netdev - Re: [PATCH] be2net: fix adapter->big_page

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Date:   Fri, 12 Jul 2019 15:46:06 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     cai@....pw
Cc:     sathya.perla@...adcom.com, ajit.khaparde@...adcom.com,
        sriharsha.basavapatna@...adcom.com, somnath.kotur@...adcom.com,
        arnd@...db.de, dhowells@...hat.com, hpa@...or.com,
        netdev@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] be2net: fix adapter->big_page_size miscaculation

From: Qian Cai <cai@....pw>
Date: Fri, 12 Jul 2019 15:23:21 -0400

> The commit d66acc39c7ce ("bitops: Optimise get_order()") introduced a
> problem for the be2net driver as "rx_frag_size" could be a module
> parameter that can be changed while loading the module.

Why is this a problem?

> That commit checks __builtin_constant_p() first in get_order() which
> cause "adapter->big_page_size" to be assigned a value based on the
> the default "rx_frag_size" value at the compilation time. It also
> generate a compilation warning,

rx_frag_size is not a constant, therefore the __builtin_constant_p()
test should not pass.

This explanation doesn't seem valid.