linux-kernel - Re: [PATCH v2 4/5] ALSA: xen-front: Implement handling of shared buffers

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Message-ID: <7abbbaa0-93c7-5c93-d653-ed5a04199f6e@suse.com>
Date:   Tue, 17 Apr 2018 13:15:51 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Oleksandr Andrushchenko <andr2000@...il.com>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, boris.ostrovsky@...cle.com,
        konrad.wilk@...cle.com, perex@...ex.cz, tiwai@...e.com
Cc:     Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [PATCH v2 4/5] ALSA: xen-front: Implement handling of shared
 buffers

On 17/04/18 11:22, Oleksandr Andrushchenko wrote:
> On 04/16/2018 04:39 PM, Juergen Gross wrote:
>> On 16/04/18 08:24, Oleksandr Andrushchenko wrote:
>>> +static int alloc_int_buffers(struct xen_snd_front_shbuf *buf,
>>> +                 int num_pages_dir, int num_pages_buffer,
>>> +                 int num_grefs)
>>> +{
>>> +    buf->grefs = kcalloc(num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
>>> +    if (!buf->grefs)
>>> +        return -ENOMEM;
>>> +
>>> +    buf->directory = kcalloc(num_pages_dir, XEN_PAGE_SIZE, GFP_KERNEL);
>>> +    if (!buf->directory)
>>> +        goto fail;
>>> +
>>> +    buf->buffer_sz = num_pages_buffer * XEN_PAGE_SIZE;
>>> +    buf->buffer = alloc_pages_exact(buf->buffer_sz, GFP_KERNEL);
>>> +    if (!buf->buffer)
>>> +        goto fail;
>>> +
>>> +    return 0;
>>> +
>>> +fail:
>>> +    kfree(buf->grefs);
>>> +    buf->grefs = NULL;
>>> +    kfree(buf->directory);
>> Why do you need to free those here? Shouldn't that be done via
>> xen_snd_front_shbuf_free() in case of an error?
> At this place we only allocate memory, but xen_snd_front_shbuf_free
> will also try to gnttab_end_foreign_access if buf->grefs != NULL.

Okay.


Juergen