When we are logging a new name for an inode, due to a link or rename
operation, if the inode has ancestor inodes that are new, created in the
current transaction, we need to log that these inodes exist. To ensure
that a subsequent explicit fsync on one of these ancestor inodes does
sync the log, we don't set the logged_trans field of these inodes.
This was done in commit 75b463d2 ("btrfs: do not commit logs and
transactions during link and rename operations"), to avoid syncing a
log after a rename or link operation.

In order to allow for future changes to do some optimizations, change
this behaviour to always update the logged_trans of any logged inode
and don't update the last_log_commit of the inode if we are logging
that it exists. This accomplishes that same objective with simpler
logic, allowing for some optimizations in the next patches.

So just do that simplification.

This patch is part of a patch set comprised of the following patches:

  btrfs: check if a log tree exists at inode_logged()
  btrfs: remove no longer needed checks for NULL log context
  btrfs: do not log new dentries when logging that a new name exists
  btrfs: always update the logged transaction when logging new names
  btrfs: avoid expensive search when dropping inode items from log
  btrfs: add helper to truncate inode items when logging inode
  btrfs: avoid expensive search when truncating inode items from the log
  btrfs: avoid search for logged i_size when logging inode if possible
  btrfs: avoid attempt to drop extents when logging inode for the first time
  btrfs: do not commit delayed inode when logging a file in full sync mode

This is patch 4/10 and test results are listed in the change log of the
last patch in the set.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>