1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Copyright (C) 2008 Oracle. All rights reserved. 4 */ 5 6 #ifndef BTRFS_LOCKING_H 7 #define BTRFS_LOCKING_H 8 9 #include <linux/atomic.h> 10 #include <linux/wait.h> 11 #include <linux/percpu_counter.h> 12 #include "extent_io.h" 13 14 #define BTRFS_WRITE_LOCK 1 15 #define BTRFS_READ_LOCK 2 16 17 /* 18 * We are limited in number of subclasses by MAX_LOCKDEP_SUBCLASSES, which at 19 * the time of this patch is 8, which is how many we use. Keep this in mind if 20 * you decide you want to add another subclass. 21 */ 22 enum btrfs_lock_nesting { 23 BTRFS_NESTING_NORMAL, 24 25 /* 26 * When we COW a block we are holding the lock on the original block, 27 * and since our lockdep maps are rootid+level, this confuses lockdep 28 * when we lock the newly allocated COW'd block. Handle this by having 29 * a subclass for COW'ed blocks so that lockdep doesn't complain. 30 */ 31 BTRFS_NESTING_COW, 32 33 /* 34 * Oftentimes we need to lock adjacent nodes on the same level while 35 * still holding the lock on the original node we searched to, such as 36 * for searching forward or for split/balance. 37 * 38 * Because of this we need to indicate to lockdep that this is 39 * acceptable by having a different subclass for each of these 40 * operations. 41 */ 42 BTRFS_NESTING_LEFT, 43 BTRFS_NESTING_RIGHT, 44 45 /* 46 * When splitting we will be holding a lock on the left/right node when 47 * we need to cow that node, thus we need a new set of subclasses for 48 * these two operations. 49 */ 50 BTRFS_NESTING_LEFT_COW, 51 BTRFS_NESTING_RIGHT_COW, 52 53 /* 54 * When splitting we may push nodes to the left or right, but still use 55 * the subsequent nodes in our path, keeping our locks on those adjacent 56 * blocks. Thus when we go to allocate a new split block we've already 57 * used up all of our available subclasses, so this subclass exists to 58 * handle this case where we need to allocate a new split block. 59 */ 60 BTRFS_NESTING_SPLIT, 61 62 /* 63 * When promoting a new block to a root we need to have a special 64 * subclass so we don't confuse lockdep, as it will appear that we are 65 * locking a higher level node before a lower level one. Copying also 66 * has this problem as it appears we're locking the same block again 67 * when we make a snapshot of an existing root. 68 */ 69 BTRFS_NESTING_NEW_ROOT, 70 71 /* 72 * We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so 73 * add this in here and add a static_assert to keep us from going over 74 * the limit. As of this writing we're limited to 8, and we're 75 * definitely using 8, hence this check to keep us from messing up in 76 * the future. 77 */ 78 BTRFS_NESTING_MAX, 79 }; 80 81 enum btrfs_lockdep_trans_states { 82 BTRFS_LOCKDEP_TRANS_COMMIT_START, 83 BTRFS_LOCKDEP_TRANS_UNBLOCKED, 84 BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED, 85 BTRFS_LOCKDEP_TRANS_COMPLETED, 86 }; 87 88 /* 89 * Lockdep annotation for wait events. 90 * 91 * @owner: The struct where the lockdep map is defined 92 * @lock: The lockdep map corresponding to a wait event 93 * 94 * This macro is used to annotate a wait event. In this case a thread acquires 95 * the lockdep map as writer (exclusive lock) because it has to block until all 96 * the threads that hold the lock as readers signal the condition for the wait 97 * event and release their locks. 98 */ 99 #define btrfs_might_wait_for_event(owner, lock) \ 100 do { \ 101 rwsem_acquire(&owner->lock##_map, 0, 0, _THIS_IP_); \ 102 rwsem_release(&owner->lock##_map, _THIS_IP_); \ 103 } while (0) 104 105 /* 106 * Protection for the resource/condition of a wait event. 107 * 108 * @owner: The struct where the lockdep map is defined 109 * @lock: The lockdep map corresponding to a wait event 110 * 111 * Many threads can modify the condition for the wait event at the same time 112 * and signal the threads that block on the wait event. The threads that modify 113 * the condition and do the signaling acquire the lock as readers (shared 114 * lock). 