diff options
Diffstat (limited to 'fs/btrfs/locking.h')
| -rw-r--r-- | fs/btrfs/locking.h | 257 |
1 files changed, 224 insertions, 33 deletions
diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h index b81e0e9a4894..a4673e7d95d7 100644 --- a/fs/btrfs/locking.h +++ b/fs/btrfs/locking.h @@ -1,60 +1,251 @@ +/* SPDX-License-Identifier: GPL-2.0 */ /* * Copyright (C) 2008 Oracle. All rights reserved. + */ + +#ifndef BTRFS_LOCKING_H +#define BTRFS_LOCKING_H + +#include <linux/atomic.h> +#include <linux/wait.h> +#include <linux/lockdep.h> +#include <linux/percpu_counter.h> +#include "extent_io.h" + +struct extent_buffer; +struct btrfs_path; +struct btrfs_root; + +#define BTRFS_WRITE_LOCK 1 +#define BTRFS_READ_LOCK 2 + +/* + * We are limited in number of subclasses by MAX_LOCKDEP_SUBCLASSES, which at + * the time of this patch is 8, which is how many we use. Keep this in mind if + * you decide you want to add another subclass. + */ +enum btrfs_lock_nesting { + BTRFS_NESTING_NORMAL, + + /* + * When we COW a block we are holding the lock on the original block, + * and since our lockdep maps are rootid+level, this confuses lockdep + * when we lock the newly allocated COW'd block. Handle this by having + * a subclass for COW'ed blocks so that lockdep doesn't complain. + */ + BTRFS_NESTING_COW, + + /* + * Oftentimes we need to lock adjacent nodes on the same level while + * still holding the lock on the original node we searched to, such as + * for searching forward or for split/balance. + * + * Because of this we need to indicate to lockdep that this is + * acceptable by having a different subclass for each of these + * operations. + */ + BTRFS_NESTING_LEFT, + BTRFS_NESTING_RIGHT, + + /* + * When splitting we will be holding a lock on the left/right node when + * we need to cow that node, thus we need a new set of subclasses for + * these two operations. + */ + BTRFS_NESTING_LEFT_COW, + BTRFS_NESTING_RIGHT_COW, + + /* + * When splitting we may push nodes to the left or right, but still use + * the subsequent nodes in our path, keeping our locks on those adjacent + * blocks. Thus when we go to allocate a new split block we've already + * used up all of our available subclasses, so this subclass exists to + * handle this case where we need to allocate a new split block. + */ + BTRFS_NESTING_SPLIT, + + /* + * When promoting a new block to a root we need to have a special + * subclass so we don't confuse lockdep, as it will appear that we are + * locking a higher level node before a lower level one. Copying also + * has this problem as it appears we're locking the same block again + * when we make a snapshot of an existing root. + */ + BTRFS_NESTING_NEW_ROOT, + + /* + * We are limited to MAX_LOCKDEP_SUBCLASSES number of subclasses, so + * add this in here and add a static_assert to keep us from going over + * the limit. As of this writing we're limited to 8, and we're + * definitely using 8, hence this check to keep us from messing up in + * the future. + */ + BTRFS_NESTING_MAX, +}; + +enum btrfs_lockdep_trans_states { + BTRFS_LOCKDEP_TRANS_COMMIT_PREP, + BTRFS_LOCKDEP_TRANS_UNBLOCKED, + BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED, + BTRFS_LOCKDEP_TRANS_COMPLETED, +}; + +/* + * Lockdep annotation for wait events. * - * 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. + * @owner: The struct where the lockdep map is defined + * @lock: The lockdep map corresponding to a wait event + * + * This macro is used to annotate a wait event. In this case a thread acquires + * the lockdep map as writer (exclusive lock) because it has to block until all + * the threads that hold the lock as readers signal the condition for the wait + * event and release their locks. + */ +#define btrfs_might_wait_for_event(owner, lock) \ + do { \ + rwsem_acquire(&owner->lock##_map, 0, 0, _THIS_IP_); \ + rwsem_release(&owner->lock##_map, _THIS_IP_); \ + } while (0) + +/* + * Protection for the resource/condition of a wait event. * - * 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. + * @owner: The struct where the lockdep map is defined + * @lock: The lockdep map corresponding to a wait event * - * 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. + * Many threads can modify the condition for the wait event at the same time + * and signal the threads that block on the wait event. The threads that modify + * the condition and do the signaling acquire the lock as readers (shared + * lock). */ +#define btrfs_lockdep_acquire(owner, lock) \ + rwsem_acquire_read(&owner->lock##_map, 0, 0, _THIS_IP_) -#ifndef __BTRFS_LOCKING_ -#define __BTRFS_LOCKING_ +/* + * Used after signaling the condition for a wait event to release the lockdep + * map held by a reader thread. + */ +#define btrfs_lockdep_release(owner, lock) \ + rwsem_release(&owner->lock##_map, _THIS_IP_) -#define BTRFS_WRITE_LOCK 1 -#define BTRFS_READ_LOCK 