Re: [PATCH v2 01/10] VFS generic copy_file_range() support

Dave Chinner
2018-12-01T22:36:22Z

On Sat, Dec 01, 2018 at 01:18:06PM -0800, Matthew Wilcox wrote:
> On Fri, Nov 30, 2018 at 03:03:39PM -0500, Olga Kornievskaia wrote:
> > Relax the condition that input files must be from the same
> > file systems.
>
> > + ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> > + count > MAX_RW_COUNT ? MAX_RW_COUNT : count, 0);
>
> Wasn't there a concern about splicing between filesystems with different
> block sizes mentioned the last time this came up? I can't find a citation
> for that now.

the filesystems should be able to handle that themselves - they are
just passes an iter that has a range of data regions in pages that
they copy the required data into/out of. The data transfer mechanism
itself is completely independent of filesystem block sizes....

There's lots of other problems with do_splice_direct, but I don't
think this is one of them. I coul dbe wrong - this code has pretty
much zero documentation on how it is supposed to work and what it is
supposed to do - so don't take my word for it...

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com