fs/btrfs/delayed-ref.h

   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
  27 struct 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
  60 struct 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  */
  74 struct 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
 102 struct btrfs_delayed_tree_ref {
 103         struct btrfs_delayed_ref_node node;
 104         u64 root;
 105         u64 parent;
 106         int level;
 107 };
 108
 109 struct 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
 117 struct 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         /*
 144          * seq number of delayed refs. We need to know if a backref was being
 145          * added before the currently processed ref or afterwards.
 146          */
 147         u64 seq;
 148
 149         /*
 150          * seq_list holds a list of all seq numbers that are currently being
 151          * added to the list. While walking backrefs (btrfs_find_all_roots,
 152          * qgroups), which might take some time, no newer ref must be processed,
 153          * as it might influence the outcome of the walk.
 154          */
 155         struct list_head seq_head;
 156
 157         /*
 158          * when the only refs we have in the list must not be processed, we want
 159          * to wait for more refs to show up or for the end of backref walking.
 160          */
 161         wait_queue_head_t seq_wait;
 162 };
 163
 164 static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
 165 {
 166         WARN_ON(atomic_read(&ref->refs) == 0);
 167         if (atomic_dec_and_test(&ref->refs)) {
 168                 WARN_ON(ref->in_tree);
 169                 kfree(ref);
 170         }
 171 }
 172
 173 int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
 174                                struct btrfs_trans_handle *trans,
 175                                u64 bytenr, u64 num_bytes, u64 parent,
 176                                u64 ref_root, int level, int action,
 177                                struct btrfs_delayed_extent_op *extent_op,
 178                                int for_cow);
 179 int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
 180                                struct btrfs_trans_handle *trans,
 181                                u64 bytenr, u64 num_bytes,
 182                                u64 parent, u64 ref_root,
 183                                u64 owner, u64 offset, int action,
 184                                struct btrfs_delayed_extent_op *extent_op,
 185                                int for_cow);
 186 int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
 187                                 struct btrfs_trans_handle *trans,
 188                                 u64 bytenr, u64 num_bytes,
 189                                 struct btrfs_delayed_extent_op *extent_op);
 190
 191 struct btrfs_delayed_ref_head *
 192 btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr);
 193 int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
 194                            struct btrfs_delayed_ref_head *head);
 195 int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
 196                            struct list_head *cluster, u64 search_start);
 197
 198 struct seq_list {
 199         struct list_head list;
 200         u64 seq;
 201 };
 202
 203 static inline u64 inc_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs)
 204 {
 205         assert_spin_locked(&delayed_refs->lock);
 206         ++delayed_refs->seq;
 207         return delayed_refs->seq;
 208 }
 209
 210 static inline void
 211 btrfs_get_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
 212                       struct seq_list *elem)
 213 {
 214         assert_spin_locked(&delayed_refs->lock);
 215         elem->seq = delayed_refs->seq;
 216         list_add_tail(&elem->list, &delayed_refs->seq_head);
 217 }
 218
 219 static inline void
 220 btrfs_put_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
 221                       struct seq_list *elem)
 222 {
 223         spin_lock(&delayed_refs->lock);
 224         list_del(&elem->list);
 225         wake_up(&delayed_refs->seq_wait);
 226         spin_unlock(&delayed_refs->lock);
 227 }
 228
 229 int btrfs_check_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
 230                             u64 seq);
 231
 232 /*
 233  * delayed refs with a ref_seq > 0 must be held back during backref walking.
 234  * this only applies to items in one of the fs-trees. for_cow items never need
 235  * to be held back, so they won't get a ref_seq number.
 236  */
 237 static inline int need_ref_seq(int for_cow, u64 rootid)
 238 {
 239         if (for_cow)
 240                 return 0;
 241
 242         if (rootid == BTRFS_FS_TREE_OBJECTID)
 243                 return 1;
 244
 245         if ((s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)
 246                 return 1;
 247
 248         return 0;
 249 }
 250
 251 /*
 252  * a node might live in a head or a regular ref, this lets you
 253  * test for the proper type to use.
 254  */
 255 static int btrfs_delayed_ref_is_head(struct btrfs_delayed_ref_node *node)
 256 {
 257         return node->is_head;
 258 }
 259
 260 /*
 261  * helper functions to cast a node into its container
 262  */
 263 static inline struct btrfs_delayed_tree_ref *
 264 btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
 265 {
 266         WARN_ON(btrfs_delayed_ref_is_head(node));
 267         return container_of(node, struct btrfs_delayed_tree_ref, node);
 268 }
 269
 270 static inline struct btrfs_delayed_data_ref *
 271 btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
 272 {
 273         WARN_ON(btrfs_delayed_ref_is_head(node));
 274         return container_of(node, struct btrfs_delayed_data_ref, node);
 275 }
 276
 277 static inline struct btrfs_delayed_ref_head *
 278 btrfs_delayed_node_to_head(struct btrfs_delayed_ref_node *node)
 279 {
 280         WARN_ON(!btrfs_delayed_ref_is_head(node));
 281         return container_of(node, struct btrfs_delayed_ref_head, node);
 282 }
 283 #endif