2 -#define BTRFS_WRITE_LOCK_BLOCKING 3 -#define BTRFS_READ_LOCK_BLOCKING 4 +/* + * Used to account for the fact that when doing io_uring encoded I/O, we can + * return to userspace with the inode lock still held. + */ +#define btrfs_lockdep_inode_acquire(owner, lock) \ + rwsem_acquire_read(&owner->vfs_inode.lock.dep_map, 0, 0, _THIS_IP_) + +#define btrfs_lockdep_inode_release(owner, lock) \ + rwsem_release(&owner->vfs_inode.lock.dep_map, _THIS_IP_) + +/* + * Macros for the transaction states wait events, similar to the generic wait + * event macros. + */ +#define btrfs_might_wait_for_state(owner, i) \ + do { \ + rwsem_acquire(&owner->btrfs_state_change_map[i], 0, 0, _THIS_IP_); \ + rwsem_release(&owner->btrfs_state_change_map[i], _THIS_IP_); \ + } while (0) + +#define btrfs_trans_state_lockdep_acquire(owner, i) \ + rwsem_acquire_read(&owner->btrfs_state_change_map[i], 0, 0, _THIS_IP_) + +#define btrfs_trans_state_lockdep_release(owner, i) \ + rwsem_release(&owner->btrfs_state_change_map[i], _THIS_IP_) + +/* Initialization of the lockdep map */ +#define btrfs_lockdep_init_map(owner, lock) \ + do { \ + static struct lock_class_key lock##_key; \ + lockdep_init_map(&owner->lock##_map, #lock, &lock##_key, 0); \ + } while (0) + +/* Initialization of the transaction states lockdep maps. */ +#define btrfs_state_lockdep_init_map(owner, lock, state) \ + do { \ + static struct lock_class_key lock##_key; \ + lockdep_init_map(&owner->btrfs_state_change_map[state], #lock, \ + &lock##_key, 0); \ + } while (0) + +static_assert(BTRFS_NESTING_MAX <= MAX_LOCKDEP_SUBCLASSES, + "too many lock subclasses defined"); + +void btrfs_tree_lock_nested(struct extent_buffer *eb, enum btrfs_lock_nesting nest); + +static inline void btrfs_tree_lock(struct extent_buffer *eb) +{ + btrfs_tree_lock_nested(eb, BTRFS_NESTING_NORMAL); +} -void btrfs_tree_lock(struct extent_buffer *eb); void btrfs_tree_unlock(struct extent_buffer *eb); -void btrfs_tree_read_lock(struct extent_buffer *eb); +void btrfs_tree_read_lock_nested(struct extent_buffer *eb, enum btrfs_lock_nesting nest); + +static inline void btrfs_tree_read_lock(struct extent_buffer *eb) +{ + btrfs_tree_read_lock_nested(eb, BTRFS_NESTING_NORMAL); +} + void btrfs_tree_read_unlock(struct extent_buffer *eb); -void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb); -void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw); -void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw); -void btrfs_assert_tree_locked(struct extent_buffer *eb); -int btrfs_try_tree_read_lock(struct extent_buffer *eb); -int btrfs_try_tree_write_lock(struct extent_buffer *eb); +bool btrfs_try_tree_read_lock(struct extent_buffer *eb); +struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root); +struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root); +struct extent_buffer *btrfs_try_read_lock_root_node(struct btrfs_root *root); + +#ifdef CONFIG_BTRFS_DEBUG +static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb) +{ + lockdep_assert_held_write(&eb->lock); +} +static inline void btrfs_assert_tree_read_locked(struct extent_buffer *eb) +{ + lockdep_assert_held_read(&eb->lock); +} +#else +static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb) { } +static inline void btrfs_assert_tree_read_locked(struct extent_buffer *eb) { } +#endif + +void btrfs_unlock_up_safe(struct btrfs_path *path, int level); static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw) { - if (rw == BTRFS_WRITE_LOCK || rw == BTRFS_WRITE_LOCK_BLOCKING) + if (rw == BTRFS_WRITE_LOCK) btrfs_tree_unlock(eb); - else if (rw == BTRFS_READ_LOCK_BLOCKING) - btrfs_tree_read_unlock_blocking(eb); else if (rw == BTRFS_READ_LOCK) btrfs_tree_read_unlock(eb); else BUG(); } -static inline void btrfs_set_lock_blocking(struct extent_buffer *eb) +struct btrfs_drew_lock { + atomic_t readers; + atomic_t writers; + wait_queue_head_t pending_writers; + wait_queue_head_t pending_readers; +}; + +void btrfs_drew_lock_init(struct btrfs_drew_lock *lock); +void btrfs_drew_write_lock(struct btrfs_drew_lock *lock); +bool btrfs_drew_try_write_lock(struct btrfs_drew_lock *lock); +void btrfs_drew_write_unlock(struct btrfs_drew_lock *lock); +void btrfs_drew_read_lock(struct btrfs_drew_lock *lock); +void btrfs_drew_read_unlock(struct btrfs_drew_lock *lock); + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb, int level); +void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, struct extent_buffer *eb); +#else +static inline void btrfs_set_buffer_lockdep_class(u64 objectid, + struct extent_buffer *eb, int level) { - btrfs_set_lock_blocking_rw(eb, BTRFS_WRITE_LOCK); } - -static inline void btrfs_clear_lock_blocking(struct extent_buffer *eb) +static inline void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, + struct extent_buffer *eb) { - btrfs_clear_lock_blocking_rw(eb, BTRFS_WRITE_LOCK_BLOCKING); } #endif + +#endif |