// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * alloc.c
 *
 * Extent allocs and frees
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/quotaops.h>
#include <linux/blkdev.h>
#include <linux/sched/signal.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "aops.h"
#include "blockcheck.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "inode.h"
#include "journal.h"
#include "localalloc.h"
#include "suballoc.h"
#include "sysfile.h"
#include "file.h"
#include "super.h"
#include "uptodate.h"
#include "xattr.h"
#include "refcounttree.h"
#include "ocfs2_trace.h"

#include "buffer_head_io.h"

enum ocfs2_contig_type {
        CONTIG_NONE = 0,
        CONTIG_LEFT,
        CONTIG_RIGHT,
        CONTIG_LEFTRIGHT,
};

static enum ocfs2_contig_type
        ocfs2_extent_rec_contig(struct super_block *sb,
                                struct ocfs2_extent_rec *ext,
                                struct ocfs2_extent_rec *insert_rec);
/*
 * Operations for a specific extent tree type.
 *
 * To implement an on-disk btree (extent tree) type in ocfs2, add
 * an ocfs2_extent_tree_operations structure and the matching
 * ocfs2_init_<thingy>_extent_tree() function.  That's pretty much it
 * for the allocation portion of the extent tree.
 */
struct ocfs2_extent_tree_operations {
        /*
         * last_eb_blk is the block number of the right most leaf extent
         * block.  Most on-disk structures containing an extent tree store
         * this value for fast access.  The ->eo_set_last_eb_blk() and
         * ->eo_get_last_eb_blk() operations access this value.  They are
         *  both required.
         */
        void (*eo_set_last_eb_blk)(struct ocfs2_extent_tree *et,
                                   u64 blkno);
        u64 (*eo_get_last_eb_blk)(struct ocfs2_extent_tree *et);

        /*
         * The on-disk structure usually keeps track of how many total
         * clusters are stored in this extent tree.  This function updates
         * that value.  new_clusters is the delta, and must be
         * added to the total.  Required.
         */
        void (*eo_update_clusters)(struct ocfs2_extent_tree *et,
                                   u32 new_clusters);

        /*
         * If this extent tree is supported by an extent map, insert
         * a record into the map.
         */
        void (*eo_extent_map_insert)(struct ocfs2_extent_tree *et,
                                     struct ocfs2_extent_rec *rec);

        /*
         * If this extent tree is supported by an extent map, truncate the
         * map to clusters,
         */
        void (*eo_extent_map_truncate)(struct ocfs2_extent_tree *et,
                                       u32 clusters);

        /*
         * If ->eo_insert_check() exists, it is called before rec is
         * inserted into the extent tree.  It is optional.
         */
        int (*eo_insert_check)(struct ocfs2_extent_tree *et,
                               struct ocfs2_extent_rec *rec);
        int (*eo_sanity_check)(struct ocfs2_extent_tree *et);

        /*
         * --------------------------------------------------------------
         * The remaining are internal to ocfs2_extent_tree and don't have
         * accessor functions
         */

        /*
         * ->eo_fill_root_el() takes et->et_object and sets et->et_root_el.
         * It is required.
         */
        void (*eo_fill_root_el)(struct ocfs2_extent_tree *et);

        /*
         * ->eo_fill_max_leaf_clusters sets et->et_max_leaf_clusters if
         * it exists.  If it does not, et->et_max_leaf_clusters is set
         * to 0 (unlimited).  Optional.
         */
        void (*eo_fill_max_leaf_clusters)(struct ocfs2_extent_tree *et);

        /*
         * ->eo_extent_contig test whether the 2 ocfs2_extent_rec
         * are contiguous or not. Optional. Don't need to set it if use
         * ocfs2_extent_rec as the tree leaf.
         */
        enum ocfs2_contig_type
                (*eo_extent_contig)(struct ocfs2_extent_tree *et,
                                    struct ocfs2_extent_rec *ext,
                                    struct ocfs2_extent_rec *insert_rec);
};


/*
 * Pre-declare ocfs2_dinode_et_ops so we can use it as a sanity check
 * in the methods.
 */
static u64 ocfs2_dinode_get_last_eb_blk(struct ocfs2_extent_tree *et);
static void ocfs2_dinode_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                         u64 blkno);
static void ocfs2_dinode_update_clusters(struct ocfs2_extent_tree *et,
                                         u32 clusters);
static void ocfs2_dinode_extent_map_insert(struct ocfs2_extent_tree *et,
                                           struct ocfs2_extent_rec *rec);
static void ocfs2_dinode_extent_map_truncate(struct ocfs2_extent_tree *et,
                                             u32 clusters);
static int ocfs2_dinode_insert_check(struct ocfs2_extent_tree *et,
                                     struct ocfs2_extent_rec *rec);
static int ocfs2_dinode_sanity_check(struct ocfs2_extent_tree *et);
static void ocfs2_dinode_fill_root_el(struct ocfs2_extent_tree *et);

static int ocfs2_reuse_blk_from_dealloc(handle_t *handle,
                                        struct ocfs2_extent_tree *et,
                                        struct buffer_head **new_eb_bh,
                                        int blk_wanted, int *blk_given);
static int ocfs2_is_dealloc_empty(struct ocfs2_extent_tree *et);

static const struct ocfs2_extent_tree_operations ocfs2_dinode_et_ops = {
        .eo_set_last_eb_blk     = ocfs2_dinode_set_last_eb_blk,
        .eo_get_last_eb_blk     = ocfs2_dinode_get_last_eb_blk,
        .eo_update_clusters     = ocfs2_dinode_update_clusters,
        .eo_extent_map_insert   = ocfs2_dinode_extent_map_insert,
        .eo_extent_map_truncate = ocfs2_dinode_extent_map_truncate,
        .eo_insert_check        = ocfs2_dinode_insert_check,
        .eo_sanity_check        = ocfs2_dinode_sanity_check,
        .eo_fill_root_el        = ocfs2_dinode_fill_root_el,
};

static void ocfs2_dinode_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                         u64 blkno)
{
        struct ocfs2_dinode *di = et->et_object;

        BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
        di->i_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_dinode_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        struct ocfs2_dinode *di = et->et_object;

        BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
        return le64_to_cpu(di->i_last_eb_blk);
}

static void ocfs2_dinode_update_clusters(struct ocfs2_extent_tree *et,
                                         u32 clusters)
{
        struct ocfs2_inode_info *oi = cache_info_to_inode(et->et_ci);
        struct ocfs2_dinode *di = et->et_object;

        le32_add_cpu(&di->i_clusters, clusters);
        spin_lock(&oi->ip_lock);
        oi->ip_clusters = le32_to_cpu(di->i_clusters);
        spin_unlock(&oi->ip_lock);
}

static void ocfs2_dinode_extent_map_insert(struct ocfs2_extent_tree *et,
                                           struct ocfs2_extent_rec *rec)
{
        struct inode *inode = &cache_info_to_inode(et->et_ci)->vfs_inode;

        ocfs2_extent_map_insert_rec(inode, rec);
}

static void ocfs2_dinode_extent_map_truncate(struct ocfs2_extent_tree *et,
                                             u32 clusters)
{
        struct inode *inode = &cache_info_to_inode(et->et_ci)->vfs_inode;

        ocfs2_extent_map_trunc(inode, clusters);
}

static int ocfs2_dinode_insert_check(struct ocfs2_extent_tree *et,
                                     struct ocfs2_extent_rec *rec)
{
        struct ocfs2_inode_info *oi = cache_info_to_inode(et->et_ci);
        struct ocfs2_super *osb = OCFS2_SB(oi->vfs_inode.i_sb);

        BUG_ON(oi->ip_dyn_features & OCFS2_INLINE_DATA_FL);
        mlog_bug_on_msg(!ocfs2_sparse_alloc(osb) &&
                        (oi->ip_clusters != le32_to_cpu(rec->e_cpos)),
                        "Device %s, asking for sparse allocation: inode %llu, "
                        "cpos %u, clusters %u\n",
                        osb->dev_str,
                        (unsigned long long)oi->ip_blkno,
                        rec->e_cpos, oi->ip_clusters);

        return 0;
}

static int ocfs2_dinode_sanity_check(struct ocfs2_extent_tree *et)
{
        struct ocfs2_dinode *di = et->et_object;

        BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
        BUG_ON(!OCFS2_IS_VALID_DINODE(di));

        return 0;
}

static void ocfs2_dinode_fill_root_el(struct ocfs2_extent_tree *et)
{
        struct ocfs2_dinode *di = et->et_object;

        et->et_root_el = &di->id2.i_list;
}


static void ocfs2_xattr_value_fill_root_el(struct ocfs2_extent_tree *et)
{
        struct ocfs2_xattr_value_buf *vb = et->et_object;

        et->et_root_el = &vb->vb_xv->xr_list;
}

static void ocfs2_xattr_value_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                              u64 blkno)
{
        struct ocfs2_xattr_value_buf *vb = et->et_object;

        vb->vb_xv->xr_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_xattr_value_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        struct ocfs2_xattr_value_buf *vb = et->et_object;

        return le64_to_cpu(vb->vb_xv->xr_last_eb_blk);
}

static void ocfs2_xattr_value_update_clusters(struct ocfs2_extent_tree *et,
                                              u32 clusters)
{
        struct ocfs2_xattr_value_buf *vb = et->et_object;

        le32_add_cpu(&vb->vb_xv->xr_clusters, clusters);
}

static const struct ocfs2_extent_tree_operations ocfs2_xattr_value_et_ops = {
        .eo_set_last_eb_blk     = ocfs2_xattr_value_set_last_eb_blk,
        .eo_get_last_eb_blk     = ocfs2_xattr_value_get_last_eb_blk,
        .eo_update_clusters     = ocfs2_xattr_value_update_clusters,
        .eo_fill_root_el        = ocfs2_xattr_value_fill_root_el,
};

static void ocfs2_xattr_tree_fill_root_el(struct ocfs2_extent_tree *et)
{
        struct ocfs2_xattr_block *xb = et->et_object;

        et->et_root_el = &xb->xb_attrs.xb_root.xt_list;
}

static void ocfs2_xattr_tree_fill_max_leaf_clusters(struct ocfs2_extent_tree *et)
{
        struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);
        et->et_max_leaf_clusters =
                ocfs2_clusters_for_bytes(sb, OCFS2_MAX_XATTR_TREE_LEAF_SIZE);
}

static void ocfs2_xattr_tree_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                             u64 blkno)
{
        struct ocfs2_xattr_block *xb = et->et_object;
        struct ocfs2_xattr_tree_root *xt = &xb->xb_attrs.xb_root;

        xt->xt_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_xattr_tree_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        struct ocfs2_xattr_block *xb = et->et_object;
        struct ocfs2_xattr_tree_root *xt = &xb->xb_attrs.xb_root;

        return le64_to_cpu(xt->xt_last_eb_blk);
}

static void ocfs2_xattr_tree_update_clusters(struct ocfs2_extent_tree *et,
                                             u32 clusters)
{
        struct ocfs2_xattr_block *xb = et->et_object;

        le32_add_cpu(&xb->xb_attrs.xb_root.xt_clusters, clusters);
}

static const struct ocfs2_extent_tree_operations ocfs2_xattr_tree_et_ops = {
        .eo_set_last_eb_blk     = ocfs2_xattr_tree_set_last_eb_blk,
        .eo_get_last_eb_blk     = ocfs2_xattr_tree_get_last_eb_blk,
        .eo_update_clusters     = ocfs2_xattr_tree_update_clusters,
        .eo_fill_root_el        = ocfs2_xattr_tree_fill_root_el,
        .eo_fill_max_leaf_clusters = ocfs2_xattr_tree_fill_max_leaf_clusters,
};

static void ocfs2_dx_root_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                          u64 blkno)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        dx_root->dr_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_dx_root_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        return le64_to_cpu(dx_root->dr_last_eb_blk);
}

static void ocfs2_dx_root_update_clusters(struct ocfs2_extent_tree *et,
                                          u32 clusters)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        le32_add_cpu(&dx_root->dr_clusters, clusters);
}

static int ocfs2_dx_root_sanity_check(struct ocfs2_extent_tree *et)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        BUG_ON(!OCFS2_IS_VALID_DX_ROOT(dx_root));

        return 0;
}

static void ocfs2_dx_root_fill_root_el(struct ocfs2_extent_tree *et)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        et->et_root_el = &dx_root->dr_list;
}

static const struct ocfs2_extent_tree_operations ocfs2_dx_root_et_ops = {
        .eo_set_last_eb_blk     = ocfs2_dx_root_set_last_eb_blk,
        .eo_get_last_eb_blk     = ocfs2_dx_root_get_last_eb_blk,
        .eo_update_clusters     = ocfs2_dx_root_update_clusters,
        .eo_sanity_check        = ocfs2_dx_root_sanity_check,
        .eo_fill_root_el        = ocfs2_dx_root_fill_root_el,
};

static void ocfs2_refcount_tree_fill_root_el(struct ocfs2_extent_tree *et)
{
        struct ocfs2_refcount_block *rb = et->et_object;

        et->et_root_el = &rb->rf_list;
}

static void ocfs2_refcount_tree_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                                u64 blkno)
{
        struct ocfs2_refcount_block *rb = et->et_object;

        rb->rf_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_refcount_tree_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        struct ocfs2_refcount_block *rb = et->et_object;

        return le64_to_cpu(rb->rf_last_eb_blk);
}

static void ocfs2_refcount_tree_update_clusters(struct ocfs2_extent_tree *et,
                                                u32 clusters)
{
        struct ocfs2_refcount_block *rb = et->et_object;

        le32_add_cpu(&rb->rf_clusters, clusters);
}

static enum ocfs2_contig_type
ocfs2_refcount_tree_extent_contig(struct ocfs2_extent_tree *et,
                                  struct ocfs2_extent_rec *ext,
                                  struct ocfs2_extent_rec *insert_rec)
{
        return CONTIG_NONE;
}

static const struct ocfs2_extent_tree_operations ocfs2_refcount_tree_et_ops = {
        .eo_set_last_eb_blk     = ocfs2_refcount_tree_set_last_eb_blk,
        .eo_get_last_eb_blk     = ocfs2_refcount_tree_get_last_eb_blk,
        .eo_update_clusters     = ocfs2_refcount_tree_update_clusters,
        .eo_fill_root_el        = ocfs2_refcount_tree_fill_root_el,
        .eo_extent_contig       = ocfs2_refcount_tree_extent_contig,
};

static void __ocfs2_init_extent_tree(struct ocfs2_extent_tree *et,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *bh,
                                     ocfs2_journal_access_func access,
                                     void *obj,
                                     const struct ocfs2_extent_tree_operations *ops)
{
        et->et_ops = ops;
        et->et_root_bh = bh;
        et->et_ci = ci;
        et->et_root_journal_access = access;
        if (!obj)
                obj = (void *)bh->b_data;
        et->et_object = obj;
        et->et_dealloc = NULL;

        et->et_ops->eo_fill_root_el(et);
        if (!et->et_ops->eo_fill_max_leaf_clusters)
                et->et_max_leaf_clusters = 0;
        else
                et->et_ops->eo_fill_max_leaf_clusters(et);
}

void ocfs2_init_dinode_extent_tree(struct ocfs2_extent_tree *et,
                                   struct ocfs2_caching_info *ci,
                                   struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_di,
                                 NULL, &ocfs2_dinode_et_ops);
}

void ocfs2_init_xattr_tree_extent_tree(struct ocfs2_extent_tree *et,
                                       struct ocfs2_caching_info *ci,
                                       struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_xb,
                                 NULL, &ocfs2_xattr_tree_et_ops);
}

