nfs: Fix cache_validity check in nfs_write_pageuptodate()

NFS_INO_INVALID_DATA cannot be ignored, even if we have a delegation.

We're still having some problems with data corruption when multiple
clients are appending to a file and those clients are being granted
write delegations on open.

To reproduce:

Client A:
vi /mnt/`hostname -s`
while :; do echo "XXXXXXXXXXXXXXX" >>/mnt/file; sleep $(( $RANDOM % 5 )); done

Client B:
vi /mnt/`hostname -s`
while :; do echo "YYYYYYYYYYYYYYY" >>/mnt/file; sleep $(( $RANDOM % 5 )); done

What's happening is that in nfs_update_inode() we're recognizing that
the file size has changed and we're setting NFS_INO_INVALID_DATA
accordingly, but then we ignore the cache_validity flags in
nfs_write_pageuptodate() because we have a delegation.  As a result,
in nfs_updatepage() we're extending the write to cover the full page
even though we've not read in the data to begin with.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Cc: <stable@vger.kernel.org> # v3.11+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
NFS: Clear NFS_INO_REVAL_PAGECACHE when we update the file size

In nfs_update_inode(), if the change attribute is seen to change on
the server, then we set NFS_INO_REVAL_PAGECACHE in order to make
sure that we check the file size.
However, if we also update the file size in the same function, we
don't need to check it again. So make sure that we clear the
NFS_INO_REVAL_PAGECACHE that was set earlier.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
NFS: Don't mark the data cache as invalid if it has been flushed

Now that we have functions such as nfs_write_pageuptodate() that use
the cache_validity flags to check if the data cache is valid or not,
it is a little more important to keep the flags in sync with the
state of the data cache.
In particular, we'd like to ensure that if the data cache is empty, we
don't start marking it as needing revalidation.

Reported-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
NFS check the return of nfs4_negotiate_security in nfs4_submount

Signed-off-by: Andy Adamson <andros@netapp.com>
Tested-By: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
NFS Return -EPERM if no supported or matching SECINFO flavor

Do not return RPC_AUTH_UNIX if SEINFO reply tests fail. This
prevents an infinite loop of NFS4ERR_WRONGSEC for non RPC_AUTH_UNIX mounts.

Without this patch, a mount with no sec= option to a server
that does not include RPC_AUTH_UNIX in the
SECINFO return can be presented with an attemtp to use RPC_AUTH_UNIX
which will result in an NFS4ERR_WRONG_SEC which will prompt the SECINFO
call which will again try RPC_AUTH_UNIX....

Signed-off-by: Andy Adamson <andros@netapp.com>
Tested-By: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
NFSv4: test SECINFO RPC_AUTH_GSS pseudoflavors for support

Fix nfs4_negotiate_security to create an rpc_clnt used to test each SECINFO
returned pseudoflavor. Check credential creation  (and gss_context creation)
which is important for RPC_AUTH_GSS pseudoflavors which can fail for multiple
reasons including mis-configuration.

Don't call nfs4_negotiate in nfs4_submount as it was just called by
nfs4_proc_lookup_mountpoint (nfs4_proc_lookup_common)

Signed-off-by: Andy Adamson <andros@netapp.com>
[Trond: fix corrupt return value from nfs_find_best_sec()]
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Merge tag 'nfs-for-3.16-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs

Pull NFS client fixes from Trond Myklebust:
 "Highlights include:

   - Stable fix for a data corruption case due to incorrect cache
     validation
   - Fix a couple of false positive cache invalidations
   - Fix NFSv4 security negotiation issues"

* tag 'nfs-for-3.16-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  NFSv4: test SECINFO RPC_AUTH_GSS pseudoflavors for support
  NFS Return -EPERM if no supported or matching SECINFO flavor
  NFS check the return of nfs4_negotiate_security in nfs4_submount
  NFS: Don't mark the data cache as invalid if it has been flushed
  NFS: Clear NFS_INO_REVAL_PAGECACHE when we update the file size
  nfs: Fix cache_validity check in nfs_write_pageuptodate()