, inode);
        unlock_kernel();
        return;
no_delete:
        clear_inode(inode);     /* We must guarantee clearing of inode... */
}

void ext3_discard_prealloc (struct inode * inode)
{
#ifdef EXT3_PREALLOCATE
        lock_kernel();
        /* Writer: ->i_prealloc* */
        if (inode->u.ext3_i.i_prealloc_count) {
                unsigned short total = inode->u.ext3_i.i_prealloc_count;
                unsigned long block = inode->u.ext3_i.i_prealloc_block;
                inode->u.ext3_i.i_prealloc_count = 0;
                inode->u.ext3_i.i_prealloc_block = 0;
                /* Writer: end */
                ext3_free_blocks (inode, block, total);
        }
        unlock_kernel();
#endif
}

static int ext3_alloc_block (handle_t *handle,
                        struct inode * inode, unsigned long goal, int *err)
{
#ifdef EXT3FS_DEBUG
        static unsigned long alloc_hits = 0, alloc_attempts = 0;
#endif
        unsigned long result;

#ifdef EXT3_PREALLOCATE
        /* Writer: ->i_prealloc* */
        if (inode->u.ext3_i.i_prealloc_count &&
            (goal == inode->u.ext3_i.i_prealloc_block ||
             goal + 1 == inode->u.ext3_i.i_prealloc_block))
        {
                result = inode->u.ext3_i.i_prealloc_block++;
                inode->u.ext3_i.i_prealloc_count--;
                /* Writer: end */
                ext3_debug ("preallocation hit (%lu/%lu).\n",
                            ++alloc_hits, ++alloc_attempts);
        } else {
                ext3_discard_prealloc (inode);
                ext3_debug ("preallocation miss (%lu/%lu).\n",
                            alloc_hits, ++alloc_attempts);
                if (S_ISREG(inode->i_mode))
                        result = ext3_new_block (inode, goal, 
                                 &inode->u.ext3_i.i_prealloc_count,
                                 &inode->u.ext3_i.i_prealloc_block, err);
                else
                        result = ext3_new_block (inode, goal, 0, 0, err);
                /*
                 * AKPM: this is somewhat sticky.  I'm not surprised it was
                 * disabled in 2.2's ext3.  Need to integrate b_committed_data
                 * guarding with preallocation, if indeed preallocation is
                 * effective.
                 */
        }
#else
        result = ext3_new_block (handle, inode, goal, 0, 0, err);
#endif
        return result;
}


typedef struct {
        u32     *p;
        u32     key;
        struct buffer_head *bh;
} Indirect;

static inline void add_chain(Indirect *p, struct buffer_head *bh, u32 *v)
{
        p->key = *(p->p = v);
        p->bh = bh;
}

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

/**
 *      ext3_block_to_path - parse the block number into array of offsets
 *      @inode: inode in question (we are only interested in its superblock)
 *      @i_block: block number to be parsed
 *      @offsets: array to store the offsets in
 *
 *      To store the locations of file's data ext3 uses a data structure common
 *      for UNIX filesystems - tree of pointers anchored in the inode, with
 *      data blocks at leaves and indirect blocks in intermediate nodes.
 *      This function translates the block number into path in that tree -
 *      return value is the path length and @offsets[n] is the offset of
 *      pointer to (n+1)th node in the nth one. If @block is out of range
 *      (negative or too large) warning is printed and zero returned.
 *
 *      Note: function doesn't find node addresses, so no IO is needed. All
 *      we need to know is the capacity of indirect blocks (taken from the
 *      inode->i_sb).
 */

/*
 * 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 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;

        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;
        } else if ( (i_block -= direct_blocks) < indirect_blocks) {
                offsets[n++] = EXT3_IND_BLOCK;
                offsets[n++] = i_block;
        } 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);
        } 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);
        } else {
                ext3_warning (inode->i_sb, "ext3_block_to_path", "block > big");
        }
        return n;
}

/**
 *      ext3_get_branch - read the chain of indirect blocks leading to data
 *      @inode: inode in question
 *      @depth: depth of the chain (1 - direct pointer, etc.)
 *      @offsets: offsets of pointers in inode/indirect blocks
 *      @chain: place to store the result
 *      @err: here we store the error value
 *
 *      Function fills the array of triples <key, p, bh> and returns %NULL
 *      if everything went OK or the pointer to the last filled triple
 *      (incomplete one) otherwise. Upon the return chain[i].key contains
 *      the number of (i+1)-th block in the chain (as it is stored in memory,
 *      i.e. little-endian 32-bit), chain[i].p contains the address of that
 *      number (it points into struct inode for i==0 and into the bh->b_data
 *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
 *      block for i>0 and NULL for i==0. In other words, it holds the block
 *      numbers of the chain, addresses they were taken from (and where we can
 *      verify that chain did not change) and buffer_heads hosting these
 *      numbers.
 *
 *      Function stops when it stumbles upon zero pointer (absent block)
 *              (pointer to last triple returned, *@err == 0)
 *      or when it gets an IO error reading an indirect block
 *              (ditto, *@err == -EIO)
 *      or when it notices that chain had been changed while it was reading
 *              (ditto, *@err == -EAGAIN)
 *      or when it reads all @depth-1 indirect blocks successfully and finds
 *      the whole chain, all way to the data (returns %NULL, *err == 0).
 */
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, inode->u.ext3_i.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, (u32*)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;
}

/**
 *      ext3_find_near - find a place for allocation with sufficient locality
 *      @inode: owner
 *      @ind: descriptor of indirect block.
 *
 *      This function returns the prefered place for block allocation.
 *      It is used when heuristic for sequential allocation fails.
 *      Rules are:
 *        + if there is a block to the left of our position - allocate near it.
 *        + if pointer will live in indirect block - allocate near that block.
 *        + if pointer will live in inode - allocate in the same
 *          cylinder group. 
 *      Caller must make sure that @ind is valid and will stay that way.
 */

static inline unsigned long ext3_find_near(struct inode *inode, Indirect *ind)
{
        u32 *start = ind->bh ? (u32*) ind->bh->b_data : inode->u.ext3_i.i_data;
        u32 *p;

        /* 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 refered from inode itself? OK, just put it into
         * the same cylinder group then.
         */
        return (inode->u.ext3_i.i_block_group * 
                EXT3_BLOCKS_PER_GROUP(inode->i_sb)) +
               le32_to_cpu(inode->i_sb->u.ext3_sb.s_es->s_first_data_block);
}

