Re: [PATCH RFC 1/3] vfs: add copy_file_range syscall and vfs helper

[Zach Brown]

On Tue, Apr 14, 2015 at 12:23:25PM -0700, Christoph Hellwig wrote:
> On Tue, Apr 14, 2015 at 11:54:08AM -0700, Zach Brown wrote:
> > Is this relying on btrfs range cloning being atomic?  It certainly
> > doesn't look atomic.  It can modify items across an arbitrarily large
> > number of leaf blocks.  It can make the changes across multiple
> > transactions which could introduce partial modification on reboot after
> > crashes.  It can fail (the dynamic duo: enomem, eio) and leave the
> > desintation partially modified.
> 
> I didn't mean atomic in the failure atomic sense, but in the sense of
> being atomic vs other writes, similar to how Posix specifies it for
> writes vs other writes.  Guess I need to express this intent better.

Ah, right, OK.

- z
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