void ocfs2_init_xattr_value_extent_tree(struct ocfs2_extent_tree *et,
                                        struct ocfs2_caching_info *ci,
                                        struct ocfs2_xattr_value_buf *vb)
{
        __ocfs2_init_extent_tree(et, ci, vb->vb_bh, vb->vb_access, vb,
                                 &ocfs2_xattr_value_et_ops);
}

void ocfs2_init_dx_root_extent_tree(struct ocfs2_extent_tree *et,
                                    struct ocfs2_caching_info *ci,
                                    struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_dr,
                                 NULL, &ocfs2_dx_root_et_ops);
}

void ocfs2_init_refcount_extent_tree(struct ocfs2_extent_tree *et,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_rb,
                                 NULL, &ocfs2_refcount_tree_et_ops);
}

static inline void ocfs2_et_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                            u64 new_last_eb_blk)
{
        et->et_ops->eo_set_last_eb_blk(et, new_last_eb_blk);
}

static inline u64 ocfs2_et_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        return et->et_ops->eo_get_last_eb_blk(et);
}

static inline void ocfs2_et_update_clusters(struct ocfs2_extent_tree *et,
                                            u32 clusters)
{
        et->et_ops->eo_update_clusters(et, clusters);
}

static inline void ocfs2_et_extent_map_insert(struct ocfs2_extent_tree *et,
                                              struct ocfs2_extent_rec *rec)
{
        if (et->et_ops->eo_extent_map_insert)
                et->et_ops->eo_extent_map_insert(et, rec);
}

static inline void ocfs2_et_extent_map_truncate(struct ocfs2_extent_tree *et,
                                                u32 clusters)
{
        if (et->et_ops->eo_extent_map_truncate)
                et->et_ops->eo_extent_map_truncate(et, clusters);
}

static inline int ocfs2_et_root_journal_access(handle_t *handle,
                                               struct ocfs2_extent_tree *et,
                                               int type)
{
        return et->et_root_journal_access(handle, et->et_ci, et->et_root_bh,
                                          type);
}

static inline enum ocfs2_contig_type
        ocfs2_et_extent_contig(struct ocfs2_extent_tree *et,
                               struct ocfs2_extent_rec *rec,
                               struct ocfs2_extent_rec *insert_rec)
{
        if (et->et_ops->eo_extent_contig)
                return et->et_ops->eo_extent_contig(et, rec, insert_rec);

        return ocfs2_extent_rec_contig(
                                ocfs2_metadata_cache_get_super(et->et_ci),
                                rec, insert_rec);
}

static inline int ocfs2_et_insert_check(struct ocfs2_extent_tree *et,
                                        struct ocfs2_extent_rec *rec)
{
        int ret = 0;

        if (et->et_ops->eo_insert_check)
                ret = et->et_ops->eo_insert_check(et, rec);
        return ret;
}

static inline int ocfs2_et_sanity_check(struct ocfs2_extent_tree *et)
{
        int ret = 0;

        if (et->et_ops->eo_sanity_check)
                ret = et->et_ops->eo_sanity_check(et);
        return ret;
}

static int ocfs2_cache_extent_block_free(struct ocfs2_cached_dealloc_ctxt *ctxt,
                                         struct ocfs2_extent_block *eb);
static void ocfs2_adjust_rightmost_records(handle_t *handle,
                                           struct ocfs2_extent_tree *et,
                                           struct ocfs2_path *path,
                                           struct ocfs2_extent_rec *insert_rec);
/*
 * Reset the actual path elements so that we can re-use the structure
 * to build another path. Generally, this involves freeing the buffer
 * heads.
 */
void ocfs2_reinit_path(struct ocfs2_path *path, int keep_root)
{
        int i, start = 0, depth = 0;
        struct ocfs2_path_item *node;

        if (keep_root)
                start = 1;

        for(i = start; i < path_num_items(path); i++) {
                node = &path->p_node[i];

                brelse(node->bh);
                node->bh = NULL;
                node->el = NULL;
        }

        /*
         * Tree depth may change during truncate, or insert. If we're
         * keeping the root extent list, then make sure that our path
         * structure reflects the proper depth.
         */
        if (keep_root)
                depth = le16_to_cpu(path_root_el(path)->l_tree_depth);
        else
                path_root_access(path) = NULL;

        path->p_tree_depth = depth;
}

void ocfs2_free_path(struct ocfs2_path *path)
{
        if (path) {
                ocfs2_reinit_path(path, 0);
                kfree(path);
        }
}

/*
 * All the elements of src into dest. After this call, src could be freed
 * without affecting dest.
 *
 * Both paths should have the same root. Any non-root elements of dest
 * will be freed.
 */
static void ocfs2_cp_path(struct ocfs2_path *dest, struct ocfs2_path *src)
{
        int i;

        BUG_ON(path_root_bh(dest) != path_root_bh(src));
        BUG_ON(path_root_el(dest) != path_root_el(src));
        BUG_ON(path_root_access(dest) != path_root_access(src));

        ocfs2_reinit_path(dest, 1);

        for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
                dest->p_node[i].bh = src->p_node[i].bh;
                dest->p_node[i].el = src->p_node[i].el;

                if (dest->p_node[i].bh)
                        get_bh(dest->p_node[i].bh);
        }
}

/*
 * Make the *dest path the same as src and re-initialize src path to
 * have a root only.
 */
static void ocfs2_mv_path(struct ocfs2_path *dest, struct ocfs2_path *src)
{
        int i;

        BUG_ON(path_root_bh(dest) != path_root_bh(src));
        BUG_ON(path_root_access(dest) != path_root_access(src));

        for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
                brelse(dest->p_node[i].bh);

                dest->p_node[i].bh = src->p_node[i].bh;
                dest->p_node[i].el = src->p_node[i].el;

                src->p_node[i].bh = NULL;
                src->p_node[i].el = NULL;
        }
}

/*
 * Insert an extent block at given index.
 *
 * This will not take an additional reference on eb_bh.
 */
static inline void ocfs2_path_insert_eb(struct ocfs2_path *path, int index,
                                        struct buffer_head *eb_bh)
{
        struct ocfs2_extent_block *eb = (struct ocfs2_extent_block *)eb_bh->b_data;

        /*
         * Right now, no root bh is an extent block, so this helps
         * catch code errors with dinode trees. The assertion can be
         * safely removed if we ever need to insert extent block
         * structures at the root.
         */
        BUG_ON(index == 0);

        path->p_node[index].bh = eb_bh;
        path->p_node[index].el = &eb->h_list;
}

static struct ocfs2_path *ocfs2_new_path(struct buffer_head *root_bh,
                                         struct ocfs2_extent_list *root_el,
                                         ocfs2_journal_access_func access)
{
        struct ocfs2_path *path;

        BUG_ON(le16_to_cpu(root_el->l_tree_depth) >= OCFS2_MAX_PATH_DEPTH);

        path = kzalloc(sizeof(*path), GFP_NOFS);
        if (path) {
                path->p_tree_depth = le16_to_cpu(root_el->l_tree_depth);
                get_bh(root_bh);
                path_root_bh(path) = root_bh;
                path_root_el(path) = root_el;
                path_root_access(path) = access;
        }

        return path;
}

struct ocfs2_path *ocfs2_new_path_from_path(struct ocfs2_path *path)
{
        return ocfs2_new_path(path_root_bh(path), path_root_el(path),
                              path_root_access(path));
}

struct ocfs2_path *ocfs2_new_path_from_et(struct ocfs2_extent_tree *et)
{
        return ocfs2_new_path(et->et_root_bh, et->et_root_el,
                              et->et_root_journal_access);
}

/*
 * Journal the buffer at depth idx.  All idx>0 are extent_blocks,
 * otherwise it's the root_access function.
 *
 * I don't like the way this function's name looks next to
 * ocfs2_journal_access_path(), but I don't have a better one.
 */
int ocfs2_path_bh_journal_access(handle_t *handle,
                                 struct ocfs2_caching_info *ci,
                                 struct ocfs2_path *path,
                                 int idx)
{
        ocfs2_journal_access_func access = path_root_access(path);

        if (!access)
                access = ocfs2_journal_access;

        if (idx)
                access = ocfs2_journal_access_eb;

        return access(handle, ci, path->p_node[idx].bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
}

