Re: [PATCH] NFS: Fix "BUG at fs/aio.c:554!"

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On Thu, Jan 20, 2011 at 10:25 AM, Trond Myklebust
<Trond.Myklebust@xxxxxxxxxx> wrote:
> On Wed, 2011-01-19 at 17:36 -0500, Chuck Lever wrote:
>> Nick Piggin reports:
>>
>> > I'm getting use after frees in aio code in NFS
>> >
>> > [ 2703.396766] Call Trace:
>> > [ 2703.396858]  [<ffffffff8100b057>] ? native_sched_clock+0x27/0x80
>> > [ 2703.396959]  [<ffffffff8108509e>] ? put_lock_stats+0xe/0x40
>> > [ 2703.397058]  [<ffffffff81088348>] ? lock_release_holdtime+0xa8/0x140
>> > [ 2703.397159]  [<ffffffff8108a2a5>] lock_acquire+0x95/0x1b0
>> > [ 2703.397260]  [<ffffffff811627db>] ? aio_put_req+0x2b/0x60
>> > [ 2703.397361]  [<ffffffff81039701>] ? get_parent_ip+0x11/0x50
>> > [ 2703.397464]  [<ffffffff81612a31>] _raw_spin_lock_irq+0x41/0x80
>> > [ 2703.397564]  [<ffffffff811627db>] ? aio_put_req+0x2b/0x60
>> > [ 2703.397662]  [<ffffffff811627db>] aio_put_req+0x2b/0x60
>> > [ 2703.397761]  [<ffffffff811647fe>] do_io_submit+0x2be/0x7c0
>> > [ 2703.397895]  [<ffffffff81164d0b>] sys_io_submit+0xb/0x10
>> > [ 2703.397995]  [<ffffffff8100307b>] system_call_fastpath+0x16/0x1b
>> >
>> > Adding some tracing, it is due to nfs completing the request then
>> > returning something other than -EIOCBQUEUED, so aio.c
>> > also completes the request.
>>
>> To address this, prevent the NFS direct I/O engine from completing
>> async iocbs when the forward path returns an error other than
>> EIOCBQUEUED.
>>
>> This appears to survive ^C during both "xfstest no. 208" and "fsx -Z."
>>
>> Cc: Stable <stable@xxxxxxxxxx>
>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>> ---
>>
>> Here's my take.
>>
>>  fs/nfs/direct.c |   32 +++++++++++++++++---------------
>>  1 files changed, 17 insertions(+), 15 deletions(-)
>>
>> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
>> index e6ace0d..c2176f4 100644
>> --- a/fs/nfs/direct.c
>> +++ b/fs/nfs/direct.c
>> @@ -407,15 +407,16 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
>>               pos += vec->iov_len;
>>       }
>>
>> -     if (put_dreq(dreq))
>> -             nfs_direct_complete(dreq);
>> -
>> -     if (requested_bytes != 0)
>> -             return 0;
>> +     /*
>> +      * If no bytes were started, return the error, and let the
>> +      * generic layer handle the completion.
>> +      */
>> +     if (requested_bytes == 0)
>> +             return result < 0 ? result : -EIO;
>>
>> -     if (result < 0)
>> -             return result;
>> -     return -EIO;
>> +     if (put_dreq(dreq))
>> +             nfs_direct_write_complete(dreq, dreq->inode);
>                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> In nfs_direct_read_schedule_iovec()? Shouldn't that be
>                nfs_direct_complete(dreq);
>
> Also, why is EIO the correct reply when no bytes were read/written? Why
> shouldn't the VFS aio code be able to cope with a zero byte reply?

What would it do?
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