Re: [PATCH v2 09/10] fs/xfs: Handle CoW for fsdax write() path

[Christoph Hellwig]

On Wed, Mar 03, 2021 at 09:57:48AM +0000, ruansy.fnst@xxxxxxxxxxx wrote:
> > What is the advantage of the ioemap_end handler here?  It adds another
> > indirect funtion call to the fast path, so if we can avoid it, I'd
> > rather do that.
> 
> These code were in xfs_file_dax_write().  I moved them into the iomap_end
> because the mmaped CoW need this.
> 
> I know this is not so good, but I could not find another better way. Do you
> have any ideas? 

mmaped copy is the copy_edge case?  Maybe just use different iomap_ops for
that case vs plain write?