Btrfs: use dget_parent where we can UPDATED

There are lots of places where we do dentry->d_parent->d_inode without holding
the dentry->d_lock.  This could cause problems with rename.  So instead we need
to use dget_parent() and hold the reference to the parent as long as we are
going to use it's inode and then dput it at the end.

Signed-off-by: Josef Bacik <josef@redhat.com>
Cc: raven@themaw.net
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 1fffbc017bdf..f50e931fc217 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -902,6 +902,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         struct btrfs_root *root = pending->root;
         struct btrfs_root *parent_root;
         struct inode *parent_inode;
+        struct dentry *parent;
         struct dentry *dentry;
         struct extent_buffer *tmp;
         struct extent_buffer *old;
@@ -941,7 +942,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         trans->block_rsv = &pending->block_rsv;
 
         dentry = pending->dentry;
-        parent_inode = dentry->d_parent->d_inode;
+        parent = dget_parent(dentry);
+        parent_inode = parent->d_inode;
         parent_root = BTRFS_I(parent_inode)->root;
         record_root_in_trans(trans, parent_root);
 
@@ -989,6 +991,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
                                  parent_inode->i_ino, index,
                                  dentry->d_name.name, dentry->d_name.len);
         BUG_ON(ret);
+        dput(parent);
 
         key.offset = (u64)-1;
         pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);