[Ocfs2-devel] [PATCH] ocfs2: kill EBUSY from dlmfs_evict_inode

[heming.zhao at suse.com]

On 6/5/22 06:27, Junxiao Bi wrote:
> 
> On 6/4/22 3:10 AM, heming.zhao at suse.com wrote:
>> Hello Junxiao,
>>
>> On 6/4/22 06:31, Junxiao Bi via Ocfs2-devel wrote:
>>> When unlink a dlmfs, first it will invoke dlmfs_unlink(), and then invoke
>>> dlmfs_evict_inode(), user_dlm_destroy_lock() is invoked in both places,
>>> the second one from dlmfs_evict_inode() will get EBUSY error because
>>> USER_LOCK_IN_TEARDOWN is already set in lockres. This doesn't affect
>>> any function, just the error log is anonying.
>>>
>>> Signed-off-by: Junxiao Bi <junxiao.bi at oracle.com>
>>> ---
>>>   fs/ocfs2/dlmfs/dlmfs.c | 14 +++++++++++---
>>>   1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
>>> index e360543ad7e7..a120610dff7e 100644
>>> --- a/fs/ocfs2/dlmfs/dlmfs.c
>>> +++ b/fs/ocfs2/dlmfs/dlmfs.c
>>> @@ -296,17 +296,25 @@ static void dlmfs_evict_inode(struct inode *inode)
>>>   {
>>>       int status;
>>>       struct dlmfs_inode_private *ip;
>>> +    struct user_lock_res *lockres;
>>> +    int destroyed;
>>>         clear_inode(inode);
>>>         mlog(0, "inode %lu\n", inode->i_ino);
>>>         ip = DLMFS_I(inode);
>>> +    lockres = &ip->ip_lockres;
>>>         if (S_ISREG(inode->i_mode)) {
>>> -        status = user_dlm_destroy_lock(&ip->ip_lockres);
>>> -        if (status < 0)
>>> -            mlog_errno(status);
>>> +        spin_lock(&lockres->l_lock);
>>> +        destroyed = !!(lockres->l_flags & USER_LOCK_IN_TEARDOWN);
>>> +        spin_unlock(&lockres->l_lock);
>>
>> This area code does the same work in user_dlm_destroy_lock(). Why not to give another
>> errno (e.g -EAGAIN) for user_dlm_destroy_lock when l_flags contains USER_LOCK_IN_TEARDOWN.
>> then change 'if (status < 0)' to 'if (status < 0 && status != -EAGAIN)'
> 
> I don't think we should do that. It's reasonable for user_dlm_destroy_lock() to return EBUSY in that case. EAGAIN is for the case, you invoke it second time you may succeed. That's not the case here.
> 

I agree the EAGAIN is not good, but do you think the errno idea is reasonable?
user_dlm_destroy_lock only has two callers: dlmfs_evict_inode & dlmfs_unlink.
the code logic is clear, we can choose another errno, or even create a new one.
it costs too much to use spin_lock to avoid print an error log.

Thanks,
Heming

>>
>>> +        if (!destroyed) {
>>> +            status = user_dlm_destroy_lock(lockres);
>>> +            if (status < 0)
>>> +                mlog_errno(status);
>>> +        }
>>>           iput(ip->ip_parent);
>>>           goto clear_fields;
>>>       }
>>