... also, this really needs to be cc'd to linux-mm. On Thu, Feb 21, 2019 at 01:56:11PM +0100, Miklos Szeredi wrote: > rsplice would serve a similar purpose as splice, but in the other > direction. I.e. instead of operating on buffers filled with data, it > would operate on empty buffers to be filled with data. rsplice is to > splice as read is to write. > > data source -> splice -> data destination > data destination -> rsplice -> data source > > One use case would be zero-copy read in fuse. Zero-copy writes work > with plain splice: page cache pages or userspace buffers are passed > through to the userspace filesystem server as pipe buffers and they > can be directed wherever the filesystem wants. The reverse doesn't > work. There's code to attempt stealing pages and inserting into the > fuse page cache, but this is far from being as generic as the write > path. > > What do people think? Is this crazy? Are there major roadblocks for > implementation? Would this have any other use cases? > > To me it looks like this is pretty symmetrical with normal splice, the > big difference being that uninitialized buffers would be passed > around. Obviously must make sure those buffers are write only, i.e. > the previous contents are inaccessible. > > Thanks, > Miklos
