Re: [dm-devel] [PATCH][RFC] dm: Do not open log and cow deviceread-write for read-only mappings

From: Alasdair G Kergon
Date: Mon Feb 14 2011 - 09:39:25 EST


On Mon, Feb 14, 2011 at 03:09:40PM +0100, Tejun Heo wrote:
> But if the underlying device is marked ro, dm shouldn't update it at
> all. The device should be opened ro and ro policy should be enforced.

Indeed, but dm isn't tracking this today because it didn't need to up-to
now.

I can think of a few scenarios where dm can have the underlying device open
read-write when it only needs read-only. (E.g. we track and cater for
read-only->read-write transitions but not the opposite and don't propagate
changes through the stack.)

We'll do an audit...

Alasdair

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