Btrfs: Add delayed iput

iput() can trigger new transactions if we are dropping the
final reference, so calling it in btrfs_commit_transaction
may end up deadlock. This patch adds delayed iput to avoid
the issue.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c1e59e33f020..009e3bd18f23 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1476,6 +1476,7 @@ static int cleaner_kthread(void *arg)
 
                 if (!(root->fs_info->sb->s_flags & MS_RDONLY) &&
                     mutex_trylock(&root->fs_info->cleaner_mutex)) {
+                        btrfs_run_delayed_iputs(root);
                         btrfs_clean_old_snapshots(root);
                         mutex_unlock(&root->fs_info->cleaner_mutex);
                 }
@@ -1605,6 +1606,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
         INIT_LIST_HEAD(&fs_info->trans_list);
         INIT_LIST_HEAD(&fs_info->dead_roots);
+        INIT_LIST_HEAD(&fs_info->delayed_iputs);
         INIT_LIST_HEAD(&fs_info->hashers);
         INIT_LIST_HEAD(&fs_info->delalloc_inodes);
         INIT_LIST_HEAD(&fs_info->ordered_operations);
@@ -1613,6 +1615,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         spin_lock_init(&fs_info->new_trans_lock);
         spin_lock_init(&fs_info->ref_cache_lock);
         spin_lock_init(&fs_info->fs_roots_radix_lock);
+        spin_lock_init(&fs_info->delayed_iput_lock);
 
         init_completion(&fs_info->kobj_unregister);
         fs_info->tree_root = tree_root;
@@ -2386,6 +2389,7 @@ int btrfs_commit_super(struct btrfs_root *root)
         int ret;
 
         mutex_lock(&root->fs_info->cleaner_mutex);
+        btrfs_run_delayed_iputs(root);
         btrfs_clean_old_snapshots(root);
         mutex_unlock(&root->fs_info->cleaner_mutex);