From: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To: 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,
Sumitra Sharma <sumitraartsy@gmail.com>
Cc: 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: Mon, 26 Jun 2023 15:07:22 +0200 [thread overview]
Message-ID: <5846758.MhkbZ0Pkbq@suse> (raw)
In-Reply-To: <20230623151644.GA434468@sumitra.com>
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 :-)
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:[~2023-06-26 13:07 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 [this message]
2023-06-27 15:01 ` Sumitra Sharma
2023-06-26 20:43 ` Ira Weiny
2023-06-29 13:40 ` patchwork-bot+netdevbpf
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