Hi Jun, On 2018/4/11 9:52, piaojun wrote: > Hi Changwei, > > It seems other codes which try to access 'iocb' will also cause error, > right? I think we should find the reason why 'iocb' is freed first.
Which code snippet do you mean? Actually, I have checked most of other parts in write_iter() and read_iter(). I don't see any risk accessing freed iocb yet. The root cause is clear for this issue. iocb is freed by aio_complete(). You can refer to path: dio_complete aio_complete kiocb_free Thanks, Changwei > > thanks, > Jun > > On 2018/4/11 9:07, Changwei Ge wrote: >> Hi Jun, >> >> On 2018/4/11 8:52, piaojun wrote: >>> Hi Changwei, >>> >>> It looks like a code bug, and 'iocb' should not be freed at this place. >>> Could this BUG reproduced easily? >> >> Actually, it's not easy to be reproduced since IO is much slower than CPU >> executing instructions. But the logic here is broken, we'd better fix this. >> >> Thanks, >> Changwei >> >>> >>> thanks, >>> Jun >>> >>> On 2018/4/10 20:00, Changwei Ge wrote: >>>> When -EIOCBQUEUED returns, it means that aio_complete() will be called >>>> from dio_complete(), which is an asynchronous progress against write_iter. >>>> Generally, IO is a very slow progress than executing instruction, but we >>>> still can't take the risk to access a freed iocb. >>>> >>>> And we do face a BUG crash issue. >>>> >From crash tool, iocb is obviously freed already. >>>> crash> struct -x kiocb ffff881a350f5900 >>>> struct kiocb { >>>> ki_filp = 0xffff881a350f5a80, >>>> ki_pos = 0x0, >>>> ki_complete = 0x0, >>>> private = 0x0, >>>> ki_flags = 0x0 >>>> } >>>> >>>> And the backtrace shows: >>>> ocfs2_file_write_iter+0xcaa/0xd00 [ocfs2] >>>> ? ocfs2_check_range_for_refcount+0x150/0x150 [ocfs2] >>>> aio_run_iocb+0x229/0x2f0 >>>> ? try_to_wake_up+0x380/0x380 >>>> do_io_submit+0x291/0x540 >>>> ? syscall_trace_leave+0xad/0x130 >>>> SyS_io_submit+0x10/0x20 >>>> system_call_fastpath+0x16/0x75 >>>> >>>> Signed-off-by: Changwei Ge <ge.chang...@h3c.com> >>>> --- >>>> fs/ocfs2/file.c | 4 ++-- >>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c >>>> index 5d1784a..1393ff2 100644 >>>> --- a/fs/ocfs2/file.c >>>> +++ b/fs/ocfs2/file.c >>>> @@ -2343,7 +2343,7 @@ static ssize_t ocfs2_file_write_iter(struct kiocb >>>> *iocb, >>>> >>>> written = __generic_file_write_iter(iocb, from); >>>> /* buffered aio wouldn't have proper lock coverage today */ >>>> - BUG_ON(written == -EIOCBQUEUED && !(iocb->ki_flags & IOCB_DIRECT)); >>>> + BUG_ON(written == -EIOCBQUEUED && !direct_io); >>>> >>>> /* >>>> * deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a >>>> ocfs2_dio_end_io >>>> @@ -2463,7 +2463,7 @@ static ssize_t ocfs2_file_read_iter(struct kiocb >>>> *iocb, >>>> trace_generic_file_aio_read_ret(ret); >>>> >>>> /* buffered aio wouldn't have proper lock coverage today */ >>>> - BUG_ON(ret == -EIOCBQUEUED && !(iocb->ki_flags & IOCB_DIRECT)); >>>> + BUG_ON(ret == -EIOCBQUEUED && !direct_io); >>>> >>>> /* see ocfs2_file_write_iter */ >>>> if (ret == -EIOCBQUEUED || !ocfs2_iocb_is_rw_locked(iocb)) { >>>> >>> >> . >> > _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel