Messages in this thread | | | Subject | Re: [RFC PATCH 1/4] Union mount documentation. | From | Arjan van de Ven <> | Date | Tue, 19 Jun 2007 22:59:51 -0700 |
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On Wed, 2007-06-20 at 11:21 +0530, Bharata B Rao wrote: > From: Bharata B Rao <bharata@linux.vnet.ibm.com> > Subject: Union mount documentation. Hi,
first of all I'm happy to see that people are still working on unionfs; I'd love to have functionality like this show up in Linux.
I'll not claim to have any VFS knowledge whatsoever, but I was just wondering what happens in the following scenario:
FS A is mounted twice, in /mnt/A and /mnt/union
FS B is mounted twice, in /mnt/B and as topmost union mount on /mnt/union
lets for simplicity say both filesystems are entirely empty
user does on FS A: mkdir /mnt/A/somedir touch /mnt/A/somedir/somefile
and then 2 things happen in parallel 1) touch /mnt/B/somefile 2) mv /mnt/union/somedir /mnt/union/somefile
since the underlying FS for 2) is FS A... how will this work out locking wise? Will the VS lock the union directory only? Or will this operate only on the underlying FS? How is dcache consistency guaranteed for scenarios like this?
Greetings, Arjan van de Ven
-- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org
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