linux-kernel - Re: [net PATCH 0/2] Address recent issues found in netdev page_frag

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Message-Id: <20190217.155026.2230689002634375366.davem@davemloft.net>
Date:   Sun, 17 Feb 2019 15:50:26 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     alexander.duyck@...il.com
Cc:     netdev@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, jannh@...gle.com
Subject: Re: [net PATCH 0/2] Address recent issues found in netdev
 page_frag_alloc usage

From: Alexander Duyck <alexander.duyck@...il.com>
Date: Fri, 15 Feb 2019 14:44:05 -0800

> This patch set addresses a couple of issues that I had pointed out to Jann
> Horn in response to a recent patch submission.
> 
> The first issue is that I wanted to avoid the need to read/modify/write the
> size value in order to generate the value for pagecnt_bias. Instead we can
> just use a fixed constant which reduces the need for memory read operations
> and the overall number of instructions to update the pagecnt bias values.
> 
> The other, and more important issue is, that apparently we were letting tun
> access the napi_alloc_cache indirectly through netdev_alloc_frag and as a
> result letting it create unaligned accesses via unaligned allocations. In
> order to prevent this I have added a call to SKB_DATA_ALIGN for the fragsz
> field so that we will keep the offset in the napi_alloc_cache
> SMP_CACHE_BYTES aligned.

Series applied, thanks Alexander.