Re: dio_get_page() lockdep complaints

[Jens Axboe <jens.axboe@oracle.com>]

On Thu, Apr 19 2007, Andrew Morton wrote:
> On Thu, 19 Apr 2007 10:01:57 +0200 Jens Axboe <jens.axboe@oracle.com> wrote:
> 
> > On Thu, Apr 19 2007, Andrew Morton wrote:
> > > On Thu, 19 Apr 2007 09:38:30 +0200 Jens Axboe <jens.axboe@oracle.com> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > Doing some testing on CFQ, I ran into this 100% reproducible report:
> > > > 
> > > > =======================================================
> > > > [ INFO: possible circular locking dependency detected ]
> > > > 2.6.21-rc7 #5
> > > > -------------------------------------------------------
> > > > fio/9741 is trying to acquire lock:
> > > >  (&mm->mmap_sem){----}, at: [<b018cb34>] dio_get_page+0x54/0x161
> > > > 
> > > > but task is already holding lock:
> > > >  (&inode->i_mutex){--..}, at: [<b038c6e5>] mutex_lock+0x1c/0x1f
> > > > 
> > > > which lock already depends on the new lock.
> > > > 
> > > 
> > > This is the correct ranking: i_mutex outside mmap_sem.
> > > 
> > > > 
> > > > the existing dependency chain (in reverse order) is:
> > > > 
> > > > -> #1 (&inode->i_mutex){--..}:
> > > >        [<b013e3fb>] __lock_acquire+0xdee/0xf9c
> > > >        [<b013e600>] lock_acquire+0x57/0x70
> > > >        [<b038c4a5>] __mutex_lock_slowpath+0x73/0x297
> > > >        [<b038c6e5>] mutex_lock+0x1c/0x1f
> > > >        [<b01b17e9>] reiserfs_file_release+0x54/0x447
> > > >        [<b016afe7>] __fput+0x53/0x101
> > > >        [<b016b0ee>] fput+0x19/0x1c
> > > >        [<b015bcd5>] remove_vma+0x3b/0x4d
> > > >        [<b015c659>] do_munmap+0x17f/0x1cf
> > > >        [<b015c6db>] sys_munmap+0x32/0x42
> > > >        [<b0103f04>] sysenter_past_esp+0x5d/0x99
> > > >        [<ffffffff>] 0xffffffff
> > > > 
> > > > -> #0 (&mm->mmap_sem){----}:
> > > >        [<b013e259>] __lock_acquire+0xc4c/0xf9c
> > > >        [<b013e600>] lock_acquire+0x57/0x70
> > > >        [<b0137b92>] down_read+0x3a/0x4c
> > > >        [<b018cb34>] dio_get_page+0x54/0x161
> > > >        [<b018d7a9>] __blockdev_direct_IO+0x514/0xe2a
> > > >        [<b01cf449>] ext3_direct_IO+0x98/0x1e5
> > > >        [<b014e8df>] generic_file_direct_IO+0x63/0x133
> > > >        [<b01500e9>] generic_file_aio_read+0x16b/0x222
> > > >        [<b017f8b6>] aio_rw_vect_retry+0x5a/0x116
> > > >        [<b0180147>] aio_run_iocb+0x69/0x129
> > > >        [<b0180a78>] io_submit_one+0x194/0x2eb
> > > >        [<b0181331>] sys_io_submit+0x92/0xe7
> > > >        [<b0103f90>] syscall_call+0x7/0xb
> > > >        [<ffffffff>] 0xffffffff
> > > 
> > > But here reiserfs is taking i_mutex in its file_operations.release(),
> > > which can be called under mmap_sem.
> > > 
> > > Vladimir's recent de14569f94513279e3d44d9571a421e9da1759ae.
> > > "resierfs: avoid tail packing if an inode was ever mmapped" comes real
> > > close to this code, but afaict it did not cause this bug.
> > > 
> > > I can't think of anything which we've done in the 2.6.21 cycle which
> > > would have caused this to start happening.  Odd.
> > 
> > The bug may be holder, let me know if you want me to check 2.6.20 or
> > earlier.
> 
> Would be great if you could test 2.6.20.  I have a feeling that I missed
> something, but what?  We didn't change the refcounting of lifetime of
> vma.vm_file...

2.6.20.7 tested, same lockdep triggers. Attached for reference.

