From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/fs/btrfs/locking.h | 122 +++++++++++++++++++++++++++++++++++++---
1 files changed, 111 insertions(+), 11 deletions(-)
diff --git a/kernel/fs/btrfs/locking.h b/kernel/fs/btrfs/locking.h
index 29135de..3ea81ed 100644
--- a/kernel/fs/btrfs/locking.h
+++ b/kernel/fs/btrfs/locking.h
@@ -6,24 +6,118 @@
#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_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);
+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)
{
@@ -37,13 +131,19 @@
BUG();
}
-static inline void btrfs_set_lock_blocking(struct extent_buffer *eb)
-{
- btrfs_set_lock_blocking_rw(eb, BTRFS_WRITE_LOCK);
-}
+struct btrfs_drew_lock {
+ atomic_t readers;
+ struct percpu_counter writers;
+ wait_queue_head_t pending_writers;
+ wait_queue_head_t pending_readers;
+};
-static inline void btrfs_clear_lock_blocking(struct extent_buffer *eb)
-{
- btrfs_clear_lock_blocking_rw(eb, BTRFS_WRITE_LOCK_BLOCKING);
-}
+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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