linux-kernel - Re: [PATCH 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

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Date:	Fri, 5 Feb 2016 12:24:34 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xen.org, konrad.wilk@...cle.com,
	david.vrabel@...rix.com
Cc:	stable@...r.kernel.org
Subject: Re: [PATCH 2/2] xen/scsiback: avoid warnings when adding multiple
 LUNs to a domain



On 02/05/2016 11:59 AM, Juergen Gross wrote:
> On 05/02/16 16:50, Boris Ostrovsky wrote:
>>
>> On 02/05/2016 08:21 AM, Juergen Gross wrote:
>>> When adding more than one LUN to a frontend a warning for a failed
>>> assignment is issued in dom0 for each already existing LUN. Avoid this
>>> warning.
>> Aren't you just factoring out the check? The warning is still printed
>> for each scsiback_add_translation_entry() invocation, no?
> I don't call scsiback_add_translation_entry() in the critical case.

Which is scsiback_do_add_lun()? If yes then perhaps you could mention it 
in the commit message since there are few changes that this patch 
provides and it's not clear which is the one that prevents the warning.

>
> @@ -962,33 +973,31 @@ static int scsiback_del_translation_entry(struct
> vscsibk_info *info,
>                          struct ids_tuple *v)
>    {
>        struct v2p_entry *entry;
> -    struct list_head *head = &(info->v2p_entry_lists);
>        unsigned long flags;
>          spin_lock_irqsave(&info->v2p_lock, flags);
>        /* Find out the translation entry specified */
> -    list_for_each_entry(entry, head, l) {
> -        if ((entry->v.chn == v->chn) &&
> -            (entry->v.tgt == v->tgt) &&
> -            (entry->v.lun == v->lun)) {
> -            goto found;
> -        }
> -    }
> -
> -    spin_unlock_irqrestore(&info->v2p_lock, flags);
> -    return 1;
> -
> -found:
> -    /* Delete the translation entry specfied */
> -    __scsiback_del_translation_entry(entry);
> +    entry = scsiback_chk_translation_entry(info, v);
> +    if (entry)
> +        __scsiback_del_translation_entry(entry);
>          spin_unlock_irqrestore(&info->v2p_lock, flags);
> -    return 0;
> +    return entry == NULL;
>> Might be better to return -ENOENT instead of 1 above and -EEXISTS if
>> entry!=NULL, given that this returns an int.
> I just didn't want to change more than necessary. In case it is
> okay to do some cleanup as well I'd rather change the return type
> to "bool".

I don't think using error code will require changing anything except the 
last line above (which is already a change anyway)

But using a bool is OK too.

-boris