linux-kernel - Re: [PATCH] lib/rhashtable: reorder some inititalization sequences

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Date:   Mon, 14 May 2018 22:52:13 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     dave@...olabs.net
Cc:     akpm@...ux-foundation.org, tgraf@...g.ch,
        herbert@...dor.apana.org.au, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, dbueso@...e.de
Subject: Re: [PATCH] lib/rhashtable: reorder some inititalization sequences

From: Davidlohr Bueso <dave@...olabs.net>
Date: Mon, 14 May 2018 08:13:32 -0700

> rhashtable_init() allocates memory at the very end of the
> call, once everything is setup; with the exception of the
> nelems parameter. However, unless the user is doing something
> bogus with params for which -EINVAL is returned, memory
> allocation is the only operation that can trigger the call
> to fail.
> 
> Thus move bucket_table_alloc() up such that we fail back to
> the caller asap, instead of doing useless checks. This is
> safe as the the table allocation isn't using the halfly
> setup 'ht' structure and bucket_table_alloc() call chain only
> ends up using the ht->nulls_base member in INIT_RHT_NULLS_HEAD.
> 
> Also move the locking initialization down to the end.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

The user potentially "doing something bogus" is why the most
expensive part of the initialization (the memory allocation)
is done after everything else is validated.

I think it's best to keep things as-is.