Re: [PATCH 01/24] Unionfs: Documentation
[Posted January 10, 2007 by corbet]
| From: |
| Josef Sipek <jsipek-AT-fsl.cs.sunysb.edu> |
| To: |
| Andrew Morton <akpm-AT-osdl.org> |
| Subject: |
| Re: [PATCH 01/24] Unionfs: Documentation |
| Date: |
| Mon, 8 Jan 2007 18:25:16 -0500 |
| Cc: |
| Shaya Potter <spotter-AT-cs.columbia.edu>,
"Josef 'Jeff' Sipek" <jsipek-AT-cs.sunysb.edu>,
linux-kernel-AT-vger.kernel.org, linux-fsdevel-AT-vger.kernel.org,
hch-AT-infradead.org, viro-AT-ftp.linux.org.uk, torvalds-AT-osdl.org,
mhalcrow-AT-us.ibm.com, David Quigley <dquigley-AT-fsl.cs.sunysb.edu>,
Erez Zadok <ezk-AT-cs.sunysb.edu> |
On Mon, Jan 08, 2007 at 01:19:57PM -0800, Andrew Morton wrote:
...
> If it's not in the changelog or the documentation, it doesn't exist.
Good point. I'll add it for next time.
> > It's the same thing as modifying a block
> > device while a file system is using it. Now, when unionfs gets confused,
> > it shouldn't oops, but would one expect ext3 to allow one to modify its
> > backing store while its using it?
>
> There's no such problem with bind mounts. It's surprising to see such a
> restriction with union mounts.
Bind mounts are a purely VFS level construct. Unionfs is, as the name
implies, a filesystem. Last year at OLS, it seemed that a lot of people
agreed that unioning is neither purely a fs construct, nor purely a vfs
construct.
I'm using Unionfs (and ecryptfs) as guinea pigs to make linux fs stacking
friendly - a topic to be discussed at LSF in about a month.
Josef "Jeff" Sipek.
--
Computer Science is no more about computers than astronomy is about
telescopes.
- Edsger Dijkstra
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