3.15.0-rc2: RECLAIM_FS-safe -> RECLAIM_FS-unsafe lock order detected

[Christian Kujau <lists@xxxxxxxxxxxxxxx>]

Hi,

I haven't run vanilla for a while, so this is pretty much a copy of
what I reported[0] back with 3.14-rc2, but now with 3.15-rc2. Full
dmesg & .config can be found here:

   http://nerdbynature.de/bits/3.15-rc2/


======================================================
[ INFO: RECLAIM_FS-safe -> RECLAIM_FS-unsafe lock order detected ]
3.15.0-rc2 #1 Not tainted
------------------------------------------------------
rm/8288 [HC0[0]:SC0[0]:HE1:SE1] is trying to acquire:
 (&mm->mmap_sem){++++++}, at: [<c00b16ac>] might_fault+0x58/0xa0

and this task is already holding:
 (&xfs_dir_ilock_class){++++-.}, at: [<c020f790>] 
xfs_ilock_data_map_shared+0x28/0x70
which would create a new lock dependency:
 (&xfs_dir_ilock_class){++++-.} -> (&mm->mmap_sem){++++++}

but this new dependency connects a RECLAIM_FS-irq-safe lock:
 (&xfs_dir_ilock_class){++++-.}
... which became RECLAIM_FS-irq-safe at:
  [<c00658a4>] lock_acquire+0x54/0x70
  [<c00600f0>] down_write_nested+0x50/0xa0
  [<c01cef9c>] xfs_reclaim_inode+0x108/0x318
  [<c01cf360>] xfs_reclaim_inodes_ag+0x1b4/0x360
  [<c01cfea4>] xfs_reclaim_inodes_nr+0x38/0x4c
  [<c00d2d00>] super_cache_scan+0x150/0x158
  [<c00a2110>] shrink_slab_node+0x138/0x228
  [<c00a2874>] shrink_slab+0x124/0x13c
  [<c00a53f4>] kswapd+0x3f8/0x884
  [<c004e654>] kthread+0xbc/0xd0
  [<c0010b7c>] ret_from_kernel_thread+0x5c/0x64
to a RECLAIM_FS-irq-unsafe lock:
 (&mm->mmap_sem){++++++}
... which became RECLAIM_FS-irq-unsafe at:
...  [<c0065f94>] lockdep_trace_alloc+0x84/0x104
  [<c00cb630>] kmem_cache_alloc+0x30/0x148
  [<c00ba038>] mmap_region+0x2fc/0x578
  [<c00ba5a0>] do_mmap_pgoff+0x2ec/0x378
  [<c00aacf8>] vm_mmap_pgoff+0x58/0x94
  [<c012124c>] load_elf_binary+0x488/0x11f4
  [<c00d5b48>] search_binary_handler+0x98/0x1f4
  [<c00d6abc>] do_execve+0x484/0x580
  [<c000425c>] try_to_run_init_process+0x18/0x58
  [<c0004a5c>] kernel_init+0xac/0x110
  [<c0010b7c>] ret_from_kernel_thread+0x5c/0x64

other info that might help us debug this:

 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&mm->mmap_sem);
                               local_irq_disable();
                               lock(&xfs_dir_ilock_class);
                               lock(&mm->mmap_sem);
  <Interrupt>
    lock(&xfs_dir_ilock_class);

 *** DEADLOCK ***
2 locks held by rm/8288:
 #0:  (&type->i_mutex_dir_key#5){+.+.+.}, at: [<c00e230c>] iterate_dir+0x3c/0xd0
 #1:  (&xfs_dir_ilock_class){++++-.}, at: [<c020f790>] 
xfs_ilock_data_map_shared+0x28/0x70

[....]


Christian.

[0] http://oss.sgi.com/archives/xfs/2014-02/msg00362.html
-- 
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Chewing gum on /dev/sd3c