// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2014 Facebook.  All rights reserved.
 */

#include <linux/sched.h>
#include <linux/stacktrace.h>
#include "ctree.h"
#include "disk-io.h"
#include "locking.h"
#include "delayed-ref.h"
#include "ref-verify.h"

/*
 * Used to keep track the roots and number of refs each root has for a given
 * bytenr.  This just tracks the number of direct references, no shared
 * references.
 */
struct root_entry {
        u64 root_objectid;
        u64 num_refs;
        struct rb_node node;
};

/*
 * These are meant to represent what should exist in the extent tree, these can
 * be used to verify the extent tree is consistent as these should all match
 * what the extent tree says.
 */
struct ref_entry {
        u64 root_objectid;
        u64 parent;
        u64 owner;
        u64 offset;
        u64 num_refs;
        struct rb_node node;
};

#define MAX_TRACE       16

/*
 * Whenever we add/remove a reference we record the action.  The action maps
 * back to the delayed ref action.  We hold the ref we are changing in the
 * action so we can account for the history properly, and we record the root we
 * were called with since it could be different from ref_root.  We also store
 * stack traces because that's how I roll.
 */
struct ref_action {
        int action;
        u64 root;
        struct ref_entry ref;
        struct list_head list;
        unsigned long trace[MAX_TRACE];
        unsigned int trace_len;
};

/*
 * One of these for every block we reference, it holds the roots and references
 * to it as well as all of the ref actions that have occurred to it.  We never
 * free it until we unmount the file system in order to make sure re-allocations
 * are happening properly.
 */
struct block_entry {
        u64 bytenr;
        u64 len;
        u64 num_refs;
        int metadata;
        int from_disk;
        struct rb_root roots;
        struct rb_root refs;
        struct rb_node node;
        struct list_head actions;
};

static struct block_entry *insert_block_entry(struct rb_root *root,
                                              struct block_entry *be)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent_node = NULL;
        struct block_entry *entry;

        while (*p) {
                parent_node = *p;
                entry = rb_entry(parent_node, struct block_entry, node);
                if (entry->bytenr > be->bytenr)
                        p = &(*p)->rb_left;
                else if (entry->bytenr < be->bytenr)
                        p = &(*p)->rb_right;
                else
                        return entry;
        }

        rb_link_node(&be->node, parent_node, p);
        rb_insert_color(&be->node, root);
        return NULL;
}

static struct block_entry *lookup_block_entry(struct rb_root *root, u64 bytenr)
{
        struct rb_node *n;
        struct block_entry *entry = NULL;

        n = root->rb_node;
        while (n) {
                entry = rb_entry(n, struct block_entry, node);
                if (entry->bytenr < bytenr)
                        n = n->rb_right;
                else if (entry->bytenr > bytenr)
                        n = n->rb_left;
                else
                        return entry;
        }
        return NULL;
}

static struct root_entry *insert_root_entry(struct rb_root *root,
                                            struct root_entry *re)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent_node = NULL;
        struct root_entry *entry;

        while (*p) {
                parent_node = *p;
                entry = rb_entry(parent_node, struct root_entry, node);
                if (entry->root_objectid > re->root_objectid)
                        p = &(*p)->rb_left;
                else if (entry->root_objectid < re->root_objectid)
                        p = &(*p)->rb_right;
                else
                        return entry;
        }

        rb_link_node(&re->node, parent_node, p);
        rb_insert_color(&re->node, root);
        return NULL;

