Re: [PATCH 1/4] xfs: lockdep needs to know about 3 dquot-deep nesting

Ben Myers
2013-09-30T21:19:18Z

On Mon, Sep 30, 2013 at 09:37:03AM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> Michael Semon reported that xfs/299 generated this lockdep warning:
>
> =============================================
> [ INFO: possible recursive locking detected ]
> 3.12.0-rc2+ #2 Not tainted
> ---------------------------------------------
> touch/21072 is trying to acquire lock:
> (&xfs_dquot_other_class){+.+...}, at: [<c12902fb>] xfs_trans_dqlockedjoin+0x57/0x64
>
> but task is already holding lock:
> (&xfs_dquot_other_class){+.+...}, at: [<c12902fb>] xfs_trans_dqlockedjoin+0x57/0x64
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&xfs_dquot_other_class);
> lock(&xfs_dquot_other_class);
>
> *** DEADLOCK ***
>
> May be due to missing lock nesting notation
>
> 7 locks held by touch/21072:
> #0: (sb_writers#10){++++.+}, at: [<c11185b6>] mnt_want_write+0x1e/0x3e
> #1: (&type->i_mutex_dir_key#4){+.+.+.}, at: [<c11078ee>] do_last+0x245/0xe40
> #2: (sb_internal#2){++++.+}, at: [<c122c9e0>] xfs_trans_alloc+0x1f/0x35
> #3: (&(&ip->i_lock)->mr_lock/1){+.+...}, at: [<c126cd1b>] xfs_ilock+0x100/0x1f1
> #4: (&(&ip->i_lock)->mr_lock){++++-.}, at: [<c126cf52>] xfs_ilock_nowait+0x105/0x22f
> #5: (&dqp->q_qlock){+.+...}, at: [<c12902fb>] xfs_trans_dqlockedjoin+0x57/0x64
> #6: (&xfs_dquot_other_class){+.+...}, at: [<c12902fb>] xfs_trans_dqlockedjoin+0x57/0x64
>
> The lockdep annotation for dquot lock nesting only understands
> locking for user and "other" dquots, not user, group and quota
> dquots. Fix the annotations to match the locking heirarchy we now
> have.
>
> Reported-by: Michael L. Semon <mlsemon35@gmail.com>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

Looks good.

Reviewed-by: Ben Myers <bpm@sgi.com>