Messages in this thread | | | Date | Mon, 14 Feb 2011 15:23:20 +0100 | From | Milan Broz <> | Subject | Re: [PATCH][RFC] dm: Do not open log and cow device read-write for read-only mappings |
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On 02/14/2011 03:09 PM, Tejun Heo wrote: > On Mon, Feb 14, 2011 at 02:14:57PM +0100, Milan Broz wrote: >>> But it doesn't fix the read-only snapshot issue and I guess there will be >>> the same problem with read-only MD code too. >>> (so the 2) issue here https://lkml.org/lkml/2011/2/12/209). > > So, the problem is caused by dm opening members rw even for ro > devices, right?
The patch uncover these shortcomings in code. (Unfortunately quite late in RC...)
>> I am not sure if this is complete fix... note that: >> - what happens during mirror resync and read-only log? >> - for COW, it there situation we need to update header in read-oly mode? (invalidated snap?) > > 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.
Sure. So we need to check these situations I described.
Btw the same pattern is in MD code in lock_rdev() ...
Milan
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