115 */ 116 #define btrfs_lockdep_acquire(owner, lock) \ 117 rwsem_acquire_read(&owner->lock##_map, 0, 0, _THIS_IP_) 118 119 /* 120 * Used after signaling the condition for a wait event to release the lockdep 121 * map held by a reader thread. 122 */ 123 #define btrfs_lockdep_release(owner, lock) \ 124 rwsem_release(&owner->lock##_map, _THIS_IP_) 125 126 /* 127 * Macros for the transaction states wait events, similar to the generic wait 128 * event macros. 129 */ 130 #define btrfs_might_wait_for_state(owner, i) \ 131 do { \ 132 rwsem_acquire(&owner->btrfs_state_change_map[i], 0, 0, _THIS_IP_); \ 133 rwsem_release(&owner->btrfs_state_change_map[i], _THIS_IP_); \ 134 } while (0) 135 136 #define btrfs_trans_state_lockdep_acquire(owner, i) \ 137 rwsem_acquire_read(&owner->btrfs_state_change_map[i], 0, 0, _THIS_IP_) 138 139 #define btrfs_trans_state_lockdep_release(owner, i) \ 140 rwsem_release(&owner->btrfs_state_change_map[i], _THIS_IP_) 141 142 /* Initialization of the lockdep map */ 143 #define btrfs_lockdep_init_map(owner, lock) \ 144 do { \ 145 static struct lock_class_key lock##_key; \ 146 lockdep_init_map(&owner->lock##_map, #lock, &lock##_key, 0); \ 147 } while (0) 148 149 /* Initialization of the transaction states lockdep maps. */ 150 #define btrfs_state_lockdep_init_map(owner, lock, state) \ 151 do { \ 152 static struct lock_class_key lock##_key; \ 153 lockdep_init_map(&owner->btrfs_state_change_map[state], #lock, \ 154 &lock##_key, 0); \ 155 } while (0) 156 157 static_assert(BTRFS_NESTING_MAX <= MAX_LOCKDEP_SUBCLASSES, 158 "too many lock subclasses defined"); 159 160 struct btrfs_path; 161 162 void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest); 163 void btrfs_tree_lock(struct extent_buffer *eb); 164 void btrfs_tree_unlock(struct extent_buffer *eb); 165 166 void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest); 167 void btrfs_tree_read_lock(struct extent_buffer *eb); 168 void btrfs_tree_read_unlock(struct extent_buffer *eb); 169 int btrfs_try_tree_read_lock(struct extent_buffer *eb); 170 int btrfs_try_tree_write_lock(struct extent_buffer *eb); 171 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root); 172 struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root); 173 struct extent_buffer *btrfs_try_read_lock_root_node(struct btrfs_root *root); 174 175 #ifdef CONFIG_BTRFS_DEBUG 176 static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb) 177 { 178 lockdep_assert_held_write(&eb->lock); 179 } 180 #else 181 static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb) { } 182 #endif 183 184 void btrfs_unlock_up_safe(struct btrfs_path *path, int level); 185 186 static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw) 187 { 188 if (rw == BTRFS_WRITE_LOCK) 189 btrfs_tree_unlock(eb); 190 else if (rw == BTRFS_READ_LOCK) 191 btrfs_tree_read_unlock(eb); 192 else 193 BUG(); 194 } 195 196 struct btrfs_drew_lock { 197 atomic_t readers; 198 struct percpu_counter writers; 199 wait_queue_head_t pending_writers; 200 wait_queue_head_t pending_readers; 201 }; 202 203 int btrfs_drew_lock_init(struct btrfs_drew_lock *lock); 204 void btrfs_drew_lock_destroy(struct btrfs_drew_lock *lock); 205 void btrfs_drew_write_lock(struct btrfs_drew_lock *lock); 206 bool btrfs_drew_try_write_lock(struct btrfs_drew_lock *lock); 207 void btrfs_drew_write_unlock(struct btrfs_drew_lock *lock); 208 void btrfs_drew_read_lock(struct btrfs_drew_lock *lock); 209 void btrfs_drew_read_unlock(struct btrfs_drew_lock *lock); 210 211 #ifdef CONFIG_DEBUG_LOCK_ALLOC 212 void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb, int level); 213 void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, struct extent_buffer *eb); 214 #else 215 static inline void btrfs_set_buffer_lockdep_class(u64 objectid, 216 struct extent_buffer *eb, int level) 217 { 218 } 219 static inline void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, 220 struct extent_buffer *eb) 221 { 222 } 223 #endif 224 225 #endif 226