From: Mina Almasry <almasrymina@google.com>
To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-rdma@vger.kernel.org
Cc: Mina Almasry <almasrymina@google.com>,
Mirko Lindner <mlindner@marvell.com>,
Stephen Hemminger <stephen@networkplumber.org>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Tariq Toukan <tariqt@nvidia.com>,
Boris Pismenny <borisp@nvidia.com>,
John Fastabend <john.fastabend@gmail.com>,
Dragos Tatulea <dtatulea@nvidia.com>
Subject: [RFC PATCH net-next v1 0/2] Minor cleanups to skb frag ref/unref
Date: Wed, 6 Mar 2024 15:59:18 -0800 [thread overview]
Message-ID: <20240306235922.282781-1-almasrymina@google.com> (raw)
This series is largely motivated by a recent discussion where there was
some confusion on how to properly ref/unref pp pages vs non pp pages:
https://lore.kernel.org/netdev/CAHS8izOoO-EovwMwAm9tLYetwikNPxC0FKyVGu1TPJWSz4bGoA@mail.gmail.com/T/#t
There is some subtely there because pp uses page->pp_ref_count for
refcounting, while non-pp uses get_page()/put_page() for ref counting.
Getting the refcounting pairs wrong can lead to kernel crash.
Additionally currently it may not be obvious to skb users unaware of
page pool internals how to properly acquire a ref on a pp frag. It
requires checking of skb->pp_recycle & is_pp_page() to make the correct
calls and may require some handling at the call site aware of arguable pp
internals.
This series is a minor refactor with a couple of goals:
1. skb users should be able to ref/unref a frag using
[__]skb_frag_[un]ref() functions without needing to understand pp
concepts and pp_ref_count vs get/put_page() differences.
2. reference counting functions should have a mirror opposite. I.e. there
should be a foo_unref() to every foo_ref() with a mirror opposite
implementation (as much as possible).
This is RFC to collect feedback if this change is desirable, but also so
that I don't race with the fix for the issue Dragos is seeing for his
crash.
https://lore.kernel.org/lkml/CAHS8izN436pn3SndrzsCyhmqvJHLyxgCeDpWXA4r1ANt3RCDLQ@mail.gmail.com/T/
Cc: Dragos Tatulea <dtatulea@nvidia.com>
Mina Almasry (2):
net: mirror skb frag ref/unref helpers
net: remove napi_frag_[un]ref
drivers/net/ethernet/marvell/sky2.c | 2 +-
drivers/net/ethernet/mellanox/mlx4/en_rx.c | 2 +-
include/linux/skbuff.h | 45 +++++++++-------
net/core/skbuff.c | 60 ++++++++--------------
net/tls/tls_device.c | 2 +-
net/tls/tls_strp.c | 2 +-
6 files changed, 51 insertions(+), 62 deletions(-)
--
2.44.0.278.ge034bb2e1d-goog
next reply other threads:[~2024-03-06 23:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-06 23:59 Mina Almasry [this message]
2024-03-06 23:59 ` [RFC PATCH net-next v1 1/2] net: mirror skb frag ref/unref helpers Mina Almasry
2024-03-07 10:44 ` Dragos Tatulea
2024-03-07 12:28 ` Yunsheng Lin
2024-03-06 23:59 ` [RFC PATCH net-next v1 2/2] net: remove napi_frag_[un]ref Mina Almasry
2024-03-07 11:08 ` Dragos Tatulea
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240306235922.282781-1-almasrymina@google.com \
--to=almasrymina@google.com \
--cc=borisp@nvidia.com \
--cc=davem@davemloft.net \
--cc=dtatulea@nvidia.com \
--cc=edumazet@google.com \
--cc=john.fastabend@gmail.com \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=mlindner@marvell.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=stephen@networkplumber.org \
--cc=tariqt@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).