> > > > The test run was fio, the job file used is:
> > > > 
> > > > # fio job file snip below
> > > > [global]
> > > > bs=4k
> > > > buffered=0
> > > > ioengine=libaio
> > > > iodepth=4
> > > > thread
> > > > 
> > > > [readers]
> > > > numjobs=8
> > > > size=128m
> > > > rw=read
> > > > # fio job file snip above
> > > > 
> > > > Filesystem was ext3, default mkfs and mount options. Kernel was
> > > > 2.6.21-rc7 as of this morning, with some CFQ patches applied.
> > > > 
> > > 
> > > It's interesting that lockdep learned the (wrong) ranking from a reiserfs
> > > operation then later detected it being violated by ext3.
> > 
> > It's a scratch test box, which for some reason has reiserfs as the
> > rootfs. So reiser gets to run first :-)
> 
> direct-io reads against reiserfs also will take i_mutex outside mmap_sem. 
> As will pagefaults inside generic_file_write() (which is where this ranking
> is primarily defined).
> 
> So an all-reiserfs system should be getting the same reports.  Obviously,
> that isn't happening.
> 
> It's a bit odd that reiserfs is playing with file contents within
> file_operations.release(): there could be other files open against that
> inode.  One would expect this sort of thing to be happening in an
> inode_operation.  But it's been like that for a long time.
> 
> Is it possible that fio was changed?  That it was changed to close() the fd
> before doing the munmapping whereas it used to hold the file open?

It's been a while since I tested on this box, so I don't really recall.
But fio does close() the fd before doing munmap(). This particular test
case doesn't use mmap(), though.


=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.20.7 #1
-------------------------------------------------------
fio/6651 is trying to acquire lock:
 (&mm->mmap_sem){----}, at: [<b01899c4>] dio_get_page+0x54/0x161

but task is already holding lock:
 (&inode->i_mutex){--..}, at: [<b0385e85>] mutex_lock+0x1c/0x1f

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&inode->i_mutex){--..}:
       [<b013ba73>] __lock_acquire+0xc86/0xd64
       [<b013bba8>] lock_acquire+0x57/0x70
       [<b0385c45>] __mutex_lock_slowpath+0x73/0x297
       [<b0385e85>] mutex_lock+0x1c/0x1f
       [<b01ae3b5>] reiserfs_file_release+0x54/0x44b
       [<b0167b27>] __fput+0x53/0x101
       [<b0167c2e>] fput+0x19/0x1c
       [<b015884c>] remove_vma+0x37/0x49
       [<b01591d0>] do_munmap+0x17f/0x1d0
       [<b0159253>] sys_munmap+0x32/0x42
       [<b0102f04>] sysenter_past_esp+0x5d/0x99
       [<ffffffff>] 0xffffffff

-> #0 (&mm->mmap_sem){----}:
       [<b013b8f5>] __lock_acquire+0xb08/0xd64
       [<b013bba8>] lock_acquire+0x57/0x70
       [<b013701e>] down_read+0x3a/0x4c
       [<b01899c4>] dio_get_page+0x54/0x161
       [<b018a639>] __blockdev_direct_IO+0x514/0xe2a
       [<b01cc009>] ext3_direct_IO+0x98/0x1e5
       [<b014b72b>] generic_file_direct_IO+0x63/0x133
       [<b014cf79>] generic_file_aio_read+0x16b/0x222
       [<b017c466>] aio_rw_vect_retry+0x5a/0x116
       [<b017ccf7>] aio_run_iocb+0x69/0x129
       [<b017d6ed>] io_submit_one+0x194/0x2ec
       [<b017dffb>] sys_io_submit+0x92/0xe6
       [<b0102f90>] syscall_call+0x7/0xb
       [<ffffffff>] 0xffffffff

other info that might help us debug this:

1 lock held by fio/6651:
 #0:  (&inode->i_mutex){--..}, at: [<b0385e85>] mutex_lock+0x1c/0x1f

stack backtrace:
 [<b0103f54>] show_trace_log_lvl+0x1a/0x30
 [<b01045f6>] show_trace+0x12/0x14
 [<b010467d>] dump_stack+0x16/0x18
 [<b0139d29>] print_circular_bug_tail+0x68/0x71
 [<b013b8f5>] __lock_acquire+0xb08/0xd64
 [<b013bba8>] lock_acquire+0x57/0x70
 [<b013701e>] down_read+0x3a/0x4c
 [<b01899c4>] dio_get_page+0x54/0x161
 [<b018a639>] __blockdev_direct_IO+0x514/0xe2a
 [<b01cc009>] ext3_direct_IO+0x98/0x1e5
 [<b014b72b>] generic_file_direct_IO+0x63/0x133
 [<b014cf79>] generic_file_aio_read+0x16b/0x222
 [<b017c466>] aio_rw_vect_retry+0x5a/0x116
 [<b017ccf7>] aio_run_iocb+0x69/0x129
 [<b017d6ed>] io_submit_one+0x194/0x2ec
 [<b017dffb>] sys_io_submit+0x92/0xe6
 [<b0102f90>] syscall_call+0x7/0xb
 =======================

-- 
Jens Axboe