nfs: support multiple requests per page

This patchset changes the read and write paths to be more flexible in dealing with requests that are not page aligned. Until now there was a 1:1 mapping of struct nfs_page (referred to as "nfs requests") to struct page, which limited the client to page aligned I/O in several pNFS scenarios.

This patchset allows multiple requests per page, loosely following the approach taken with struct buffer_head (part of kernel bio interface).

With this patchset the client now supports:
- non-page-aligned O_DIRECT I/O to DSes (instead of reverting to MDS)
- arbitrary pnfs layout segment boundaries
- arbitrary pnfs filelayout stripe sizes

This patchset also includes a lot of cleanup - notably we no longer need a separate code path to support rsize/wsize < PAGE_SIZE.

This new approach opens the door to many optimizations, such as not having to flush a page on a non-contiguous write, but for the time being we are focusing on correctness -- this patchset touches the read and write path for *all* versions of NFS!

This has been tested against v2, v3, v4.0 and v4.1 (no pnfs) servers with different rsize/wsize settings, and against pynfs filelayout servers hacked to have non page aligned stripe sizes.

I had some code review already (with changes applied) and we've been testing this pretty extensively for the last month+ - focusing mostly on v2, v3, v4.x (no pnfs).

The patchset applies against Trond's testing branch, but should also include the fix I posted earlier today: "pnfs: fix race in filelayout commit path" as the race seems to be easier to hit with this patchset applied.

I'm pretty sure I didn't break anything in the object and block layouts, but some extra attention there would be helpful.

I plan on sharing some performance numbers once I'm able to run some nfsometer workloads.

Changes in V3:
- rebased to Anna's newest patches, which merges pageio.c into pagelist.c

Upcoming:
- ~5 patch patchset that cleans up nfs_pgio_header and nfs_pgio_data

I just pushed an updated version of my ‘pgio’ branch to:

git://git.linux-nfs.org/projects/dros/linux-nfs

The branch has the following patches:

from me (this patchset!):

7d8976b nfs: support page groups in nfs_read_completion f0d7a82 pnfs: filelayout: support non page aligned layouts 79a9c89 pnfs: allow non page aligned pnfs layout segments cf25fb9 pnfs: support multiple verfs per direct req c081af5 nfs: remove data list from pgio header 6313def nfs: use > 1 request to handle bsize < PAGE_SIZE 9f89e40 nfs: chain calls to pg_test
d65d153 nfs: allow coalescing of subpage requests 12cf560 pnfs: clean up filelayout_alloc_commit_info 49fa6d6 nfs: page group support in nfs_mark_uptodate ba94674 nfs: page group syncing in write path 00ddd94 nfs: page group syncing in read path d6dec2d nfs: add support for multiple nfs reqs per page 1ea228a nfs: call nfs_can_coalesce_requests for every req 104ab5c nfs: modify pg_test interface to return size_t 27f3d0c nfs: remove unused arg from nfs_create_request fc9eeaa nfs: clean up PG_* flags
366d632 pnfs: fix race in filelayout commit path

from Anna:

6e35ebf NFS: Create a common nfs_pageio_ops struct
9a0dabd NFS: Create a common generic_pg_pgios()
9a074ee NFS: Create a common multiple_pgios() function a7c7f54 NFS: Create a common initiate_pgio() function fd42750 NFS: Create a generic_pgio function
4003d02 NFS: Create a common pgio_error function
c9f494c NFS: Create a common rpcsetup function for reads and writes 1220495 NFS: Create a common rpc_call_ops struct
4e07fcf NFS: Create a common nfs_pgio_result_common function 1986d26 NFS: Create a common pgio_rpc_prepare function 9892bb1 NFS: Create a common rw_header_alloc and rw_header_free function 76c449c NFS: Create a common pgio_alloc and pgio_release function 4fca7e6 NFS: Move the write verifier into the nfs_pgio_header fd279ad NFS: Create a common read and write header struct 59d6da2 NFS: Create a common read and write data struct 9726903 NFS: Create a common results structure for reads and writes 0ec19c2 NFS: Create a common argument structure for reads and writes

from Christoph:

140c1e0 nfs: remove ->read_pageio_init from rpc ops 75fd2e5 nfs: remove ->write_pageio_init from rpc ops

The diffstat of pgio branch (including patches from Anna and Christoph):

 fs/nfs/blocklayout/blocklayout.c |  38 ++-
 fs/nfs/direct.c                  | 117 +++++++-
 fs/nfs/internal.h                |  33 +--
 fs/nfs/nfs2xdr.c                 |  14 +-
 fs/nfs/nfs3proc.c                |  21 +-
 fs/nfs/nfs3xdr.c                 |  16 +-
 fs/nfs/nfs4_fs.h                 |   4 +-
 fs/nfs/nfs4filelayout.c          | 182 ++++++------
 fs/nfs/nfs4proc.c                |  54 ++--
 fs/nfs/nfs4trace.h               |   8 +-
 fs/nfs/nfs4xdr.c                 |  19 +-
 fs/nfs/objlayout/objio_osd.c     |  24 +-
 fs/nfs/objlayout/objlayout.c     |  16 +-
 fs/nfs/objlayout/objlayout.h     |   8 +-
 fs/nfs/pagelist.c                | 617 ++++++++++++++++++++++++++++++++++++---
 fs/nfs/pnfs.c                    | 146 ++++-----
 fs/nfs/pnfs.h                    |  30 +-
 fs/nfs/proc.c                    |  21 +-
 fs/nfs/read.c                    | 414 +++++---------------------
 fs/nfs/write.c                   | 561 ++++++++++-------------------------
 include/linux/nfs.h              |   5 +-
 include/linux/nfs_fs.h           |   2 -
 include/linux/nfs_page.h         |  46 ++-
 include/linux/nfs_xdr.h          | 106 +++----
 24 files changed, 1276 insertions(+), 1226 deletions(-)

-dros

Weston Andros Adamson (18):
pnfs: fix race in filelayout commit path
nfs: clean up PG_* flags
nfs: remove unused arg from nfs_create_request
nfs: modify pg_test interface to return size_t
nfs: call nfs_can_coalesce_requests for every req
nfs: add support for multiple nfs reqs per page
nfs: page group syncing in read path
nfs: page group syncing in write path
nfs: page group support in nfs_mark_uptodate
pnfs: clean up filelayout_alloc_commit_info
nfs: allow coalescing of subpage requests
nfs: chain calls to pg_test
nfs: use > 1 request to handle bsize < PAGE_SIZE
nfs: remove data list from pgio header
pnfs: support multiple verfs per direct req
pnfs: allow non page aligned pnfs layout segments
pnfs: filelayout: support non page aligned layouts
nfs: support page groups in nfs_read_completion

 fs/nfs/blocklayout/blocklayout.c |  16 +-
 fs/nfs/direct.c                  | 111 ++++++++++-
 fs/nfs/nfs4filelayout.c          | 142 +++++++-------
 fs/nfs/objlayout/objio_osd.c     |  18 +-
 fs/nfs/pagelist.c                | 387 ++++++++++++++++++++++++++-------------
 fs/nfs/pnfs.c                    |  77 ++++----
 fs/nfs/pnfs.h                    |   3 +-
 fs/nfs/read.c                    |  51 ++++--
 fs/nfs/write.c                   | 119 ++++++++++--
 include/linux/nfs.h              |   5 +-
 include/linux/nfs_page.h         |  33 ++--
 include/linux/nfs_xdr.h          |   7 +-
 12 files changed, 666 insertions(+), 303 deletions(-)

1.8.5.2 (Apple Git-48)