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- /* 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/percpu_counter.h>
- #include "extent_io.h"
- #define BTRFS_WRITE_LOCK 1
- #define BTRFS_READ_LOCK 2
- #define BTRFS_WRITE_LOCK_BLOCKING 3
- #define BTRFS_READ_LOCK_BLOCKING 4
- /*
- * 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_SUBLCLASSES 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,
- };
- static_assert(BTRFS_NESTING_MAX <= MAX_LOCKDEP_SUBCLASSES,
- "too many lock subclasses defined");
- struct btrfs_path;
- void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest);
- 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, enum btrfs_lock_nesting nest,
- bool recurse);
- void btrfs_tree_read_lock(struct extent_buffer *eb);
- void btrfs_tree_read_unlock(struct extent_buffer *eb);
- void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb);
- void btrfs_set_lock_blocking_read(struct extent_buffer *eb);
- void btrfs_set_lock_blocking_write(struct extent_buffer *eb);
- int btrfs_try_tree_read_lock(struct extent_buffer *eb);
- int btrfs_try_tree_write_lock(struct extent_buffer *eb);
- int btrfs_tree_read_lock_atomic(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,
- bool recurse);
- static inline struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
- {
- return __btrfs_read_lock_root_node(root, false);
- }
- #ifdef CONFIG_BTRFS_DEBUG
- static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) {
- BUG_ON(!eb->write_locks);
- }
- #else
- static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) { }
- #endif
- void btrfs_set_path_blocking(struct btrfs_path *p);
- 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)
- 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();
- }
- struct btrfs_drew_lock {
- atomic_t readers;
- struct percpu_counter writers;
- wait_queue_head_t pending_writers;
- wait_queue_head_t pending_readers;
- };
- int btrfs_drew_lock_init(struct btrfs_drew_lock *lock);
- void btrfs_drew_lock_destroy(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);
- #endif
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