linux-kernel - Re: [PATCH] ixgbe: Don't call kmap() on page allocated with GFP

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Message-ID: <CAKgT0UcGvjczCZXBS_OunwnZ5Xc7ytDRqjpymiXQni0ugrdmug@mail.gmail.com>
Date:   Tue, 5 Jul 2022 12:52:36 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH] ixgbe: Don't call kmap() on page allocated with GFP_ATOMIC

On Tue, Jul 5, 2022 at 11:22 AM Ira Weiny <ira.weiny@...el.com> wrote:
>
> On Mon, Jul 04, 2022 at 04:01:29PM +0200, Fabio M. De Francesco wrote:
> > Pages allocated with GFP_ATOMIC cannot come from Highmem. This is why
> > there is no need to call kmap() on them.
>
> I'm still not 100% sure where this page gets allocated but AFAICT it is
> allocated in ixgbe_alloc_mapped_page() which calls dev_alloc_pages() for the
> allocation which is where the GFP_ATOMIC is specified.
>
> I think I would add this detail here.
>
> That said, and assuming my analysis is correct, the code looks fine so:

Yeah, this is actually called out in other spots in the buffer
cleaning path. This is just something I had overlooked and left in
place back a few refactors ago.. :-)

https://elixir.bootlin.com/linux/latest/source/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c#L1795

Reviewed-by: Alexander Duyck <alexanderduyck@...com>