linux-kernel - Re: idr_get_new

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Message-ID: <adaiq20f90h.fsf@cisco.com>
Date:	Mon, 20 Sep 2010 13:35:42 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	Ohad Ben-Cohen <ohad@...ery.com>
Cc:	linux-kernel@...r.kernel.org,
	"Jean Delvare \(PC drivers\, core\)" <khali@...ux-fr.org>,
	"Ben Dooks \(embedded platforms\)" <ben-linux@...ff.org>,
	Roland Dreier <rolandd@...co.com>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Steve Wise <swise@...lsio.com>, Neil Brown <neilb@...e.de>,
	Paul Mackerras <paulus@...ba.org>, linux-i2c@...r.kernel.org,
	linux-rdma@...r.kernel.org, dm-devel@...hat.com,
	linux-raid@...r.kernel.org, linux-ppp@...r.kernel.org,
	netdev@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: idr_get_new_exact ?

 > Occasionally, drivers care about the value that idr associates with
 > their pointers.
 > 
 > Today we have idr_get_new_above() which allocates a new idr entry
 > above or equal to a given starting id, but sometimes drivers need to
 > force an exact value.
 > 
 > To overcome this small API gap, drivers are wrapping idr_get_new_above
 > and then either BUG_ON() or just call idr_remove() and returns -EBUSY
 > when idr allocates them an id which is different than their requested
 > value.

Looks fine to me as an improvement over the status quo, but I wonder how
many of these places could use the radix_tree stuff instead?  If you're
not using the ability of the idr code to assign an id for you, then it
seems the radix_tree API is a better fit.

 - R.
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