/*
 * Convenience function to journal all components in a path.
 */
int ocfs2_journal_access_path(struct ocfs2_caching_info *ci,
                              handle_t *handle,
                              struct ocfs2_path *path)
{
        int i, ret = 0;

        if (!path)
                goto out;

        for(i = 0; i < path_num_items(path); i++) {
                ret = ocfs2_path_bh_journal_access(handle, ci, path, i);
                if (ret < 0) {
                        mlog_errno(ret);
                        goto out;
                }
        }

out:
        return ret;
}

/*
 * Return the index of the extent record which contains cluster #v_cluster.
 * -1 is returned if it was not found.
 *
 * Should work fine on interior and exterior nodes.
 */
int ocfs2_search_extent_list(struct ocfs2_extent_list *el, u32 v_cluster)
{
        int ret = -1;
        int i;
        struct ocfs2_extent_rec *rec;
        u32 rec_end, rec_start, clusters;

        for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
                rec = &el->l_recs[i];

                rec_start = le32_to_cpu(rec->e_cpos);
                clusters = ocfs2_rec_clusters(el, rec);

                rec_end = rec_start + clusters;

                if (v_cluster >= rec_start && v_cluster < rec_end) {
                        ret = i;
                        break;
                }
        }

        return ret;
}

/*
 * NOTE: ocfs2_block_extent_contig(), ocfs2_extents_adjacent() and
 * ocfs2_extent_rec_contig only work properly against leaf nodes!
 */
static int ocfs2_block_extent_contig(struct super_block *sb,
                                     struct ocfs2_extent_rec *ext,
                                     u64 blkno)
{
        u64 blk_end = le64_to_cpu(ext->e_blkno);

        blk_end += ocfs2_clusters_to_blocks(sb,
                                    le16_to_cpu(ext->e_leaf_clusters));

        return blkno == blk_end;
}

static int ocfs2_extents_adjacent(struct ocfs2_extent_rec *left,
                                  struct ocfs2_extent_rec *right)
{
        u32 left_range;

        left_range = le32_to_cpu(left->e_cpos) +
                le16_to_cpu(left->e_leaf_clusters);

        return (left_range == le32_to_cpu(right->e_cpos));
}

static enum ocfs2_contig_type
        ocfs2_extent_rec_contig(struct super_block *sb,
                                struct ocfs2_extent_rec *ext,
                                struct ocfs2_extent_rec *insert_rec)
{
        u64 blkno = le64_to_cpu(insert_rec->e_blkno);

        /*
         * Refuse to coalesce extent records with different flag
         * fields - we don't want to mix unwritten extents with user
         * data.
         */
        if (ext->e_flags != insert_rec->e_flags)
                return CONTIG_NONE;

        if (ocfs2_extents_adjacent(ext, insert_rec) &&
            ocfs2_block_extent_contig(sb, ext, blkno))
                        return CONTIG_RIGHT;

        blkno = le64_to_cpu(ext->e_blkno);
        if (ocfs2_extents_adjacent(insert_rec, ext) &&
            ocfs2_block_extent_contig(sb, insert_rec, blkno))
                return CONTIG_LEFT;

        return CONTIG_NONE;
}

/*
 * NOTE: We can have pretty much any combination of contiguousness and
 * appending.
 *
 * The usefulness of APPEND_TAIL is more in that it lets us know that
 * we'll have to update the path to that leaf.
 */
enum ocfs2_append_type {
        APPEND_NONE = 0,
        APPEND_TAIL,
};

enum ocfs2_split_type {
        SPLIT_NONE = 0,
        SPLIT_LEFT,
        SPLIT_RIGHT,
};

struct ocfs2_insert_type {
        enum ocfs2_split_type   ins_split;
        enum ocfs2_append_type  ins_appending;
        enum ocfs2_contig_type  ins_contig;
        int                     ins_contig_index;
        int                     ins_tree_depth;
};

struct ocfs2_merge_ctxt {
        enum ocfs2_contig_type  c_contig_type;
        int                     c_has_empty_extent;
        int                     c_split_covers_rec;
};

static int ocfs2_validate_extent_block(struct super_block *sb,
                                       struct buffer_head *bh)
{
        int rc;
        struct ocfs2_extent_block *eb =
                (struct ocfs2_extent_block *)bh->b_data;

        trace_ocfs2_validate_extent_block((unsigned long long)bh->b_blocknr);

        BUG_ON(!buffer_uptodate(bh));

        /*
         * If the ecc fails, we return the error but otherwise
         * leave the filesystem running.  We know any error is
         * local to this block.
         */
        rc = ocfs2_validate_meta_ecc(sb, bh->b_data, &eb->h_check);
        if (rc) {
                mlog(ML_ERROR, "Checksum failed for extent block %llu\n",
                     (unsigned long long)bh->b_blocknr);
                return rc;
        }

        /*
         * Errors after here are fatal.
         */

        if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
                rc = ocfs2_error(sb,
                                 "Extent block #%llu has bad signature %.*s\n",
                                 (unsigned long long)bh->b_blocknr, 7,
                                 eb->h_signature);
                goto bail;
        }

        if (le64_to_cpu(eb->h_blkno) != bh->b_blocknr) {
                rc = ocfs2_error(sb,
                                 "Extent block #%llu has an invalid h_blkno of %llu\n",
                                 (unsigned long long)bh->b_blocknr,
                                 (unsigned long long)le64_to_cpu(eb->h_blkno));
                goto bail;
        }

        if (le32_to_cpu(eb->h_fs_generation) != OCFS2_SB(sb)->fs_generation)
                rc = ocfs2_error(sb,
                                 "Extent block #%llu has an invalid h_fs_generation of #%u\n",
                                 (unsigned long long)bh->b_blocknr,
                                 le32_to_cpu(eb->h_fs_generation));
bail:
        return rc;
}

int ocfs2_read_extent_block(struct ocfs2_caching_info *ci, u64 eb_blkno,
                            struct buffer_head **bh)
{
        int rc;
        struct buffer_head *tmp = *bh;

        rc = ocfs2_read_block(ci, eb_blkno, &tmp,
                              ocfs2_validate_extent_block);

        /* If ocfs2_read_block() got us a new bh, pass it up. */
        if (!rc && !*bh)
                *bh = tmp;

        return rc;
}


/*
 * How many free extents have we got before we need more meta data?
 */
int ocfs2_num_free_extents(struct ocfs2_extent_tree *et)
{
        int retval;
        struct ocfs2_extent_list *el = NULL;
        struct ocfs2_extent_block *eb;
        struct buffer_head *eb_bh = NULL;
        u64 last_eb_blk = 0;

        el = et->et_root_el;
        last_eb_blk = ocfs2_et_get_last_eb_blk(et);

        if (last_eb_blk) {
                retval = ocfs2_read_extent_block(et->et_ci, last_eb_blk,
                                                 &eb_bh);
                if (retval < 0) {
                        mlog_errno(retval);
                        goto bail;
                }
                eb = (struct ocfs2_extent_block *) eb_bh->b_data;
                el = &eb->h_list;
        }