/**
 *      ext3_find_goal - find a prefered place for allocation.
 *      @inode: owner
 *      @block:  block we want
 *      @chain:  chain of indirect blocks
 *      @partial: pointer to the last triple within a chain
 *      @goal:  place to store the result.
 *
 *      Normally this function find the prefered place for block allocation,
 *      stores it in *@goal and returns zero. If the branch had been changed
 *      under us we return -EAGAIN.
 */

static int ext3_find_goal(struct inode *inode, long block, Indirect chain[4],
                          Indirect *partial, unsigned long *goal)
{
        /* Writer: ->i_next_alloc* */
        if (block == inode->u.ext3_i.i_next_alloc_block + 1) {
                inode->u.ext3_i.i_next_alloc_block++;
                inode->u.ext3_i.i_next_alloc_goal++;
        }
#ifdef SEARCH_FROM_ZERO
        inode->u.ext3_i.i_next_alloc_block = 0;
        inode->u.ext3_i.i_next_alloc_goal = 0;
#endif
        /* Writer: end */
        /* Reader: pointers, ->i_next_alloc* */
        if (verify_chain(chain, partial)) {
                /*
                 * try the heuristic for sequential allocation,
                 * failing that at least try to get decent locality.
                 */
                if (block == inode->u.ext3_i.i_next_alloc_block)
                        *goal = inode->u.ext3_i.i_next_alloc_goal;
                if (!*goal)
                        *goal = ext3_find_near(inode, partial);
#ifdef SEARCH_FROM_ZERO
                *goal = 0;
#endif
                return 0;
        }
        /* Reader: end */
        return -EAGAIN;
}

/**
 *      ext3_alloc_branch - allocate and set up a chain of blocks.
 *      @inode: owner
 *      @num: depth of the chain (number of blocks to allocate)
 *      @offsets: offsets (in the blocks) to store the pointers to next.
 *      @branch: place to store the chain in.
 *
 *      This function allocates @num blocks, zeroes out all but the last one,
 *      links them into chain and (if we are synchronous) writes them to disk.
 *      In other words, it prepares a branch that can be spliced onto the
 *      inode. It stores the information about that chain in the branch[], in
 *      the same format as ext3_get_branch() would do. We are calling it after
 *      we had read the existing part of chain and partial points to the last
 *      triple of that (one with zero ->key). Upon the exit we have the same
 *      picture as after the successful ext3_get_block(), excpet that in one
 *      place chain is disconnected - *branch->p is still zero (we did not
 *      set the last link), but branch->key contains the number that should
 *      be placed into *branch->p to fill that gap.
 *
 *      If allocation fails we free all blocks we've allocated (and forget
 *      their buffer_heads) and return the error value the from failed
 *      ext3_alloc_block() (normally -ENOSPC). Otherwise we set the chain
 *      as described above and return 0.
 */

static int ext3_alloc_branch(handle_t *handle, struct inode *inode,
                             int num,
                             unsigned long goal,
                             int *offsets,
                             Indirect *branch)
{
        int blocksize = inode->i_sb->s_blocksize;
        int n = 0, keys = 0;
        int err = 0;
        int i;
        int parent = ext3_alloc_block(handle, inode, goal, &err);

        branch[0].key = cpu_to_le32(parent);
        if (parent) {
                for (n = 1; n < num; n++) {
                        struct buffer_head *bh;
                        /* Allocate the next block */
                        int nr = ext3_alloc_block(handle, inode, parent, &err);
                        if (!nr)
                                break;
                        branch[n].key = cpu_to_le32(nr);
                        keys = n+1;
                        
                        /*
                         * 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, parent);
                        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);
                                break;
                        }

                        memset(bh->b_data, 0, blocksize);
                        branch[n].p = (u32*) bh->b_data + offsets[n];
                        *branch[n].p = branch[n].key;
                        BUFFER_TRACE(bh, "marking uptodate");
                        mark_buffer_uptodate(bh, 1);
                        unlock_buffer(bh);

                        BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
                        err = ext3_journal_dirty_metadata(handle, bh);
                        if (err)
                                break;
                        
                        parent = nr;
                }
        }
        if (n == num)
                return 0;

        /* Allocation failed, free what we already allocated */
        for (i = 1; i < keys; i++) {
                BUFFER_TRACE(branch[i].bh, "call journal_forget");
                ext3_journal_forget(handle, branch[i].bh);
        }
        for (i = 0; i < keys; i++)
                ext3_free_blocks(handle, inode, le32_to_cpu(branch[i].key), 1);
        return err;
}

/**
 *      ext3_splice_branch - splice the allocated branch onto inode.
 *      @inode: owner
 *      @block: (logical) number of block we are adding
 *      @chain: chain of indirect blocks (with a missing link - see
 *              ext3_alloc_branch)
 *      @where: location of missing link
 *      @num:   number of blocks we are adding
 *
 *      This function verifies that chain (up to the missing link) had not
 *      changed, fills the missing link and does all housekeeping needed in
 *      inode (->i_blocks, etc.). In case of success we end up with the full
 *      chain to new block and return 0. Otherwise (== chain had been changed)
 *      we free the new blocks (forgetting their buffer_heads, indeed) and
 *      return -EAGAIN.
 */

static int ext3_splice_branch(handle_t *handle, struct inode *inode, long block,
                              Indirect chain[4], Indirect *where, int num)
{
        int i;
        int err = 0;

        /*
         * 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;
        }
        /* Verify that place we are splicing to is still there and vacant */

        /* Writer: pointers, ->i_next_alloc* */
        if (!verify_chain(chain, where-1) || *where->p)
                /* Writer: end */
                goto changed;

        /* That's it */

        *where->p = where->key;
        inode->u.ext3_i.i_next_alloc_block = block;
        inode->u.ext3_i.i_next_alloc_goal = le32_to_cpu(where[num-1].key);
#ifdef SEARCH_FROM_ZERO
        inode->u.ext3_i.i_next_alloc_block = 0;
        inode->u.ext3_i.i_next_alloc_goal = 0;
#endif
        /* Writer: end */

        /* We are done with atomic stuff, now do the rest of housekeeping */

        inode->i_ctime = CURRENT_TIME;
        ext3_mark_inode_dirty(handle, inode);

