4 files changed, 14 insertions, 10 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 17ad92c29cfd..38eeb6c49c8a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -827,6 +827,7 @@ struct btrfs_fs_info {
         struct mutex drop_mutex;
         struct mutex volume_mutex;
         struct mutex tree_reloc_mutex;
+        struct rw_semaphore extent_commit_sem;
 
         /*
          * this protects the ordered operations list only while we are
@@ -961,9 +962,6 @@ struct btrfs_root {
         /* the node lock is held while changing the node pointer */
         spinlock_t node_lock;
 
-        /* taken when updating the commit root */
-        struct rw_semaphore commit_root_sem;
-
         struct extent_buffer *commit_root;
         struct btrfs_root *log_root;
         struct btrfs_root *reloc_root;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3a9b88759880..3cf4cfa575c8 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -907,7 +907,6 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
         spin_lock_init(&root->inode_lock);
         mutex_init(&root->objectid_mutex);
         mutex_init(&root->log_mutex);
-        init_rwsem(&root->commit_root_sem);
         init_waitqueue_head(&root->log_writer_wait);
         init_waitqueue_head(&root->log_commit_wait[0]);
         init_waitqueue_head(&root->log_commit_wait[1]);
@@ -1624,6 +1623,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         mutex_init(&fs_info->cleaner_mutex);
         mutex_init(&fs_info->volume_mutex);
         mutex_init(&fs_info->tree_reloc_mutex);
+        init_rwsem(&fs_info->extent_commit_sem);
 
         btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
         btrfs_init_free_cluster(&fs_info->data_alloc_cluster);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index fadf69a2764b..2fe21fa74913 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -267,7 +267,7 @@ static int caching_kthread(void *data)
         last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
 again:
         /* need to make sure the commit_root doesn't disappear */
-        down_read(&fs_info->extent_root->commit_root_sem);
+        down_read(&fs_info->extent_commit_sem);
 
         /*
          * We don't want to deadlock with somebody trying to allocate a new
@@ -304,7 +304,7 @@ again:
 
                         if (need_resched()) {
                                 btrfs_release_path(fs_info->extent_root, path);
-                                up_read(&fs_info->extent_root->commit_root_sem);
+                                up_read(&fs_info->extent_commit_sem);
                                 cond_resched();
                                 goto again;
                         }
@@ -345,7 +345,7 @@ next:
 
 err:
         btrfs_free_path(path);
-        up_read(&fs_info->extent_root->commit_root_sem);
+        up_read(&fs_info->extent_commit_sem);
         atomic_dec(&block_group->space_info->caching_threads);
         wake_up(&block_group->caching_q);
 
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index e51d2bc532f8..de48e4ec808c 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -42,10 +42,8 @@ static noinline void put_transaction(struct btrfs_transaction *transaction)
 
 static noinline void switch_commit_root(struct btrfs_root *root)
 {
-        down_write(&root->commit_root_sem);
         free_extent_buffer(root->commit_root);
         root->commit_root = btrfs_root_node(root);
-        up_write(&root->commit_root_sem);
 }
 
 /*
@@ -466,7 +464,10 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
                 ret = btrfs_write_dirty_block_groups(trans, root);
                 BUG_ON(ret);
         }
-        switch_commit_root(root);
+
+        if (root != root->fs_info->extent_root)
+                switch_commit_root(root);
+
         return 0;
 }
 
@@ -499,6 +500,11 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
 
                 update_cowonly_root(trans, root);
         }
+
+        down_write(&fs_info->extent_commit_sem);
+        switch_commit_root(fs_info->extent_root);
+        up_write(&fs_info->extent_commit_sem);
+
         return 0;
 }