        BUG_ON(el->l_tree_depth != 0);

        retval = le16_to_cpu(el->l_count) - le16_to_cpu(el->l_next_free_rec);
bail:
        brelse(eb_bh);

        trace_ocfs2_num_free_extents(retval);
        return retval;
}

/* expects array to already be allocated
 *
 * sets h_signature, h_blkno, h_suballoc_bit, h_suballoc_slot, and
 * l_count for you
 */
static int ocfs2_create_new_meta_bhs(handle_t *handle,
                                     struct ocfs2_extent_tree *et,
                                     int wanted,
                                     struct ocfs2_alloc_context *meta_ac,
                                     struct buffer_head *bhs[])
{
        int count, status, i;
        u16 suballoc_bit_start;
        u32 num_got;
        u64 suballoc_loc, first_blkno;
        struct ocfs2_super *osb =
                OCFS2_SB(ocfs2_metadata_cache_get_super(et->et_ci));
        struct ocfs2_extent_block *eb;

        count = 0;
        while (count < wanted) {

                status = ocfs2_claim_metadata(handle,
                                              meta_ac,
                                              wanted - count,
                                              &suballoc_loc,
                                              &suballoc_bit_start,
                                              &num_got,
                                              &first_blkno);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

                for(i = count;  i < (num_got + count); i++) {
                        bhs[i] = sb_getblk(osb->sb, first_blkno);
                        if (bhs[i] == NULL) {
                                status = -ENOMEM;
                                mlog_errno(status);
                                goto bail;
                        }
                        ocfs2_set_new_buffer_uptodate(et->et_ci, bhs[i]);

                        status = ocfs2_journal_access_eb(handle, et->et_ci,
                                                         bhs[i],
                                                         OCFS2_JOURNAL_ACCESS_CREATE);
                        if (status < 0) {
                                mlog_errno(status);
                                goto bail;
                        }

                        memset(bhs[i]->b_data, 0, osb->sb->s_blocksize);
                        eb = (struct ocfs2_extent_block *) bhs[i]->b_data;
                        /* Ok, setup the minimal stuff here. */
                        strcpy(eb->h_signature, OCFS2_EXTENT_BLOCK_SIGNATURE);
                        eb->h_blkno = cpu_to_le64(first_blkno);
                        eb->h_fs_generation = cpu_to_le32(osb->fs_generation);
                        eb->h_suballoc_slot =
                                cpu_to_le16(meta_ac->ac_alloc_slot);
                        eb->h_suballoc_loc = cpu_to_le64(suballoc_loc);
                        eb->h_suballoc_bit = cpu_to_le16(suballoc_bit_start);
                        eb->h_list.l_count =
                                cpu_to_le16(ocfs2_extent_recs_per_eb(osb->sb));

                        suballoc_bit_start++;
                        first_blkno++;

                        /* We'll also be dirtied by the caller, so
                         * this isn't absolutely necessary. */
                        ocfs2_journal_dirty(handle, bhs[i]);
                }

                count += num_got;
        }

        status = 0;
bail:
        if (status < 0) {
                for(i = 0; i < wanted; i++) {
                        brelse(bhs[i]);
                        bhs[i] = NULL;
                }
        }
        return status;
}

/*
 * Helper function for ocfs2_add_branch() and ocfs2_shift_tree_depth().
 *
 * Returns the sum of the rightmost extent rec logical offset and
 * cluster count.
 *
 * ocfs2_add_branch() uses this to determine what logical cluster
 * value should be populated into the leftmost new branch records.
 *
 * ocfs2_shift_tree_depth() uses this to determine the # clusters
 * value for the new topmost tree record.
 */
static inline u32 ocfs2_sum_rightmost_rec(struct ocfs2_extent_list  *el)
{
        int i;

        i = le16_to_cpu(el->l_next_free_rec) - 1;

        return le32_to_cpu(el->l_recs[i].e_cpos) +
                ocfs2_rec_clusters(el, &el->l_recs[i]);
}

/*
 * Change range of the branches in the right most path according to the leaf
 * extent block's rightmost record.
 */
static int ocfs2_adjust_rightmost_branch(handle_t *handle,
                                         struct ocfs2_extent_tree *et)
{
        int status;
        struct ocfs2_path *path = NULL;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_rec *rec;

        path = ocfs2_new_path_from_et(et);
        if (!path) {
                status = -ENOMEM;
                return status;
        }

        status = ocfs2_find_path(et->et_ci, path, UINT_MAX);
        if (status < 0) {
                mlog_errno(status);
                goto out;
        }

        status = ocfs2_extend_trans(handle, path_num_items(path));
        if (status < 0) {
                mlog_errno(status);
                goto out;
        }

        status = ocfs2_journal_access_path(et->et_ci, handle, path);
        if (status < 0) {
                mlog_errno(status);
                goto out;
        }

        el = path_leaf_el(path);
        rec = &el->l_recs[le16_to_cpu(el->l_next_free_rec) - 1];

        ocfs2_adjust_rightmost_records(handle, et, path, rec);

out:
        ocfs2_free_path(path);
        return status;
}

/*
 * Add an entire tree branch to our inode. eb_bh is the extent block
 * to start at, if we don't want to start the branch at the root
 * structure.
 *
 * last_eb_bh is required as we have to update it's next_leaf pointer
 * for the new last extent block.
 *
 * the new branch will be 'empty' in the sense that every block will
 * contain a single record with cluster count == 0.
 */
static int ocfs2_add_branch(handle_t *handle,
                            struct ocfs2_extent_tree *et,
                            struct buffer_head *eb_bh,
                            struct buffer_head **last_eb_bh,
                            struct ocfs2_alloc_context *meta_ac)
{
        int status, new_blocks, i, block_given = 0;
        u64 next_blkno, new_last_eb_blk;
        struct buffer_head *bh;
        struct buffer_head **new_eb_bhs = NULL;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list  *eb_el;
        struct ocfs2_extent_list  *el;
        u32 new_cpos, root_end;

        BUG_ON(!last_eb_bh || !*last_eb_bh);

        if (eb_bh) {
                eb = (struct ocfs2_extent_block *) eb_bh->b_data;
                el = &eb->h_list;
        } else
                el = et->et_root_el;

        /* we never add a branch to a leaf. */
        BUG_ON(!el->l_tree_depth);

        new_blocks = le16_to_cpu(el->l_tree_depth);

        eb = (struct ocfs2_extent_block *)(*last_eb_bh)->b_data;
        new_cpos = ocfs2_sum_rightmost_rec(&eb->h_list);
        root_end = ocfs2_sum_rightmost_rec(et->et_root_el);

        /*
         * If there is a gap before the root end and the real end
         * of the righmost leaf block, we need to remove the gap
         * between new_cpos and root_end first so that the tree
         * is consistent after we add a new branch(it will start
         * from new_cpos).
         */
        if (root_end > new_cpos) {
                trace_ocfs2_adjust_rightmost_branch(
                        (unsigned long long)
                        ocfs2_metadata_cache_owner(et->et_ci),
                        root_end, new_cpos);

                status = ocfs2_adjust_rightmost_branch(handle, et);
                if (status) {
                        mlog_errno(status);
                        goto bail;
                }
        }

        /* allocate the number of new eb blocks we need */
        new_eb_bhs = kcalloc(new_blocks, sizeof(struct buffer_head *),
                             GFP_KERNEL);
        if (!new_eb_bhs) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        /* Firstyly, try to reuse dealloc since we have already estimated how
         * many extent blocks we may use.
         */
        if (!ocfs2_is_dealloc_empty(et)) {
                status = ocfs2_reuse_blk_from_dealloc(handle, et,
                                                      new_eb_bhs, new_blocks,
                                                      &block_given);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
        }

        BUG_ON(block_given > new_blocks);

        if (block_given < new_blocks) {
                BUG_ON(!meta_ac);
                status = ocfs2_create_new_meta_bhs(handle, et,
                                                   new_blocks - block_given,
                                                   meta_ac,
                                                   &new_eb_bhs[block_given]);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
        }

