This fixes a regression due to commit 130d1f956a (locks: ensure that
fl_owner is always initialized properly in flock and lease codepaths). I
had mistakenly thought that the fl_owner wasn't used in the lease code,
but I missed the place in __break_lease that does use it.
The i_have_this_lease check in generic_add_lease uses it. While I'm not
sure that check is terribly helpful [1], reset it back to using
current->files in order to ensure that there's no behavior change here.
[1]: leases are owned by the file description. It's possible that this
is a threaded program, and the lease breaker and the task that
would handle the signal are different, even if they have the same
file table. So, there is the potential for false positives with
this check.
Fixes: 130d1f956a (locks: ensure that fl_owner is always initialized properly in flock and lease codepaths)
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
v2: add a __break_lease tracepoint for non-blocking case
Recently, I needed these to help track down a softlockup when recalling a
delegation, but they might be helpful in other situations as well.
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
Currently, the fl_owner isn't set for flock locks. Some filesystems use
byte-range locks to simulate flock locks and there is a common idiom in
those that does:
fl->fl_owner = (fl_owner_t)filp;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
Since flock locks are generally "owned" by the open file description,
move this into the common flock lock setup code. The fl_start and fl_end
fields are already set appropriately, so remove the unneeded setting of
that in flock ops in those filesystems as well.
Finally, the lease code also sets the fl_owner as if they were owned by
the process and not the open file description. This is incorrect as
leases have the same ownership semantics as flock locks. Set them the
same way. The lease code doesn't actually use the fl_owner value for
anything, so this is more for consistency's sake than a bugfix.
Reported-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> (Staging portion)
Acked-by: J. Bruce Fields <bfields@fieldses.org>
v2: replace missing break in switch statement (as pointed out by Dave
Jones)
commit bce7560d49 (locks: consolidate checks for compatible
filp->f_mode values in setlk handlers) introduced a regression in the
F_GETLK handler.
flock64_to_posix_lock is a shared codepath between F_GETLK and F_SETLK,
but the f_mode checks should only be applicable to the F_SETLK codepaths
according to POSIX.
Instead of just reverting the patch, add a new function to do this
checking and have the F_SETLK handlers call it.
Cc: Dave Jones <davej@redhat.com>
Reported-and-Tested-by: Reuben Farrelly <reuben@reub.net>
Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
File-private locks have been re-christened as "open file description"
locks. Finish the symbol name cleanup in the internal implementation.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
File-private locks have been merged into Linux for v3.15, and *now*
people are commenting that the name and macro definitions for the new
file-private locks suck.
...and I can't even disagree. The names and command macros do suck.
We're going to have to live with these for a long time, so it's
important that we be happy with the names before we're stuck with them.
The consensus on the lists so far is that they should be rechristened as
"open file description locks".
The name isn't a big deal for the kernel, but the command macros are not
visually distinct enough from the traditional POSIX lock macros. The
glibc and documentation folks are recommending that we change them to
look like F_OFD_{GETLK|SETLK|SETLKW}. That lessens the chance that a
programmer will typo one of the commands wrong, and also makes it easier
to spot this difference when reading code.
This patch makes the following changes that I think are necessary before
v3.15 ships:
1) rename the command macros to their new names. These end up in the uapi
headers and so are part of the external-facing API. It turns out that
glibc doesn't actually use the fcntl.h uapi header, but it's hard to
be sure that something else won't. Changing it now is safest.
2) make the the /proc/locks output display these as type "OFDLCK"
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Carlos O'Donell <carlos@redhat.com>
Cc: Stefan Metzmacher <metze@samba.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Frank Filz <ffilzlnx@mindspring.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
A fl->fl_break_time of 0 has a special meaning to the lease break code
that basically means "never break the lease". knfsd uses this to ensure
that leases don't disappear out from under it.
Unfortunately, the code in __break_lease can end up passing this value
to wait_event_interruptible as a timeout, which prevents it from going
to sleep at all. This makes __break_lease to spin in a tight loop and
causes soft lockups.
Fix this by ensuring that we pass a minimum value of 1 as a timeout
instead.
Cc: <stable@vger.kernel.org>
Cc: J. Bruce Fields <bfields@fieldses.org>
Reported-by: Terry Barnaby <terry1@beam.ltd.uk>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Allow locks_mandatory_area() to handle file-private locks correctly.
If there is a file-private lock set on an open file and we're doing I/O
via the same, then that should not cause anything to block.
Handle this by first doing a non-blocking FL_ACCESS check for a
file-private lock, and then fall back to checking for a classic POSIX
lock (and possibly blocking).
Note that this approach is subject to the same races that have always
plagued mandatory locking on Linux.
Reported-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
As Trond pointed out, you can currently deadlock yourself by setting a
file-private lock on a file that requires mandatory locking and then
trying to do I/O on it.
Avoid this problem by plumbing some knowledge of file-private locks into
the mandatory locking code. In order to do this, we must pass down
information about the struct file that's being used to
locks_verify_locked.