}

static int comp_refs(struct ref_entry *ref1, struct ref_entry *ref2)
{
        if (ref1->root_objectid < ref2->root_objectid)
                return -1;
        if (ref1->root_objectid > ref2->root_objectid)
                return 1;
        if (ref1->parent < ref2->parent)
                return -1;
        if (ref1->parent > ref2->parent)
                return 1;
        if (ref1->owner < ref2->owner)
                return -1;
        if (ref1->owner > ref2->owner)
                return 1;
        if (ref1->offset < ref2->offset)
                return -1;
        if (ref1->offset > ref2->offset)
                return 1;
        return 0;
}

static struct ref_entry *insert_ref_entry(struct rb_root *root,
                                          struct ref_entry *ref)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent_node = NULL;
        struct ref_entry *entry;
        int cmp;

        while (*p) {
                parent_node = *p;
                entry = rb_entry(parent_node, struct ref_entry, node);
                cmp = comp_refs(entry, ref);
                if (cmp > 0)
                        p = &(*p)->rb_left;
                else if (cmp < 0)
                        p = &(*p)->rb_right;
                else
                        return entry;
        }

        rb_link_node(&ref->node, parent_node, p);
        rb_insert_color(&ref->node, root);
        return NULL;

}

static struct root_entry *lookup_root_entry(struct rb_root *root, u64 objectid)
{
        struct rb_node *n;
        struct root_entry *entry = NULL;

        n = root->rb_node;
        while (n) {
                entry = rb_entry(n, struct root_entry, node);
                if (entry->root_objectid < objectid)
                        n = n->rb_right;
                else if (entry->root_objectid > objectid)
                        n = n->rb_left;
                else
                        return entry;
        }
        return NULL;
}

#ifdef CONFIG_STACKTRACE
static void __save_stack_trace(struct ref_action *ra)
{
        ra->trace_len = stack_trace_save(ra->trace, MAX_TRACE, 2);
}

static void __print_stack_trace(struct btrfs_fs_info *fs_info,
                                struct ref_action *ra)
{
        if (ra->trace_len == 0) {
                btrfs_err(fs_info, "  ref-verify: no stacktrace");
                return;
        }
        stack_trace_print(ra->trace, ra->trace_len, 2);
}
#else
static void inline __save_stack_trace(struct ref_action *ra)
{
}

static void inline __print_stack_trace(struct btrfs_fs_info *fs_info,
                                       struct ref_action *ra)
{
        btrfs_err(fs_info, "  ref-verify: no stacktrace support");
}
#endif

static void free_block_entry(struct block_entry *be)
{
        struct root_entry *re;
        struct ref_entry *ref;
        struct ref_action *ra;
        struct rb_node *n;

        while ((n = rb_first(&be->roots))) {
                re = rb_entry(n, struct root_entry, node);
                rb_erase(&re->node, &be->roots);
                kfree(re);
        }

        while((n = rb_first(&be->refs))) {
                ref = rb_entry(n, struct ref_entry, node);
                rb_erase(&ref->node, &be->refs);
                kfree(ref);
        }

        while (!list_empty(&be->actions)) {
                ra = list_first_entry(&be->actions, struct ref_action,
                                      list);
                list_del(&ra->list);
                kfree(ra);
        }
        kfree(be);
}

static struct block_entry *add_block_entry(struct btrfs_fs_info *fs_info,
                                           u64 bytenr, u64 len,
                                           u64 root_objectid)
{
        struct block_entry *be = NULL, *exist;
        struct root_entry *re = NULL;

        re = kzalloc(sizeof(struct root_entry), GFP_KERNEL);
        be = kzalloc(sizeof(struct block_entry), GFP_KERNEL);
        if (!be || !re) {
                kfree(re);
                kfree(be);
                return ERR_PTR(-ENOMEM);
        }
        be->bytenr = bytenr;
        be->len = len;

        re->root_objectid = root_objectid;
        re->num_refs = 0;

        spin_lock(&fs_info->ref_verify_lock);
        exist = insert_block_entry(&fs_info->block_tree, be);
        if (exist) {
                if (root_objectid) {
                        struct root_entry *exist_re;

