Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NJeff Layton <jlayton@redhat.com>

As Al Viro points out, there is an unlikely, but possible race between
opening a file and setting a lease on it. generic_add_lease is done with
the i_lock held, but the inode->i_flock check in break_lease is
lockless. It's possible for another task doing an open to do the entire
pathwalk and call break_lease between the point where generic_add_lease
checks for a conflicting open and adds the lease to the list. If this
occurs, we can end up with a lease set on the file with a conflicting
open.

To guard against that, check again for a conflicting open after adding
the lease to the i_flock list. If the above race occurs, then we can
simply unwind the lease setting and return -EAGAIN.

Because we take dentry references and acquire write access on the file
before calling break_lease, we know that if the i_flock list is empty
when the open caller goes to check it then the necessary refcounts have
already been incremented. Thus the additional check for a conflicting
open will see that there is one and the setlease call will fail.

Cc: Bruce Fields <bfields@fieldses.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Reported-by: NAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@fieldses.org>

We should unlock here before returning.

Fixes: df4e8d2c ('locks: implement delegations')
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Implement NFSv4 delegations at the vfs level using the new FL_DELEG lock
type.

Note nfsd is the only delegation user and is only using read
delegations.  Warn on any attempt to set a write delegation for now.
We'll come back to that case later.
Acked-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

For now FL_DELEG is just a synonym for FL_LEASE.  So this patch doesn't
change behavior.

Next we'll modify break_lease to treat FL_DELEG leases differently, to
account for the fact that NFSv4 delegations should be broken in more
situations than Windows oplocks.
Acked-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

The file_lock_list is only used for /proc/locks. The vastly common case
is for locks to be put onto the list and come off again, without ever
being traversed.

Help optimize for this use-case by moving to percpu hlist_head-s. At the
same time, we can make the locking less contentious by moving to an
lglock. When iterating over the lists for /proc/locks, we must take the
global lock and then iterate over each CPU's list in turn.

This change necessitates a new fl_link_cpu field to keep track of which
CPU the entry is on. On x86_64 at least, this field is placed within an
existing hole in the struct to avoid growing the size.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

There's no reason we have to protect the blocked_hash and file_lock_list
with the same spinlock. With the tests I have, breaking it in two gives
a barely measurable performance benefit, but it seems reasonable to make
this locking as granular as possible.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Currently, the hashing that the locking code uses to add these values
to the blocked_hash is simply calculated using fl_owner field. That's
valid in most cases except for server-side lockd, which validates the
owner of a lock based on fl_owner and fl_pid.

In the case where you have a small number of NFS clients doing a lot
of locking between different processes, you could end up with all
the blocked requests sitting in a very small number of hash buckets.

Add a new lm_owner_key operation to the lock_manager_operations that
will generate an unsigned long to use as the key in the hashtable.
That function is only implemented for server-side lockd, and simply
XORs the fl_owner and fl_pid.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Break up the blocked_list into a hashtable, using the fl_owner as a key.
This speeds up searching the hash chains, which is especially significant
for deadlock detection.

Note that the initial implementation assumes that hashing on fl_owner is
sufficient. In most cases it should be, with the notable exception being
server-side lockd, which compares ownership using a tuple of the
nlm_host and the pid sent in the lock request. So, this may degrade to a
single hash bucket when you only have a single NFS client. That will be
addressed in a later patch.

The careful observer may note that this patch leaves the file_lock_list
alone. There's much less of a case for turning the file_lock_list into a
hashtable. The only user of that list is the code that generates
/proc/locks, and it always walks the entire list.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Testing has shown that iterating over the blocked_list for deadlock
detection turns out to be a bottleneck. In order to alleviate that,
begin the process of turning it into a hashtable. We start by turning
the fl_link into a hlist_node and the global lists into hlists. A later
patch will do the conversion of the blocked_list to a hashtable.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Since we always hold the i_lock when inserting a new waiter onto the
fl_block list, we can avoid taking the global lock at all if we find
that it's empty when we go to wake up blocked waiters.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Having a global lock that protects all of this code is a clear
scalability problem. Instead of doing that, move most of the code to be
protected by the i_lock instead. The exceptions are the global lists
that the ->fl_link sits on, and the ->fl_block list.

->fl_link is what connects these structures to the
global lists, so we must ensure that we hold those locks when iterating
over or updating these lists.

Furthermore, sound deadlock detection requires that we hold the
blocked_list state steady while checking for loops. We also must ensure
that the search and update to the list are atomic.

For the checking and insertion side of the blocked_list, push the
acquisition of the global lock into __posix_lock_file and ensure that
checking and update of the  blocked_list is done without dropping the
lock in between.

On the removal side, when waking up blocked lock waiters, take the
global lock before walking the blocked list and dequeue the waiters from
the global list prior to removal from the fl_block list.

With this, deadlock detection should be race free while we minimize
excessive file_lock_lock thrashing.

Finally, in order to avoid a lock inversion problem when handling
/proc/locks output we must ensure that manipulations of the fl_block
list are also protected by the file_lock_lock.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Move the fl_link list handling routines into a separate set of helpers.
Also ensure that locks and requests are always put on global lists
last (after fully initializing them) and are taken off before unintializing
them.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

commit 66189be7 (CIFS: Fix VFS lock usage for oplocked files) exported
the locks_delete_block symbol. There's already an exported helper
function that provides this capability however, so make cifs use that
instead and turn locks_delete_block back into a static function.

Note that if fl->fl_next == NULL then this lock has already been through
locks_delete_block(), so we should be OK to ignore an ENOENT error here
and simply not retry the lock.

