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Gerd Bayer 0d52759710 net/smc: Fix setsockopt and sysctl to specify same buffer size again 
[ Upstream commit 833bac7ec3 ]

Commit 0227f058aa ("net/smc: Unbind r/w buffer size from clcsock
and make them tunable") introduced the net.smc.rmem and net.smc.wmem
sysctls to specify the size of buffers to be used for SMC type
connections. This created a regression for users that specified the
buffer size via setsockopt() as the effective buffer size was now
doubled.

Re-introduce the division by 2 in the SMC buffer create code and level
this out by duplicating the net.smc.[rw]mem values used for initializing
sk_rcvbuf/sk_sndbuf at socket creation time. This gives users of both
methods (setsockopt or sysctl) the effective buffer size that they
expect.

Initialize net.smc.[rw]mem from its own constant of 64kB, respectively.
Internal performance tests show that this value is a good compromise
between throughput/latency and memory consumption. Also, this decouples
it from any tuning that was done to net.ipv4.tcp_[rw]mem[1] before the
module for SMC protocol was loaded. Check that no more than INT_MAX / 2
is assigned to net.smc.[rw]mem, in order to avoid any overflow condition
when that is doubled for use in sk_sndbuf or sk_rcvbuf.

While at it, drop the confusing sk_buf_size variable from
__smc_buf_create and name "compressed" buffer size variables more
consistently.

Background:

Before the commit mentioned above, SMC's buffer allocator in
__smc_buf_create() always used half of the sockets' sk_rcvbuf/sk_sndbuf
value as initial value to search for appropriate buffers. If the search
resorted to using a bigger buffer when all buffers of the specified
size were busy, the duplicate of the used effective buffer size is
stored back to sk_rcvbuf/sk_sndbuf.

When available, buffers of exactly the size that a user had specified as
input to setsockopt() were used, despite setsockopt()'s documentation in
"man 7 socket" talking of a mandatory duplication:

[...]
       SO_SNDBUF
              Sets  or  gets the maximum socket send buffer in bytes.
              The kernel doubles this value (to allow space for book‐
              keeping  overhead)  when it is set using setsockopt(2),
              and this doubled value is  returned  by  getsockopt(2).
              The     default     value     is     set     by     the
              /proc/sys/net/core/wmem_default file  and  the  maximum
              allowed value is set by the /proc/sys/net/core/wmem_max
              file.  The minimum (doubled) value for this  option  is
              2048.
[...]

Fixes: 0227f058aa ("net/smc: Unbind r/w buffer size from clcsock and make them tunable")
Co-developed-by: Jan Karcher <jaka@linux.ibm.com>
Signed-off-by: Jan Karcher <jaka@linux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2023-08-23 17:52:18 +02:00
Documentation iommu/arm-smmu-v3: Document nesting-related errata 2023-08-11 12:08:09 +02:00
LICENSES
…
arch alpha: remove __init annotation from exported page_is_ram() 2023-08-16 18:27:31 +02:00
block blk-mq: Fix stall due to recursive flush plug 2023-08-03 10:23:48 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:21:42 +02:00
drivers cpuidle: psci: Move enabling OSI mode after power domains creation 2023-08-23 17:52:17 +02:00
fs btrfs: set cache_block_group_error if we find an error 2023-08-16 18:27:30 +02:00
include netfilter: nf_tables: report use refcount overflow 2023-08-16 18:27:30 +02:00
init x86/mm: Initialize text poking earlier 2023-08-08 20:03:49 +02:00
io_uring io_uring: correct check for O_TMPFILE 2023-08-16 18:27:24 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf, cpumap: Make sure kthread is running before map update returns 2023-08-11 12:08:23 +02:00
lib debugobjects: Recheck debug_objects_enabled before reporting 2023-08-11 12:08:23 +02:00
mm zsmalloc: fix races between modifications of fullness and isolated 2023-08-23 17:52:17 +02:00
net net/smc: Fix setsockopt and sysctl to specify same buffer size again 2023-08-23 17:52:18 +02:00
rust rust: allocator: Prevent mis-aligned allocation 2023-08-11 12:08:18 +02:00
samples samples: ftrace: Save required argument registers in sample trampolines 2023-07-23 13:49:44 +02:00
scripts gcc-plugins: Reorganize gimple includes for GCC 13 2023-08-16 18:27:20 +02:00
security security: keys: Modify mismatched function name 2023-07-27 08:50:43 +02:00
sound ASoC: wm8904: Fill the cache for WM8904_ADC_TEST_0 register 2023-08-03 10:24:16 +02:00
tools selftests: forwarding: tc_actions: Use ncat instead of nc 2023-08-23 17:52:18 +02:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:24:08 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig
…
.get_maintainer.ignore
…
.gitattributes
…
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml
…
COPYING
…
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
…
MAINTAINERS smb: move client and server files to common directory fs/smb 2023-06-28 11:12:40 +02:00
Makefile Linux 6.1.46 2023-08-16 18:27:31 +02:00
README
…

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 Restructured Text 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.