linux-kernel - Re: [PATCH] Syscalls: reboot: Add options to the reboot syscall to remount filesystems ro

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Date:	Thu, 3 Mar 2011 15:23:23 -0800
From:	Ken Sumrall <ksumrall@...roid.com>
To:	Mark Lord <kernel@...savvy.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.cz>, Jens Axboe <axboe@...nel.dk>,
	Matthew Wilcox <matthew@....cx>,
	Eric Paris <eparis@...hat.com>,
	Dave Young <hidave.darkstar@...il.com>,
	Jiri Slaby <jslaby@...e.cz>, James Morris <jmorris@...ei.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] Syscalls: reboot: Add options to the reboot syscall to
 remount filesystems ro

Thanks for the feedback.  I suspected the kernel community might not
like this change.  The suggestions by Linus seem worth trying out.

___
Ken


On Thu, Mar 3, 2011 at 10:29 AM, Mark Lord <kernel@...savvy.com> wrote:
> On 11-03-03 01:17 PM, Linus Torvalds wrote:
>> On Thu, Mar 3, 2011 at 9:45 AM, Linus Torvalds
>> <torvalds@...ux-foundation.org> wrote:
>>>
>>> How many mounted filesystems do you have that it's so hard to keep track of?
>>
>> Btw, /proc/mounts will track them for you even if you don't have a
>> 'mount' binary that does.
>>
>> Parsing that is pretty trivial. If you have spaces or special
>> characters in your pathnames (you may control the mount paths, you may
>> not - I have no idea), you'll need to be able to handle the escape
>> format (\oct). But other than that, it's literally just
>>
>>  - read all of /proc/mounts into a buffer
>>
>>  - for each line, split by space, and you'll have the directory name
>> right there in the second field
>>
>>  - do the unescaping ("\oct" -> character) if needed. It's good
>> practice. Test it.
>>
>>  - just do a read-only remount on it.
>>
>> All done. No kernel changes necessary. It just works.
>
>
> This might be much less complex:
>
>   #!/bin/sh
>   echo s > /proc/sysrq-trigger
>   echo u > /proc/sysrq-trigger
>
>
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