        /* Note: new_eb_bhs[new_blocks - 1] is the guy which will be
         * linked with the rest of the tree.
         * conversly, new_eb_bhs[0] is the new bottommost leaf.
         *
         * when we leave the loop, new_last_eb_blk will point to the
         * newest leaf, and next_blkno will point to the topmost extent
         * block. */
        next_blkno = new_last_eb_blk = 0;
        for(i = 0; i < new_blocks; i++) {
                bh = new_eb_bhs[i];
                eb = (struct ocfs2_extent_block *) bh->b_data;
                /* ocfs2_create_new_meta_bhs() should create it right! */
                BUG_ON(!OCFS2_IS_VALID_EXTENT_BLOCK(eb));
                eb_el = &eb->h_list;

                status = ocfs2_journal_access_eb(handle, et->et_ci, bh,
                                                 OCFS2_JOURNAL_ACCESS_CREATE);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

                eb->h_next_leaf_blk = 0;
                eb_el->l_tree_depth = cpu_to_le16(i);
                eb_el->l_next_free_rec = cpu_to_le16(1);
                /*
                 * This actually counts as an empty extent as
                 * c_clusters == 0
                 */
                eb_el->l_recs[0].e_cpos = cpu_to_le32(new_cpos);
                eb_el->l_recs[0].e_blkno = cpu_to_le64(next_blkno);
                /*
                 * eb_el isn't always an interior node, but even leaf
                 * nodes want a zero'd flags and reserved field so
                 * this gets the whole 32 bits regardless of use.
                 */
                eb_el->l_recs[0].e_int_clusters = cpu_to_le32(0);
                if (!eb_el->l_tree_depth)
                        new_last_eb_blk = le64_to_cpu(eb->h_blkno);

                ocfs2_journal_dirty(handle, bh);
                next_blkno = le64_to_cpu(eb->h_blkno);
        }

        /* This is a bit hairy. We want to update up to three blocks
         * here without leaving any of them in an inconsistent state
         * in case of error. We don't have to worry about
         * journal_dirty erroring as it won't unless we've aborted the
         * handle (in which case we would never be here) so reserving
         * the write with journal_access is all we need to do. */
        status = ocfs2_journal_access_eb(handle, et->et_ci, *last_eb_bh,
                                         OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }
        status = ocfs2_et_root_journal_access(handle, et,
                                              OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }
        if (eb_bh) {
                status = ocfs2_journal_access_eb(handle, et->et_ci, eb_bh,
                                                 OCFS2_JOURNAL_ACCESS_WRITE);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
        }

        /* Link the new branch into the rest of the tree (el will
         * either be on the root_bh, or the extent block passed in. */
        i = le16_to_cpu(el->l_next_free_rec);
        el->l_recs[i].e_blkno = cpu_to_le64(next_blkno);
        el->l_recs[i].e_cpos = cpu_to_le32(new_cpos);
        el->l_recs[i].e_int_clusters = 0;
        le16_add_cpu(&el->l_next_free_rec, 1);

        /* fe needs a new last extent block pointer, as does the
         * next_leaf on the previously last-extent-block. */
        ocfs2_et_set_last_eb_blk(et, new_last_eb_blk);

        eb = (struct ocfs2_extent_block *) (*last_eb_bh)->b_data;
        eb->h_next_leaf_blk = cpu_to_le64(new_last_eb_blk);

        ocfs2_journal_dirty(handle, *last_eb_bh);
        ocfs2_journal_dirty(handle, et->et_root_bh);
        if (eb_bh)
                ocfs2_journal_dirty(handle, eb_bh);

        /*
         * Some callers want to track the rightmost leaf so pass it
         * back here.
         */
        brelse(*last_eb_bh);
        get_bh(new_eb_bhs[0]);
        *last_eb_bh = new_eb_bhs[0];

        status = 0;
bail:
        if (new_eb_bhs) {
                for (i = 0; i < new_blocks; i++)
                        brelse(new_eb_bhs[i]);
                kfree(new_eb_bhs);
        }

        return status;
}

/*
 * adds another level to the allocation tree.
 * returns back the new extent block so you can add a branch to it
 * after this call.
 */
static int ocfs2_shift_tree_depth(handle_t *handle,
                                  struct ocfs2_extent_tree *et,
                                  struct ocfs2_alloc_context *meta_ac,
                                  struct buffer_head **ret_new_eb_bh)
{
        int status, i, block_given = 0;
        u32 new_clusters;
        struct buffer_head *new_eb_bh = NULL;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list  *root_el;
        struct ocfs2_extent_list  *eb_el;

        if (!ocfs2_is_dealloc_empty(et)) {
                status = ocfs2_reuse_blk_from_dealloc(handle, et,
                                                      &new_eb_bh, 1,
                                                      &block_given);
        } else if (meta_ac) {
                status = ocfs2_create_new_meta_bhs(handle, et, 1, meta_ac,
                                                   &new_eb_bh);

        } else {
                BUG();
        }

        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        eb = (struct ocfs2_extent_block *) new_eb_bh->b_data;
        /* ocfs2_create_new_meta_bhs() should create it right! */
        BUG_ON(!OCFS2_IS_VALID_EXTENT_BLOCK(eb));

        eb_el = &eb->h_list;
        root_el = et->et_root_el;

        status = ocfs2_journal_access_eb(handle, et->et_ci, new_eb_bh,
                                         OCFS2_JOURNAL_ACCESS_CREATE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        /* copy the root extent list data into the new extent block */
        eb_el->l_tree_depth = root_el->l_tree_depth;
        eb_el->l_next_free_rec = root_el->l_next_free_rec;
        for (i = 0; i < le16_to_cpu(root_el->l_next_free_rec); i++)
                eb_el->l_recs[i] = root_el->l_recs[i];

        ocfs2_journal_dirty(handle, new_eb_bh);

        status = ocfs2_et_root_journal_access(handle, et,
                                              OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        new_clusters = ocfs2_sum_rightmost_rec(eb_el);

        /* update root_bh now */
        le16_add_cpu(&root_el->l_tree_depth, 1);
        root_el->l_recs[0].e_cpos = 0;
        root_el->l_recs[0].e_blkno = eb->h_blkno;
        root_el->l_recs[0].e_int_clusters = cpu_to_le32(new_clusters);
        for (i = 1; i < le16_to_cpu(root_el->l_next_free_rec); i++)
                memset(&root_el->l_recs[i], 0, sizeof(struct ocfs2_extent_rec));
        root_el->l_next_free_rec = cpu_to_le16(1);

        /* If this is our 1st tree depth shift, then last_eb_blk
         * becomes the allocated extent block */
        if (root_el->l_tree_depth == cpu_to_le16(1))
                ocfs2_et_set_last_eb_blk(et, le64_to_cpu(eb->h_blkno));

        ocfs2_journal_dirty(handle, et->et_root_bh);

        *ret_new_eb_bh = new_eb_bh;
        new_eb_bh = NULL;
        status = 0;
bail:
        brelse(new_eb_bh);

        return status;
}

/*
 * Should only be called when there is no space left in any of the
 * leaf nodes. What we want to do is find the lowest tree depth
 * non-leaf extent block with room for new records. There are three
 * valid results of this search:
 *
 * 1) a lowest extent block is found, then we pass it back in
 *    *lowest_eb_bh and return '0'
 *
 * 2) the search fails to find anything, but the root_el has room. We
 *    pass NULL back in *lowest_eb_bh, but still return '0'
 *
 * 3) the search fails to find anything AND the root_el is full, in
 *    which case we return > 0
 *
 * return status < 0 indicates an error.
 */
static int ocfs2_find_branch_target(struct ocfs2_extent_tree *et,
                                    struct buffer_head **target_bh)
{
        int status = 0, i;
        u64 blkno;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list  *el;
        struct buffer_head *bh = NULL;
        struct buffer_head *lowest_bh = NULL;

        *target_bh = NULL;

        el = et->et_root_el;

        while(le16_to_cpu(el->l_tree_depth) > 1) {
                if (le16_to_cpu(el->l_next_free_rec) == 0) {
                        status = ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                                        "Owner %llu has empty extent list (next_free_rec == 0)\n",
                                        (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci));
                        goto bail;
                }
                i = le16_to_cpu(el->l_next_free_rec) - 1;
                blkno = le64_to_cpu(el->l_recs[i].e_blkno);
                if (!blkno) {
                        status = ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                                        "Owner %llu has extent list where extent # %d has no physical block start\n",
                                        (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci), i);
                        goto bail;
                }

                brelse(bh);
                bh = NULL;

                status = ocfs2_read_extent_block(et->et_ci, blkno, &bh);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

                eb = (struct ocfs2_extent_block *) bh->b_data;
                el = &eb->h_list;

                if (le16_to_cpu(el->l_next_free_rec) <
                    le16_to_cpu(el->l_count)) {
                        brelse(lowest_bh);
                        lowest_bh = bh;
                        get_bh(lowest_bh);
                }
        }

