[PULL REQUEST] writeback changes for 3.2-rc1

[Wu Fengguang <fengguang.wu@intel.com>]

Hi Linus,

The following changes since commit 9b13776977d45505469edc6decc93e9e3799afe2:

  Merge branch 'for-linus' of git://git.infradead.org/users/sameo/mfd-2.6 (2011-10-02 19:23:44 -0700)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux.git writeback-for-linus

There are two patch series:

1) IO-less dirty throttling

By not submitting writeback IO from the dirtier tasks' context,
IO seeks _and_ CPU contentions could be greatly reduced.

Users may also notice much smoothed pause times in balance_dirty_pages()
and hence in the write() syscall, especially in cases NFS, JBOD and 2+
concurrent dd's.  This will in general reduce stalls in the "pipeline"
type workloads that have the write() syscall inside its loop, such as

        loop {
                read() from network
                write() to disk
        }

The change will inevitably trigger regressions in some FS and/or
unknown workloads. However I've managed to address the known issues
and built the tracing/visualization scripts for debugging new ones
in the easy way :-)

2) report writeback reason in tracing events

I apologize for rebasing the writeback reason patches, which would
otherwise cost a merge commit. Either way is not good and I'll take
care next time to make the multiple topic branches either
fast-forwardable or base one series on top of the other.

Curt Wohlgemuth (2):
      writeback: send work item to queue_io, move_expired_inodes
      writeback: Add a 'reason' to wb_writeback_work

Wu Fengguang (14):
      writeback: account per-bdi accumulated dirtied pages
      writeback: dirty position control
      writeback: add bg_threshold parameter to __bdi_update_bandwidth()
      writeback: dirty rate control
      writeback: stabilize bdi->dirty_ratelimit
      writeback: per task dirty rate limit
      writeback: IO-less balance_dirty_pages()
      writeback: limit max dirty pause time
      writeback: control dirty pause time
      writeback: dirty position control - bdi reserve area
      writeback: per-bdi background threshold
      writeback: fix ppc compile warnings on do_div(long long, unsigned long)
      writeback: trace event bdi_dirty_ratelimit
      writeback: trace event balance_dirty_pages

 fs/btrfs/extent-tree.c           |    3 +-
 fs/buffer.c                      |    2 +-
 fs/ext4/inode.c                  |    2 +-
 fs/fs-writeback.c                |   84 +++--
 fs/quota/quota.c                 |    2 +-
 fs/sync.c                        |    4 +-
 fs/ubifs/budget.c                |    2 +-
 include/linux/backing-dev.h      |   14 +-
 include/linux/sched.h            |    7 +
 include/linux/writeback.h        |   33 ++-
 include/trace/events/writeback.h |  161 +++++++--
 kernel/fork.c                    |    3 +
 mm/backing-dev.c                 |    7 +-
 mm/page-writeback.c              |  704 ++++++++++++++++++++++++++++++--------
 mm/vmscan.c                      |    3 +-
 15 files changed, 806 insertions(+), 225 deletions(-)

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