[Ocfs2-devel] [Question] deadlock on chmod when running discontigous block group multiple node testing

[Eric Ren]

Hello Guys,

This is indeed another deadlock caused by:

        Commit 743b5f1434f5 ("ocfs2: take inode lock in ocfs2_iop_set/get_acl()")

The reason had been explained well by Tariq Saeed in this thread:

https://oss.oracle.com/pipermail/ocfs2-devel/2015-September/011085.html

For this case, the ocfs2_inode_lock() is misused recursively as below:

do_sys_open
    do_filp_open
      path_openat
        may_open
           inode_permission
              __inode_permission
                 ocfs2_permission  <====== ocfs2_inode_lock()
                    generic_permission
                        get_acl
                             ocfs2_iop_get_acl  <====== ocfs2_inode_lock()
                                  ocfs2_inode_lock_full_nested <===== deadlock if a remote 
EX request comes between two ocfs2_inode_lock()

Welcome any thoughts to deal with this issue!

Thanks,
Eric

On 10/12/2016 09:23 AM, Eric Ren wrote:
> Hi Junxiao,
>
>> Hi Eric,
>>
>> On 10/11/2016 10:42 AM, Eric Ren wrote:
>>> Hi Junxiao,
>>>
>>> As the subject, the testing hung there on a kernel without your patches:
>>>
>>> "ocfs2: revert using ocfs2_acl_chmod to avoid inode cluster lock hang"
>>> and
>>> "ocfs2: fix posix_acl_create deadlock"
>>>
>>> The stack trace is:
>>> ```
>>> ocfs2cts1:~ # pstree -pl 24133
>>> discontig_runne(24133)───activate_discon(21156)───mpirun(15146)─┬─fillup_contig_b(15149)───sudo(15231)───chmod(15232)
>>>
>>> ocfs2cts1:~ # pgrep -a chmod
>>> 15232 /bin/chmod -R 777 /mnt/ocfs2
>>>
>>> ocfs2cts1:~ # cat /proc/15232/stack
>>> [<ffffffffa05377ef>] __ocfs2_cluster_lock.isra.39+0x1bf/0x620 [ocfs2]
>>> [<ffffffffa053856d>] ocfs2_inode_lock_full_nested+0x12d/0x840 [ocfs2]
>>> [<ffffffffa0538dbb>] ocfs2_inode_lock_atime+0xcb/0x170 [ocfs2]
>>> [<ffffffffa0531e61>] ocfs2_readdir+0x41/0x1b0 [ocfs2]
>>> [<ffffffff8120d03c>] iterate_dir+0x9c/0x110
>>> [<ffffffff8120d453>] SyS_getdents+0x83/0xf0
>>> [<ffffffff815e126e>] entry_SYSCALL_64_fastpath+0x12/0x6d
>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>> ```
>>>
>>> Do you think this issue can be fixed by your patches?
>> Looks not. Those two patches are to fix recursive locking deadlock. But
>> from above call trace, there is no recursive lock.
> Sorry, the call trace on another node was missing.  Here it is:
>
> ocfs2cts2:~ # pstree -lp
> sshd(4292)─┬─sshd(4745)───sshd(4753)───bash(4754)───orted(4781)───fillup_contig_b(4782)───sudo(4864)───chmod(4865)
>
> ocfs2cts2:~ # cat /proc/4865/stack
> [<ffffffffa053e7ef>] __ocfs2_cluster_lock.isra.39+0x1bf/0x620 [ocfs2]
> [<ffffffffa053f56d>] ocfs2_inode_lock_full_nested+0x12d/0x840 [ocfs2]
> [<ffffffffa059c860>] ocfs2_iop_get_acl+0x40/0xf0 [ocfs2]
> [<ffffffff812044e6>] generic_permission+0x166/0x1c0
> [<ffffffffa0542aca>] ocfs2_permission+0xaa/0xd0 [ocfs2]
> [<ffffffff81204596>] __inode_permission+0x56/0xb0
> [<ffffffff812068fa>] link_path_walk+0x29a/0x560
> [<ffffffff81206cbf>] path_lookupat+0x7f/0x110
> [<ffffffff8120929c>] filename_lookup+0x9c/0x150
> [<ffffffff811f96c3>] SyS_fchmodat+0x33/0x90
> [<ffffffff815e126e>] entry_SYSCALL_64_fastpath+0x12/0x6d
> [<ffffffffffffffff>] 0xffffffffffffffff
>
> Thanks,
> Eric
>
>
>> Thanks,
>> Junxiao.
>>> I will try your patches later, but I am little worried the possibility
>>> of reproduction may not be 100%.
>>> So ask you to confirm;-)
>>>
>>> Eric
>
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