Add Ramdisks sub-repository

Change-Id: I5df3170a9b66383941c923424c736fe646cbce96
Revert "aio: convert the ioctx list to radix tree"

This reverts commit 749506995cb447c11b37ccef5ce3474b09c48aa9.
Revert "tmpfs: add support for read_iter and write_iter"

This reverts commit 520d5272af619a06129d78cb8968301f5aef0c70.
Revert "iov_iter: move into its own file (bug fix)"

This reverts commit f945446c0920e9b64c52486d8c34a28e5558eea0.
Revert "ecrpytfs: Convert aio_read/write ops to read/write_iter"

This reverts commit 3dcf080e6d0b1457ad847535ebc1c953f30d7f47.
Revert "ext4: add support for read_iter and write_iter"

This reverts commit fc12155658949cff7a2a15e495609483bc19c18c.
Revert "fs: add read_iter and write_iter to several file systems"

This reverts commit 49d1414eb9f39868b0cbea6dc1c774fb9af37a27.
Revert "fs: use read_iter and write_iter rather than aio_read and aio_write"

This reverts commit 9116afc91201351aed7831987d39f42179c1ef22.
Revert "fs: create file_readable() and file_writable() functions"

This reverts commit c26875d6f6e0bd6c5bbfa533c04eca99d56984d5.
Revert "loop: use aio to perform io on the underlying file"

This reverts commit 0eba264b1c41eee87b847688d78decb7f195a930.
Revert "bio: add bvec_length(), like iov_length()"

This reverts commit 3dfd8888ff15be0e3051a38d8963074ae27dd78e.
Revert "aio: add aio support for iov_iter arguments"

This reverts commit 08536de92267f7527a74132d71b0998cedf343f3.
Revert "aio: add aio_kernel_() interface"

This reverts commit 6038b2fa28dbe33171902be34346ceb502309694.
Revert "fs: pull iov_iter use higher up the stack"

This reverts commit 19b3b8cc84b744887b310d6fec79572487d54cbd.
Revert "dio: add bio_vec support to __blockdev_direct_IO()"

This reverts commit 1c8bf4ae5760af4f798ed065f61ff9b1f1ee13ea.
Revert "dio: Convert direct_IO to use iov_iter"

This reverts commit a3940ac30927057750918098bf53063090e2e9f0.
Revert "iov_iter: let callers extract iovecs and bio_vecs"

This reverts commit 2b0a690a730fce04c02d0e2cecd3c760a92687cc.
Revert "iov_iter: add a shorten call"

This reverts commit 00f5935eb8911eb357c0b8b26d5f5dd2051c3517.
Revert "iov_iter: add bvec support"

This reverts commit 6301c08ce778cdde8667cba99b43616eb668e55c.
Revert "iov_iter: hide iovec details behind ops function pointers"

This reverts commit 5471ae53bdac2d2fd5bb564d1cc0df569fe79e9b.