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a12c76a033
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Xin Long a12c76a033 net: sched: refine software bypass handling in tc_run 
This patch addresses issues with filter counting in block (tcf_block),
particularly for software bypass scenarios, by introducing a more
accurate mechanism using useswcnt.

Previously, filtercnt and skipswcnt were introduced by:

  Commit 2081fd3445 ("net: sched: cls_api: add filter counter") and
  Commit f631ef39d8 ("net: sched: cls_api: add skip_sw counter")

  filtercnt tracked all tp (tcf_proto) objects added to a block, and
  skipswcnt counted tp objects with the skipsw attribute set.

The problem is: a single tp can contain multiple filters, some with skipsw
and others without. The current implementation fails in the case:

  When the first filter in a tp has skipsw, both skipswcnt and filtercnt
  are incremented, then adding a second filter without skipsw to the same
  tp does not modify these counters because tp->counted is already set.

  This results in bypass software behavior based solely on skipswcnt
  equaling filtercnt, even when the block includes filters without
  skipsw. Consequently, filters without skipsw are inadvertently bypassed.

To address this, the patch introduces useswcnt in block to explicitly count
tp objects containing at least one filter without skipsw. Key changes
include:

  Whenever a filter without skipsw is added, its tp is marked with usesw
  and counted in useswcnt. tc_run() now uses useswcnt to determine software
  bypass, eliminating reliance on filtercnt and skipswcnt.

  This refined approach prevents software bypass for blocks containing
  mixed filters, ensuring correct behavior in tc_run().

Additionally, as atomic operations on useswcnt ensure thread safety and
tp->lock guards access to tp->usesw and tp->counted, the broader lock
down_write(&block->cb_lock) is no longer required in tc_new_tfilter(),
and this resolves a performance regression caused by the filter counting
mechanism during parallel filter insertions.

  The improvement can be demonstrated using the following script:

  # cat insert_tc_rules.sh

    tc qdisc add dev ens1f0np0 ingress
    for i in $(seq 16); do
        taskset -c $i tc -b rules_$i.txt &
    done
    wait

  Each of rules_$i.txt files above includes 100000 tc filter rules to a
  mlx5 driver NIC ens1f0np0.

  Without this patch:

  # time sh insert_tc_rules.sh

    real    0m50.780s
    user    0m23.556s
    sys	    4m13.032s

  With this patch:

  # time sh insert_tc_rules.sh

    real    0m17.718s
    user    0m7.807s
    sys     3m45.050s

Fixes: 047f340b36 ("net: sched: make skip_sw actually skip software")
Reported-by: Shuang Li <shuali@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Reviewed-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Tested-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2025-01-20 09:21:27 +00:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-01-16 10:34:59 -08:00
block block, bfq: fix waker_bfqq UAF after bfq_split_bfqq() 2025-01-09 06:52:46 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: rsassa-pkcs1 - Copy source data for SG list 2024-12-10 13:34:05 +08:00
Documentation This cleanup patchset includes the following patches: 2025-01-18 17:57:31 -08:00
drivers bluetooth-next pull request for net-next: 2025-01-18 17:51:58 -08:00
fs for-6.13-rc7-tag 2025-01-16 08:54:33 -08:00
include net: sched: refine software bypass handling in tc_run 2025-01-20 09:21:27 +00:00
init - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
io_uring io_uring-6.13-20250111 2025-01-11 10:59:43 -08:00
ipc - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-01-16 10:34:59 -08:00
lib pldmfw: enable selected component update 2025-01-16 13:04:41 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: fix assertion in folio_end_read() 2025-01-12 19:03:38 -08:00
net net: sched: refine software bypass handling in tc_run 2025-01-20 09:21:27 +00:00
rust Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-01-09 16:11:47 -08:00
samples BPF fixes: 2024-12-06 15:07:48 -08:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-01-16 10:34:59 -08:00
security selinux/stable-6.13 PR 20250107 2025-01-07 14:49:48 -08:00
sound sound fixes for 6.13-final 2025-01-14 09:54:57 -08:00
tools selftests: net: give up on the cmsg_time accuracy on slow machines 2025-01-17 18:36:14 -08:00
usr kbuild: Drop support for include/asm-<arch> in headers_check.pl 2024-12-21 11:43:17 +09:00
virt VFIO updates for v6.13 2024-11-27 12:57:03 -08:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2024-10-07 21:39:57 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.13 2024-11-30 13:41:50 -08:00
.mailmap This cleanup patchset includes the following patches: 2025-01-18 17:57:31 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: remove Andy Gospodarek from bonding 2025-01-09 08:30:01 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS This cleanup patchset includes the following patches: 2025-01-18 17:57:31 -08:00
Makefile Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-01-16 10:34:59 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.