Re: nfsd changes for 2.6.37

J. Bruce Fields
2010-10-26T22:12:01Z

On Tue, Oct 26, 2010 at 05:44:41PM -0400, J. Bruce Fields wrote:
> On Tue, Oct 26, 2010 at 02:37:26PM -0700, Linus Torvalds wrote:
> > On Tue, Oct 26, 2010 at 2:24 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > >
> > > I did a couple connectathon runs just now with no obvious ill effects
> > > except for some sleep-within-spinlock warnings in the lease code.
> >
> > Hmm. Those sleep-within-spinlock warnings are very likely serious
> > bugs.
>
> Yeah, didn't mean to belittle them.
>
> > Can you quote the whole warning with stack trace?
>
> It's just obvious allocations in setlease:
>
> BUG: sleeping function called from invalid context at mm/slab.c:3101
> in_atomic(): 1, irqs_disabled(): 0, pid: 4345, name: lease_tests
> 1 lock held by lease_tests/4345:
> #0: (file_lock_lock){+.+.+.}, at: [<ffffffff81128be5>] lock_flocks+0x15/0x20
> Pid: 4345, comm: lease_tests Not tainted 2.6.36-05858-gbd5e20b #1028
> Call Trace:
> [<ffffffff8103141d>] __might_sleep+0x10d/0x140
> [<ffffffff810e3ad3>] kmem_cache_alloc+0x1f3/0x230
> [<ffffffff8112a4d2>] generic_setlease+0x112/0x2c0
> [<ffffffff8112a6b5>] __vfs_setlease+0x35/0x40
> [<ffffffff8112acfe>] fcntl_setlease+0xce/0x180
> [<ffffffff810f7c2e>] sys_fcntl+0x2fe/0x630
> [<ffffffff81961999>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [<ffffffff81002658>] system_call_fastpath+0x16/0x1b
>
> I'm testing a patch.

This works for me.

I'm not saying it's correct, but it does at least pass my dumb tests
without complaining.

--b.

diff --git a/fs/locks.c b/fs/locks.c
index 02b6e0e..db3afa0 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1379,7 +1379,9 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
if (error)
return error;

+ lock_flocks();
time_out_leases(inode);
+ unlock_flocks();

BUG_ON(!(*flp)->fl_lmops->fl_break);

@@ -1400,6 +1402,7 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
goto out;
}

+ lock_flocks();
/*
* At this point, we know that if there is an exclusive
* lease on this file, then we hold it on this filp
@@ -1427,28 +1430,31 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
error = -EAGAIN;
if ((arg == F_RDLCK && (wrlease_count > 0)) ||
(arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0)))
- goto out;
+ goto out_unlock;

if (my_before != NULL) {
*flp = *my_before;
error = lease->fl_lmops->fl_change(my_before, arg);
- goto out;
+ goto out_unlock;
}

error = 0;
if (arg == F_UNLCK)
- goto out;
+ goto out_unlock;

error = -EINVAL;
if (!leases_enable)
- goto out;
+ goto out_unlock;

locks_copy_lock(new_fl, lease);
locks_insert_lock(before, new_fl);

*flp = new_fl;
+ unlock_flocks();
return 0;

+out_unlock:
+ unlock_flocks();
out:
if (new_fl != NULL)
locks_free_lock(new_fl);
@@ -1495,9 +1501,7 @@ int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
{
int error;

- lock_flocks();
error = __vfs_setlease(filp, arg, lease);
- unlock_flocks();

return error;
}
@@ -1524,8 +1528,6 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
if (error)
return error;

- lock_flocks();
-
error = __vfs_setlease(filp, arg, &flp);
if (error || arg == F_UNLCK)
goto out_unlock;
@@ -1541,7 +1543,6 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)

error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
out_unlock:
- unlock_flocks();
return error;
}