                        exist_re = insert_root_entry(&exist->roots, re);
                        if (exist_re)
                                kfree(re);
                }
                kfree(be);
                return exist;
        }

        be->num_refs = 0;
        be->metadata = 0;
        be->from_disk = 0;
        be->roots = RB_ROOT;
        be->refs = RB_ROOT;
        INIT_LIST_HEAD(&be->actions);
        if (root_objectid)
                insert_root_entry(&be->roots, re);
        else
                kfree(re);
        return be;
}

static int add_tree_block(struct btrfs_fs_info *fs_info, u64 ref_root,
                          u64 parent, u64 bytenr, int level)
{
        struct block_entry *be;
        struct root_entry *re;
        struct ref_entry *ref = NULL, *exist;

        ref = kmalloc(sizeof(struct ref_entry), GFP_KERNEL);
        if (!ref)
                return -ENOMEM;

        if (parent)
                ref->root_objectid = 0;
        else
                ref->root_objectid = ref_root;
        ref->parent = parent;
        ref->owner = level;
        ref->offset = 0;
        ref->num_refs = 1;

        be = add_block_entry(fs_info, bytenr, fs_info->nodesize, ref_root);
        if (IS_ERR(be)) {
                kfree(ref);
                return PTR_ERR(be);
        }
        be->num_refs++;
        be->from_disk = 1;
        be->metadata = 1;

        if (!parent) {
                ASSERT(ref_root);
                re = lookup_root_entry(&be->roots, ref_root);
                ASSERT(re);
                re->num_refs++;
        }
        exist = insert_ref_entry(&be->refs, ref);
        if (exist) {
                exist->num_refs++;
                kfree(ref);
        }
        spin_unlock(&fs_info->ref_verify_lock);

        return 0;
}

static int add_shared_data_ref(struct btrfs_fs_info *fs_info,
                               u64 parent, u32 num_refs, u64 bytenr,
                               u64 num_bytes)
{
        struct block_entry *be;
        struct ref_entry *ref;

        ref = kzalloc(sizeof(struct ref_entry), GFP_KERNEL);
        if (!ref)
                return -ENOMEM;
        be = add_block_entry(fs_info, bytenr, num_bytes, 0);
        if (IS_ERR(be)) {
                kfree(ref);
                return PTR_ERR(be);
        }
        be->num_refs += num_refs;

        ref->parent = parent;
        ref->num_refs = num_refs;
        if (insert_ref_entry(&be->refs, ref)) {
                spin_unlock(&fs_info->ref_verify_lock);
                btrfs_err(fs_info, "existing shared ref when reading from disk?");
                kfree(ref);
                return -EINVAL;
        }
        spin_unlock(&fs_info->ref_verify_lock);
        return 0;
}

static int add_extent_data_ref(struct btrfs_fs_info *fs_info,
                               struct extent_buffer *leaf,
                               struct btrfs_extent_data_ref *dref,
                               u64 bytenr, u64 num_bytes)
{
        struct block_entry *be;
        struct ref_entry *ref;
        struct root_entry *re;
        u64 ref_root = btrfs_extent_data_ref_root(leaf, dref);
        u64 owner = btrfs_extent_data_ref_objectid(leaf, dref);
        u64 offset = btrfs_extent_data_ref_offset(leaf, dref);
        u32 num_refs = btrfs_extent_data_ref_count(leaf, dref);

        ref = kzalloc(sizeof(struct ref_entry), GFP_KERNEL);
        if (!ref)
                return -ENOMEM;
        be = add_block_entry(fs_info, bytenr, num_bytes, ref_root);
        if (IS_ERR(be)) {
                kfree(ref);
                return PTR_ERR(be);
        }
        be->num_refs += num_refs;

        ref->parent = 0;
        ref->owner = owner;
        ref->root_objectid = ref_root;
        ref->offset = offset;
        ref->num_refs = num_refs;
        if (insert_ref_entry(&be->refs, ref)) {
                spin_unlock(&fs_info->ref_verify_lock);
                btrfs_err(fs_info, "existing ref when reading from disk?");
                kfree(ref);
                return -EINVAL;
        }

        re = lookup_root_entry(&be->roots, ref_root);
        if (!re) {
                spin_unlock(&fs_info->ref_verify_lock);
                btrfs_err(fs_info, "missing root in new block entry?");
                return -EINVAL;
        }
        re->num_refs += num_refs;
        spin_unlock(&fs_info->ref_verify_lock);
        return 0;
}

static int process_extent_item(struct btrfs_fs_info *fs_info,
                               struct btrfs_path *path, struct btrfs_key *key,
                               int slot, int *tree_block_level)
{
        struct btrfs_extent_item *ei;
        struct btrfs_extent_inline_ref *iref;
        struct btrfs_extent_data_ref *dref;
        struct btrfs_shared_data_ref *sref;
        struct extent_buffer *leaf = path->nodes[0];
        u32 item_size = btrfs_item_size_nr(leaf, slot);
        unsigned long end, ptr;
        u64 offset, flags, count;
        int type, ret;

        ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
        flags = btrfs_extent_flags(leaf, ei);

        if ((key->type == BTRFS_EXTENT_ITEM_KEY) &&
            flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
                struct btrfs_tree_block_info *info;

                info = (struct btrfs_tree_block_info *)(ei + 1);
                *tree_block_level = btrfs_tree_block_level(leaf, info);
                iref = (struct btrfs_extent_inline_ref *)(info + 1);
        } else {
                if (key->type == BTRFS_METADATA_ITEM_KEY)
                        *tree_block_level = key->offset;
                iref = (struct btrfs_extent_inline_ref *)(ei + 1);
        }

        ptr = (unsigned long)iref;
        end = (unsigned long)ei + item_size;
        while (ptr < end) {
                iref = (struct btrfs_extent_inline_ref *)ptr;
                type = btrfs_extent_inline_ref_type(leaf, iref);
                offset = btrfs_extent_inline_ref_offset(leaf, iref);
                switch (type) {
                case BTRFS_TREE_BLOCK_REF_KEY:
                        ret = add_tree_block(fs_info, offset, 0, key->objectid,
                                             *tree_block_level);
                        break;
                case BTRFS_SHARED_BLOCK_REF_KEY:
                        ret = add_tree_block(fs_info, 0, offset, key->objectid,
                                             *tree_block_level);
                        break;
                case BTRFS_EXTENT_DATA_REF_KEY:
                        dref = (struct btrfs_extent_data_ref *)(&iref->offset);
                        ret = add_extent_data_ref(fs_info, leaf, dref,
                                                  key->objectid, key->offset);
                        break;
                case BTRFS_SHARED_DATA_REF_KEY:
                        sref = (struct btrfs_shared_data_ref *)(iref + 1);
                        count = btrfs_shared_data_ref_count(leaf, sref);
                        ret = add_shared_data_ref(fs_info, offset, count,
                                                  key->objectid, key->offset);
                        break;
                default:
                        btrfs_err(fs_info, "invalid key type in iref");
                        ret = -EINVAL;
                        break;
                }
                if (ret)
                        break;
                ptr += btrfs_extent_inline_ref_size(type);
        }
        return ret;
}

static int process_leaf(struct btrfs_root *root,
                        struct btrfs_path *path, u64 *bytenr, u64 *num_bytes)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct extent_buffer *leaf = path->nodes[0];
        struct btrfs_extent_data_ref *dref;
        struct btrfs_shared_data_ref *sref;
        u32 count;
        int i = 0, tree_block_level = 0, ret;
        struct btrfs_key key;
        int nritems = btrfs_header_nritems(leaf);

        for (i = 0; i < nritems; i++) {
                btrfs_item_key_to_cpu(leaf, &key, i);
                switch (key.type) {
                case BTRFS_EXTENT_ITEM_KEY:
                        *num_bytes = key.offset;
                        /* fall through */
                case BTRFS_METADATA_ITEM_KEY:
                        *bytenr = key.objectid;
                        ret = process_extent_item(fs_info, path, &key, i,
                                                  &tree_block_level);
                        break;
                case BTRFS_TREE_BLOCK_REF_KEY:
                        ret = add_tree_block(fs_info, key.offset, 0,
                                             key.objectid, tree_block_level);
                        break;
                case BTRFS_SHARED_BLOCK_REF_KEY:
                        ret = add_tree_block(fs_info, 0, key.offset,
                                             key.objectid, tree_block_level);
                        break;
                case BTRFS_EXTENT_DATA_REF_KEY:
                        dref = btrfs_item_ptr(leaf, i,
                                              struct btrfs_extent_data_ref);
                        ret = add_extent_data_ref(fs_info, leaf, dref, *bytenr,
                                                  *num_bytes);
                        break;
                case BTRFS_SHARED_DATA_REF_KEY:
                        sref = btrfs_item_ptr(leaf, i,
                                              struct btrfs_shared_data_ref);
                        count = btrfs_shared_data_ref_count(leaf, sref);
                        ret = add_shared_data_ref(fs_info, key.offset, count,
                                                  *bytenr, *num_bytes);
                        break;
                default:
                        break;
                }
                if (ret)
                        break;
        }
        return ret;
}

