linux-kernel - Re: [Ocfs2-devel] [PATCH 1/1 linux-next] ocfs2: remove unnecessary sizeof(char)

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Message-Id: <20141222133501.916a0944e5f0719e60e2c4eb@linux-foundation.org>
Date:	Mon, 22 Dec 2014 13:35:01 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Fabian Frederick <fabf@...net.be>
Cc:	linux-kernel@...r.kernel.org, joe@...ches.com,
	ocfs2-devel@....oracle.com, Mark Fasheh <mfasheh@...e.com>
Subject: Re: [Ocfs2-devel] [PATCH 1/1 linux-next] ocfs2: remove unnecessary
 sizeof(char)

On Mon, 22 Dec 2014 20:05:09 +0100 Fabian Frederick <fabf@...net.be> wrote:

> sizeof(char) is always 1.
> 
> ...
>
> --- a/fs/ocfs2/journal.c
> +++ b/fs/ocfs2/journal.c
> @@ -129,8 +129,8 @@ int ocfs2_compute_replay_slots(struct ocfs2_super *osb)
>  	if (osb->replay_map)
>  		return 0;
>  
> -	replay_map = kzalloc(sizeof(struct ocfs2_replay_map) +
> -			     (osb->max_slots * sizeof(char)), GFP_KERNEL);
> +	replay_map = kzalloc(sizeof(struct ocfs2_replay_map) + osb->max_slots,
> +			     GFP_KERNEL);
>  
>  	if (!replay_map) {
>  		mlog_errno(-ENOMEM);

I dunno.  The code at present isn't particularly idiomatic, but it has
some documentation value and says "I know what I'm doing".

It would be better if it was

	kzalloc(sizeof(struct ocfs2_replay_map) *
		sizeof(struct ocfs2_replay_map.rm_replay_slots[0]), ...);

And it would be better if C permitted that ;)

	kzalloc(sizeof(struct ocfs2_replay_map) *
		sizeof((struct ocfs2_replay_map *)0)->rm_replay_slots[0]), ...);

yuk.

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