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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2008 Oracle.  All rights reserved.
  */
 
 #include <linux/sched.h>
 #include <linux/pagemap.h>
 #include <linux/spinlock.h>
 #include <linux/page-flags.h>
 #include <asm/bug.h>
 #include "misc.h"
 #include "ctree.h"
 #include "extent_io.h"
 #include "locking.h"
 
 /*
  * Lockdep class keys for extent_buffer->lock's in this root.  For a given
  * eb, the lockdep key is determined by the btrfs_root it belongs to and
  * the level the eb occupies in the tree.
  *
  * Different roots are used for different purposes and may nest inside each
  * other and they require separate keysets.  As lockdep keys should be
  * static, assign keysets according to the purpose of the root as indicated
  * by btrfs_root->root_key.objectid.  This ensures that all special purpose
  * roots have separate keysets.
  *
  * Lock-nesting across peer nodes is always done with the immediate parent
  * node locked thus preventing deadlock.  As lockdep doesn't know this, use
  * subclass to avoid triggering lockdep warning in such cases.
  *
  * The key is set by the readpage_end_io_hook after the buffer has passed
  * csum validation but before the pages are unlocked.  It is also set by
  * btrfs_init_new_buffer on freshly allocated blocks.
  *
  * We also add a check to make sure the highest level of the tree is the
  * same as our lockdep setup here.  If BTRFS_MAX_LEVEL changes, this code
  * needs update as well.
  */
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 #if BTRFS_MAX_LEVEL != 8
 #error
 #endif
 
 #define DEFINE_LEVEL(stem, level)                   \
     .names[level] = "btrfs-" stem "-0" #level,
 
 #define DEFINE_NAME(stem)                       \
     DEFINE_LEVEL(stem, 0)                       \
     DEFINE_LEVEL(stem, 1)                       \
     DEFINE_LEVEL(stem, 2)                       \
     DEFINE_LEVEL(stem, 3)                       \
     DEFINE_LEVEL(stem, 4)                       \
     DEFINE_LEVEL(stem, 5)                       \
     DEFINE_LEVEL(stem, 6)                       \
     DEFINE_LEVEL(stem, 7)
 
 static struct btrfs_lockdep_keyset {
     u64         id;     /* root objectid */
     /* Longest entry: btrfs-free-space-00 */
     char            names[BTRFS_MAX_LEVEL][20];
     struct lock_class_key   keys[BTRFS_MAX_LEVEL];
 } btrfs_lockdep_keysets[] = {
     { .id = BTRFS_ROOT_TREE_OBJECTID,   DEFINE_NAME("root") },
     { .id = BTRFS_EXTENT_TREE_OBJECTID, DEFINE_NAME("extent")   },
     { .id = BTRFS_CHUNK_TREE_OBJECTID,  DEFINE_NAME("chunk")    },
     { .id = BTRFS_DEV_TREE_OBJECTID,    DEFINE_NAME("dev")  },
     { .id = BTRFS_CSUM_TREE_OBJECTID,   DEFINE_NAME("csum") },
     { .id = BTRFS_QUOTA_TREE_OBJECTID,  DEFINE_NAME("quota")    },
     { .id = BTRFS_TREE_LOG_OBJECTID,    DEFINE_NAME("log")  },
     { .id = BTRFS_TREE_RELOC_OBJECTID,  DEFINE_NAME("treloc")   },
     { .id = BTRFS_DATA_RELOC_TREE_OBJECTID, DEFINE_NAME("dreloc")   },
     { .id = BTRFS_UUID_TREE_OBJECTID,   DEFINE_NAME("uuid") },
     { .id = BTRFS_FREE_SPACE_TREE_OBJECTID, DEFINE_NAME("free-space") },
     { .id = 0,              DEFINE_NAME("tree") },
 };
 
 #undef DEFINE_LEVEL
 #undef DEFINE_NAME
 
 void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb, int level)
 {
     struct btrfs_lockdep_keyset *ks;
 
     BUG_ON(level >= ARRAY_SIZE(ks->keys));
 