Cc: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NJ. Bruce Fields <bfields@fieldses.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

The rules for fl_type are rather convoluted. Typically it's treated as
holding specific values, except in the case of LOCK_MAND, in which case
it can be or'ed with LOCK_READ|LOCK_WRITE.

On some arches F_WRLCK == 2 and F_UNLCK == 3, so and'ing with F_WRLCK will also
catch the F_UNLCK case. It's unlikely in either case here that we'd ever see
F_UNLCK since those shouldn't end up on any lists, but it's still best to be
consistent.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

In commit 3b6e2723 ("locks: prevent side-effects of
locks_release_private before file_lock is initialized") we removed the
last user of lm_release_private without removing the field itself.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

No point putting something only used by one caller into common code.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

When calling fcntl(fd, F_SETLEASE, lck) [with lck=F_WRLCK or F_RDLCK],
the custom signal or owner (if any were previously set using F_SETSIG
or F_SETOWN fcntls) would be reset when F_SETLEASE was called for the
second time on the same file descriptor.

This bug is a regression of 2.6.37 and is described here:
https://bugzilla.kernel.org/show_bug.cgi?id=43336

This patch reverts a commit from Oct 2004 (with subject "nfs4 lease:
move the f_delown processing") which originally introduced the
lm_release_private callback.
Signed-off-by: NFilipe Brandenburger <filbranden@gmail.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

The only checks of the long argument passed to fcntl(fd,F_SETLEASE,.)
are done after converting the long to an int.  Thus some illegal values
may be let through and cause problems in later code.

[ They actually *don't* cause problems in mainline, as of Dave Jones's
  commit 8d657eb3 "Remove easily user-triggerable BUG from
  generic_setlease", but we should fix this anyway.  And this patch will
  be necessary to fix real bugs on earlier kernels. ]

Cc: stable@vger.kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This can be trivially triggered from userspace by passing in something unexpected.

    kernel BUG at fs/locks.c:1468!
    invalid opcode: 0000 [#1] SMP
    RIP: 0010:generic_setlease+0xc2/0x100
    Call Trace:
      __vfs_setlease+0x35/0x40
      fcntl_setlease+0x76/0x150
      sys_fcntl+0x1c6/0x810
      system_call_fastpath+0x1a/0x1f
Signed-off-by: NDave Jones <davej@redhat.com>
Cc: stable@kernel.org # 3.2+
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

We can deadlock if we have a write oplock and two processes
use the same file handle. In this case the first process can't
unlock its lock if the second process blocked on the lock in the
same time.

Fix it by using posix_lock_file rather than posix_lock_file_wait
under cinode->lock_mutex. If we request a blocking lock and
posix_lock_file indicates that there is another lock that prevents
us, wait untill that lock is released and restart our call.

Cc: stable@kernel.org
Acked-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NPavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: NSteve French <sfrench@us.ibm.com>

Bruce Fields notes that commit 778fc546 ("locks: fix tracking of
inprogress lease breaks") introduced a possible error pointer
dereference on failure to allocate memory.  locks_conflict() will
dereference the passed-in new lease lock structure that may be an error pointer.

This means an open (without O_NONBLOCK set) on a file with a lease
applied (generally only done when Samba or nfsd (with v4) is running)
could crash if a kmalloc() fails.

So instead of playing games with IS_ERROR() all over the place, just
check the allocation failure early.  That makes the code more
straightforward, and avoids this possible bad pointer dereference.
Based-on-patch-by: NJ. Bruce Fields <bfields@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There are numerous broken references to Documentation files (in other
Documentation files, in comments, etc.). These broken references are
caused by typo's in the references, and by renames or removals of the
Documentation files. Some broken references are simply odd.

Fix these broken references, sometimes by dropping the irrelevant text
they were part of.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Eventually we should probably do the same thing to the file operations
as well.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

There's an incorrect comment here.  Also clean up the logic: the
"rdlease" and "wrlease" locals are confusingly named, and don't really
add anything since we can make a decision as soon as we hit one of these
cases.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

We currently use a bit in fl_flags to record whether a lease is being
broken, and set fl_type to the type (RDLCK or UNLCK) that it will
eventually have.  This means that once the lease break starts, we forget
what the lease's type *used* to be.  Breaking a read lease will then
result in blocking read opens, even though there's no conflict--because
the lease type is now F_UNLCK and we can no longer tell whether it was
previously a read or write lease.

So, instead keep fl_type as the original type (the type which we
enforce), and keep track of whether we're unlocking or merely
downgrading by replacing the single FL_INPROGRESS flag by
FL_UNLOCK_PENDING and FL_DOWNGRADE_PENDING flags.

To get this right we also need to track separate downgrade and break
times, to handle the case where a write-leased file gets conflicting
opens first for read, then later for write.

(I first considered just eliminating the downgrade behavior
completely--nfsv4 doesn't need it, and nobody as far as I can tell
actually uses it currently--but Jeremy Allison tells me that Windows
oplocks do behave this way, so Samba will probably use this some day.)
Reviewed-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

F_INPROGRESS isn't exposed to userspace.  To me it makes more sense in
fl_flags....
Reviewed-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Use a helper function, to simplify upcoming changes.
Reviewed-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Both the filesystem and the lock manager can associate operations with a
lock.  Confusingly, one of them (fl_release_private) actually has the
same name in both operation structures.

It would save some confusion to give the lock-manager ops different
names.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

From: Miklos Szeredi <mszeredi@suse.cz>

Remove SLAB initialization entirely, as suggested by Bruce and Linus.
Allocate with __GFP_ZERO instead and only initialize list heads.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>