Re: [RFC PATCH 00/18] ceph, rbd: Collapse all the I/O types down to something iov_iter-based

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On 8/4/23 21:13, David Howells wrote:
Hi Ilya, Xiubo,

[!] NOTE: This is a preview of a work in progress and doesn't yet fully
     compile, let alone actually work!

Here are some patches that (mostly) collapse the different I/O types
(PAGES, PAGELIST, BVECS, BIO) down to a single one.  I added a new type,
ceph_databuf, to make this easier.  The page list is attached to that as a
bio_vec[] with an iov_iter, but could also be some other type supported by
the iov_iter.  The iov_iter defines the data or buffer to be used.  I have
an additional iov_iter type implemented that allows use of a straight
folio[] or page[] instead of a bio_vec[] that I can deploy if that proves
more useful.

The conversion isn't quite complete:

  (1) rbd is done; BVECS and BIO types are replaced with ceph_databuf.

  (2) ceph_osd_linger_request::preply_pages needs switching over to a
      ceph_databuf, but I haven't yet managed to work out how the pages that
      handle_watch_notify() sticks in there come about.

  (3) I haven't altered data transmission in net/ceph/messenger*.c yet.  The
      aim is to reduce it to a single sendmsg() call for each ceph_msg_data
      struct, using the iov_iter therein.

  (4) The data reception routines in net/ceph/messenger*.c also need
      modifying to pass each ceph_msg_data::iter to recvmsg() in turn.

  (5) It might be possible to merge struct ceph_databuf into struct
      ceph_msg_data and eliminate the former.

  (6) fs/ceph/ still needs some work to clean up the use of page arrays.

  (7) I would like to change front and middle buffers with a ceph_databuf,
      vmapping them when we need to access them.

I added a kmap_ceph_databuf_page() macro and used that to get a page and
use kmap_local_page() on it to hide the bvec[] inside to make it easier to
replace.

Anyway, if anyone has any thoughts...


I've pushed the patches here also:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-extract

David

David Howells (18):
   iov_iter: Add function to see if buffer is all zeros
   ceph: Rename alignment to offset
   ceph: Add a new data container type, ceph_databuf
   ceph: Convert ceph_mds_request::r_pagelist to a databuf
   rbd: Use ceph_databuf for rbd_obj_read_sync()
   ceph: Change ceph_osdc_call()'s reply to a ceph_databuf
   ceph: Unexport osd_req_op_cls_request_data_pages()
   ceph: Remove osd_req_op_cls_response_data_pages()

David,

I think the titles should be prefixed with "libceph: XXX" for the patches in net/ceph/ ?

Thanks

- Xiubo


   ceph: Convert notify_id_pages to a ceph_databuf
   rbd: Switch from using bvec_iter to iov_iter
   ceph: Remove bvec and bio data container types
   ceph: Convert some page arrays to ceph_databuf
   ceph: Convert users of ceph_pagelist to ceph_databuf
   ceph: Remove ceph_pagelist
   ceph: Convert ceph_osdc_notify() reply to ceph_databuf
   ceph: Remove CEPH_OS_DATA_TYPE_PAGES and its attendant helpers
   ceph: Remove CEPH_MSG_DATA_PAGES and its helpers
   ceph: Don't use data_pages

  drivers/block/rbd.c             | 645 ++++++++++----------------------
  fs/ceph/acl.c                   |  39 +-
  fs/ceph/addr.c                  |  18 +-
  fs/ceph/file.c                  | 157 ++++----
  fs/ceph/inode.c                 |  85 ++---
  fs/ceph/locks.c                 |  23 +-
  fs/ceph/mds_client.c            | 134 ++++---
  fs/ceph/mds_client.h            |   2 +-
  fs/ceph/super.h                 |   8 +-
  fs/ceph/xattr.c                 |  68 ++--
  include/linux/ceph/databuf.h    |  65 ++++
  include/linux/ceph/messenger.h  | 141 +------
  include/linux/ceph/osd_client.h |  97 ++---
  include/linux/ceph/pagelist.h   |  72 ----
  include/linux/uio.h             |   1 +
  lib/iov_iter.c                  |  22 ++
  net/ceph/Makefile               |   5 +-
  net/ceph/cls_lock_client.c      |  40 +-
  net/ceph/databuf.c              | 149 ++++++++
  net/ceph/messenger.c            | 376 +------------------
  net/ceph/osd_client.c           | 430 +++++++--------------
  net/ceph/pagelist.c             | 171 ---------
  22 files changed, 876 insertions(+), 1872 deletions(-)
  create mode 100644 include/linux/ceph/databuf.h
  delete mode 100644 include/linux/ceph/pagelist.h
  create mode 100644 net/ceph/databuf.c
  delete mode 100644 net/ceph/pagelist.c





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