        /* If we didn't find one and the fe doesn't have any room,
         * then return '1' */
        el = et->et_root_el;
        if (!lowest_bh && (el->l_next_free_rec == el->l_count))
                status = 1;

        *target_bh = lowest_bh;
bail:
        brelse(bh);

        return status;
}

/*
 * Grow a b-tree so that it has more records.
 *
 * We might shift the tree depth in which case existing paths should
 * be considered invalid.
 *
 * Tree depth after the grow is returned via *final_depth.
 *
 * *last_eb_bh will be updated by ocfs2_add_branch().
 */
static int ocfs2_grow_tree(handle_t *handle, struct ocfs2_extent_tree *et,
                           int *final_depth, struct buffer_head **last_eb_bh,
                           struct ocfs2_alloc_context *meta_ac)
{
        int ret, shift;
        struct ocfs2_extent_list *el = et->et_root_el;
        int depth = le16_to_cpu(el->l_tree_depth);
        struct buffer_head *bh = NULL;

        BUG_ON(meta_ac == NULL && ocfs2_is_dealloc_empty(et));

        shift = ocfs2_find_branch_target(et, &bh);
        if (shift < 0) {
                ret = shift;
                mlog_errno(ret);
                goto out;
        }

        /* We traveled all the way to the bottom of the allocation tree
         * and didn't find room for any more extents - we need to add
         * another tree level */
        if (shift) {
                BUG_ON(bh);
                trace_ocfs2_grow_tree(
                        (unsigned long long)
                        ocfs2_metadata_cache_owner(et->et_ci),
                        depth);

                /* ocfs2_shift_tree_depth will return us a buffer with
                 * the new extent block (so we can pass that to
                 * ocfs2_add_branch). */
                ret = ocfs2_shift_tree_depth(handle, et, meta_ac, &bh);
                if (ret < 0) {
                        mlog_errno(ret);
                        goto out;
                }
                depth++;
                if (depth == 1) {
                        /*
                         * Special case: we have room now if we shifted from
                         * tree_depth 0, so no more work needs to be done.
                         *
                         * We won't be calling add_branch, so pass
                         * back *last_eb_bh as the new leaf. At depth
                         * zero, it should always be null so there's
                         * no reason to brelse.
                         */
                        BUG_ON(*last_eb_bh);
                        get_bh(bh);
                        *last_eb_bh = bh;
                        goto out;
                }
        }

        /* call ocfs2_add_branch to add the final part of the tree with
         * the new data. */
        ret = ocfs2_add_branch(handle, et, bh, last_eb_bh,
                               meta_ac);
        if (ret < 0)
                mlog_errno(ret);

out:
        if (final_depth)
                *final_depth = depth;
        brelse(bh);
        return ret;
}

/*
 * This function will discard the rightmost extent record.
 */
static void ocfs2_shift_records_right(struct ocfs2_extent_list *el)
{
        int next_free = le16_to_cpu(el->l_next_free_rec);
        int count = le16_to_cpu(el->l_count);
        unsigned int num_bytes;

        BUG_ON(!next_free);
        /* This will cause us to go off the end of our extent list. */
        BUG_ON(next_free >= count);

        num_bytes = sizeof(struct ocfs2_extent_rec) * next_free;

        memmove(&el->l_recs[1], &el->l_recs[0], num_bytes);
}

static void ocfs2_rotate_leaf(struct ocfs2_extent_list *el,
                              struct ocfs2_extent_rec *insert_rec)
{
        int i, insert_index, next_free, has_empty, num_bytes;
        u32 insert_cpos = le32_to_cpu(insert_rec->e_cpos);
        struct ocfs2_extent_rec *rec;

        next_free = le16_to_cpu(el->l_next_free_rec);
        has_empty = ocfs2_is_empty_extent(&el->l_recs[0]);

        BUG_ON(!next_free);

        /* The tree code before us didn't allow enough room in the leaf. */
        BUG_ON(el->l_next_free_rec == el->l_count && !has_empty);

        /*
         * The easiest way to approach this is to just remove the
         * empty extent and temporarily decrement next_free.
         */
        if (has_empty) {
                /*
                 * If next_free was 1 (only an empty extent), this
                 * loop won't execute, which is fine. We still want
                 * the decrement above to happen.
                 */
                for(i = 0; i < (next_free - 1); i++)
                        el->l_recs[i] = el->l_recs[i+1];

                next_free--;
        }

        /*
         * Figure out what the new record index should be.
         */
        for(i = 0; i < next_free; i++) {
                rec = &el->l_recs[i];

                if (insert_cpos < le32_to_cpu(rec->e_cpos))
                        break;
        }
        insert_index = i;

        trace_ocfs2_rotate_leaf(insert_cpos, insert_index,
                                has_empty, next_free,
                                le16_to_cpu(el->l_count));

        BUG_ON(insert_index < 0);
        BUG_ON(insert_index >= le16_to_cpu(el->l_count));
        BUG_ON(insert_index > next_free);

        /*
         * No need to memmove if we're just adding to the tail.
         */
        if (insert_index != next_free) {
                BUG_ON(next_free >= le16_to_cpu(el->l_count));

                num_bytes = next_free - insert_index;
                num_bytes *= sizeof(struct ocfs2_extent_rec);
                memmove(&el->l_recs[insert_index + 1],
                        &el->l_recs[insert_index],
                        num_bytes);
        }

        /*
         * Either we had an empty extent, and need to re-increment or
         * there was no empty extent on a non full rightmost leaf node,
         * in which case we still need to increment.
         */
        next_free++;
        el->l_next_free_rec = cpu_to_le16(next_free);
        /*
         * Make sure none of the math above just messed up our tree.
         */
        BUG_ON(le16_to_cpu(el->l_next_free_rec) > le16_to_cpu(el->l_count));

        el->l_recs[insert_index] = *insert_rec;

}

static void ocfs2_remove_empty_extent(struct ocfs2_extent_list *el)
{
        int size, num_recs = le16_to_cpu(el->l_next_free_rec);

        BUG_ON(num_recs == 0);

        if (ocfs2_is_empty_extent(&el->l_recs[0])) {
                num_recs--;
                size = num_recs * sizeof(struct ocfs2_extent_rec);
                memmove(&el->l_recs[0], &el->l_recs[1], size);
                memset(&el->l_recs[num_recs], 0,
                       sizeof(struct ocfs2_extent_rec));
                el->l_next_free_rec = cpu_to_le16(num_recs);
        }
}

/*
 * Create an empty extent record .
 *
 * l_next_free_rec may be updated.
 *
 * If an empty extent already exists do nothing.
 */
static void ocfs2_create_empty_extent(struct ocfs2_extent_list *el)
{
        int next_free = le16_to_cpu(el->l_next_free_rec);

        BUG_ON(le16_to_cpu(el->l_tree_depth) != 0);

        if (next_free == 0)
                goto set_and_inc;

        if (ocfs2_is_empty_extent(&el->l_recs[0]))
                return;

        mlog_bug_on_msg(el->l_count == el->l_next_free_rec,
                        "Asked to create an empty extent in a full list:\n"
                        "count = %u, tree depth = %u",
                        le16_to_cpu(el->l_count),
                        le16_to_cpu(el->l_tree_depth));

        ocfs2_shift_records_right(el);

set_and_inc:
        le16_add_cpu(&el->l_next_free_rec, 1);
        memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
}

/*
 * For a rotation which involves two leaf nodes, the "root node" is
 * the lowest level tree node which contains a path to both leafs. This
 * resulting set of information can be used to form a complete "subtree"
 *
 * This function is passed two full paths from the dinode down to a
 * pair of adjacent leaves. It's task is to figure out which path
 * index contains the subtree root - this can be the root index itself
 * in a worst-case rotation.
 *
 * The array index of the subtree root is passed back.
 */
int ocfs2_find_subtree_root(struct ocfs2_extent_tree *et,
                            struct ocfs2_path *left,
                            struct ocfs2_path *right)
{
        int i = 0;