        /* had we spliced it onto indirect block? */
        if (where->bh) {
                /*
                 * akpm: 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;

changed:
        /*
         * AKPM: if where[i].bh isn't part of the current updating
         * transaction then we explode nastily.  Test this code path.
         */
        jbd_debug(1, "the chain changed: try again\n");
        err = -EAGAIN;
        
err_out:
        for (i = 1; i < num; i++) {
                BUFFER_TRACE(where[i].bh, "call journal_forget");
                ext3_journal_forget(handle, where[i].bh);
        }
        /* For the normal collision cleanup case, we free up the blocks.
         * On genuine filesystem errors we don't even think about doing
         * that. */
        if (err == -EAGAIN)
                for (i = 0; i < num; i++)
                        ext3_free_blocks(handle, inode, 
                                         le32_to_cpu(where[i].key), 1);
        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.
 *
 * akpm: `handle' can be NULL if create == 0.
 *
 * The BKL may not be held on entry here.  Be sure to take it early.
 */

static int ext3_get_block_handle(handle_t *handle, struct inode *inode, 
                                 long iblock,
                                 struct buffer_head *bh_result, int create)
{
        int err = -EIO;
        int offsets[4];
        Indirect chain[4];
        Indirect *partial;
        unsigned long goal;
        int left;
        int depth = ext3_block_to_path(inode, iblock, offsets);
        loff_t new_size;

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

        if (depth == 0)
                goto out;

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

        /* Simplest case - block found, no allocation needed */
        if (!partial) {
                bh_result->b_state &= ~(1UL << BH_New);
got_it:
                bh_result->b_dev = inode->i_dev;
                bh_result->b_blocknr = le32_to_cpu(chain[depth-1].key);
                bh_result->b_state |= (1UL << BH_Mapped);
                /* Clean up and exit */
                partial = chain+depth-1; /* the whole chain */
                goto cleanup;
        }

        /* Next simple case - plain lookup or failed read of indirect block */
        if (!create || err == -EIO) {
cleanup:
                while (partial > chain) {
                        BUFFER_TRACE(partial->bh, "call brelse");
                        brelse(partial->bh);
                        partial--;
                }
                BUFFER_TRACE(bh_result, "returned");
                unlock_kernel();
out:
                return err;
        }

        /*
         * Indirect block might be removed by truncate while we were
         * reading it. Handling of that case (forget what we've got and
         * reread) is taken out of the main path.
         */
        if (err == -EAGAIN)
                goto changed;

        if (ext3_find_goal(inode, iblock, chain, partial, &goal) < 0)
                goto changed;

        left = (chain + depth) - partial;

        /*
         * Block out ext3_truncate while we alter the tree
         */
        down_read(&inode->u.ext3_i.truncate_sem);
        err = ext3_alloc_branch(handle, inode, left, 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, chain,
                                         partial, left);
        up_read(&inode->u.ext3_i.truncate_sem);
        if (err == -EAGAIN)
                goto changed;
        if (err)
                goto cleanup;

        new_size = inode->i_size;
        /*
         * This is not racy against ext3_truncate's modification of i_disksize
         * because VM/VFS ensures that the file cannot be extended while
         * truncate is in progress.  It is racy between multiple parallel
         * instances of get_block, but we have the BKL.
         */
        if (new_size > inode->u.ext3_i.i_disksize)
                inode->u.ext3_i.i_disksize = new_size;

        bh_result->b_state |= (1UL << BH_New);
        goto got_it;

changed:
        while (partial > chain) {
                jbd_debug(1, "buffer chain changed, retrying\n");
                BUFFER_TRACE(partial->bh, "brelsing");
                brelse(partial->bh);
                partial--;
        }
        goto reread;
}

/*
 * The BKL is not held on entry here.
 */
static int ext3_get_block(struct inode *inode, long iblock,
                        struct buffer_head *bh_result, int create)
{
        handle_t *handle = 0;
        int ret;

        if (create) {
                handle = ext3_journal_current_handle();
                J_ASSERT(handle != 0);
        }
        ret = ext3_get_block_handle(handle, inode, iblock, bh_result, create);
        return ret;
}

/*
 * `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);
        *errp = ext3_get_block_handle(handle, inode, block, &dummy, create);
        if (!*errp && buffer_mapped(&dummy)) {
                struct buffer_head *bh;
                bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
                if (buffer_new(&dummy)) {
                        J_ASSERT(create != 0);
                        J_ASSERT(handle != 0);

                        /* 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_kernel();
                        lock_buffer(bh);
                        BUFFER_TRACE(bh, "call get_create_access");
                        fatal = ext3_journal_get_create_access(handle, bh);
                        if (!fatal) {
                                memset(bh->b_data, 0,
                                       inode->i_sb->s_blocksize);
                                mark_buffer_uptodate(bh, 1);
                        }
                        unlock_buffer(bh);
                        BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
                        err = ext3_journal_dirty_metadata(handle, bh);
                        if (!fatal) fatal = err;
                        unlock_kernel();
                } else {
                        BUFFER_TRACE(bh, "not a new buffer");
                }
                if (fatal) {
                        *errp = fatal;
                        brelse(bh);
                        bh = NULL;
                }
                return bh;
        }
        return NULL;
}

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

        prev_blocks = inode->i_blocks;

        bh = ext3_getblk (handle, inode, block, create, err);
        if (!bh)
                return bh;
#ifdef EXT3_PREALLOCATE
        /*
         * If the inode has grown, and this is a directory, then use a few
         * more of the preallocated blocks to keep directory fragmentation
         * down.  The preallocated blocks are guaranteed to be contiguous.
         */
        if (create &&
            S_ISDIR(inode->i_mode) &&
            inode->i_blocks > prev_blocks &&
            EXT3_HAS_COMPAT_FEATURE(inode->i_sb,
                                    EXT3_FEATURE_COMPAT_DIR_PREALLOC)) {
                int i;
                struct buffer_head *tmp_bh;

                for (i = 1;
                     inode->u.ext3_i.i_prealloc_count &&
                     i < EXT3_SB(inode->i_sb)->s_es->s_prealloc_dir_blocks;
                     i++) {
                        /*
                         * ext3_getblk will zero out the contents of the
                         * directory for us
                         */
                        tmp_bh = ext3_getblk(handle, inode,
                                                block+i, create, err);
                        if (!tmp_bh) {
                                brelse (bh);
                                return 0;
                        }
                        brelse (tmp_bh);
                }
        }
#endif
        if (buffer_uptodate(bh))
                return bh;
        ll_rw_block (READ, 1, &bh);
        wait_on_buffer (bh);
        if (buffer_uptodate(bh))
                return bh;
        brelse (bh);
        *err = -EIO;
        return NULL;
}