/* Walk down to the leaf from the given level */
static int walk_down_tree(struct btrfs_root *root, struct btrfs_path *path,
                          int level, u64 *bytenr, u64 *num_bytes)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct extent_buffer *eb;
        u64 block_bytenr, gen;
        int ret = 0;

        while (level >= 0) {
                if (level) {
                        struct btrfs_key first_key;

                        block_bytenr = btrfs_node_blockptr(path->nodes[level],
                                                           path->slots[level]);
                        gen = btrfs_node_ptr_generation(path->nodes[level],
                                                        path->slots[level]);
                        btrfs_node_key_to_cpu(path->nodes[level], &first_key,
                                              path->slots[level]);
                        eb = read_tree_block(fs_info, block_bytenr, gen,
                                             level - 1, &first_key);
                        if (IS_ERR(eb))
                                return PTR_ERR(eb);
                        if (!extent_buffer_uptodate(eb)) {
                                free_extent_buffer(eb);
                                return -EIO;
                        }
                        btrfs_tree_read_lock(eb);
                        btrfs_set_lock_blocking_read(eb);
                        path->nodes[level-1] = eb;
                        path->slots[level-1] = 0;
                        path->locks[level-1] = BTRFS_READ_LOCK_BLOCKING;
                } else {
                        ret = process_leaf(root, path, bytenr, num_bytes);
                        if (ret)
                                break;
                }
                level--;
        }
        return ret;
}

/* Walk up to the next node that needs to be processed */
static int walk_up_tree(struct btrfs_path *path, int *level)
{
        int l;

        for (l = 0; l < BTRFS_MAX_LEVEL; l++) {
                if (!path->nodes[l])
                        continue;
                if (l) {
                        path->slots[l]++;
                        if (path->slots[l] <
                            btrfs_header_nritems(path->nodes[l])) {
                                *level = l;
                                return 0;
                        }
                }
                btrfs_tree_unlock_rw(path->nodes[l], path->locks[l]);
                free_extent_buffer(path->nodes[l]);
                path->nodes[l] = NULL;
                path->slots[l] = 0;
                path->locks[l] = 0;
        }

        return 1;
}

static void dump_ref_action(struct btrfs_fs_info *fs_info,
                            struct ref_action *ra)
{
        btrfs_err(fs_info,
"  Ref action %d, root %llu, ref_root %llu, parent %llu, owner %llu, offset %llu, num_refs %llu",
                  ra->action, ra->root, ra->ref.root_objectid, ra->ref.parent,
                  ra->ref.owner, ra->ref.offset, ra->ref.num_refs);
        __print_stack_trace(fs_info, ra);
}

/*
 * Dumps all the information from the block entry to printk, it's going to be
 * awesome.
 */
static void dump_block_entry(struct btrfs_fs_info *fs_info,
                             struct block_entry *be)
{
        struct ref_entry *ref;
        struct root_entry *re;
        struct ref_action *ra;
        struct rb_node *n;

        btrfs_err(fs_info,
"dumping block entry [%llu %llu], num_refs %llu, metadata %d, from disk %d",
                  be->bytenr, be->len, be->num_refs, be->metadata,
                  be->from_disk);

        for (n = rb_first(&be->refs); n; n = rb_next(n)) {
                ref = rb_entry(n, struct ref_entry, node);
                btrfs_err(fs_info,
"  ref root %llu, parent %llu, owner %llu, offset %llu, num_refs %llu",
                          ref->root_objectid, ref->parent, ref->owner,
                          ref->offset, ref->num_refs);
        }

        for (n = rb_first(&be->roots); n; n = rb_next(n)) {
                re = rb_entry(n, struct root_entry, node);
                btrfs_err(fs_info, "  root entry %llu, num_refs %llu",
                          re->root_objectid, re->num_refs);
        }

        list_for_each_entry(ra, &be->actions, list)
                dump_ref_action(fs_info, ra);
}

