[PATCH 0/8] clean up and generalize swap-over-NFS

[Omar Sandoval <osandov@osandov.com>]

Hi, everyone,

This patch series contains all of the non-BTRFS changes that I've made
as a part of implementing swap file support on BTRFS. The BTRFS parts of
that series (https://lkml.org/lkml/2014/12/9/718) are still undergoing
development, and the non-BTRFS changes now outnumber those within BTRFS,
so it'll probably work best to get these in separately.

Long story short, the generic swap file infrastructure introduced for
swap-over-NFS isn't quite ready for other clients without making some
changes.

Before I forget, this patch series was built against cbfe0de in Linus'
tree (to avoid conflicts with the recent iov_iter work).

Patches 1 and 2 fix an issue with NFS and the swap file infrastructure
not following the direct_IO locking conventions, leading to locking
issues for anyone else trying to use the interface (discussed here:
https://lkml.org/lkml/2014/12/12/677).

Patch 3 removes the ITER_BVEC flag from the rw argument passed to
direct_IO, as many, but not all, direct_IO implementations expect either
rw == READ or rw == WRITE. The lack of documentation about what's
correct here is probably going to break something at some point, but
that's another conversation.

Patch 4 adds iov_iter_bvec for swap_writepage, the upcoming
swap_readpage change, and splice.

Patches 5 and 6 are preparation for patch 7, teaching the VFS and NFS to
handle ITER_BVEC reads.

Patch 7 is the biggest change in the series: it changes swap_readpage to
proxy through ->direct_IO rather than ->readpage. Using readpage for a
swapcache page requires all sorts of messy workarounds (see here for
context: https://lkml.org/lkml/2014/11/19/46). Patch 8 updates the
documentation accordingly.

Thanks!

Omar Sandoval (8):
  nfs: follow direct I/O write locking convention
  swap: lock i_mutex for swap_writepage direct_IO
  swap: don't add ITER_BVEC flag to direct_IO rw
  iov_iter: add iov_iter_bvec and convert callers
  direct-io: don't dirty ITER_BVEC pages on read
  nfs: don't dirty ITER_BVEC pages read through direct I/O
  swap: use direct I/O for SWP_FILE swap_readpage
  vfs: update swap_{,de}activate documentation

 Documentation/filesystems/Locking |  7 +++---
 Documentation/filesystems/vfs.txt |  7 +++---
 fs/direct-io.c                    |  8 ++++---
 fs/nfs/direct.c                   | 17 ++++++++-------
 fs/nfs/file.c                     |  8 +++++--
 fs/splice.c                       |  7 ++----
 include/linux/uio.h               |  2 ++
 mm/iov_iter.c                     | 12 +++++++++++
 mm/page_io.c                      | 45 ++++++++++++++++++++++++++++-----------
 9 files changed, 76 insertions(+), 37 deletions(-)

-- 
2.1.3