From: Sumitra Sharma <sumitraartsy@gmail.com>
To: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Ira Weiny <ira.weiny@intel.com>, Deepak R Varma <drv@mailo.com>,
Sumitra Sharma <sumitraartsy@gmail.com>
Subject: Re: [PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag
Date: Tue, 27 Jun 2023 08:01:38 -0700 [thread overview]
Message-ID: <20230627150138.GB452923@sumitra.com> (raw)
In-Reply-To: <5846758.MhkbZ0Pkbq@suse>
On Mon, Jun 26, 2023 at 03:07:22PM +0200, Fabio M. De Francesco wrote:
> On venerdì 23 giugno 2023 17:16:44 CEST Sumitra Sharma wrote:
> > generate_test_data() acquires a page with alloc_page(GFP_KERNEL).
> > The GFP_KERNEL is typical for kernel-internal allocations.
> > The caller requires ZONE_NORMAL or a lower zone for direct access.
> >
> > Therefore the page cannot come from ZONE_HIGHMEM. Thus there's
> > no need to map it with kmap().
> >
> > Also, the kmap() is being deprecated in favor of kmap_local_page() [1].
> >
> > Hence, use a plain page_address() directly.
> >
> > Since the page passed to the page_address() is not from the highmem
> > zone, the page_address() function will always return a valid kernel
> > virtual address and will not return NULL. Hence, remove the check
> > 'if (!ptr)'.
> >
> > Remove the unused variable 'ptr' and label 'err_free_page'.
> >
> > [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/
> >
> > Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
>
> I can't see no more things that prevent my tag, then it is...
>
> Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
>
> Thanks for working on it for all the time it took to get to v4 and for
> listening to what you've been suggested to change.
>
> Well done :-)
Thank you, Fabio and Ira, for your tags and kind words :)
Thanks & regards
Sumitra
>
> Fabio
>
> > Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>
> > ---
> >
> > - Link to v1:
> > https://lore.kernel.org/bpf/20230613073020.GA359792@sumitra.com/T/ - Link to
> > v2: https://lore.kernel.org/all/20230613071756.GA359746@sumitra.com/ - Link
> > to v3: https://lore.kernel.org/all/20230622080729.GA426913@sumitra.com/
> >
> > Changes in v4:
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes:
> > https://lore.kernel.org/oe-kbuild-all/202306230559.hU5Aonpl-lkp@intel.com/ -
> > Remove unused label 'err_free_page'.
> >
> > Changes in v3:
> > Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> > - Remove the check 'if (!ptr)'.
> > - Remove the unused variable 'ptr'.
> > - Change the commit message.
> >
> > Changes in v2:
> > Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> > - Remove the kmap() call and call page_address() instead.
> > - Change the commit subject and message.
> >
> > lib/test_bpf.c | 10 +---------
> > 1 file changed, 1 insertion(+), 9 deletions(-)
> >
> > diff --git a/lib/test_bpf.c b/lib/test_bpf.c
> > index ade9ac672adb..a5cc5f9fc4e8 100644
> > --- a/lib/test_bpf.c
> > +++ b/lib/test_bpf.c
> > @@ -14381,25 +14381,17 @@ static void *generate_test_data(struct bpf_test
> > *test, int sub) * single fragment to the skb, filled with
> > * test->frag_data.
> > */
> > - void *ptr;
> > -
> > page = alloc_page(GFP_KERNEL);
> >
> > if (!page)
> > goto err_kfree_skb;
> >
> > - ptr = kmap(page);
> > - if (!ptr)
> > - goto err_free_page;
> > - memcpy(ptr, test->frag_data, MAX_DATA);
> > - kunmap(page);
> > + memcpy(page_address(page), test->frag_data, MAX_DATA);
> > skb_add_rx_frag(skb, 0, page, 0, MAX_DATA, MAX_DATA);
> > }
> >
> > return skb;
> >
> > -err_free_page:
> > - __free_page(page);
> > err_kfree_skb:
> > kfree_skb(skb);
> > return NULL;
> > --
> > 2.25.1
>
>
>
>
next prev parent reply other threads:[~2023-06-27 15:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-23 15:16 [PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag Sumitra Sharma
2023-06-26 13:07 ` Fabio M. De Francesco
2023-06-27 15:01 ` Sumitra Sharma [this message]
2023-06-26 20:43 ` Ira Weiny
2023-06-29 13:40 ` patchwork-bot+netdevbpf
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