From: Daniel Borkmann <daniel@iogearbox.net>
To: "Björn Töpel" <bjorn.topel@gmail.com>,
"Davidlohr Bueso" <dave@stgolabs.net>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
LKML <linux-kernel@vger.kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Bjorn Topel <bjorn.topel@intel.com>,
Magnus Karlsson <magnus.karlsson@intel.com>,
Netdev <netdev@vger.kernel.org>, Davidlohr Bueso <dbueso@suse.de>,
dan.j.williams@intel.com
Subject: Re: [PATCH 1/2] xsk: do not use mmap_sem
Date: Mon, 11 Feb 2019 16:33:29 +0100 [thread overview]
Message-ID: <d92b7b49-81e6-1ac5-4ae4-4909f87bbea8@iogearbox.net> (raw)
In-Reply-To: <CAJ+HfNg=Wikc_uY9W1QiVCONq3c1GyS44-xbrq-J4gqfth2kwQ@mail.gmail.com>
[ +Dan ]
On 02/07/2019 08:43 AM, Björn Töpel wrote:
> Den tors 7 feb. 2019 kl 06:38 skrev Davidlohr Bueso <dave@stgolabs.net>:
>>
>> Holding mmap_sem exclusively for a gup() is an overkill.
>> Lets replace the call for gup_fast() and let the mm take
>> it if necessary.
>>
>> Cc: David S. Miller <davem@davemloft.net>
>> Cc: Bjorn Topel <bjorn.topel@intel.com>
>> Cc: Magnus Karlsson <magnus.karlsson@intel.com>
>> CC: netdev@vger.kernel.org
>> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
>> ---
>> net/xdp/xdp_umem.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
>> index 5ab236c5c9a5..25e1e76654a8 100644
>> --- a/net/xdp/xdp_umem.c
>> +++ b/net/xdp/xdp_umem.c
>> @@ -265,10 +265,8 @@ static int xdp_umem_pin_pages(struct xdp_umem *umem)
>> if (!umem->pgs)
>> return -ENOMEM;
>>
>> - down_write(¤t->mm->mmap_sem);
>> - npgs = get_user_pages(umem->address, umem->npgs,
>> - gup_flags, &umem->pgs[0], NULL);
>> - up_write(¤t->mm->mmap_sem);
>> + npgs = get_user_pages_fast(umem->address, umem->npgs,
>> + gup_flags, &umem->pgs[0]);
>>
>
> Thanks for the patch!
>
> The lifetime of the pinning is similar to RDMA umem mapping, so isn't
> gup_longterm preferred?
Seems reasonable from reading what gup_longterm seems to do. Davidlohr
or Dan, any thoughts on the above?
Thanks,
Daniel
next prev parent reply other threads:[~2019-02-11 15:33 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-07 5:37 [PATCH -tip 0/2] more get_user_pages mmap_sem cleanups Davidlohr Bueso
2019-02-07 5:37 ` [PATCH 1/2] xsk: do not use mmap_sem Davidlohr Bueso
2019-02-07 7:43 ` Björn Töpel
2019-02-11 15:33 ` Daniel Borkmann [this message]
2019-02-11 16:37 ` Dan Williams
2019-02-11 17:16 ` Weiny, Ira
2019-02-11 16:15 ` [PATCH v2] xsk: share the mmap_sem for page pinning Davidlohr Bueso
2019-02-11 16:21 ` Björn Töpel
2019-02-11 19:53 ` Daniel Borkmann
2019-02-07 5:37 ` [PATCH 2/2] MIPS/c-r4k: do no use mmap_sem for gup_fast() Davidlohr Bueso
2019-02-07 19:00 ` Paul Burton
2019-02-07 19:25 ` Davidlohr Bueso
2019-02-07 5:50 ` [PATCH -tip 0/2] more get_user_pages mmap_sem cleanups Davidlohr Bueso
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