linux-kernel - Re: [PATCH] block: fix memory leak in bio

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Message-ID: <20090309192122.GZ11787@kernel.dk>
Date:	Mon, 9 Mar 2009 20:21:22 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc:	Li Zefan <lizf@...fujitsu.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] block: fix memory leak in bio_clone()

On Mon, Mar 09 2009, Martin K. Petersen wrote:
> Jens> The second bug is that it should be using its own bioset, as it is
> Jens> illegal to do multiple __GFP_WAIT allocations on a single mempool
> Jens> and always expect progress.
> 
> So how do you propose I go about this?
> 
> The original intent was to contain all the integrity blah inside the
> bio_set to make it completely transparent to the caller.  That's why the
> bip mempool is hanging off of the bio_set.  But obviously two bvecs are
> needed per bio, one to describe data and to describe the integrity
> buffer.
> 
> Having two bvec mempools per bio_set seems icky.  I guess what you are
> suggesting is that we could have a dedicated bio_integrity_set akin to
> the bio_split_pool.  That removes the caller's option of passing a
> dedicated bio_set to the clone command, though.  Will that have forward
> progress implications for stacking drivers?

I was just wondering why you wanted to pass the bio_set in to
bio_integrity_clone(), why would the caller care?

Even two mempools isn't that bad. You can reuse the slab of course, and
the mempool should only have a single entry preallocated. But I agree,
it should not be in the bio_set. A dedicated bio_set for the integrity
stuff would be the way to go, and that should provide you all the
forward progress guarantees you need.

-- 
Jens Axboe

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