/*
 * btrfs_ref_tree_mod: called when we modify a ref for a bytenr
 *
 * This will add an action item to the given bytenr and do sanity checks to make
 * sure we haven't messed something up.  If we are making a new allocation and
 * this block entry has history we will delete all previous actions as long as
 * our sanity checks pass as they are no longer needed.
 */
int btrfs_ref_tree_mod(struct btrfs_fs_info *fs_info,
                       struct btrfs_ref *generic_ref)
{
        struct ref_entry *ref = NULL, *exist;
        struct ref_action *ra = NULL;
        struct block_entry *be = NULL;
        struct root_entry *re = NULL;
        int action = generic_ref->action;
        int ret = 0;
        bool metadata;
        u64 bytenr = generic_ref->bytenr;
        u64 num_bytes = generic_ref->len;
        u64 parent = generic_ref->parent;
        u64 ref_root;
        u64 owner;
        u64 offset;

        if (!btrfs_test_opt(fs_info, REF_VERIFY))
                return 0;

        if (generic_ref->type == BTRFS_REF_METADATA) {
                ref_root = generic_ref->tree_ref.root;
                owner = generic_ref->tree_ref.level;
                offset = 0;
        } else {
                ref_root = generic_ref->data_ref.ref_root;
                owner = generic_ref->data_ref.ino;
                offset = generic_ref->data_ref.offset;
        }
        metadata = owner < BTRFS_FIRST_FREE_OBJECTID;

        ref = kzalloc(sizeof(struct ref_entry), GFP_NOFS);
        ra = kmalloc(sizeof(struct ref_action), GFP_NOFS);
        if (!ra || !ref) {
                kfree(ref);
                kfree(ra);
                ret = -ENOMEM;
                goto out;
        }

        if (parent) {
                ref->parent = parent;
        } else {
                ref->root_objectid = ref_root;
                ref->owner = owner;
                ref->offset = offset;
        }
        ref->num_refs = (action == BTRFS_DROP_DELAYED_REF) ? -1 : 1;

        memcpy(&ra->ref, ref, sizeof(struct ref_entry));
        /*
         * Save the extra info from the delayed ref in the ref action to make it
         * easier to figure out what is happening.  The real ref's we add to the
         * ref tree need to reflect what we save on disk so it matches any
         * on-disk refs we pre-loaded.
         */
        ra->ref.owner = owner;
        ra->ref.offset = offset;
        ra->ref.root_objectid = ref_root;
        __save_stack_trace(ra);

        INIT_LIST_HEAD(&ra->list);
        ra->action = action;
        ra->root = generic_ref->real_root;

        /*
         * This is an allocation, preallocate the block_entry in case we haven't
         * used it before.
         */
        ret = -EINVAL;
        if (action == BTRFS_ADD_DELAYED_EXTENT) {
                /*
                 * For subvol_create we'll just pass in whatever the parent root
                 * is and the new root objectid, so let's not treat the passed
                 * in root as if it really has a ref for this bytenr.
                 */
                be = add_block_entry(fs_info, bytenr, num_bytes, ref_root);
                if (IS_ERR(be)) {
                        kfree(ra);
                        ret = PTR_ERR(be);
                        goto out;
                }
                be->num_refs++;
                if (metadata)
                        be->metadata = 1;

                if (be->num_refs != 1) {
                        btrfs_err(fs_info,
                        "re-allocated a block that still has references to it!");
                        dump_block_entry(fs_info, be);
                        dump_ref_action(fs_info, ra);
                        goto out_unlock;
                }

                while (!list_empty(&be->actions)) {
                        struct ref_action *tmp;