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

        for (   bh = head, block_start = 0;
                ret == 0 && (bh != head || !block_start);
                block_start = block_end, bh = 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, inode, 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 inode *inode,
                                       struct buffer_head *bh)
{
        return ext3_journal_get_write_access(handle, bh);
}

static int ext3_prepare_write(struct file *file, struct page *page,
                              unsigned from, unsigned to)
{
        struct inode *inode = page->mapping->host;
        int ret, needed_blocks = ext3_writepage_trans_blocks(inode);
        handle_t *handle;

        lock_kernel();
        handle = ext3_journal_start(inode, needed_blocks);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                goto out;
        }
        unlock_kernel();
        ret = block_prepare_write(page, from, to, ext3_get_block);
        lock_kernel();
        if (ret != 0)
                goto prepare_write_failed;

        if (ext3_should_journal_data(inode)) {
                ret = walk_page_buffers(handle, inode, page->buffers,
                                from, to, NULL, do_journal_get_write_access);
                if (ret) {
                        /*
                         * We're going to fail this prepare_write(),
                         * so commit_write() will not be called.
                         * We need to undo block_prepare_write()'s kmap().
                         * AKPM: Do we need to clear PageUptodate?  I don't
                         * think so.
                         */
                        kunmap(page);
                }
        }
prepare_write_failed:
        if (ret)
                ext3_journal_stop(handle, inode);
out:
        unlock_kernel();
        return ret;
}

static int journal_dirty_sync_data(handle_t *handle, struct inode *inode,
                                   struct buffer_head *bh)
{
        int ret = ext3_journal_dirty_data(handle, bh, 0);
        buffer_insert_inode_data_queue(bh, inode);
        return ret;
}

/*
 * For ext3_writepage().  We also brelse() the buffer to account for
 * the bget() which ext3_writepage() performs.
 */
static int journal_dirty_async_data(handle_t *handle, struct inode *inode, 
                                    struct buffer_head *bh)
{
        int ret = ext3_journal_dirty_data(handle, bh, 1);
        buffer_insert_inode_data_queue(bh, inode);
        __brelse(bh);
        return ret;
}

/* For commit_write() in data=journal mode */
static int commit_write_fn(handle_t *handle, struct inode *inode, 
                           struct buffer_head *bh)
{
        set_bit(BH_Uptodate, &bh->b_state);
        return ext3_journal_dirty_metadata(handle, bh);
}

/*
 * We need to pick up the new inode size which generic_commit_write gave us
 * `file' can be NULL - eg, when called from block_symlink().
 *
 * ext3 inode->i_dirty_buffers policy:  If we're journalling data we
 * definitely don't want them to appear on the inode at all - instead
 * we need to manage them at the JBD layer and we need to intercept
 * the relevant sync operations and translate them into journal operations.
 *
 * If we're not journalling data then we can just leave the buffers
 * on ->i_dirty_buffers.  If someone writes them out for us then thanks.
 * Otherwise we'll do it in commit, if we're using ordered data.
 */

static int ext3_commit_write(struct file *file, struct page *page,
                             unsigned from, unsigned to)
{
        handle_t *handle = ext3_journal_current_handle();
        struct inode *inode = page->mapping->host;
        int ret = 0, ret2;

        lock_kernel();
        if (ext3_should_journal_data(inode)) {
                /*
                 * Here we duplicate the generic_commit_write() functionality
                 */
                int partial = 0;
                loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;

                ret = walk_page_buffers(handle, inode, page->buffers,
                        from, to, &partial, commit_write_fn);
                if (!partial)
                        SetPageUptodate(page);
                kunmap(page);
                if (pos > inode->i_size)
                        inode->i_size = pos;
                EXT3_I(inode)->i_state |= EXT3_STATE_JDATA;
        } else {
                if (ext3_should_order_data(inode)) {
                        ret = walk_page_buffers(handle, inode, page->buffers,
                                from, to, NULL, journal_dirty_sync_data);
                }
                /* Be careful here if generic_commit_write becomes a
                 * required invocation after block_prepare_write. */
                if (ret == 0) {
                        ret = generic_commit_write(file, page, from, to);
                } else {
                        /*
                         * block_prepare_write() was called, but we're not
                         * going to call generic_commit_write().  So we
                         * need to perform generic_commit_write()'s kunmap
                         * by hand.
                         */
                        kunmap(page);
                }
        }
        if (inode->i_size > inode->u.ext3_i.i_disksize) {
                inode->u.ext3_i.i_disksize = inode->i_size;
                ret2 = ext3_mark_inode_dirty(handle, inode);
                if (!ret) 
                        ret = ret2;
        }
        ret2 = ext3_journal_stop(handle, inode);
        unlock_kernel();
        if (!ret)
                ret = ret2;
        return ret;
}

/* 
 * 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 int ext3_bmap(struct address_space *mapping, long block)
{
        struct inode *inode = mapping->host;
        journal_t *journal;
        int err;
        
        if (EXT3_I(inode)->i_state & 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_I(inode)->i_state &= ~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 inode *inode, 
                    struct buffer_head *bh)
{
        atomic_inc(&bh->b_count);
        return 0;
}

/*
 * 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_sem.
 *
 * 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.
 */
static int ext3_writepage(struct page *page)
{
        struct inode *inode = page->mapping->host;
        struct buffer_head *page_buffers;
        handle_t *handle = NULL;
        int ret = 0, err;
        int needed;
        int order_data;

        J_ASSERT(PageLocked(page));
        
        /*
         * We give up here if we're reentered, because it might be
         * for a different filesystem.  One *could* look for a
         * nested transaction opportunity.
         */
        lock_kernel();
        if (ext3_journal_current_handle())
                goto out_fail;

        needed = ext3_writepage_trans_blocks(inode);
        if (current->flags & PF_MEMALLOC)
                handle = ext3_journal_try_start(inode, needed);
        else
                handle = ext3_journal_start(inode, needed);
                                
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                goto out_fail;
        }

        order_data = ext3_should_order_data(inode) ||
                        ext3_should_journal_data(inode);

        unlock_kernel();

        page_buffers = NULL;    /* Purely to prevent compiler warning */

        /* bget() all the buffers */
        if (order_data) {
                if (!page->buffers)
                        create_empty_buffers(page,
                                inode->i_dev, inode->i_sb->s_blocksize);
                page_buffers = page->buffers;
                walk_page_buffers(handle, inode, page_buffers, 0,
                                PAGE_CACHE_SIZE, NULL, bget_one);
        }

        ret = block_write_full_page(page, ext3_get_block);

        /*
         * 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_buffers is
         * safe due to elevated refcount.
         */

        handle = ext3_journal_current_handle();
        lock_kernel();

        /* And attach them to the current transaction */
        if (order_data) {
                err = walk_page_buffers(handle, inode, page_buffers,
                        0, PAGE_CACHE_SIZE, NULL, journal_dirty_async_data);
                if (!ret)
                        ret = err;
        }

        err = ext3_journal_stop(handle, inode);
        if (!ret)
                ret = err;
        unlock_kernel();
        return ret;

out_fail:
        
        unlock_kernel();
        SetPageDirty(page);
        UnlockPage(page);
        return ret;
}

