• Theodore Ts'o's avatar
    ext4: fix a potential deadlock in __ext4_es_shrink() · 3f1f9b85
    Theodore Ts'o authored
    This fixes the following lockdep complaint:
    
    [ INFO: possible circular locking dependency detected ]
    3.16.0-rc2-mm1+ #7 Tainted: G           O  
    -------------------------------------------------------
    kworker/u24:0/4356 is trying to acquire lock:
     (&(&sbi->s_es_lru_lock)->rlock){+.+.-.}, at: [<ffffffff81285fff>] __ext4_es_shrink+0x4f/0x2e0
    
    but task is already holding lock:
     (&ei->i_es_lock){++++-.}, at: [<ffffffff81286961>] ext4_es_insert_extent+0x71/0x180
    
    which lock already depends on the new lock.
    
     Possible unsafe locking scenario:
    
           CPU0                    CPU1
           ----                    ----
      lock(&ei->i_es_lock);
                                   lock(&(&sbi->s_es_lru_lock)->rlock);
                                   lock(&ei->i_es_lock);
      lock(&(&sbi->s_es_lru_lock)->rlock);
    
     *** DEADLOCK ***
    
    6 locks held by kworker/u24:0/4356:
     #0:  ("writeback"){.+.+.+}, at: [<ffffffff81071d00>] process_one_work+0x180/0x560
     #1:  ((&(&wb->dwork)->work)){+.+.+.}, at: [<ffffffff81071d00>] process_one_work+0x180/0x560
     #2:  (&type->s_umount_key#22){++++++}, at: [<ffffffff811a9c74>] grab_super_passive+0x44/0x90
     #3:  (jbd2_handle){+.+...}, at: [<ffffffff812979f9>] start_this_handle+0x189/0x5f0
     #4:  (&ei->i_data_sem){++++..}, at: [<ffffffff81247062>] ext4_map_blocks+0x132/0x550
     #5:  (&ei->i_es_lock){++++-.}, at: [<ffffffff81286961>] ext4_es_insert_extent+0x71/0x180
    
    stack backtrace:
    CPU: 0 PID: 4356 Comm: kworker/u24:0 Tainted: G           O   3.16.0-rc2-mm1+ #7
    Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
    Workqueue: writeback bdi_writeback_workfn (flush-253:0)
     ffffffff8213dce0 ffff880014b07538 ffffffff815df0bb 0000000000000007
     ffffffff8213e040 ffff880014b07588 ffffffff815db3dd ffff880014b07568
     ffff880014b07610 ffff88003b868930 ffff88003b868908 ffff88003b868930
    Call Trace:
     [<ffffffff815df0bb>] dump_stack+0x4e/0x68
     [<ffffffff815db3dd>] print_circular_bug+0x1fb/0x20c
     [<ffffffff810a7a3e>] __lock_acquire+0x163e/0x1d00
     [<ffffffff815e89dc>] ? retint_restore_args+0xe/0xe
     [<ffffffff815ddc7b>] ? __slab_alloc+0x4a8/0x4ce
     [<ffffffff81285fff>] ? __ext4_es_shrink+0x4f/0x2e0
     [<ffffffff810a8707>] lock_acquire+0x87/0x120
     [<ffffffff81285fff>] ? __ext4_es_shrink+0x4f/0x2e0
     [<ffffffff8128592d>] ? ext4_es_free_extent+0x5d/0x70
     [<ffffffff815e6f09>] _raw_spin_lock+0x39/0x50
     [<ffffffff81285fff>] ? __ext4_es_shrink+0x4f/0x2e0
     [<ffffffff8119760b>] ? kmem_cache_alloc+0x18b/0x1a0
     [<ffffffff81285fff>] __ext4_es_shrink+0x4f/0x2e0
     [<ffffffff812869b8>] ext4_es_insert_extent+0xc8/0x180
     [<ffffffff812470f4>] ext4_map_blocks+0x1c4/0x550
     [<ffffffff8124c4c4>] ext4_writepages+0x6d4/0xd00
    	...
    Reported-by: default avatarMinchan Kim <minchan@kernel.org>
    Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
    Reported-by: default avatarMinchan Kim <minchan@kernel.org>
    Cc: stable@vger.kernel.org
    Cc: Zheng Liu <gnehzuil.liu@gmail.com>
    3f1f9b85
extents_status.c 30.2 KB