delayed-ref.h

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/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */
#ifndef __DELAYED_REF__
#define __DELAYED_REF__

/* these are the possible values of struct btrfs_delayed_ref_node->action */
#define BTRFS_ADD_DELAYED_REF    1 /* add one backref to the tree */
#define BTRFS_DROP_DELAYED_REF   2 /* delete one backref from the tree */
#define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
#define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */

struct btrfs_delayed_ref_node {
    struct rb_node rb_node;

    /* the starting bytenr of the extent */
    u64 bytenr;

    /* the size of the extent */
    u64 num_bytes;

    /* seq number to keep track of insertion order */
    u64 seq;

    /* ref count on this data structure */
    atomic_t refs;

    /*
     * how many refs is this entry adding or deleting.  For
     * head refs, this may be a negative number because it is keeping
     * track of the total mods done to the reference count.
     * For individual refs, this will always be a positive number
     *
     * It may be more than one, since it is possible for a single
     * parent to have more than one ref on an extent
     */
    int ref_mod;

    unsigned int action:8;
    unsigned int type:8;
    /* is this node still in the rbtree? */
    unsigned int is_head:1;
    unsigned int in_tree:1;
};

struct btrfs_delayed_extent_op {
    struct btrfs_disk_key key;
    u64 flags_to_set;
    unsigned int update_key:1;
    unsigned int update_flags:1;
    unsigned int is_data:1;
};

/*
 * the head refs are used to hold a lock on a given extent, which allows us
 * to make sure that only one process is running the delayed refs
 * at a time for a single extent.  They also store the sum of all the
 * reference count modifications we've queued up.
 */
struct btrfs_delayed_ref_head {
    struct btrfs_delayed_ref_node node;

    /*
     * the mutex is held while running the refs, and it is also
     * held when checking the sum of reference modifications.
     */
    struct mutex mutex;

    struct list_head cluster;

    struct btrfs_delayed_extent_op *extent_op;
    /*
     * when a new extent is allocated, it is just reserved in memory
     * The actual extent isn't inserted into the extent allocation tree
     * until the delayed ref is processed.  must_insert_reserved is
     * used to flag a delayed ref so the accounting can be updated
     * when a full insert is done.
     *
     * It is possible the extent will be freed before it is ever
     * inserted into the extent allocation tree.  In this case
     * we need to update the in ram accounting to properly reflect
     * the free has happened.
     */
    unsigned int must_insert_reserved:1;
    unsigned int is_data:1;
};

struct btrfs_delayed_tree_ref {
    struct btrfs_delayed_ref_node node;
    u64 root;
    u64 parent;
    int level;
};

struct btrfs_delayed_data_ref {
    struct btrfs_delayed_ref_node node;
    u64 root;
    u64 parent;
    u64 objectid;
    u64 offset;
};

struct btrfs_delayed_ref_root {
    struct rb_root root;

    /* this spin lock protects the rbtree and the entries inside */
    spinlock_t lock;

    /* how many delayed ref updates we've queued, used by the
     * throttling code
     */
    unsigned long num_entries;

    /* total number of head nodes in tree */
    unsigned long num_heads;

    /* total number of head nodes ready for processing */
    unsigned long num_heads_ready;

    /*
     * set when the tree is flushing before a transaction commit,
     * used by the throttling code to decide if new updates need
     * to be run right away
     */
    int flushing;

    u64 run_delayed_start;
};

static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
{
    WARN_ON(atomic_read(&ref->refs) == 0);
    if (atomic_dec_and_test(&ref->refs)) {
        WARN_ON(ref->in_tree);
        kfree(ref);
    }
}

int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
                   struct btrfs_trans_handle *trans,
                   u64 bytenr, u64 num_bytes, u64 parent,
                   u64 ref_root, int level, int action,
                   struct btrfs_delayed_extent_op *extent_op,
                   int for_cow);
int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
                   struct btrfs_trans_handle *trans,
                   u64 bytenr, u64 num_bytes,
                   u64 parent, u64 ref_root,
                   u64 owner, u64 offset, int action,
                   struct btrfs_delayed_extent_op *extent_op,
                   int for_cow);
int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
                struct btrfs_trans_handle *trans,
                u64 bytenr, u64 num_bytes,
                struct btrfs_delayed_extent_op *extent_op);
void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
                  struct btrfs_fs_info *fs_info,
                  struct btrfs_delayed_ref_root *delayed_refs,
                  struct btrfs_delayed_ref_head *head);

struct btrfs_delayed_ref_head *
btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr);
int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
               struct btrfs_delayed_ref_head *head);
int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
               struct list_head *cluster, u64 search_start);

int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
                struct btrfs_delayed_ref_root *delayed_refs,
                u64 seq);

/*
 * delayed refs with a ref_seq > 0 must be held back during backref walking.
 * this only applies to items in one of the fs-trees. for_cow items never need
 * to be held back, so they won't get a ref_seq number.
 */
static inline int need_ref_seq(int for_cow, u64 rootid)
{
    if (for_cow)
        return 0;

    if (rootid == BTRFS_FS_TREE_OBJECTID)
        return 1;

    if ((s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)
        return 1;

    return 0;
}

/*
 * a node might live in a head or a regular ref, this lets you
 * test for the proper type to use.
 */
static int btrfs_delayed_ref_is_head(struct btrfs_delayed_ref_node *node)
{
    return node->is_head;
}

/*
 * helper functions to cast a node into its container
 */
static inline struct btrfs_delayed_tree_ref *
btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
{
    WARN_ON(btrfs_delayed_ref_is_head(node));
    return container_of(node, struct btrfs_delayed_tree_ref, node);
}

static inline struct btrfs_delayed_data_ref *
btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
{
    WARN_ON(btrfs_delayed_ref_is_head(node));
    return container_of(node, struct btrfs_delayed_data_ref, node);
}

static inline struct btrfs_delayed_ref_head *
btrfs_delayed_node_to_head(struct btrfs_delayed_ref_node *node)
{
    WARN_ON(!btrfs_delayed_ref_is_head(node));
    return container_of(node, struct btrfs_delayed_ref_head, node);
}
#endif