• T
    ext4: Fix potential fiemap deadlock (mmap_sem vs. i_data_sem) · fab3a549
    Theodore Ts'o 提交于
    Fix the following potential circular locking dependency between
    mm->mmap_sem and ei->i_data_sem:
    
        =======================================================
        [ INFO: possible circular locking dependency detected ]
        2.6.32-04115-gec044c5 #37
        -------------------------------------------------------
        ureadahead/1855 is trying to acquire lock:
         (&mm->mmap_sem){++++++}, at: [<ffffffff81107224>] might_fault+0x5c/0xac
    
        but task is already holding lock:
         (&ei->i_data_sem){++++..}, at: [<ffffffff811be1fd>] ext4_fiemap+0x11b/0x159
    
        which lock already depends on the new lock.
    
        the existing dependency chain (in reverse order) is:
    
        -> #1 (&ei->i_data_sem){++++..}:
               [<ffffffff81099bfa>] __lock_acquire+0xb67/0xd0f
               [<ffffffff81099e7e>] lock_acquire+0xdc/0x102
               [<ffffffff81516633>] down_read+0x51/0x84
               [<ffffffff811a2414>] ext4_get_blocks+0x50/0x2a5
               [<ffffffff811a3453>] ext4_get_block+0xab/0xef
               [<ffffffff81154f39>] do_mpage_readpage+0x198/0x48d
               [<ffffffff81155360>] mpage_readpages+0xd0/0x114
               [<ffffffff811a104b>] ext4_readpages+0x1d/0x1f
               [<ffffffff810f8644>] __do_page_cache_readahead+0x12f/0x1bc
               [<ffffffff810f86f2>] ra_submit+0x21/0x25
               [<ffffffff810f0cfd>] filemap_fault+0x19f/0x32c
               [<ffffffff81107b97>] __do_fault+0x55/0x3a2
               [<ffffffff81109db0>] handle_mm_fault+0x327/0x734
               [<ffffffff8151aaa9>] do_page_fault+0x292/0x2aa
               [<ffffffff81518205>] page_fault+0x25/0x30
               [<ffffffff812a34d8>] clear_user+0x38/0x3c
               [<ffffffff81167e16>] padzero+0x20/0x31
               [<ffffffff81168b47>] load_elf_binary+0x8bc/0x17ed
               [<ffffffff81130e95>] search_binary_handler+0xc2/0x259
               [<ffffffff81166d64>] load_script+0x1b8/0x1cc
               [<ffffffff81130e95>] search_binary_handler+0xc2/0x259
               [<ffffffff8113255f>] do_execve+0x1ce/0x2cf
               [<ffffffff81027494>] sys_execve+0x43/0x5a
               [<ffffffff8102918a>] stub_execve+0x6a/0xc0
    
        -> #0 (&mm->mmap_sem){++++++}:
               [<ffffffff81099aa4>] __lock_acquire+0xa11/0xd0f
               [<ffffffff81099e7e>] lock_acquire+0xdc/0x102
               [<ffffffff81107251>] might_fault+0x89/0xac
               [<ffffffff81139382>] fiemap_fill_next_extent+0x95/0xda
               [<ffffffff811bcb43>] ext4_ext_fiemap_cb+0x138/0x157
               [<ffffffff811be069>] ext4_ext_walk_space+0x178/0x1f1
               [<ffffffff811be21e>] ext4_fiemap+0x13c/0x159
               [<ffffffff811390e6>] do_vfs_ioctl+0x348/0x4d6
               [<ffffffff811392ca>] sys_ioctl+0x56/0x79
               [<ffffffff81028cb2>] system_call_fastpath+0x16/0x1b
    
        other info that might help us debug this:
    
        1 lock held by ureadahead/1855:
         #0:  (&ei->i_data_sem){++++..}, at: [<ffffffff811be1fd>] ext4_fiemap+0x11b/0x159
    
        stack backtrace:
        Pid: 1855, comm: ureadahead Not tainted 2.6.32-04115-gec044c5 #37
        Call Trace:
         [<ffffffff81098c70>] print_circular_bug+0xa8/0xb7
         [<ffffffff81099aa4>] __lock_acquire+0xa11/0xd0f
         [<ffffffff8102f229>] ? sched_clock+0x9/0xd
         [<ffffffff81099e7e>] lock_acquire+0xdc/0x102
         [<ffffffff81107224>] ? might_fault+0x5c/0xac
         [<ffffffff81107251>] might_fault+0x89/0xac
         [<ffffffff81107224>] ? might_fault+0x5c/0xac
         [<ffffffff81124b44>] ? __kmalloc+0x13b/0x18c
         [<ffffffff81139382>] fiemap_fill_next_extent+0x95/0xda
         [<ffffffff811bcb43>] ext4_ext_fiemap_cb+0x138/0x157
         [<ffffffff811bca0b>] ? ext4_ext_fiemap_cb+0x0/0x157
         [<ffffffff811be069>] ext4_ext_walk_space+0x178/0x1f1
         [<ffffffff811be21e>] ext4_fiemap+0x13c/0x159
         [<ffffffff81107224>] ? might_fault+0x5c/0xac
         [<ffffffff811390e6>] do_vfs_ioctl+0x348/0x4d6
         [<ffffffff8129f6d0>] ? __up_read+0x8d/0x95
         [<ffffffff81517fb5>] ? retint_swapgs+0x13/0x1b
         [<ffffffff811392ca>] sys_ioctl+0x56/0x79
         [<ffffffff81028cb2>] system_call_fastpath+0x16/0x1b
    Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
    fab3a549
extents.c 96.8 KB