On 8/12/11 10:55 AM, Michael Tokarev wrote:
> 12.08.2011 17:07, Jan Kara wrote:
> []
>>>>> [ 76.982985] EXT4-fs (dm-1): Unaligned AIO/DIO on inode 3407879 by oracle; performance will be poor.
>>>>> [ 1469.734114] SysRq : Show Blocked State
>>>>> [ 1469.734157] task PC stack pid father
>>>>> [ 1469.734473] oracle D 0000000000000000 0 6146 1 0x00000000
>>>>> [ 1469.734525] ffff88103f604810 0000000000000082 ffff881000000000 ffff881079791040
>>>>> [ 1469.734603] ffff880432c19fd8 ffff880432c19fd8 ffff880432c19fd8 ffff88103f604810
>>>>> [ 1469.734681] ffffea000ec13590 ffffffff00000000 ffff881438c8dad8 ffffffff810eeda2
>>>>> [ 1469.734760] Call Trace:
>>>>> [ 1469.734800] [<ffffffff810eeda2>] ? __do_fault+0x422/0x520
>>>>> [ 1469.734863] [<ffffffffa0123e6d>] ? ext4_file_write+0x20d/0x260 [ext4]
>>>>> [ 1469.734909] [<ffffffff8106aee0>] ? abort_exclusive_wait+0xb0/0xb0
>>>>> [ 1469.734956] [<ffffffffa0123c60>] ? ext4_llseek+0x120/0x120 [ext4]
>>>>> [ 1469.734999] [<ffffffff81162173>] ? aio_rw_vect_retry+0x73/0x1d0
>>>>> [ 1469.735039] [<ffffffff8116302f>] ? aio_run_iocb+0x5f/0x160
>>>>> [ 1469.735078] [<ffffffff81164258>] ? do_io_submit+0x4f8/0x600
>>>>> [ 1469.735122] [<ffffffff81359b52>] ? system_call_fastpath+0x16/0x1b
> []
>> Probably not, just garbage on stack confuses the stack unwinder. Note
>> that e.g. ext4_llseek() is at the end of function as well as
>> abort_exclusive_wait() which probably means these functions have already
>> finished and just left their addresses on stack. Could you disasseble
>> your ext4_file_write() function and check where offset 0x20d is? Sadly you
>> won't see where calls are going when ext4 is compiled as a module (module
>> is linked when loaded into kernel) so it might be easier to compile ext4
>> into the kernel and disassemble the function in vmlinux file.
>>
>>> Btw, does ext4_llseek() look sane here? Note it's called from
>>> aio_submit() -- does it _ever_ implement SEEKs?
>>>
>>> Maybe some debugging is neecessary here?
>> Yes. The trouble is I'm not completely sure where we are hanging yet.
>> We should know more from your disassembly. But you can try running with
>> attached debug patch - maybe it shows something interesting.
>
> With ext4 built-in and your patch applied:
>
> [ 429.061524] EXT4-fs (sda11): Unaligned AIO/DIO on inode 5767181 by oracle; performance will be poor.
> [ 429.061669] Going to wait for 18446744073709551199 aios
> [ 437.717942] SysRq : Show Blocked State
> [ 437.718109] task PC stack pid father
> [ 437.718528] oracle D 0000000000000000 0 3844 1 0x00000000
> [ 437.718767] ffff88203e330080 0000000000000082 0000000000000000 ffff881078e3f7d0
> [ 437.719156] ffff88203dc15fd8 ffff88203dc15fd8 ffff88203dc15fd8 ffff88203e330080
> [ 437.719546] 0000001e0000000f 0000000000000246 205b88103f806680 3136302e39323420
> [ 437.719935] Call Trace:
> [ 437.720043] [<ffffffff8139b976>] ? printk+0x43/0x48
> [ 437.720155] [<ffffffff8118e16d>] ? ext4_file_write+0x21d/0x290
> [ 437.720267] [<ffffffff8106aee0>] ? abort_exclusive_wait+0xb0/0xb0
> [ 437.720376] [<ffffffff8118df50>] ? ext4_llseek+0x120/0x120
> [ 437.720485] [<ffffffff81162173>] ? aio_rw_vect_retry+0x73/0x1d0
> [ 437.720593] [<ffffffff8116302f>] ? aio_run_iocb+0x5f/0x160
> [ 437.720699] [<ffffffff81164258>] ? do_io_submit+0x4f8/0x600
> [ 437.720811] [<ffffffff813a3152>] ? system_call_fastpath+0x16/0x1b
>
> Trying to find how to disassemble things now...
> And yes, 18446744073709551199 aios sounds quite alot ;)
looks like it went negative.
I see that in one case we set EXT4_IO_END_UNWRITTEN, but don't increment the counter.
We decrement the counter for every EXT4_IO_END_UNWRITTEN completion, I think.
I'm not quite sure if that was intentional or not, but it might be a place to start.
I haven't though hard about this, in the middle of something else right now,
but this looks like it's a probllem in my code from that unaligned AIO patch,
perhaps...
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3e5191f..7366488 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3640,6 +3640,7 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate)
io_end->flag = EXT4_IO_END_UNWRITTEN;
inode = io_end->inode;
+ atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
/* Add the io_end to per-inode completed io list*/
spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
> Thanks,
>
> /mjt
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