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

From: Christoph Hellwig
Date: Tue Apr 14 2015 - 15:23:50 EST

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.
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