lockdep warning in 3.14-rc1

[Dave Chinner]

On Fri, Feb 07, 2014 at 04:46:36PM -0800, Cody P Schafer wrote:
> Appears consistently during boot up.
....

> [    2.080292]        CPU0                    CPU1
> [    2.080295]        ----                    ----
> [    2.080298]   lock(&(&ip->i_lock)->mr_lock);
> [    2.080303]                                lock(&mm->mmap_sem);
> [    2.080307]                                lock(&(&ip->i_lock)->mr_lock);
> [    2.080312]   lock(&mm->mmap_sem);
> [    2.080316] 
>  *** DEADLOCK ***
> 
> [    2.080321] 2 locks held by systemd/1:
> [    2.080323]  #0:  (&type->i_mutex_dir_key#2){+.+.+.}, at: [<c000000000297470>] .iterate_dir+0xa0/0x160
> [    2.080334]  #1:  (&(&ip->i_lock)->mr_lock){++++..}, at: [<c00000000042e7ec>] .xfs_ilock+0x15c/0x1b0
> [    2.080343] 
> stack backtrace:
> [    2.080348] CPU: 2 PID: 1 Comm: systemd Tainted: G        W    3.14.0-rc1-24x7+ #8
> [    2.080353] Call Trace:
> [    2.080357] [c0000001fa103370] [c000000000016590] .show_stack+0x170/0x290 (unreliable)
> [    2.080364] [c0000001fa103460] [c000000000934f5c] .dump_stack+0xa0/0xdc
> [    2.080370] [c0000001fa1034e0] [c00000000092b6b4] .print_circular_bug+0x364/0x39c
> [    2.080376] [c0000001fa103590] [c00000000010ba70] .check_prev_add+0x8d0/0x8e0
> [    2.080381] [c0000001fa1036a0] [c00000000010c364] .validate_chain.isra.31+0x8e4/0xc40
> [    2.080386] [c0000001fa103790] [c00000000010de08] .__lock_acquire+0x488/0xd40
> [    2.080391] [c0000001fa1038b0] [c00000000010f08c] .lock_acquire+0xac/0x190
> [    2.080397] [c0000001fa103980] [c00000000021fe44] .might_fault+0xa4/0xe0
> [    2.080402] [c0000001fa1039f0] [c000000000297924] .filldir+0x1f4/0x290
> [    2.080407] [c0000001fa103ab0] [c0000000003cebc8] .xfs_dir2_block_getdents+0x218/0x2b0
> [    2.080413] [c0000001fa103b80] [c0000000003cf1e8] .xfs_readdir+0x168/0x1d0
> [    2.080418] [c0000001fa103c30] [c0000000003d2508] .xfs_file_readdir+0x48/0x80
> [    2.080423] [c0000001fa103cc0] [c0000000002974ec] .iterate_dir+0x11c/0x160
> [    2.080428] [c0000001fa103d60] [c000000000297df0] .SyS_getdents+0xa0/0x190
> [    2.080433] [c0000001fa103e30] [c00000000000a164] syscall_exit+0x0/0x98

False positive. We need to add new lockdep annotations because
lockdep doesn't know the difference between directory locking and
file IO path locking.

Ben, can you look at this? It is being caused by the addition of the
iolock to the directory readdir code, so directory inodes need a
different lockdep context to regular file inodes...

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com