linux/fs/btrfs/delayed-ref.h
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   1/*
   2 * Copyright (C) 2008 Oracle.  All rights reserved.
   3 *
   4 * This program is free software; you can redistribute it and/or
   5 * modify it under the terms of the GNU General Public
   6 * License v2 as published by the Free Software Foundation.
   7 *
   8 * This program is distributed in the hope that it will be useful,
   9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11 * General Public License for more details.
  12 *
  13 * You should have received a copy of the GNU General Public
  14 * License along with this program; if not, write to the
  15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16 * Boston, MA 021110-1307, USA.
  17 */
  18#ifndef __DELAYED_REF__
  19#define __DELAYED_REF__
  20
  21/* these are the possible values of struct btrfs_delayed_ref->action */
  22#define BTRFS_ADD_DELAYED_REF    1 /* add one backref to the tree */
  23#define BTRFS_DROP_DELAYED_REF   2 /* delete one backref from the tree */
  24#define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
  25#define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */
  26
  27struct btrfs_delayed_ref_node {
  28        struct rb_node rb_node;
  29
  30        /* the starting bytenr of the extent */
  31        u64 bytenr;
  32
  33        /* the size of the extent */
  34        u64 num_bytes;
  35
  36        /* seq number to keep track of insertion order */
  37        u64 seq;
  38
  39        /* ref count on this data structure */
  40        atomic_t refs;
  41
  42        /*
  43         * how many refs is this entry adding or deleting.  For
  44         * head refs, this may be a negative number because it is keeping
  45         * track of the total mods done to the reference count.
  46         * For individual refs, this will always be a positive number
  47         *
  48         * It may be more than one, since it is possible for a single
  49         * parent to have more than one ref on an extent
  50         */
  51        int ref_mod;
  52
  53        unsigned int action:8;
  54        unsigned int type:8;
  55        /* is this node still in the rbtree? */
  56        unsigned int is_head:1;
  57        unsigned int in_tree:1;
  58};
  59
  60struct btrfs_delayed_extent_op {
  61        struct btrfs_disk_key key;
  62        u64 flags_to_set;
  63        unsigned int update_key:1;
  64        unsigned int update_flags:1;
  65        unsigned int is_data:1;
  66};
  67
  68/*
  69 * the head refs are used to hold a lock on a given extent, which allows us
  70 * to make sure that only one process is running the delayed refs
  71 * at a time for a single extent.  They also store the sum of all the
  72 * reference count modifications we've queued up.
  73 */
  74struct btrfs_delayed_ref_head {
  75        struct btrfs_delayed_ref_node node;
  76
  77        /*
  78         * the mutex is held while running the refs, and it is also
  79         * held when checking the sum of reference modifications.
  80         */
  81        struct mutex mutex;
  82
  83        struct list_head cluster;
  84
  85        struct btrfs_delayed_extent_op *extent_op;
  86        /*
  87         * when a new extent is allocated, it is just reserved in memory
  88         * The actual extent isn't inserted into the extent allocation tree
  89         * until the delayed ref is processed.  must_insert_reserved is
  90         * used to flag a delayed ref so the accounting can be updated
  91         * when a full insert is done.
  92         *
  93         * It is possible the extent will be freed before it is ever
  94         * inserted into the extent allocation tree.  In this case
  95         * we need to update the in ram accounting to properly reflect
  96         * the free has happened.
