Re: [PATCHv3 15/41] filemap: handle huge pages in do_generic_file_read()

[Christoph Hellwig]

On Mon, Nov 07, 2016 at 02:13:05PM +0300, Kirill A. Shutemov wrote:
> It looks like a huge limitation to me.

The DAX PMD fault code can live just fine with it.  And without it
performance would suck anyway.

> I'm looking onto iomap_write_actor(): we still calculate 'offset' and
> 'bytes' based on PAGE_SIZE before we even get the page.
> This way we limit outself to PAGE_SIZE per-iteration.

Of course it does, given that it does not support huge pages _yet_.
But the important part is that this is now isolate to the highlevel
code, and the fs can get iomap_begin calls for a huge page (or in fact
much larger sizes than that).