On Tue, Nov 18, 2014 at 11:22:35PM -0800, Omar Sandoval wrote: > Here's a nice little bit of insanity I put together in that direction -- > consider it a discussion point more than a patch. It does two things: > > - Uses an ITER_BVEC iov_iter to do direct_IO for swap_readpage. This makes > swap_readpage a synchronous operation, but I think that's the best we can do > with the existing interface.
Note that ->read_iter for direct-io supports async I/O in general. By resurrecting some of the older attempts to do in-kernel aio this could be made async easily. > - Unless I'm missing something, there don't appear to be any instances of > ITER_BVEC | READ in the kernel, so the dio path doesn't know not to dirty > pages it gets that way. Dave Kleikamp and Ming Lei each previously submitted > patches doing this as part of adding an aio_kernel interface. (The NFS > direct > I/O implementation doesn't know how to deal with these either, so this patch > actually breaks the only existing user of this code path, but in the > interest > of keeping the patch short, I didn't try to fix it :) Right, we'd need to look into. Bonus points of allowing this as a zero copy read. Btw, in the long run I would much prefer killing of the current horrible swap using bmap path in favor of an enhanced direct I/O path. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
