linux-kernel - Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers)

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Message-ID: <20150917151026.GB7205@mtj.duckdns.org>
Date:	Thu, 17 Sep 2015 11:10:26 -0400
From:	Tejun Heo <htejun@...il.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>, Suman Anna <s-anna@...com>,
	Ohad Ben-Cohen <ohad@...ery.com>, linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	linux-scsi@...r.kernel.org, open-iscsi@...glegroups.com
Subject: Re: DEFINE_IDA causing memory leaks? (was  Re: [PATCH 1/2] virtio:
 fix memory leak of virtio ida cache layers)

Hello,

On Thu, Sep 17, 2015 at 07:15:44AM -0700, James Bottomley wrote:
> I don't understand why you'd want to forbid DEFINE_IDA ... all it does

I guess to require the use of explicit init / creation so that it's
clear the data structure needs to be destroyed?

> is pre-initialise a usually static ida structure.  The initialised
> structure will have a NULL bitmap cache that's allocated in the first
> ida_pre_get() ... that all seems to work as expected and no different
> from a dynamically allocated struct ida.  Or are you thinking because
> ida_destory() doesn't set bitmap to NULL, it damages the reuse?  In
> which case I'm not sure there's much benefit to making it reusable, but
> I suppose we could by adding a memset into ida_destroy().

I don't know.  Data structures which do lazy anything would likely
need explicit destruction and I'm not sure we'd wanna ban static
initialization for all such cases.  Seems like an unnecessary
restriction.

Thanks.

-- 
tejun
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