On 06/22/2015 03:53 PM, Miklos Szeredi wrote:
On Mon, Jun 22, 2015 at 3:45 PM, Jan Olszak <j.olszak@xxxxxxxxxxx> wrote:
The lower fs is most likely ext4.
Unfortunately making a file immutable won't solve the problem. There's
nothing wrong in modifying the file and it should stay possible.
I just want to switch off copy on write for some files. Can you see another
way?
Ah, you want to allow modification of file on the lower layer?
Exactly
You can bind mount individual files from the lower layer to the
overlay. That fixes the "allow modification" part.
Well bind mounting every file that should have COW is unmaintainable -
if new files appear admin has to mount each one.
Plus all the unnecessary mounts. It's much easier to do it the opposite
way - by default have COW and only for some files switch it off.
But what should happen on rename or unlink?
Both would operate on the original inode.
Setting "trusted.overlay.cow" is a privileged operation so it's admin's
decision to allow this.
Each layer could potentially make the a file COW again by
setting/removing "trusted.overlay.cow" attr.
Thanks,
Jan
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