                        tmp = list_first_entry(&be->actions, struct ref_action,
                                               list);
                        list_del(&tmp->list);
                        kfree(tmp);
                }
        } else {
                struct root_entry *tmp;

                if (!parent) {
                        re = kmalloc(sizeof(struct root_entry), GFP_NOFS);
                        if (!re) {
                                kfree(ref);
                                kfree(ra);
                                ret = -ENOMEM;
                                goto out;
                        }
                        /*
                         * This is the root that is modifying us, so it's the
                         * one we want to lookup below when we modify the
                         * re->num_refs.
                         */
                        ref_root = generic_ref->real_root;
                        re->root_objectid = generic_ref->real_root;
                        re->num_refs = 0;
                }

                spin_lock(&fs_info->ref_verify_lock);
                be = lookup_block_entry(&fs_info->block_tree, bytenr);
                if (!be) {
                        btrfs_err(fs_info,
"trying to do action %d to bytenr %llu num_bytes %llu but there is no existing entry!",
                                  action, (unsigned long long)bytenr,
                                  (unsigned long long)num_bytes);
                        dump_ref_action(fs_info, ra);
                        kfree(ref);
                        kfree(ra);
                        goto out_unlock;
                }

                if (!parent) {
                        tmp = insert_root_entry(&be->roots, re);
                        if (tmp) {
                                kfree(re);
                                re = tmp;
                        }
                }
        }

        exist = insert_ref_entry(&be->refs, ref);
        if (exist) {
                if (action == BTRFS_DROP_DELAYED_REF) {
                        if (exist->num_refs == 0) {
                                btrfs_err(fs_info,
"dropping a ref for a existing root that doesn't have a ref on the block");
                                dump_block_entry(fs_info, be);
                                dump_ref_action(fs_info, ra);
                                kfree(ra);
                                goto out_unlock;
                        }
                        exist->num_refs--;
                        if (exist->num_refs == 0) {
                                rb_erase(&exist->node, &be->refs);
                                kfree(exist);
                        }
                } else if (!be->metadata) {
                        exist->num_refs++;
                } else {
                        btrfs_err(fs_info,
"attempting to add another ref for an existing ref on a tree block");
                        dump_block_entry(fs_info, be);
                        dump_ref_action(fs_info, ra);
                        kfree(ra);
                        goto out_unlock;
                }
                kfree(ref);
        } else {
                if (action == BTRFS_DROP_DELAYED_REF) {
                        btrfs_err(fs_info,
"dropping a ref for a root that doesn't have a ref on the block");
                        dump_block_entry(fs_info, be);
                        dump_ref_action(fs_info, ra);
                        kfree(ra);
                        goto out_unlock;
                }
        }

        if (!parent && !re) {
                re = lookup_root_entry(&be->roots, ref_root);
                if (!re) {
                        /*
                         * This shouldn't happen because we will add our re
                         * above when we lookup the be with !parent, but just in
                         * case catch this case so we don't panic because I
                         * didn't think of some other corner case.
                         */
                        btrfs_err(fs_info, "failed to find root %llu for %llu",
                                  generic_ref->real_root, be->bytenr);
                        dump_block_entry(fs_info, be);
                        dump_ref_action(fs_info, ra);
                        kfree(ra);
                        goto out_unlock;
                }
        }
        if (action == BTRFS_DROP_DELAYED_REF) {
                if (re)
                        re->num_refs--;
                be->num_refs--;
        } else if (action == BTRFS_ADD_DELAYED_REF) {
                be->num_refs++;
                if (re)
                        re->num_refs++;
        }
        list_add_tail(&ra->list, &be->actions);
        ret = 0;
out_unlock:
        spin_unlock(&fs_info->ref_verify_lock);
out:
        if (ret)
                btrfs_clear_opt(fs_info->mount_opt, REF_VERIFY);
        return ret;
}

