Btrfs fixes

Hi everyone,

This pull request is bigger than I wanted it to be, but Josef has commits in here for some long running ENOSPC bugs in btrfs. This is a few weeks of tracing our delalloc reservations from Josef, and then fixing up the related bugs.

Outside of Josef's patches we have some assorted fixes. Arne figured out we were orphaning whole snapshots if you unmounted enough times while the snapshot was being deleted.

Josef Bacik (6) commits (+212/-117):
Btrfs: fix how we do delalloc reservations and how we free reservations on error (+44/-13)
Btrfs: fix num_workers_starting bug and other bugs in async thread (+83/-78)
Btrfs: only set cache_generation if we setup the block group (+1/-1)
Btrfs: deal with enospc from dirtying inodes properly (+80/-22)
Btrfs: don't panic if orphan item already exists (+1/-1)
Btrfs: fix leaked space in truncate (+3/-2)

Chris Mason (4) commits (+10/-4):
Btrfs: fix btrfs_end_bio to deal with write errors to a single mirror (+1/-1)
Btrfs: deal with NULL srv_rsv in the delalloc inode reservation code (+2/-2)
Btrfs: add a cond_resched() into the worker loop (+1/-1)
Btrfs: unplug every once and a while (+6/-0)

Miao Xie (3) commits (+29/-13):
Btrfs: fix wrong i_size when truncating a file to a larger size (+12/-6)
Btrfs: fix inaccurate available space on raid0 profile (+13/-6)
Btrfs: fix wrong disk space information of the files (+4/-1)

Casey Schaufler (1) commits (+26/-5):
BTRFS: Establish i_ops before calling d_instantiate

Arne Jansen (1) commits (+32/-0):
btrfs: keep orphans for subvolume deletion

Li Zefan (1) commits (+2/-2):
Btrfs: fix ctime update of on-disk inode

Total: (16) commits (+309/-140)

 fs/btrfs/async-thread.c  |  117 ++++++++++++++----------------
 fs/btrfs/async-thread.h  |    4 +-
 fs/btrfs/ctree.h         |    3 +-
 fs/btrfs/delayed-inode.c |    4 +-
 fs/btrfs/disk-io.c       |   34 ++++++----
 fs/btrfs/extent-tree.c   |   45 ++++++++----
 fs/btrfs/file.c          |    6 ++-
 fs/btrfs/inode.c         |  180 +++++++++++++++++++++++++++++++++++++---------
 fs/btrfs/ioctl.c         |    6 +-
 fs/btrfs/relocation.c    |    2 +
 fs/btrfs/scrub.c         |    8 ++-
 fs/btrfs/super.c         |   32 +++++++--
 fs/btrfs/volumes.c       |    8 ++-
 13 files changed, 309 insertions(+), 140 deletions(-)

Sorry, this part is missing:

git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs.git for-linus

% git log --no-merges --grep="enospc" | grep commit | wc -l
45
% git log --no-merges --grep="enospc"|grep "Date:"

Date:   Fri Oct 7 11:55:34 2011 -0400
Date:   Mon Sep 26 17:12:22 2011 -0400
Date:   Tue Aug 30 10:19:10 2011 -0400
Date:   Mon Aug 29 14:06:00 2011 -0400
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Date:   Thu Dec 17 15:47:17 2009 -0500
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Date:   Mon Nov 17 21:12:00 2008 -0500
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Date:   Mon Sep 17 11:00:51 2007 -0400
Date:   Wed Aug 29 09:11:44 2007 -0400