If we create the object and then return failure to the client, we're
left with an unexpected file in the filesystem.

I'm trying to eliminate such cases but not 100% sure I have so an
assertion might be helpful for now.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Acked-by: NJim Rees <rees@umich.edu>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

A client that wants to execute a file must be able to read it.  Read
opens over nfs are therefore implicitly allowed for executable files
even when those files are not readable.

NFSv2/v3 get this right by using a passed-in NFSD_MAY_OWNER_OVERRIDE on
read requests, but NFSv4 has gotten this wrong ever since
dc730e17 "nfsd4: fix owner-override on
open", when we realized that the file owner shouldn't override
permissions on non-reclaim NFSv4 opens.

So we can't use NFSD_MAY_OWNER_OVERRIDE to tell nfsd_permission to allow
reads of executable files.

So, do the same thing we do whenever we encounter another weird NFS
permission nit: define yet another NFSD_MAY_* flag.

The industry's future standardization on 128-bit processors will be
motivated primarily by the need for integers with enough bits for all
the NFSD_MAY_* flags.
Reported-by: NLeonardo Borda <leonardoborda@gmail.com>
Cc: stable@kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

The NFS server uses nfsd_create_v3 to handle EXCLUSIVE4_1 opens, but
that function is not prepared to handle them.

Rename nfsd_create_v3() to do_nfsd_create(), and add handling of
EXCLUSIVE4_1.
Signed-off-by: NMi Jinlong <mijinlong@cn.fujitsu.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Most of the NFSD_MAY_* flags actually request permissions, but over the
years we've accreted a few that modify the behavior of the permission or
open code in other ways.

Distinguish the two cases a little more.  In particular, allow the
shortcut at the start of nfsd_permission to ignore the
non-permission-requesting bits.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Christoph points that the NFSv2/v3 callers know which case they want
here, so we may as well just call the file=NULL case directly instead of
making this conditional.

Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

This is the second attempt to fix the problem whereby a COMMIT call
causes a lease break and triggers a possible deadlock.

The problem is that nfsd attempts to break a lease on a COMMIT call.
This triggers a delegation recall if the lease is held for a delegation.
If the client is the one holding the delegation and it's the same one on
which it's issuing the COMMIT, then it can't return that delegation
until the COMMIT is complete. But, nfsd won't complete the COMMIT until
the delegation is returned. The client and server are essentially
deadlocked until the state is marked bad (due to the client not
responding on the callback channel).

The first patch attempted to deal with this by eliminating the open of
the file altogether and simply had nfsd_commit pass a NULL file pointer
to the vfs_fsync_range. That would conflict with some work in progress
by Christoph Hellwig to clean up the fsync interface, so this patch
takes a different approach.

This declares a new NFSD_MAY_NOT_BREAK_LEASE access flag that indicates
to nfsd_open that it should not break any leases when opening the file,
and has nfsd_commit set that flag on the nfsd_open call.

For now, this patch leaves nfsd_commit opening the file with write
access since I'm not clear on what sort of access would be more
appropriate.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Cc: stable@kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>

Most of this can be trivially moved to a private header as well.
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>

As with lookup, we treat every boject as a mountpoint and pretend it
doesn't exist if it isn't exported.

The preexisting code here is confusing, but I haven't yet figured out
how to make it clearer.
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>

None of this stuff is used outside nfsd, so move it out of the common
linux include directory.

Actually, probably none of the stuff in include/linux/nfsd/nfsd.h really
belongs there, so later we may remove that file entirely.
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>