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

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Message-ID: <20110307110020.GA13712@opensource.wolfsonmicro.com>
Date:	Mon, 7 Mar 2011 11:00:20 +0000
From:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ken Sumrall <ksumrall@...roid.com>, 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

On Thu, Mar 03, 2011 at 10:17:32AM -0800, 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.

That or using setmntent() etc.

Thanks,
Dimitris
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