Re: [PATCH 01/11] get rid of ...lookup...fdget_rcu() family

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On Mon, Aug 12, 2024 at 07:44:17AM GMT, Al Viro wrote:
> Once upon a time, predecessors of those used to do file lookup
> without bumping a refcount, provided that caller held rcu_read_lock()
> across the lookup and whatever it wanted to read from the struct
> file found.  When struct file allocation switched to SLAB_TYPESAFE_BY_RCU,
> that stopped being feasible and these primitives started to bump the
> file refcount for lookup result, requiring the caller to call fput()
> afterwards.
> 
> But that turned them pointless - e.g.
> 	rcu_read_lock();
> 	file = lookup_fdget_rcu(fd);
> 	rcu_read_unlock();
> is equivalent to
> 	file = fget_raw(fd);
> and all callers of lookup_fdget_rcu() are of that form.  Similarly,
> task_lookup_fdget_rcu() calls can be replaced with calling fget_task().
> task_lookup_next_fdget_rcu() doesn't have direct counterparts, but
> its callers would be happier if we replaced it with an analogue that
> deals with RCU internally.
> 
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---

Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>




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