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-rw-r--r--fs/btrfs/locking.h224
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diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h
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+++ b/fs/btrfs/locking.h
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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
+
+/*
+ * 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,
+};
+
+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.
+ *
+ * @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.
+ *
+ * @owner: The struct where the lockdep map is defined
+ * @lock: The lockdep map corresponding to a wait event
+ *
+ * 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_)
+
+/*
+ * 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_)
+
+/*
+ * 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");
+
+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);
+void btrfs_tree_read_lock(struct extent_buffer *eb);
+void btrfs_tree_read_unlock(struct extent_buffer *eb);
+int btrfs_try_tree_read_lock(struct extent_buffer *eb);
+int btrfs_try_tree_write_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);
+}
+#else
+static inline void btrfs_assert_tree_write_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)
+ btrfs_tree_unlock(eb);
+ else if (rw == BTRFS_READ_LOCK)
+ btrfs_tree_read_unlock(eb);
+ else
+ BUG();
+}
+
+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)
+{
+}
+static inline void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root,
+ struct extent_buffer *eb)
+{
+}
+#endif
+
+#endif