btrfs: simplify condition for logging new dentries at btrfs_log_inode_parent()

There's no point in checking if the inode is a directory as
ctx->log_new_dentries is only set in case we are logging a directory down
the call chain of btrfs_log_inode(). So remove that check making the logic
more simple and while at it add a comment about why use a local variable
to track if we later need to log new dentries.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/tree-log.c

@@ -7036,7 +7036,7 @@ static int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
 	struct btrfs_root *root = inode->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	int ret = 0;
-	bool log_dentries = false;
+	bool log_dentries;
 
 	if (btrfs_test_opt(fs_info, NOTREELOG)) {
 		ret = BTRFS_LOG_FORCE_COMMIT;
@@ -7090,8 +7090,11 @@ static int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
 		goto end_trans;
 	}
 
-	if (S_ISDIR(inode->vfs_inode.i_mode) && ctx->log_new_dentries)
-		log_dentries = true;
+	/*
+	 * Track if we need to log dentries because ctx->log_new_dentries can
+	 * be modified in the call chains below.
+	 */
+	log_dentries = ctx->log_new_dentries;
 
 	/*
 	 * On unlink we must make sure all our current and old parent directory