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From: Vlastimil Babka <vbabka@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Iurii Zaikin <yzaikin@google.com>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	linux-mm@kvack.org, Ivan Teterevkov <ivan.teterevkov@nutanix.com>,
	Michal Hocko <mhocko@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"Guilherme G . Piccoli" <gpiccoli@canonical.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH v3 1/5] kernel/sysctl: support setting sysctl parameters from kernel command line
Date: Tue, 28 Apr 2020 10:09:37 +0200	[thread overview]
Message-ID: <d7d01e9e-6b6d-47ce-c750-cd7296e30613@suse.cz> (raw)
In-Reply-To: <20200427113331.f0c1e8e7cee98644260448d3@linux-foundation.org>

On 4/27/20 8:33 PM, Andrew Morton wrote:
> On Mon, 27 Apr 2020 20:04:29 +0200 Vlastimil Babka <vbabka@suse.cz> wrote:
> 
>> ...
>>  
>> +	sysctl.*=	[KNL]
>> +			Set a sysctl parameter, right before loading the init
>> +			process, as if the value was written to the respective
>> +			/proc/sys/... file. Both '.' and '/' are recognized as
>> +			separators. Unrecognized parameters and invalid values
>> +			are reported in the kernel log. Sysctls registered
>> +			later by a loaded module cannot be set this way.
>> +			Example: sysctl.vm.swappiness=40
> 
> Why support "."?  I think only supporting "/" is perfectly adequate and
> simplifies documentation.  It aligns the command-line syntax with the
> rest of the sysctl documentation.  I'm not seeing the need to provide
> two ways of doing the same thing?

AFAIK the "." is traditional, and "/" is a newer artefact of moving from the 
binary syscall form to procfs based form. So by "command-line syntax" you mean 
echo and cat, not sysctl tool? Because "man sysctl" says:

variable
	The name of a key to read from.  An example is kernel.ostype.  The '/' 
separator is also accepted in place of a '.'.

So I'm not strongly against supporting only / but I expect most people are used 
to the . and it will take them two attempts to pass the sysctl boot parameter 
correctly if they don't use it regularly - first trying . form, wonder why it 
doesn't work, then read the doc and realize it's not supported?

Vlastimil

  reply	other threads:[~2020-04-28  8:09 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-27 18:04 [PATCH v3 0/5] support setting sysctl parameters from kernel command line Vlastimil Babka
2020-04-27 18:04 ` [PATCH v3 1/5] kernel/sysctl: " Vlastimil Babka
2020-04-27 18:33   ` Andrew Morton
2020-04-28  8:09     ` Vlastimil Babka [this message]
2020-04-28 10:18       ` Michal Hocko
2020-04-27 18:04 ` [PATCH v3 2/5] kernel/sysctl: support handling command line aliases Vlastimil Babka
2020-04-27 18:04 ` [PATCH v3 3/5] kernel/hung_task convert hung_task_panic boot parameter to sysctl Vlastimil Babka
2020-04-27 18:04 ` [PATCH v3 4/5] tools/testing/selftests/sysctl/sysctl.sh: support CONFIG_TEST_SYSCTL=y Vlastimil Babka
2020-04-27 18:39   ` Luis Chamberlain
2020-04-27 18:04 ` [PATCH v3 5/5] lib/test_sysctl: support testing of sysctl. boot parameter Vlastimil Babka
2020-04-27 18:39   ` Luis Chamberlain
2020-05-11 11:05     ` Vlastimil Babka
2020-05-11 18:31       ` Luis Chamberlain
2020-05-13  8:58         ` Vlastimil Babka
2020-05-13 13:15           ` Luis Chamberlain
2020-05-13 13:17             ` Luis Chamberlain
2020-05-13 13:17               ` Luis Chamberlain
2020-05-15 16:02               ` Vlastimil Babka

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