Re: [PATCH v3 8/9] vfs: copy_file_range() can do a pagecache copy with splice

On 09/25/2015 08:14 PM, Andy Lutomirski wrote:

On Fri, Sep 25, 2015 at 1:48 PM, Anna Schumaker
[off-list ref] wrote:

quoted

The NFS server will need some kind offallback for filesystems that don't
have any kind of copy acceleration, and it should be generally useful to
have an in-kernel copy to avoid lots of switches between kernel and user
space.

I make this configurable by adding two new flags.  Users who only want a
reflink can pass COPY_FR_REFLINK, and users who want a full data copy can
pass COPY_FR_COPY.  The default (flags=0) means to first attempt a
reflink, but use the pagecache if that fails.

Can you clarify how the subject line fits in?  I'm a bit lost.

I'll try!  I use the splice interface to copy file data from the pagecache, and this implements an in-kernel copy that can be controlled using the two flags I added.

I plan on using this in the NFS server when I add server-side copy support.

Let me know if that doesn't answer your question!
Anna

--Andy