linux-stable.git/fs/locks.c, branch v4.1.2

proc: show locks in /proc/pid/fdinfo/X

2015-04-17T13:04:12+00:00

Let's show locks which are associated with a file descriptor in
its fdinfo file.

Currently we don't have a reliable way to determine who holds a lock.  We
can find some information in /proc/locks, but PID which is reported there
can be wrong.  For example, a process takes a lock, then forks a child and
dies.  In this case /proc/locks contains the parent pid, which can be
reused by another process.

$ cat /proc/locks
...
6: FLOCK  ADVISORY  WRITE 324 00:13:13431 0 EOF
...

$ ps -C rpcbind
  PID TTY          TIME CMD
  332 ?        00:00:00 rpcbind

$ cat /proc/332/fdinfo/4
pos:	0
flags:	0100000
mnt_id:	22
lock:	1: FLOCK  ADVISORY  WRITE 324 00:13:13431 0 EOF

$ ls -l /proc/332/fd/4
lr-x------ 1 root root 64 Mar  5 14:43 /proc/332/fd/4 -> /run/rpcbind.lock

$ ls -l /proc/324/fd/
total 0
lrwx------ 1 root root 64 Feb 27 14:50 0 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:50 1 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:49 2 -> /dev/pts/0

You can see that the process with the 324 pid doesn't hold the lock.

This information is required for proper dumping and restoring file
locks.

Signed-off-by: Andrey Vagin 
Cc: Jonathan Corbet 
Cc: Alexander Viro 
Acked-by: Jeff Layton 
Acked-by: "J. Bruce Fields" 
Acked-by: Cyrill Gorcunov 
Cc: Pavel Emelyanov 
Cc: Joe Perches 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

locks: use cmpxchg to assign i_flctx pointer

2015-04-03T13:04:04+00:00

During the v3.20/v4.0 cycle, I had originally had the code manage the
inode->i_flctx pointer using a compare-and-swap operation instead of the
i_lock.

Sasha Levin though hit a problem while testing with trinity that made me
believe that that wasn't safe. At the time, changing the code to protect
the i_flctx pointer seemed to fix the issue, but I now think that was
just coincidence.

The issue was likely the same race that Kirill Shutemov hit while
testing the pre-rc1 v4.0 kernel and that Linus spotted. Due to the way
that the spinlock was dropped in the middle of flock_lock_file, you
could end up with multiple flock locks for the same struct file on the
inode.

Reinstate the use of a CAS operation to assign this pointer since it's
likely to be more efficient and gets the i_lock completely out of the
file locking business.

Signed-off-by: Jeff Layton

locks: get rid of WE_CAN_BREAK_LSLK_NOW dead code

2015-04-03T13:04:04+00:00

As Bruce points out, there's no compelling reason to change /proc/locks
output at this point. If we did want to do this, then we'd almost
certainly want to introduce a new file to display this info (maybe via
debugfs?).

Let's remove the dead WE_CAN_BREAK_LSLK_NOW ifdef here and just plan to
stay with the legacy format.

Reported-by: J. Bruce Fields 
Signed-off-by: Jeff Layton

locks: change lm_get_owner and lm_put_owner prototypes

2015-04-03T13:04:04+00:00

The current prototypes for these operations are somewhat awkward as they
deal with fl_owners but take struct file_lock arguments. In the future,
we'll want to be able to take references without necessarily dealing
with a struct file_lock.

Change them to take fl_owner_t arguments instead and have the callers
deal with assigning the values to the file_lock structs.

Signed-off-by: Jeff Layton

locks: don't allocate a lock context for an F_UNLCK request

2015-04-03T13:04:03+00:00

In the event that we get an F_UNLCK request on an inode that has no lock
context, there is no reason to allocate one. Change
locks_get_lock_context to take a "type" pointer and avoid allocating a
new context if it's F_UNLCK.

Then, fix the callers to return appropriately if that function returns
NULL.

Signed-off-by: Jeff Layton

locks: Add lockdep assertion for blocked_lock_lock

2015-04-03T13:04:03+00:00

Annonate insert, remove and iterate function that we need
blocked_lock_lock held.

Signed-off-by: Daniel Wagner 
Signed-off-by: Jeff Layton

locks: remove extraneous IS_POSIX and IS_FLOCK tests

2015-04-03T13:04:02+00:00

We know that the locks being passed into this function are of the
correct type, now that they live on their own lists.

Signed-off-by: Jeff Layton

locks: Remove unnecessary IS_POSIX test

2015-04-03T13:04:02+00:00

Since following change

commit bd61e0a9c852de2d705b6f1bb2cc54c5774db570
Author: Jeff Layton 
Date:   Fri Jan 16 15:05:55 2015 -0500

    locks: convert posix locks to file_lock_context

all Posix locks are kept on their a separate list, so the test is
redudant.

Signed-off-by: Daniel Wagner 
Cc: Jeff Layton 
Cc: "J. Bruce Fields" 
Cc: Alexander Viro 
Signed-off-by: Jeff Layton

locks: fix file_lock deletion inside loop

2015-03-27T11:18:20+00:00

locks_delete_lock_ctx() is called inside the loop, so we
should use list_for_each_entry_safe.

Fixes: 8634b51f6ca2 (locks: convert lease handling to file_lock_context)
Signed-off-by: "Yan, Zheng" 
Signed-off-by: Jeff Layton

locks: fix generic_delete_lease tracepoint to use victim pointer

2015-03-14T13:45:35+00:00

It's possible that "fl" won't point at a valid lock at this point, so
use "victim" instead which is either a valid lock or NULL.

Signed-off-by: Jeff Layton