        /*
         * Check that the caller passed in two paths from the same tree.
         */
        BUG_ON(path_root_bh(left) != path_root_bh(right));

        do {
                i++;

                /*
                 * The caller didn't pass two adjacent paths.
                 */
                mlog_bug_on_msg(i > left->p_tree_depth,
                                "Owner %llu, left depth %u, right depth %u\n"
                                "left leaf blk %llu, right leaf blk %llu\n",
                                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                                left->p_tree_depth, right->p_tree_depth,
                                (unsigned long long)path_leaf_bh(left)->b_blocknr,
                                (unsigned long long)path_leaf_bh(right)->b_blocknr);
        } while (left->p_node[i].bh->b_blocknr ==
                 right->p_node[i].bh->b_blocknr);

        return i - 1;
}

typedef void (path_insert_t)(void *, struct buffer_head *);

/*
 * Traverse a btree path in search of cpos, starting at root_el.
 *
 * This code can be called with a cpos larger than the tree, in which
 * case it will return the rightmost path.
 */
static int __ocfs2_find_path(struct ocfs2_caching_info *ci,
                             struct ocfs2_extent_list *root_el, u32 cpos,
                             path_insert_t *func, void *data)
{
        int i, ret = 0;
        u32 range;
        u64 blkno;
        struct buffer_head *bh = NULL;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_rec *rec;

        el = root_el;
        while (el->l_tree_depth) {
                if (le16_to_cpu(el->l_next_free_rec) == 0) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                                    "Owner %llu has empty extent list at depth %u\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                                    le16_to_cpu(el->l_tree_depth));
                        ret = -EROFS;
                        goto out;

                }

                for(i = 0; i < le16_to_cpu(el->l_next_free_rec) - 1; i++) {
                        rec = &el->l_recs[i];

                        /*
                         * In the case that cpos is off the allocation
                         * tree, this should just wind up returning the
                         * rightmost record.
                         */
                        range = le32_to_cpu(rec->e_cpos) +
                                ocfs2_rec_clusters(el, rec);
                        if (cpos >= le32_to_cpu(rec->e_cpos) && cpos < range)
                            break;
                }

                blkno = le64_to_cpu(el->l_recs[i].e_blkno);
                if (blkno == 0) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                                    "Owner %llu has bad blkno in extent list at depth %u (index %d)\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                                    le16_to_cpu(el->l_tree_depth), i);
                        ret = -EROFS;
                        goto out;
                }

                brelse(bh);
                bh = NULL;
                ret = ocfs2_read_extent_block(ci, blkno, &bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                eb = (struct ocfs2_extent_block *) bh->b_data;
                el = &eb->h_list;

                if (le16_to_cpu(el->l_next_free_rec) >
                    le16_to_cpu(el->l_count)) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                                    "Owner %llu has bad count in extent list at block %llu (next free=%u, count=%u)\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                                    (unsigned long long)bh->b_blocknr,
                                    le16_to_cpu(el->l_next_free_rec),
                                    le16_to_cpu(el->l_count));
                        ret = -EROFS;
                        goto out;
                }

                if (func)
                        func(data, bh);
        }

out:
        /*
         * Catch any trailing bh that the loop didn't handle.
         */
        brelse(bh);

        return ret;
}

/*
 * Given an initialized path (that is, it has a valid root extent
 * list), this function will traverse the btree in search of the path
 * which would contain cpos.
 *
 * The path traveled is recorded in the path structure.
 *
 * Note that this will not do any comparisons on leaf node extent
 * records, so it will work fine in the case that we just added a tree
 * branch.
 */
struct find_path_data {
        int index;
        struct ocfs2_path *path;
};
static void find_path_ins(void *data, struct buffer_head *bh)
{
        struct find_path_data *fp = data;

        get_bh(bh);
        ocfs2_path_insert_eb(fp->path, fp->index, bh);
        fp->index++;
}
int ocfs2_find_path(struct ocfs2_caching_info *ci,
                    struct ocfs2_path *path, u32 cpos)
{
        struct find_path_data data;

        data.index = 1;
        data.path = path;
        return __ocfs2_find_path(ci, path_root_el(path), cpos,
                                 find_path_ins, &data);
}

static void find_leaf_ins(void *data, struct buffer_head *bh)
{
        struct ocfs2_extent_block *eb =(struct ocfs2_extent_block *)bh->b_data;
        struct ocfs2_extent_list *el = &eb->h_list;
        struct buffer_head **ret = data;

        /* We want to retain only the leaf block. */
        if (le16_to_cpu(el->l_tree_depth) == 0) {
                get_bh(bh);
                *ret = bh;
        }
}
/*
 * Find the leaf block in the tree which would contain cpos. No
 * checking of the actual leaf is done.
 *
 * Some paths want to call this instead of allocating a path structure
 * and calling ocfs2_find_path().
 *
 * This function doesn't handle non btree extent lists.
 */
int ocfs2_find_leaf(struct ocfs2_caching_info *ci,
                    struct ocfs2_extent_list *root_el, u32 cpos,
                    struct buffer_head **leaf_bh)
{
        int ret;
        struct buffer_head *bh = NULL;

        ret = __ocfs2_find_path(ci, root_el, cpos, find_leaf_ins, &bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        *leaf_bh = bh;
out:
        return ret;
}

/*
 * Adjust the adjacent records (left_rec, right_rec) involved in a rotation.
 *
 * Basically, we've moved stuff around at the bottom of the tree and
 * we need to fix up the extent records above the changes to reflect
 * the new changes.
 *
 * left_rec: the record on the left.
 * right_rec: the record to the right of left_rec
 * right_child_el: is the child list pointed to by right_rec
 *
 * By definition, this only works on interior nodes.
 */
static void ocfs2_adjust_adjacent_records(struct ocfs2_extent_rec *left_rec,
                                  struct ocfs2_extent_rec *right_rec,
                                  struct ocfs2_extent_list *right_child_el)
{
        u32 left_clusters, right_end;

        /*
         * Interior nodes never have holes. Their cpos is the cpos of
         * the leftmost record in their child list. Their cluster
         * count covers the full theoretical range of their child list
         * - the range between their cpos and the cpos of the record
         * immediately to their right.
         */
        left_clusters = le32_to_cpu(right_child_el->l_recs[0].e_cpos);
        if (!ocfs2_rec_clusters(right_child_el, &right_child_el->l_recs[0])) {
                BUG_ON(right_child_el->l_tree_depth);
                BUG_ON(le16_to_cpu(right_child_el->l_next_free_rec) <= 1);
                left_clusters = le32_to_cpu(right_child_el->l_recs[1].e_cpos);
        }
        left_clusters -= le32_to_cpu(left_rec->e_cpos);
        left_rec->e_int_clusters = cpu_to_le32(left_clusters);

        /*
         * Calculate the rightmost cluster count boundary before
         * moving cpos - we will need to adjust clusters after
         * updating e_cpos to keep the same highest cluster count.
         */
        right_end = le32_to_cpu(right_rec->e_cpos);
        right_end += le32_to_cpu(right_rec->e_int_clusters);

        right_rec->e_cpos = left_rec->e_cpos;
        le32_add_cpu(&right_rec->e_cpos, left_clusters);

        right_end -= le32_to_cpu(right_rec->e_cpos);
        right_rec->e_int_clusters = cpu_to_le32(right_end);
}

/*
 * Adjust the adjacent root node records involved in a
 * rotation. left_el_blkno is passed in as a key so that we can easily
 * find it's index in the root list.
 */
static void ocfs2_adjust_root_records(struct ocfs2_extent_list *root_el,
                                      struct ocfs2_extent_list *left_el,
                                      struct ocfs2_extent_list *right_el,
                                      u64 left_el_blkno)