On Sat, Jan 18, 2014 at 07:46:49AM +0000, Al Viro wrote: > On Fri, Jan 17, 2014 at 11:22:04PM -0800, Linus Torvalds wrote: > > On Fri, Jan 17, 2014 at 10:40 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > Objections, comments? > > > > I certainly object to the "map, then unmap" approach. No VM games. [snip] > > But if it can be done more naturally as a writev, then that may well > > be ok. As long as we're talking about just the > > default_file_splice_write() case, and people who want to do special > > things with page movement can continue to do so.. > > The thing is, after such change default_file_splice_write() is no worse than > generic_file_splice_write(). The only instances that really want something > else are the ones that try to steal pages (e.g. virtio_console, fuse miscdev) > or sockets, with their "do DMA from the sodding page, don't copy it at > anywhere" ->sendpage() method. IOW, ones those special things you are > talking about. Normal filesystems do not - not on pipe-to-file splice. > file-to-pipe - sure, that one plays with pagecache and tries hard to > do zero-copy, but that's ->splice_read(), not ->splice_write()... BTW, would sockets benefit from having ->sendpages() that would take an array of (page, offset, len) triples? It would be trivial to do and some of the helpers that are falling out of writing that writev-based default_file_splice_write() look like they could be reused for calling that one... Dave? _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