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


static int ext3_flushpage(struct page *page, unsigned long offset)
{
        journal_t *journal = EXT3_JOURNAL(page->mapping->host);
        return journal_flushpage(journal, page, offset);
}

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


struct address_space_operations ext3_aops = {
        readpage:       ext3_readpage,          /* BKL not held.  Don't need */
        writepage:      ext3_writepage,         /* BKL not held.  We take it */
        sync_page:      block_sync_page,
        prepare_write:  ext3_prepare_write,     /* BKL not held.  We take it */
        commit_write:   ext3_commit_write,      /* BKL not held.  We take it */
        bmap:           ext3_bmap,              /* BKL held */
        flushpage:      ext3_flushpage,         /* BKL not held.  Don't need */
        releasepage:    ext3_releasepage,       /* BKL not held.  Don't need */
};

/*
 * 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(handle_t *handle,
                struct address_space *mapping, loff_t from)
{
        unsigned long index = from >> PAGE_CACHE_SHIFT;
        unsigned offset = from & (PAGE_CACHE_SIZE-1);
        unsigned blocksize, iblock, length, pos;
        struct inode *inode = mapping->host;
        struct page *page;
        struct buffer_head *bh;
        int err;

        blocksize = inode->i_sb->s_blocksize;
        length = offset & (blocksize - 1);

        /* Block boundary? Nothing to do */
        if (!length)
                return 0;

        length = blocksize - length;
        iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);

        page = grab_cache_page(mapping, index);
        err = -ENOMEM;
        if (!page)
                goto out;

        if (!page->buffers)
                create_empty_buffers(page, inode->i_dev, blocksize);

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

        err = 0;
        if (!buffer_mapped(bh)) {
                /* Hole? Nothing to do */
                if (buffer_uptodate(bh))
                        goto unlock;
                ext3_get_block(inode, iblock, bh, 0);
                /* Still unmapped? Nothing to do */
                if (!buffer_mapped(bh))
                        goto unlock;
        }

        /* Ok, it's mapped. Make sure it's up-to-date */
        if (Page_Uptodate(page))
                set_bit(BH_Uptodate, &bh->b_state);

        if (!buffer_uptodate(bh)) {
                err = -EIO;
                ll_rw_block(READ, 1, &bh);
                wait_on_buffer(bh);
                /* Uhhuh. Read error. Complain and punt. */
                if (!buffer_uptodate(bh))
                        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 unlock;
        }
        
        memset(kmap(page) + offset, 0, length);
        flush_dcache_page(page);
        kunmap(page);

        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, 0);
                __mark_buffer_dirty(bh);
        }

unlock:
        UnlockPage(page);
        page_cache_release(page);
out:
        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(u32 *p, u32 *q)
{
        while (p < q)
                if (*p++)
                        return 0;
        return 1;
}

/**
 *      ext3_find_shared - find the indirect blocks for partial truncation.
 *      @inode:   inode in question
 *      @depth:   depth of the affected branch
 *      @offsets: offsets of pointers in that branch (see ext3_block_to_path)
 *      @chain:   place to store the pointers to partial indirect blocks
 *      @top:     place to the (detached) top of branch
 *
 *      This is a helper function used by ext3_truncate().
 *
 *      When we do truncate() we may have to clean the ends of several
 *      indirect blocks but leave the blocks themselves alive. Block is
 *      partially truncated if some data below the new i_size is refered
 *      from it (and it is on the path to the first completely truncated
 *      data block, indeed).  We have to free the top of that path along
 *      with everything to the right of the path. Since no allocation
 *      past the truncation point is possible until ext3_truncate()
 *      finishes, we may safely do the latter, but top of branch may
 *      require special attention - pageout below the truncation point
 *      might try to populate it.
 *
 *      We atomically detach the top of branch from the tree, store the
 *      block number of its root in *@top, pointers to buffer_heads of
 *      partially truncated blocks - in @chain[].bh and pointers to
 *      their last elements that should not be removed - in
 *      @chain[].p. Return value is the pointer to last filled element
 *      of @chain.
 *
 *      The work left to caller to do the actual freeing of subtrees:
 *              a) free the subtree starting from *@top
 *              b) free the subtrees whose roots are stored in
 *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
 *              c) free the subtrees growing from the inode past the @chain[0].
 *                      (no partially truncated stuff there).  */

static Indirect *ext3_find_shared(struct inode *inode,
                                int depth,
                                int offsets[4],
                                Indirect chain[4],
                                u32 *top)
{
        Indirect *partial, *p;
        int k, err;

        *top = 0;
        /* Make k index the deepest non-null offest + 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((u32*)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,
                unsigned long block_to_free, unsigned long count,
                u32 *first, u32 *last)
{
        u32 *p;
        if (try_to_extend_transaction(handle, inode)) {
                if (bh) {
                        BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
                        ext3_journal_dirty_metadata(handle, bh);
                }
                ext3_mark_inode_dirty(handle, inode);
                ext3_journal_test_restart(handle, inode);
                if (bh) {
                        BUFFER_TRACE(bh, "retaking write access");
                        ext3_journal_get_write_access(handle, bh);
                }
        }

        /*
         * 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_get_hash_table(inode->i_sb, nr);
                        ext3_forget(handle, 0, inode, bh, nr);
                }
        }

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

/**
 * ext3_free_data - free a list of data blocks
 * @handle:     handle for this transaction
 * @inode:      inode we are dealing with
 * @this_bh:    indirect buffer_head which contains *@first and *@last
 * @first:      array of block numbers
 * @last:       points immediately past the end of array
 *
 * We are freeing all blocks refered from that array (numbers are stored as
 * little-endian 32-bit) and updating @inode->i_blocks appropriately.
 *
 * We accumulate contiguous runs of blocks to free.  Conveniently, if these
 * blocks are contiguous then releasing them at one time will only affect one
 * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
 * actually use a lot of journal space.
 *
 * @this_bh will be %NULL if @first and @last point into the inode's direct
 * block pointers.
 */
static void ext3_free_data(handle_t *handle, struct inode *inode,
                           struct buffer_head *this_bh, u32 *first, u32 *last)
{
        unsigned long block_to_free = 0;    /* Starting block # of a run */
        unsigned long count = 0;            /* Number of blocks in the run */ 
        u32 *block_to_free_p = NULL;        /* Pointer into inode/ind
                                               corresponding to
                                               block_to_free */
        unsigned long nr;                   /* Current block # */
        u32 *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");
                ext3_journal_dirty_metadata(handle, this_bh);
        }
}

