linux-kernel - Re: [PATCH net-next 9/9] net: ipa: use a bitmap for enabled endpoints

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Date:   Wed, 2 Nov 2022 07:44:35 -0500
From:   Alex Elder <elder@...aro.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        mka@...omium.org, evgreen@...omium.org, andersson@...nel.org,
        quic_cpratapa@...cinc.com, quic_avuyyuru@...cinc.com,
        quic_jponduru@...cinc.com, quic_subashab@...cinc.com,
        elder@...nel.org, netdev@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 9/9] net: ipa: use a bitmap for enabled endpoints

On 11/1/22 11:34 PM, Jakub Kicinski wrote:
> On Sat, 29 Oct 2022 19:18:28 -0500 Alex Elder wrote:
>>   	/* Set up the defined endpoint bitmap */
>>   	ipa->defined = bitmap_zalloc(ipa->endpoint_count, GFP_KERNEL);
>>   	ipa->set_up = bitmap_zalloc(ipa->endpoint_count, GFP_KERNEL);
>> +	ipa->enabled = bitmap_zalloc(ipa->endpoint_count, GFP_KERNEL);
>>   	if (!ipa->defined || !ipa->set_up) {
> 
> This condition should now check if ipa->enabled

You're right.

> And the error handling patch needs to free it, in case it was something
> else that didn't get allocated?

See below, but in any case, I'll make sure this is right.

> Frankly I have gotten mass-NULL-checks wrong more than once myself so
> I'd steer clear of those, they are strangely error prone.

I don't typically do it, and generally don't like it,
but I think I was trying to make it look cleaner
somehow.  I'll check every one in separately in v2.

>>   		dev_err(dev, "unable to allocate endpoint bitmaps\n");
> 
> this error message should not be here (patch 5 adds it I think)
> memory allocation failures produce a splat, no need to print errors

At the end of the series, the structure of this
error handling changes, and I think this is
correct.  But now that you point this out I
think the way this evolves in the series could
use some improvement so I'll take another look
at it and hopefully make it better.

I don't normally report anything on allocation
failures for that reason; thanks for pointing
this out.

I really appreciate your feedback.  I'll send
out version 2 today.

					-Alex

>> +		bitmap_free(ipa->set_up);
>> +		ipa->set_up = NULL;
>>   		bitmap_free(ipa->defined);