btrfs: move common inode creation code into btrfs_create_new_inode()

All of our inode creation code paths duplicate the calls to
btrfs_init_inode_security() and btrfs_add_link(). Subvolume creation
additionally duplicates property inheritance and the call to
btrfs_set_inode_index(). Fix this by moving the common code into
btrfs_create_new_inode(). This accomplishes a few things at once:

1. It reduces code duplication.

2. It allows us to set up the inode completely before inserting the
   inode item, removing calls to btrfs_update_inode().

3. It fixes a leak of an inode on disk in some error cases. For example,
   in btrfs_create(), if btrfs_new_inode() succeeds, then we have
   inserted an inode item and its inode ref. However, if something after
   that fails (e.g., btrfs_init_inode_security()), then we end the
   transaction and then decrement the link count on the inode. If the
   transaction is committed and the system crashes before the failed
   inode is deleted, then we leak that inode on disk. Instead, this
   refactoring aborts the transaction when we can't recover more
   gracefully.

4. It exposes various ways that subvolume creation diverges from mkdir
   in terms of inheriting flags, properties, permissions, and POSIX
   ACLs, a lot of which appears to be accidental. This patch explicitly
   does _not_ change the existing non-standard behavior, but it makes
   those differences more clear in the code and documents them so that
   we can discuss whether they should be changed.

Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 5 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 768339a3f99d..9addfd5cdf4e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3302,14 +3302,10 @@ struct btrfs_new_inode_args {
 int btrfs_new_inode_prepare(struct btrfs_new_inode_args *args,
 			    unsigned int *trans_num_items);
 int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
-			   struct btrfs_new_inode_args *args,
-			   u64 *index);
+			   struct btrfs_new_inode_args *args);
 void btrfs_new_inode_args_destroy(struct btrfs_new_inode_args *args);
 struct inode *btrfs_new_subvol_inode(struct user_namespace *mnt_userns,
 				     struct inode *dir);
-int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
-			     struct btrfs_root *parent_root,
-			     struct btrfs_new_inode_args *args);
  void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state,
 			       unsigned *bits);
 void btrfs_clear_delalloc_extent(struct inode *inode,