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, 16 insertions, 4 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 6b4bfa72bf8d..f1c9bb4079ed 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -233,7 +233,8 @@ static noinline int create_subvol(struct btrfs_root *root,
         struct btrfs_inode_item *inode_item;
         struct extent_buffer *leaf;
         struct btrfs_root *new_root;
-        struct inode *dir = dentry->d_parent->d_inode;
+        struct dentry *parent = dget_parent(dentry);
+        struct inode *dir;
         int ret;
         int err;
         u64 objectid;
@@ -242,8 +243,13 @@ static noinline int create_subvol(struct btrfs_root *root,
 
         ret = btrfs_find_free_objectid(NULL, root->fs_info->tree_root,
                                        0, &objectid);
-        if (ret)
+        if (ret) {
+                dput(parent);
                 return ret;
+        }
+
+        dir = parent->d_inode;
+
         /*
          * 1 - inode item
          * 2 - refs
@@ -251,8 +257,10 @@ static noinline int create_subvol(struct btrfs_root *root,
          * 2 - dir items
          */
         trans = btrfs_start_transaction(root, 6);
-        if (IS_ERR(trans))
+        if (IS_ERR(trans)) {
+                dput(parent);
                 return PTR_ERR(trans);
+        }
 
         leaf = btrfs_alloc_free_block(trans, root, root->leafsize,
                                       0, objectid, NULL, 0, 0, 0);
@@ -339,6 +347,7 @@ static noinline int create_subvol(struct btrfs_root *root,
 
         d_instantiate(dentry, btrfs_lookup_dentry(dir, dentry));
 fail:
+        dput(parent);
         if (async_transid) {
                 *async_transid = trans->transid;
                 err = btrfs_commit_transaction_async(trans, root, 1);
@@ -354,6 +363,7 @@ static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
                            char *name, int namelen, u64 *async_transid)
 {
         struct inode *inode;
+        struct dentry *parent;
         struct btrfs_pending_snapshot *pending_snapshot;
         struct btrfs_trans_handle *trans;
         int ret;
@@ -396,7 +406,9 @@ static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
 
         btrfs_orphan_cleanup(pending_snapshot->snap);
 
-        inode = btrfs_lookup_dentry(dentry->d_parent->d_inode, dentry);
+        parent = dget_parent(dentry);
+        inode = btrfs_lookup_dentry(parent->d_inode, dentry);
+        dput(parent);
         if (IS_ERR(inode)) {
                 ret = PTR_ERR(inode);
                 goto fail;