linux-kernel - Re: [PATCH 01/17] Add ida and idr helper routines.

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Date:	Tue, 15 Sep 2015 14:27:55 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Lee Duncan <lduncan@...e.com>
Cc:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Hannes Reinecke <hare@...e.com>,
	Johannes Thumshirn <jthumshirn@...e.de>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 01/17] Add ida and idr helper routines.

Hello,

On Tue, Sep 15, 2015 at 09:46:01AM -0700, Lee Duncan wrote:
> +/**
> + * ida_get_index - allocate a ida index value
> + * @ida		idr handle
> + * @lock	spinlock handle protecting this index
> + * @p_id	pointer to allocated index value
> + *
> + * A helper function for safely allocating an index value (id),
> + * returning a negative errno value on failure, else 0.
> + */
> +static inline int ida_get_index(struct ida *ida, spinlock_t *lock, int *p_id)
> +{
> +	int error = -ENOMEM;
> +
> +	do {
> +		if (!ida_pre_get(ida, GFP_KERNEL))
> +			break;
> +		spin_lock(lock);
> +		error = ida_get_new(ida, p_id);
> +		spin_unlock(lock);
> +	} while (error == -EAGAIN);
> +
> +	return error;
> +}

Obviously ida allocation doesn't need to be synchronized against
anything else.  Why not just use ida_simple_get/remove()?

Thanks.

-- 
tejun
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