/**
 *      ext3_free_branches - free an array of branches
 *      @handle: JBD handle for this transaction
 *      @inode: inode we are dealing with
 *      @parent_bh: the buffer_head which contains *@first and *@last
 *      @first: array of block numbers
 *      @last:  pointer immediately past the end of array
 *      @depth: depth of the branches to free
 *
 *      We are freeing all blocks refered from these branches (numbers are
 *      stored as little-endian 32-bit) and updating @inode->i_blocks
 *      appropriately.
 */
static void ext3_free_branches(handle_t *handle, struct inode *inode,
                               struct buffer_head *parent_bh,
                               u32 *first, u32 *last, int depth)
{
        unsigned long nr;
        u32 *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=%ld, block=%ld",
                                           inode->i_ino, nr);
                                continue;
                        }

                        /* This zaps the entire block.  Bottom up. */
                        BUFFER_TRACE(bh, "free child branches");
                        ext3_free_branches(handle, inode, bh, (u32*)bh->b_data,
                                           (u32*)bh->b_data + addr_per_block,
                                           depth);

                        /*
                         * 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.
                         *
                         * If this block has already been committed to the
                         * journal, a revoke record will be written.  And
                         * revoke records must be emitted *before* clearing
                         * this block's bit in the bitmaps.
                         */
                        ext3_forget(handle, 1, inode, bh, bh->b_blocknr);

                        /*
                         * 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);
                                ext3_journal_test_restart(handle, inode);
                        }

                        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);
        }
}

/*
 * 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 commmit 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;
        u32 *i_data = inode->u.ext3_i.i_data;
        int addr_per_block = EXT3_ADDR_PER_BLOCK(inode->i_sb);
        int offsets[4];
        Indirect chain[4];
        Indirect *partial;
        int nr = 0;
        int n;
        long last_block;
        unsigned blocksize;

        if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
            S_ISLNK(inode->i_mode)))
                return;
        if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
                return;

        ext3_discard_prealloc(inode);

        handle = start_transaction(inode);
        if (IS_ERR(handle))
                return;         /* AKPM: return what? */

        blocksize = inode->i_sb->s_blocksize;
        last_block = (inode->i_size + blocksize-1)
                                        >> EXT3_BLOCK_SIZE_BITS(inode->i_sb);

        ext3_block_truncate_page(handle, inode->i_mapping, inode->i_size);
                

        n = ext3_block_to_path(inode, last_block, offsets);
        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.
         */
        inode->u.ext3_i.i_disksize = inode->i_size;

        /*
         * From here we block out all ext3_get_block() callers who want to
         * modify the block allocation tree.
         */
        down_write(&inode->u.ext3_i.truncate_sem);

        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 */
                        BUFFER_TRACE(partial->bh, "get_write_access");
                        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,
                                   (u32*)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:
                        ;
        }
        up_write(&inode->u.ext3_i.truncate_sem);
        inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        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_delete_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, inode);
}

/* 
 * ext3_get_inode_loc returns with an extra refcount against the
 * inode's underlying buffer_head on success. 
 */

int ext3_get_inode_loc (struct inode *inode, struct ext3_iloc *iloc)
{
        struct buffer_head *bh = 0;
        unsigned long block;
        unsigned long block_group;
        unsigned long group_desc;
        unsigned long desc;
        unsigned long offset;
        struct ext3_group_desc * gdp;
                
        if ((inode->i_ino != EXT3_ROOT_INO &&
                inode->i_ino != EXT3_ACL_IDX_INO &&
                inode->i_ino != EXT3_ACL_DATA_INO &&
                inode->i_ino != EXT3_JOURNAL_INO &&
                inode->i_ino < EXT3_FIRST_INO(inode->i_sb)) ||
                inode->i_ino > le32_to_cpu(
                        inode->i_sb->u.ext3_sb.s_es->s_inodes_count)) {
                ext3_error (inode->i_sb, "ext3_get_inode_loc",
                            "bad inode number: %lu", inode->i_ino);
                goto bad_inode;
        }
        block_group = (inode->i_ino - 1) / EXT3_INODES_PER_GROUP(inode->i_sb);
        if (block_group >= inode->i_sb->u.ext3_sb.s_groups_count) {
                ext3_error (inode->i_sb, "ext3_get_inode_loc",
                            "group >= groups count");
                goto bad_inode;
        }
        group_desc = block_group >> EXT3_DESC_PER_BLOCK_BITS(inode->i_sb);
        desc = block_group & (EXT3_DESC_PER_BLOCK(inode->i_sb) - 1);
        bh = inode->i_sb->u.ext3_sb.s_group_desc[group_desc];
        if (!bh) {
                ext3_error (inode->i_sb, "ext3_get_inode_loc",
                            "Descriptor not loaded");
                goto bad_inode;
        }

        gdp = (struct ext3_group_desc *) bh->b_data;
        /*
         * Figure out the offset within the block group inode table
         */
        offset = ((inode->i_ino - 1) % EXT3_INODES_PER_GROUP(inode->i_sb)) *
                EXT3_INODE_SIZE(inode->i_sb);
        block = le32_to_cpu(gdp[desc].bg_inode_table) +
                (offset >> EXT3_BLOCK_SIZE_BITS(inode->i_sb));
        if (!(bh = sb_bread(inode->i_sb, block))) {
                ext3_error (inode->i_sb, "ext3_get_inode_loc",
                            "unable to read inode block - "
                            "inode=%lu, block=%lu", inode->i_ino, block);
                goto bad_inode;
        }
        offset &= (EXT3_BLOCK_SIZE(inode->i_sb) - 1);

        iloc->bh = bh;
        iloc->raw_inode = (struct ext3_inode *) (bh->b_data + offset);
        iloc->block_group = block_group;
        
        return 0;
        
 bad_inode:
        return -EIO;
}

void ext3_read_inode(struct inode * inode)
{
        struct ext3_iloc iloc;
        struct ext3_inode *raw_inode;
        struct buffer_head *bh;
        int block;
        
