Re: [PATCH] sendfile removal

On Thu, May 31 2007, Hugh Dickins wrote:
On Thu, 31 May 2007, Jens Axboe wrote:

This patch removes the ->sendfile() hook from the file_operations
structure, and replaces the sys_sendfile() mechanism to be based on
->splice_read() instead. There should be no functional changes.

Work to be done:

- The ext2 xip support needs a splice_read() implementation, currently I
just if 0'ed out the send xip_file_sendfile(). CC'ed Carsten, who
seems to be the author of this code.

- shmem needs a splice_read() implementation. Optimistically CC'ed Hugh.

I'll take that "Optimistically" as a special compliment,
rather than as a particular insult ;)

It's a compliment for sure, the "optimistically" was just mentioned
because there are lots of people mentioned in that file, but I mostly
remember you doing some heavy lifting there :-)

Yes, thanks, please leave shmem_file_splice_read() to me, I'll give
it priority now. Not deep enough in yet, but I'll probably aim for
something simple-minded (correct but slow once it hits swap).

Super, thanks!!

- nfds: The ->rq_sendfile_ok optimization is gone for now. I can't
determine the value of it, but I'm assuming it's there for a reason.
Any chance this can be converted to splice, or use something else than
->sendfile()? CC'ed Neil.

- relay: needs a splice_read() implementation. I think Tom already has
one, CC'ed him.

Apart from that, it was mostly straight forward. Almost everybody uses
generic_file_sendfile(), which makes the conversion easy. I changed loop
to use do_generic_file_read() instead of sendfile, it works for me...

Christoph already picked up on that, and it's of interest to shmem too:
loop over tmpfs in 2.6 was relying on shmem_file_sendfile, for which
the generic route is not good enough.

If we're giving a .splice_read to everything which used to have a
.sendfile, then I think you just need to make do_lo_read() use
->splice_read now?

Yes, I will make that change myself. I can do that, as I seem to have
sucessfully pushed out the remaining work to others :-)

--
Jens Axboe

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