     /* Find the matching keyset, id 0 is the default entry */
     for (ks = btrfs_lockdep_keysets; ks->id; ks++)
         if (ks->id == objectid)
             break;
 
     lockdep_set_class_and_name(&eb->lock, &ks->keys[level], ks->names[level]);
 }
 
 void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, struct extent_buffer *eb)
 {
     if (test_bit(BTRFS_ROOT_RESET_LOCKDEP_CLASS, &root->state))
         btrfs_set_buffer_lockdep_class(root->root_key.objectid,
                            eb, btrfs_header_level(eb));
 }
 
 #endif
 
 /*
  * Extent buffer locking
  * =====================
  *
  * We use a rw_semaphore for tree locking, and the semantics are exactly the
  * same:
  *
  * - reader/writer exclusion
  * - writer/writer exclusion
  * - reader/reader sharing
  * - try-lock semantics for readers and writers
  *
  * The rwsem implementation does opportunistic spinning which reduces number of
  * times the locking task needs to sleep.
  */
 
 /*
  * __btrfs_tree_read_lock - lock extent buffer for read
  * @eb:     the eb to be locked
  * @nest:   the nesting level to be used for lockdep
  *
  * This takes the read lock on the extent buffer, using the specified nesting
  * level for lockdep purposes.
  */
 void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest)
 {
     u64 start_ns = 0;
 
     if (trace_btrfs_tree_read_lock_enabled())
         start_ns = ktime_get_ns();
 
     down_read_nested(&eb->lock, nest);
     trace_btrfs_tree_read_lock(eb, start_ns);
 }
 
 void btrfs_tree_read_lock(struct extent_buffer *eb)
 {
     __btrfs_tree_read_lock(eb, BTRFS_NESTING_NORMAL);
 }
 
 /*
  * Try-lock for read.
  *
  * Return 1 if the rwlock has been taken, 0 otherwise
  */
 int btrfs_try_tree_read_lock(struct extent_buffer *eb)
 {
     if (down_read_trylock(&eb->lock)) {
         trace_btrfs_try_tree_read_lock(eb);
         return 1;
     }
     return 0;
 }
 
 /*
  * Try-lock for write.
  *
  * Return 1 if the rwlock has been taken, 0 otherwise
  */
 int btrfs_try_tree_write_lock(struct extent_buffer *eb)
 {
     if (down_write_trylock(&eb->lock)) {
         eb->lock_owner = current->pid;
         trace_btrfs_try_tree_write_lock(eb);
         return 1;
     }
     return 0;
 }
 
 /*
  * Release read lock.
  */
 void btrfs_tree_read_unlock(struct extent_buffer *eb)
 {
     trace_btrfs_tree_read_unlock(eb);
     up_read(&eb->lock);
 }
 
 /*
  * __btrfs_tree_lock - lock eb for write
  * @eb:     the eb to lock
  * @nest:   the nesting to use for the lock
  *
  * Returns with the eb->lock write locked.
  */
 void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest)
     __acquires(&eb->lock)
 {
     u64 start_ns = 0;
 
     if (trace_btrfs_tree_lock_enabled())
         start_ns = ktime_get_ns();
 
     down_write_nested(&eb->lock, nest);
     eb->lock_owner = current->pid;
     trace_btrfs_tree_lock(eb, start_ns);
 }
 
 void btrfs_tree_lock(struct extent_buffer *eb)
 {
     __btrfs_tree_lock(eb, BTRFS_NESTING_NORMAL);
 }
 
 /*
  * Release the write lock.
  */
 void btrfs_tree_unlock(struct extent_buffer *eb)
 {
     trace_btrfs_tree_unlock(eb);
     eb->lock_owner = 0;
     up_write(&eb->lock);
 }
 
 /*
  * This releases any locks held in the path starting at level and going all the
  * way up to the root.
  *
  * btrfs_search_slot will keep the lock held on higher nodes in a few corner
  * cases, such as COW of the block at slot zero in the node.  This ignores
  * those rules, and it should only be called when there are no more updates to
  * be done higher up in the tree.
  */
 void btrfs_unlock_up_safe(struct btrfs_path *path, int level)
 {
     int i;
 
     if (path->keep_locks)
         return;
 
     for (i = level; i < BTRFS_MAX_LEVEL; i++) {
         if (!path->nodes[i])
             continue;
         if (!path->locks[i])
             continue;
         btrfs_tree_unlock_rw(path->nodes[i], path->locks[i]);
         path->locks[i] = 0;
     }
 }
 
