Implement NFSv4 delegations, take 9

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

Changes since version 8, thanks to dchinner and jlayton for review:

- additional warnings in lock_two_nondirectories
- lock_two_nondirectories handles NULL second argument, simplifying vfs_rename_other
- kerneldoc comments on notify_change, vfs_link, vfs_rename, vfs_unlink, to explain delegated_inode argument.
- make clear non-support of write delegations in generic_add_lease
- rebase to 3.11-rc1

Introduction copied from previous posting:

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 (16):
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
nfsd4: minor nfs4_setlease cleanup
nfsd4: delay setting current_fh in open
nfsd4: close open-deleg/unlink/rename race
nfsd4: break only delegations when appropriate

 Documentation/filesystems/directory-locking |   31 ++++--
 drivers/base/devtmpfs.c                     |    6 +-
 fs/attr.c                                   |   25 ++++-
 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                                  |   42 ++++++++-
 fs/locks.c                                  |   57 ++++++++---
 fs/namei.c                                  |  135 +++++++++++++++++++++++----
 fs/nfsd/nfs4proc.c                          |   36 +++----
 fs/nfsd/nfs4state.c                         |   66 ++++++++++---
 fs/nfsd/vfs.c                               |   41 ++------
 fs/nfsd/xdr4.h                              |    3 +-
 fs/open.c                                   |   22 ++++-
 fs/utimes.c                                 |    9 +-
 include/linux/fs.h                          |   72 +++++++++++---
 ipc/mqueue.c                                |    2 +-
 21 files changed, 433 insertions(+), 176 deletions(-)

1.7.9.5