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

[Dave Chinner]

On Fri, Apr 25, 2014 at 03:21:16AM -0700, Christian Kujau wrote:
> 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);

Known false positive. Directory inodes can't be mmap()d or execv()d,
nor can referenced inodes be reclaimed.

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com