linux-kernel - Re: [PATCH V4 10/12] block: call __bio_free in bio

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Date:   Wed, 28 Jun 2017 23:29:08 +0200
From:   Christoph Hellwig <hch@....de>
To:     Shaohua Li <shli@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        tj@...nel.org, gregkh@...uxfoundation.org, hch@....de,
        axboe@...com, rostedt@...dmis.org, lizefan@...wei.com,
        Kernel-team@...com, Shaohua Li <shli@...com>
Subject: Re: [PATCH V4 10/12] block: call __bio_free in bio_endio

On Wed, Jun 28, 2017 at 09:30:00AM -0700, Shaohua Li wrote:
> From: Shaohua Li <shli@...com>
> 
> bio_free isn't a good place to free cgroup/integrity info. There are a
> lot of cases bio is allocated in special way (for example, in stack) and
> never gets called by bio_put hence bio_free, we are leaking memory. This
> patch moves the free to bio endio, which should be called anyway. The
> __bio_free call in bio_free is kept, in case the bio never gets called
> bio endio.
> 
> This assumes ->bi_end_io() doesn't access cgroup/integrity info, which
> seems true in my audit. Otherwise, we probably must add a flag to
> distinguish if bio will be called by bio_put.

bio_integrity_endio -> bio_integrity_verify_fn -> bio_integrity_process
access the integrity data, so I don't think this works as-is.