  97         */
  98        unsigned int must_insert_reserved:1;
  99        unsigned int is_data:1;
 100};
 101
 102struct btrfs_delayed_tree_ref {
 103        struct btrfs_delayed_ref_node node;
 104        u64 root;
 105        u64 parent;
 106        int level;
 107};
 108
 109struct btrfs_delayed_data_ref {
 110        struct btrfs_delayed_ref_node node;
 111        u64 root;
 112        u64 parent;
 113        u64 objectid;
 114        u64 offset;
 115};
 116
 117struct btrfs_delayed_ref_root {
 118        struct rb_root root;
 119
 120        /* this spin lock protects the rbtree and the entries inside */
 121        spinlock_t lock;
 122
 123        /* how many delayed ref updates we've queued, used by the
 124         * throttling code
 125         */
 126        unsigned long num_entries;
 127
 128        /* total number of head nodes in tree */
 129        unsigned long num_heads;
 130
 131        /* total number of head nodes ready for processing */
 132        unsigned long num_heads_ready;
 133
 134        /*
 135         * set when the tree is flushing before a transaction commit,
 136         * used by the throttling code to decide if new updates need
 137         * to be run right away
 138         */
 139        int flushing;
 140
 141        u64 run_delayed_start;
 142};
 143
 144static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
 145{
 146        WARN_ON(atomic_read(&ref->refs) == 0);
 147        if (atomic_dec_and_test(&ref->refs)) {
 148                WARN_ON(ref->in_tree);
 149                kfree(ref);
 150        }
 151}
 152
 153int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
 154                               struct btrfs_trans_handle *trans,
 155                               u64 bytenr, u64 num_bytes, u64 parent,
 156                               u64 ref_root, int level, int action,
 157                               struct btrfs_delayed_extent_op *extent_op,
 158                               int for_cow);
 159int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
 160                               struct btrfs_trans_handle *trans,
 161                               u64 bytenr, u64 num_bytes,
 162                               u64 parent, u64 ref_root,
 163                               u64 owner, u64 offset, int action,
 164                               struct btrfs_delayed_extent_op *extent_op,
 165                               int for_cow);
 166int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
 167                                struct btrfs_trans_handle *trans,
 168                                u64 bytenr, u64 num_bytes,
 169                                struct btrfs_delayed_extent_op *extent_op);
 170void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
 171                              struct btrfs_fs_info *fs_info,
 172                              struct btrfs_delayed_ref_root *delayed_refs,
 173                              struct btrfs_delayed_ref_head *head);
 174
 175struct btrfs_delayed_ref_head *
 176btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr);
 177int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
 178                           struct btrfs_delayed_ref_head *head);
 179int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
 180                           struct list_head *cluster, u64 search_start);
 181
 182int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
 183                            struct btrfs_delayed_ref_root *delayed_refs,
 184                            u64 seq);
 185
 186/*
 187 * delayed refs with a ref_seq > 0 must be held back during backref walking.
 188 * this only applies to items in one of the fs-trees. for_cow items never need
 189 * to be held back, so they won't get a ref_seq number.
 190 */
 191static inline int need_ref_seq(int for_cow, u64 rootid)
 192{
 193        if (for_cow)
 194                return 0;
 195
 196        if (rootid == BTRFS_FS_TREE_OBJECTID)
 197                return 1;
 198
 199        if ((s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)
 200                return 1;
 201
 202        return 0;
 203}
 204
 205/*
 206 * a node might live in a head or a regular ref, this lets you
 207 * test for the proper type to use.
 208 */
 209static int btrfs_delayed_ref_is_head(struct btrfs_delayed_ref_node *node)
 210{
 211        return node->is_head;
 212}
 213
 214/*
 215 * helper functions to cast a node into its container
 216 */
 217static inline struct btrfs_delayed_tree_ref *
 218btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
 219{
 220        WARN_ON(btrfs_delayed_ref_is_head(node));
 221        return container_of(node, struct btrfs_delayed_tree_ref, node);
 222}
 223
 224static inline struct btrfs_delayed_data_ref *
 225btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
 226{
 227        WARN_ON(btrfs_delayed_ref_is_head(node));
 228        return container_of(node, struct btrfs_delayed_data_ref, node);
 229}
 230
 231static inline struct btrfs_delayed_ref_head *
 232btrfs_delayed_node_to_head(struct btrfs_delayed_ref_node *node)
 233{
 234        WARN_ON(!btrfs_delayed_ref_is_head(node));
 235        return container_of(node, struct btrfs_delayed_ref_head, node);
 236}
 237#endif
 238
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