        if(ext3_get_inode_loc(inode, &iloc))
                goto bad_inode;
        bh = iloc.bh;
        raw_inode = iloc.raw_inode;
        init_rwsem(&inode->u.ext3_i.truncate_sem);
        inode->i_mode = le16_to_cpu(raw_inode->i_mode);
        inode->i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
        inode->i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
        if(!(test_opt (inode->i_sb, NO_UID32))) {
                inode->i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
                inode->i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
        }
        inode->i_nlink = le16_to_cpu(raw_inode->i_links_count);
        inode->i_size = le32_to_cpu(raw_inode->i_size);
        inode->i_atime = le32_to_cpu(raw_inode->i_atime);
        inode->i_ctime = le32_to_cpu(raw_inode->i_ctime);
        inode->i_mtime = le32_to_cpu(raw_inode->i_mtime);
        inode->u.ext3_i.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 ||
                    !(inode->i_sb->u.ext3_sb.s_mount_state & EXT3_ORPHAN_FS)) {
                        /* this inode is deleted */
                        brelse (bh);
                        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_blksize = PAGE_SIZE;   /* This is the optimal IO size
                                         * (for stat), not the fs block
                                         * size */  
        inode->i_blocks = le32_to_cpu(raw_inode->i_blocks);
        inode->i_version = ++event;
        inode->u.ext3_i.i_flags = le32_to_cpu(raw_inode->i_flags);
#ifdef EXT3_FRAGMENTS
        inode->u.ext3_i.i_faddr = le32_to_cpu(raw_inode->i_faddr);
        inode->u.ext3_i.i_frag_no = raw_inode->i_frag;
        inode->u.ext3_i.i_frag_size = raw_inode->i_fsize;
#endif
        inode->u.ext3_i.i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
        if (!S_ISREG(inode->i_mode)) {
                inode->u.ext3_i.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;
        }
        inode->u.ext3_i.i_disksize = inode->i_size;
        inode->i_generation = le32_to_cpu(raw_inode->i_generation);
#ifdef EXT3_PREALLOCATE
        inode->u.ext3_i.i_prealloc_count = 0;
#endif
        inode->u.ext3_i.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++)
                inode->u.ext3_i.i_data[block] = iloc.raw_inode->i_block[block];
        INIT_LIST_HEAD(&inode->u.ext3_i.i_orphan);

        brelse (iloc.bh);

        if (inode->i_ino == EXT3_ACL_IDX_INO ||
            inode->i_ino == EXT3_ACL_DATA_INO)
                /* Nothing to do */ ;
        else if (S_ISREG(inode->i_mode)) {
                inode->i_op = &ext3_file_inode_operations;
                inode->i_fop = &ext3_file_operations;
                inode->i_mapping->a_ops = &ext3_aops;
        } 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 (!inode->i_blocks)
                        inode->i_op = &ext3_fast_symlink_inode_operations;
                else {
                        inode->i_op = &page_symlink_inode_operations;
                        inode->i_mapping->a_ops = &ext3_aops;
                }
        } else 
                init_special_inode(inode, inode->i_mode,
                                   le32_to_cpu(iloc.raw_inode->i_block[0]));
        /* inode->i_attr_flags = 0;                             unused */
        if (inode->u.ext3_i.i_flags & EXT3_SYNC_FL) {
                /* inode->i_attr_flags |= ATTR_FLAG_SYNCRONOUS; unused */
                inode->i_flags |= S_SYNC;
        }
        if (inode->u.ext3_i.i_flags & EXT3_APPEND_FL) {
                /* inode->i_attr_flags |= ATTR_FLAG_APPEND;     unused */
                inode->i_flags |= S_APPEND;
        }
        if (inode->u.ext3_i.i_flags & EXT3_IMMUTABLE_FL) {
                /* inode->i_attr_flags |= ATTR_FLAG_IMMUTABLE;  unused */
                inode->i_flags |= S_IMMUTABLE;
        }
        if (inode->u.ext3_i.i_flags & EXT3_NOATIME_FL) {
                /* inode->i_attr_flags |= ATTR_FLAG_NOATIME;    unused */
                inode->i_flags |= S_NOATIME;
        }
        return;
        
bad_inode:
        make_bad_inode(inode);
        return;
}

/*
 * 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.  
 */

static int ext3_do_update_inode(handle_t *handle, 
                                struct inode *inode, 
                                struct ext3_iloc *iloc)
{
        struct ext3_inode *raw_inode = iloc->raw_inode;
        struct buffer_head *bh = iloc->bh;
        int err = 0, rc, block;

        if (handle) {
                BUFFER_TRACE(bh, "get_write_access");
                err = ext3_journal_get_write_access(handle, bh);
                if (err)
                        goto out_brelse;
        }
        raw_inode->i_mode = cpu_to_le16(inode->i_mode);
        if(!(test_opt(inode->i_sb, NO_UID32))) {
                raw_inode->i_uid_low = cpu_to_le16(low_16_bits(inode->i_uid));
                raw_inode->i_gid_low = cpu_to_le16(low_16_bits(inode->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(!inode->u.ext3_i.i_dtime) {
                        raw_inode->i_uid_high =
                                cpu_to_le16(high_16_bits(inode->i_uid));
                        raw_inode->i_gid_high =
                                cpu_to_le16(high_16_bits(inode->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(inode->i_uid));
                raw_inode->i_gid_low =
                        cpu_to_le16(fs_high2lowgid(inode->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);
        raw_inode->i_size = cpu_to_le32(inode->u.ext3_i.i_disksize);
        raw_inode->i_atime = cpu_to_le32(inode->i_atime);
        raw_inode->i_ctime = cpu_to_le32(inode->i_ctime);
        raw_inode->i_mtime = cpu_to_le32(inode->i_mtime);
        raw_inode->i_blocks = cpu_to_le32(inode->i_blocks);
        raw_inode->i_dtime = cpu_to_le32(inode->u.ext3_i.i_dtime);
        raw_inode->i_flags = cpu_to_le32(inode->u.ext3_i.i_flags);
#ifdef EXT3_FRAGMENTS
        raw_inode->i_faddr = cpu_to_le32(inode->u.ext3_i.i_faddr);
        raw_inode->i_frag = inode->u.ext3_i.i_frag_no;
        raw_inode->i_fsize = inode->u.ext3_i.i_frag_size;
#else
        /* If we are not tracking these fields in the in-memory inode,
         * then preserve them on disk, but still initialise them to zero
         * for new inodes. */
        if (EXT3_I(inode)->i_state & EXT3_STATE_NEW) {
                raw_inode->i_faddr = 0;
                raw_inode->i_frag = 0;
                raw_inode->i_fsize = 0;
        }
#endif
        raw_inode->i_file_acl = cpu_to_le32(inode->u.ext3_i.i_file_acl);
        if (!S_ISREG(inode->i_mode)) {
                raw_inode->i_dir_acl = cpu_to_le32(inode->u.ext3_i.i_dir_acl);
        } else {
                raw_inode->i_size_high =
                        cpu_to_le32(inode->u.ext3_i.i_disksize >> 32);
                if (inode->u.ext3_i.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.
                                */
                                err = ext3_journal_get_write_access(handle,
                                                sb->u.ext3_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);
                                sb->s_dirt = 1;
                                handle->h_sync = 1;
                                err = ext3_journal_dirty_metadata(handle,
                                                sb->u.ext3_sb.s_sbh);
                        }
                }
        }
        raw_inode->i_generation = cpu_to_le32(inode->i_generation);
        if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode))
                raw_inode->i_block[0] =
                        cpu_to_le32(kdev_t_to_nr(inode->i_rdev));
        else for (block = 0; block < EXT3_N_BLOCKS; block++)
                raw_inode->i_block[block] = inode->u.ext3_i.i_data[block];