Reported-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Neil Brown suggested potentially overloading the l_pid value as a "lock
context" field for file-private locks. While I don't think we will
probably want to do that here, it's probably a good idea to ensure that
in the future we could extend this API without breaking existing
callers.
Typically the l_pid value is ignored for incoming struct flock
arguments, serving mainly as a place to return the pid of the owner if
there is a conflicting lock. For file-private locks, require that it
currently be set to 0 and return EINVAL if it isn't. If we eventually
want to make a non-zero l_pid mean something, then this will help ensure
that we don't break legacy programs that are using file-private locks.
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Due to some unfortunate history, POSIX locks have very strange and
unhelpful semantics. The thing that usually catches people by surprise
is that they are dropped whenever the process closes any file descriptor
associated with the inode.
This is extremely problematic for people developing file servers that
need to implement byte-range locks. Developers often need a "lock
management" facility to ensure that file descriptors are not closed
until all of the locks associated with the inode are finished.
Additionally, "classic" POSIX locks are owned by the process. Locks
taken between threads within the same process won't conflict with one
another, which renders them useless for synchronization between threads.
This patchset adds a new type of lock that attempts to address these
issues. These locks conflict with classic POSIX read/write locks, but
have semantics that are more like BSD locks with respect to inheritance
and behavior on close.
This is implemented primarily by changing how fl_owner field is set for
these locks. Instead of having them owned by the files_struct of the
process, they are instead owned by the filp on which they were acquired.
Thus, they are inherited across fork() and are only released when the
last reference to a filp is put.
These new semantics prevent them from being merged with classic POSIX
locks, even if they are acquired by the same process. These locks will
also conflict with classic POSIX locks even if they are acquired by
the same process or on the same file descriptor.
The new locks are managed using a new set of cmd values to the fcntl()
syscall. The initial implementation of this converts these values to
"classic" cmd values at a fairly high level, and the details are not
exposed to the underlying filesystem. We may eventually want to push
this handing out to the lower filesystem code but for now I don't
see any need for it.
Also, note that with this implementation the new cmd values are only
available via fcntl64() on 32-bit arches. There's little need to
add support for legacy apps on a new interface like this.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
It's not really feasible to do deadlock detection with FL_FILE_PVT
locks since they aren't owned by a single task, per-se. Deadlock
detection also tends to be rather expensive so just skip it for
these sorts of locks.
Also, add a FIXME comment about adding more limited deadlock detection
that just applies to ro -> rw upgrades, per Andy's request.
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Once we introduce file private locks, we'll need to know what cmd value
was used, as that affects the ownership and whether a conflict would
arise.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
FL_FILE_PVT locks are no longer tied to a particular pid, and are
instead inheritable by child processes. Report a l_pid of '-1' for
these sorts of locks since the pid is somewhat meaningless for them.
This precedent comes from FreeBSD. There, POSIX and flock() locks can
conflict with one another. If fcntl(F_GETLK, ...) returns a lock set
with flock() then the l_pid member cannot be a process ID because the
lock is not held by a process as such.
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
In a later patch, we'll be adding a new type of lock that's owned by
the struct file instead of the files_struct. Those sorts of locks
will be flagged with a new FL_FILE_PVT flag.
Report these types of locks as "FLPVT" in /proc/locks to distinguish
them from "classic" POSIX locks.
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
This function currently removes leases in addition to flock locks and in
a later patch we'll have it deal with file-private locks too. Rename it
to locks_remove_file to indicate that it removes locks that are
associated with a particular struct file, and not just flock locks.
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Move this check into flock64_to_posix_lock instead of duplicating it in
two places. This also fixes a minor wart in the code where we continue
referring to the struct flock after converting it to struct file_lock.
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
In the 32-bit case fcntl assigns the 64-bit f_pos and i_size to a 32-bit
off_t.
The existing range checks also seem to depend on signed arithmetic
wrapping when it overflows. In practice maybe that works, but we can be
more careful. That also allows us to make a more reliable distinction
between -EINVAL and -EOVERFLOW.
Note that in the 32-bit case SEEK_CUR or SEEK_END might allow the caller
to set a lock with starting point no longer representable as a 32-bit
value. We could return -EOVERFLOW in such cases, but the locks code is
capable of handling such ranges, so we choose to be lenient here. The
only problem is that subsequent GETLK calls on such a lock will fail
with EOVERFLOW.
While we're here, do some cleanup including consolidating code for the
flock and flock64 cases.
Signed-off-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
A leftover lock on the list is surely a sign of a problem of some sort,
but it's not necessarily a reason to panic the box. Instead, just log a
warning with some info about the lock, and then delete it like we would
any other lock.
In the event that the filesystem declares a ->lock f_op, we may end up
leaking something, but that's generally preferable to an immediate
panic.
Acked-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff 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: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@fieldses.org>
