[Ocfs2-devel] [DRAFT 2/2] ocfs2: fix deadlock caused by recursive cluster locking

[piaojun <piaojun@huawei.com>]

Hi Eric,

On 2016-11-1 9:45, Eric Ren wrote:
> Hi,
> 
> On 10/31/2016 06:55 PM, piaojun wrote:
>> Hi Eric,
>>
>> On 2016-10-19 13:19, Eric Ren wrote:
>>> The deadlock issue happens when running discontiguous block
>>> group testing on multiple nodes. The easier way to reproduce
>>> is to do "chmod -R 777 /mnt/ocfs2" things like this on multiple
>>> nodes at the same time by pssh.
>>>
>>> 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
>> Do you mean another node wants to get ex of the inode? or another process?
> Remote EX request means "another node wants to get ex of the inode";-)
> 
> Eric
If another node wants to get ex, it will get blocked as this node has
got pr. Why will the ex request make this node get blocked? Expect your
detailed description.

thanks,
Jun
>>> comes between two ocfs2_inode_lock()
>>>
>>> Fix by checking if the cluster lock has been acquired aready in the call-chain
>>> path.
>>>
>>> Fixes: commit 743b5f1434f5 ("ocfs2: take inode lock in ocfs2_iop_set/get_acl()")
>>> Signed-off-by: Eric Ren <zren@suse.com>
>>> ---
>>>   fs/ocfs2/acl.c | 39 +++++++++++++++++++++++++++------------
>>>   1 file changed, 27 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
>>> index bed1fcb..7e3544e 100644
>>> --- a/fs/ocfs2/acl.c
>>> +++ b/fs/ocfs2/acl.c
>>> @@ -283,16 +283,24 @@ int ocfs2_set_acl(handle_t *handle,
>>>   int ocfs2_iop_set_acl(struct inode *inode, struct posix_acl *acl, int type)
>>>   {
>>>       struct buffer_head *bh = NULL;
>>> +    struct ocfs2_holder *oh;
>>> +    struct ocfs2_lock_res *lockres = &OCFS2_I(inode)->ip_inode_lockres;
>>>       int status = 0;
>>>   -    status = ocfs2_inode_lock(inode, &bh, 1);
>>> -    if (status < 0) {
>>> -        if (status != -ENOENT)
>>> -            mlog_errno(status);
>>> -        return status;
>>> +    oh = ocfs2_is_locked_by_me(lockres);
>>> +    if (!oh) {
>>> +        status = ocfs2_inode_lock(inode, &bh, 1);
>>> +        if (status < 0) {
>>> +            if (status != -ENOENT)
>>> +                mlog_errno(status);
>>> +            return status;
>>> +        }
>>>       }
>>> +
>>>       status = ocfs2_set_acl(NULL, inode, bh, type, acl, NULL, NULL);
>>> -    ocfs2_inode_unlock(inode, 1);
>>> +
>>> +    if (!oh)
>>> +        ocfs2_inode_unlock(inode, 1);
>>>       brelse(bh);
>>>       return status;
>>>   }
>>> @@ -302,21 +310,28 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
>>>       struct ocfs2_super *osb;
>>>       struct buffer_head *di_bh = NULL;
>>>       struct posix_acl *acl;
>>> +    struct ocfs2_holder *oh;
>>> +    struct ocfs2_lock_res *lockres = &OCFS2_I(inode)->ip_inode_lockres;
>>>       int ret;
>>>         osb = OCFS2_SB(inode->i_sb);
>>>       if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
>>>           return NULL;
>>> -    ret = ocfs2_inode_lock(inode, &di_bh, 0);
>>> -    if (ret < 0) {
>>> -        if (ret != -ENOENT)
>>> -            mlog_errno(ret);
>>> -        return ERR_PTR(ret);
>>> +
>>> +    oh = ocfs2_is_locked_by_me(lockres);
>>> +    if (!oh) {
>>> +        ret = ocfs2_inode_lock(inode, &di_bh, 0);
>>> +        if (ret < 0) {
>>> +            if (ret != -ENOENT)
>>> +                mlog_errno(ret);
>>> +            return ERR_PTR(ret);
>>> +        }
>>>       }
>>>         acl = ocfs2_get_acl_nolock(inode, type, di_bh);
>>>   -    ocfs2_inode_unlock(inode, 0);
>>> +    if (!oh)
>>> +        ocfs2_inode_unlock(inode, 0);
>>>       brelse(di_bh);
>>>       return acl;
>>>   }
>>>
>>
> 
> 
> .
>