Re: btrfs_clone_files and bind mounts

[Hristo Venev <hristo@venev.name>]

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On Tue, 2018-02-20 at 18:41 +0200, Nikolay Borisov wrote:
> 
> On 20.02.2018 17:50, Hristo Venev wrote:
> > What is the problem with cloning files between different
> > (vfs)mounts of
> > the same filesystem?
> > 
> 
> The "problem" is not really a problem, but rather a well-imposed
> restriction:
> 
> From  http://man7.org/linux/man-pages/man2/ioctl_ficlonerange.2.html
> 
> "Both files must reside within the same filesystem."
> 
> And as a matter of fact this is enforced in the generic
> vfs_clone_file_range. Of course if we were to do this across
> filesystem
> then we'd have all the problems associated with not being able to
> ensure
> atomicity of operations.

My question was about doing this within the same filesystem. In my case
(and I think it's relatively common), subvolumes of the same filesystem
are mounted separately, and I can't think of a good reason why
FICLONERANGE can't be made to work (it works if the subvolumes are
accessed within the same mount point).

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