Implement NFSv4 delegations, take 8

From: "J. Bruce Fields" <[email protected]>

This is just a rebase to 3.10 of the previous posting. As far as I can tell, it's ready to be merged. Introduction (repeated from before) follows:

This patch series implements read delegations, which allow NFSv4 clients to perform read opens without contacting the server, by promising to call back to clients before modifying the data, metadata, or set of links pointing to a file.

The main recent change was in response to review from Linus, who didn't want us to hang under directory i_mutex's on timeouts communicating with unresponsive clients.

So, this version of the series drops the i_mutex before waiting. The logic ends up looking something like:

acquire locks
look up inode
test for delegation; if found:
take reference on inode
release locks
wait for delegation break
drop reference on inode
retry

The initial test for a delegation happens after the lock on the delegated inode is acquired, but additional directory mutexes may have been acquired further up the call stack. I therefore add a "struct inode **" argument to any intervening functions, which we use to pass the inode back up to the caller in the case it needs to wait for the delegation to be broken.

I also allow callers to pass in NULL for the "struct inode **" argument to indicate they'd rather just fail than wait for a delegation. For example, as long as ecryptfs isn't exportable I assume they'd rather not see retry logic there that they won't use. But I may have misjudged in some of these cases.

J. Bruce Fields (12):
vfs: pull ext4's double-i_mutex-locking into common code
vfs: don't use PARENT/CHILD lock classes for non-directories
vfs: rename I_MUTEX_QUOTA now that it's not used for quotas
vfs: take i_mutex on renamed file
locks: introduce new FL_DELEG lock flag
locks: implement delegations
namei: minor vfs_unlink cleanup
locks: break delegations on unlink
locks: helper functions for delegation breaking
locks: break delegations on rename
locks: break delegations on link
locks: break delegations on any attribute modification

 Documentation/filesystems/directory-locking |   31 ++++++++---
 drivers/base/devtmpfs.c                     |    6 +-
 fs/attr.c                                   |    5 +-
 fs/cachefiles/interface.c                   |    4 +-
 fs/cachefiles/namei.c                       |    4 +-
 fs/ecryptfs/inode.c                         |    6 +-
 fs/ext4/ext4.h                              |    2 -
 fs/ext4/ioctl.c                             |    4 +-
 fs/ext4/move_extent.c                       |   40 +-------------
 fs/hpfs/namei.c                             |    2 +-
 fs/inode.c                                  |   35 +++++++++++-
 fs/locks.c                                  |   51 +++++++++++++----
 fs/namei.c                                  |   79 +++++++++++++++++++++------
 fs/nfsd/nfs4state.c                         |    2 +-
 fs/nfsd/vfs.c                               |   14 +++--
 fs/open.c                                   |   21 +++++--
 fs/utimes.c                                 |    9 ++-
 include/linux/fs.h                          |   72 ++++++++++++++++++++----
 ipc/mqueue.c                                |    2 +-
 19 files changed, 273 insertions(+), 116 deletions(-)