 /*
  * Loop around taking references on and locking the root node of the tree until
  * we end up with a lock on the root node.
  *
  * Return: root extent buffer with write lock held
  */
 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root)
 {
     struct extent_buffer *eb;
 
     while (1) {
         eb = btrfs_root_node(root);
 
         btrfs_maybe_reset_lockdep_class(root, eb);
         btrfs_tree_lock(eb);
         if (eb == root->node)
             break;
         btrfs_tree_unlock(eb);
         free_extent_buffer(eb);
     }
     return eb;
 }
 
 /*
  * Loop around taking references on and locking the root node of the tree until
  * we end up with a lock on the root node.
  *
  * Return: root extent buffer with read lock held
  */
 struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
 {
     struct extent_buffer *eb;
 
     while (1) {
         eb = btrfs_root_node(root);
 
         btrfs_maybe_reset_lockdep_class(root, eb);
         btrfs_tree_read_lock(eb);
         if (eb == root->node)
             break;
         btrfs_tree_read_unlock(eb);
         free_extent_buffer(eb);
     }
     return eb;
 }
 
 /*
  * DREW locks
  * ==========
  *
  * DREW stands for double-reader-writer-exclusion lock. It's used in situation
  * where you want to provide A-B exclusion but not AA or BB.
  *
  * Currently implementation gives more priority to reader. If a reader and a
  * writer both race to acquire their respective sides of the lock the writer
  * would yield its lock as soon as it detects a concurrent reader. Additionally
  * if there are pending readers no new writers would be allowed to come in and
  * acquire the lock.
  */
 
 int btrfs_drew_lock_init(struct btrfs_drew_lock *lock)
 {
     int ret;
 
     ret = percpu_counter_init(&lock->writers, 0, GFP_KERNEL);
     if (ret)
         return ret;
 
     atomic_set(&lock->readers, 0);
     init_waitqueue_head(&lock->pending_readers);
     init_waitqueue_head(&lock->pending_writers);
 
     return 0;
 }
 
 void btrfs_drew_lock_destroy(struct btrfs_drew_lock *lock)
 {
     percpu_counter_destroy(&lock->writers);
 }
 
 /* Return true if acquisition is successful, false otherwise */
 bool btrfs_drew_try_write_lock(struct btrfs_drew_lock *lock)
 {
     if (atomic_read(&lock->readers))
         return false;
 
     percpu_counter_inc(&lock->writers);
 
     /* Ensure writers count is updated before we check for pending readers */
     smp_mb();
     if (atomic_read(&lock->readers)) {
         btrfs_drew_write_unlock(lock);
         return false;
     }
 
     return true;
 }
 
 void btrfs_drew_write_lock(struct btrfs_drew_lock *lock)
 {
     while (true) {
         if (btrfs_drew_try_write_lock(lock))
             return;
         wait_event(lock->pending_writers, !atomic_read(&lock->readers));
     }
 }
 
 void btrfs_drew_write_unlock(struct btrfs_drew_lock *lock)
 {
     percpu_counter_dec(&lock->writers);
     cond_wake_up(&lock->pending_readers);
 }
 
 void btrfs_drew_read_lock(struct btrfs_drew_lock *lock)
 {
     atomic_inc(&lock->readers);
 
     /*
      * Ensure the pending reader count is perceieved BEFORE this reader
      * goes to sleep in case of active writers. This guarantees new writers
      * won't be allowed and that the current reader will be woken up when
      * the last active writer finishes its jobs.
      */
     smp_mb__after_atomic();
 
     wait_event(lock->pending_readers,
            percpu_counter_sum(&lock->writers) == 0);
 }
 
 void btrfs_drew_read_unlock(struct btrfs_drew_lock *lock)
 {
     /*
      * atomic_dec_and_test implies a full barrier, so woken up writers
      * are guaranteed to see the decrement
      */
     if (atomic_dec_and_test(&lock->readers))
         wake_up(&lock->pending_writers);
 }

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