        BUFFER_TRACE(bh, "call ext3_journal_dirty_metadata");
        rc = ext3_journal_dirty_metadata(handle, bh);
        if (!err)
                err = rc;
        EXT3_I(inode)->i_state &= ~EXT3_STATE_NEW;

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
 *   trasnaction 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.
 */
void ext3_write_inode(struct inode *inode, int wait)
{
        if (current->flags & PF_MEMALLOC)
                return;

        if (ext3_journal_current_handle()) {
                jbd_debug(0, "called recursively, non-PF_MEMALLOC!\n");
                return;
        }

        if (!wait)
                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.)  
 *
 * This is only needed for regular files.  rmdir() has its own path, and
 * we can never truncate a direcory except on final unlink (at which
 * point i_nlink is zero so recovery is easy.)
 *
 * Called with the BKL.  
 */

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 ((ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
                (ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid)) {
                error = DQUOT_TRANSFER(inode, attr) ? -EDQUOT : 0;
                if (error)
                        return error;
        }

        if (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);
                inode->u.ext3_i.i_disksize = attr->ia_size;
                rc = ext3_mark_inode_dirty(handle, inode);
                if (!error)
                        error = rc;
                ext3_journal_stop(handle, inode);
        }
        
        rc = inode_setattr(inode, attr);

        /* If inode_setattr's call to ext3_truncate failed to get a
         * transaction handle at all, we need to clean up the in-core
         * orphan list manually. */
        if (inode->i_nlink)
                ext3_orphan_del(NULL, inode);

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


/*
 * akpm: 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.
 */

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) + 2;

#ifdef CONFIG_QUOTA
        ret += 2 * EXT3_SINGLEDATA_TRANS_BLOCKS;
#endif

        return ret;
}

int
ext3_mark_iloc_dirty(handle_t *handle, 
                     struct inode *inode,
                     struct ext3_iloc *iloc)
{
        int err = 0;

        if (handle) {
                /* the do_update_inode consumes one bh->b_count */
                atomic_inc(&iloc->bh->b_count);
                err = ext3_do_update_inode(handle, inode, iloc);
                /* ext3_do_update_inode() does journal_dirty_metadata */
                brelse(iloc->bh);
        } else {
                printk(KERN_EMERG "%s: called with no handle!\n", __FUNCTION__);
        }
        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;
}

/*
 * akpm: 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.
 *
 * Is this efficient/effective?  Well, we're being nice to the system
 * by cleaning up our inodes proactively so they can be reaped
 * without I/O.  But we are potentially leaving up to five seconds'
 * worth of inodes floating about which prune_icache wants us to
 * write out.  One way to fix that would be to get prune_icache()
 * to do a write_super() to free up some memory.  It has the desired
 * effect.
 */
int ext3_mark_inode_dirty(handle_t *handle, struct inode *inode)
{
        struct ext3_iloc iloc;
        int err;

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

/*
 * akpm: 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)
{
        handle_t *current_handle = ext3_journal_current_handle();
        handle_t *handle;

        lock_kernel();
        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",
                        __FUNCTION__);
        } else {
                jbd_debug(5, "marking dirty.  outer handle=%p\n",
                                current_handle);
                ext3_mark_inode_dirty(handle, inode);
        }
        ext3_journal_stop(handle, inode);
out:
        unlock_kernel();
}

#ifdef AKPM
/* 
 * 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 inline 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) || IS_RDONLY(inode))
                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)
                inode->u.ext3_i.i_flags |= EXT3_JOURNAL_DATA_FL;
        else
                inode->u.ext3_i.i_flags &= ~EXT3_JOURNAL_DATA_FL;

        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, inode);
        ext3_std_error(inode->i_sb, err);
        
        return err;
}


/*
 * ext3_aops_journal_start().
 *
 * <This function died, but the comment lives on>
 *
 * We need to take the inode semaphore *outside* the
 * journal_start/journal_stop.  Otherwise, a different task could do a
 * wait_for_commit() while holding ->i_sem, which deadlocks.  The rule
 * is: transaction open/closes are considered to be a locking operation
 * and they nest *inside* ->i_sem.
 * ----------------------------------------------------------------------------
 * Possible problem:
 *      ext3_file_write()
 *      -> generic_file_write()
 *         -> __alloc_pages()
 *            -> page_launder()
 *               -> ext3_writepage()
 *
 * And the writepage can be on a different fs while we have a
 * transaction open against this one!  Bad.
 *
 * I tried making the task PF_MEMALLOC here, but that simply results in
 * 0-order allocation failures passed back to generic_file_write().
 * Instead, we rely on the reentrancy protection in ext3_writepage().
 * ----------------------------------------------------------------------------
 * When we do the journal_start() here we don't really need to reserve
 * any blocks - we won't need any until we hit ext3_prepare_write(),
 * which does all the needed journal extending.  However!  There is a
 * problem with quotas:
 *
 * Thread 1:
 * sys_sync
 * ->sync_dquots
 *   ->commit_dquot
 *     ->lock_dquot
 *     ->write_dquot
 *       ->ext3_file_write
 *         ->journal_start
 *         ->ext3_prepare_write
 *           ->journal_extend
 *           ->journal_start
 * Thread 2:
 * ext3_create          (for example)
 * ->ext3_new_inode
 *   ->dquot_initialize
 *     ->lock_dquot
 *
 * Deadlock.  Thread 1's journal_start blocks because thread 2 has a
 * transaction open.  Thread 2's transaction will never close because
 * thread 2 is stuck waiting for the dquot lock.
 *
 * So.  We must ensure that thread 1 *never* needs to extend the journal
 * for quota writes.  We do that by reserving enough journal blocks
 * here, in ext3_aops_journal_start() to ensure that the forthcoming "see if we
 * need to extend" test in ext3_prepare_write() succeeds.  
 */