134 lines
4.3 KiB
C
134 lines
4.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2008 Oracle. All rights reserved.
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*/
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#ifndef BTRFS_LOCKING_H
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#define BTRFS_LOCKING_H
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#include <linux/atomic.h>
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#include <linux/wait.h>
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#include <linux/percpu_counter.h>
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#include "extent_io.h"
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#define BTRFS_WRITE_LOCK 1
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#define BTRFS_READ_LOCK 2
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/*
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* We are limited in number of subclasses by MAX_LOCKDEP_SUBCLASSES, which at
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* the time of this patch is 8, which is how many we use. Keep this in mind if
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* you decide you want to add another subclass.
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*/
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enum btrfs_lock_nesting {
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BTRFS_NESTING_NORMAL,
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/*
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* When we COW a block we are holding the lock on the original block,
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* and since our lockdep maps are rootid+level, this confuses lockdep
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* when we lock the newly allocated COW'd block. Handle this by having
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* a subclass for COW'ed blocks so that lockdep doesn't complain.
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*/
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BTRFS_NESTING_COW,
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/*
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* Oftentimes we need to lock adjacent nodes on the same level while
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* still holding the lock on the original node we searched to, such as
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* for searching forward or for split/balance.
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*
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* Because of this we need to indicate to lockdep that this is
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* acceptable by having a different subclass for each of these
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* operations.
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*/
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BTRFS_NESTING_LEFT,
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BTRFS_NESTING_RIGHT,
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/*
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* When splitting we will be holding a lock on the left/right node when
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* we need to cow that node, thus we need a new set of subclasses for
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* these two operations.
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*/
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BTRFS_NESTING_LEFT_COW,
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BTRFS_NESTING_RIGHT_COW,
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/*
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* When splitting we may push nodes to the left or right, but still use
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* the subsequent nodes in our path, keeping our locks on those adjacent
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* blocks. Thus when we go to allocate a new split block we've already
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* used up all of our available subclasses, so this subclass exists to
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* handle this case where we need to allocate a new split block.
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*/
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BTRFS_NESTING_SPLIT,
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/*
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* When promoting a new block to a root we need to have a special
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* subclass so we don't confuse lockdep, as it will appear that we are
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* locking a higher level node before a lower level one. Copying also
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* has this problem as it appears we're locking the same block again
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* when we make a snapshot of an existing root.
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*/
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BTRFS_NESTING_NEW_ROOT,
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/*
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* We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so
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* add this in here and add a static_assert to keep us from going over
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* the limit. As of this writing we're limited to 8, and we're
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* definitely using 8, hence this check to keep us from messing up in
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* the future.
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*/
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BTRFS_NESTING_MAX,
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};
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static_assert(BTRFS_NESTING_MAX <= MAX_LOCKDEP_SUBCLASSES,
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"too many lock subclasses defined");
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struct btrfs_path;
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void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest);
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void btrfs_tree_lock(struct extent_buffer *eb);
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void btrfs_tree_unlock(struct extent_buffer *eb);
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void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest);
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void btrfs_tree_read_lock(struct extent_buffer *eb);
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void btrfs_tree_read_unlock(struct extent_buffer *eb);
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int btrfs_try_tree_read_lock(struct extent_buffer *eb);
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int btrfs_try_tree_write_lock(struct extent_buffer *eb);
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struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root);
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struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root);
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#ifdef CONFIG_BTRFS_DEBUG
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static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) {
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lockdep_assert_held(&eb->lock);
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}
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#else
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static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) { }
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#endif
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void btrfs_unlock_up_safe(struct btrfs_path *path, int level);
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static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw)
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{
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if (rw == BTRFS_WRITE_LOCK)
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btrfs_tree_unlock(eb);
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else if (rw == BTRFS_READ_LOCK)
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btrfs_tree_read_unlock(eb);
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else
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BUG();
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}
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struct btrfs_drew_lock {
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atomic_t readers;
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struct percpu_counter writers;
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wait_queue_head_t pending_writers;
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wait_queue_head_t pending_readers;
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};
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int btrfs_drew_lock_init(struct btrfs_drew_lock *lock);
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void btrfs_drew_lock_destroy(struct btrfs_drew_lock *lock);
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void btrfs_drew_write_lock(struct btrfs_drew_lock *lock);
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bool btrfs_drew_try_write_lock(struct btrfs_drew_lock *lock);
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void btrfs_drew_write_unlock(struct btrfs_drew_lock *lock);
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void btrfs_drew_read_lock(struct btrfs_drew_lock *lock);
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void btrfs_drew_read_unlock(struct btrfs_drew_lock *lock);
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#endif
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