/* Free up the ref cache */
void btrfs_free_ref_cache(struct btrfs_fs_info *fs_info)
{
        struct block_entry *be;
        struct rb_node *n;

        if (!btrfs_test_opt(fs_info, REF_VERIFY))
                return;

        spin_lock(&fs_info->ref_verify_lock);
        while ((n = rb_first(&fs_info->block_tree))) {
                be = rb_entry(n, struct block_entry, node);
                rb_erase(&be->node, &fs_info->block_tree);
                free_block_entry(be);
                cond_resched_lock(&fs_info->ref_verify_lock);
        }
        spin_unlock(&fs_info->ref_verify_lock);
}

void btrfs_free_ref_tree_range(struct btrfs_fs_info *fs_info, u64 start,
                               u64 len)
{
        struct block_entry *be = NULL, *entry;
        struct rb_node *n;

        if (!btrfs_test_opt(fs_info, REF_VERIFY))
                return;

        spin_lock(&fs_info->ref_verify_lock);
        n = fs_info->block_tree.rb_node;
        while (n) {
                entry = rb_entry(n, struct block_entry, node);
                if (entry->bytenr < start) {
                        n = n->rb_right;
                } else if (entry->bytenr > start) {
                        n = n->rb_left;
                } else {
                        be = entry;
                        break;
                }
                /* We want to get as close to start as possible */
                if (be == NULL ||
                    (entry->bytenr < start && be->bytenr > start) ||
                    (entry->bytenr < start && entry->bytenr > be->bytenr))
                        be = entry;
        }

        /*
         * Could have an empty block group, maybe have something to check for
         * this case to verify we were actually empty?
         */
        if (!be) {
                spin_unlock(&fs_info->ref_verify_lock);
                return;
        }

        n = &be->node;
        while (n) {
                be = rb_entry(n, struct block_entry, node);
                n = rb_next(n);
                if (be->bytenr < start && be->bytenr + be->len > start) {
                        btrfs_err(fs_info,
                                "block entry overlaps a block group [%llu,%llu]!",
                                start, len);
                        dump_block_entry(fs_info, be);
                        continue;
                }
                if (be->bytenr < start)
                        continue;
                if (be->bytenr >= start + len)
                        break;
                if (be->bytenr + be->len > start + len) {
                        btrfs_err(fs_info,
                                "block entry overlaps a block group [%llu,%llu]!",
                                start, len);
                        dump_block_entry(fs_info, be);
                }
                rb_erase(&be->node, &fs_info->block_tree);
                free_block_entry(be);
        }
        spin_unlock(&fs_info->ref_verify_lock);
}

/* Walk down all roots and build the ref tree, meant to be called at mount */
int btrfs_build_ref_tree(struct btrfs_fs_info *fs_info)
{
        struct btrfs_path *path;
        struct extent_buffer *eb;
        u64 bytenr = 0, num_bytes = 0;
        int ret, level;

        if (!btrfs_test_opt(fs_info, REF_VERIFY))
                return 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        eb = btrfs_read_lock_root_node(fs_info->extent_root);
        btrfs_set_lock_blocking_read(eb);
        level = btrfs_header_level(eb);
        path->nodes[level] = eb;
        path->slots[level] = 0;
        path->locks[level] = BTRFS_READ_LOCK_BLOCKING;

        while (1) {
                /*
                 * We have to keep track of the bytenr/num_bytes we last hit
                 * because we could have run out of space for an inline ref, and
                 * would have had to added a ref key item which may appear on a
                 * different leaf from the original extent item.
                 */
                ret = walk_down_tree(fs_info->extent_root, path, level,

                                     &bytenr, &num_bytes);
                if (ret)
                        break;
                ret = walk_up_tree(path, &level);
                if (ret < 0)
                        break;
                if (ret > 0) {
                        ret = 0;
                        break;
                }
        }
        if (ret) {
                btrfs_clear_opt(fs_info->mount_opt, REF_VERIFY);
                btrfs_free_ref_cache(fs_info);
        }
        btrfs_free_path(path);
        return ret;
}