Re: [PATCH v6 11/16] xfs: Check for -ENOATTR or -EEXIST

From: Allison Collins <allison.henderson@oracle.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH v6 11/16] xfs: Check for -ENOATTR or -EEXIST
Date: Sat, 25 Jan 2020 09:41:47 -0700	[thread overview]
Message-ID: <26a49cf4-52df-55bd-67bb-9c0c981a860d@oracle.com> (raw)
In-Reply-To: <68dcf7a7-9e10-2d64-9c5c-d520d2372c2b@oracle.com>

On 1/21/20 9:29 PM, Allison Collins wrote:
> 
> 
> On 1/21/20 4:15 PM, Darrick J. Wong wrote:
>> On Sat, Jan 18, 2020 at 03:50:30PM -0700, Allison Collins wrote:
>>> Delayed operations cannot return error codes.  So we must check for
>>> these conditions first before starting set or remove operations
>>
>> Answering my own question from earlier -- I see here you actually /are/
>> checking the attr existence w.r.t. ATTR_{CREATE,REPLACE} right after we
>> allocate a transaction and ILOCK the inode, so
>>
>> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> Alrighty, thank you!
> 
>>
>> Though I am wondering if you could discard the predicates from the
>> second patch in favor of doing a normal lookup of the attr with a zero
>> valuelen to determine if there's already an attribute?
> I think I likely answered this in the response to that patch.  Because 
> it's used as part of the remove procedures, we still need it.  We could 
> make a simpler version just for this application I suppose, but it seems 
> like it'd just be extra code since we still need the former.
> 
> Thank you for the reviews!
> Allison
> 
>>
>> --D
>>
>>> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
>>> ---
>>>   fs/xfs/libxfs/xfs_attr.c | 12 ++++++++++++
>>>   1 file changed, 12 insertions(+)
>>>
>>> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
>>> index a2673fe..e9d22c1 100644
>>> --- a/fs/xfs/libxfs/xfs_attr.c
>>> +++ b/fs/xfs/libxfs/xfs_attr.c
>>> @@ -457,6 +457,14 @@ xfs_attr_set(
>>>           goto out_trans_cancel;
>>>       xfs_trans_ijoin(args.trans, dp, 0);
>>> +
>>> +    error = xfs_has_attr(&args);
>>> +    if (error == -EEXIST && (name->type & ATTR_CREATE))
>>> +        goto out_trans_cancel;
>>> +
>>> +    if (error == -ENOATTR && (name->type & ATTR_REPLACE))
>>> +        goto out_trans_cancel;
>>> +
>>>       error = xfs_attr_set_args(&args);
So I was thinking of adding this one to a smaller 3 patch series I 
mentioned earlier.  I was also thinking of adding in some asserts here:

ASSERT(error != -EEXIST)
ASSERT(error != -ENOATTR)

Just to make sure the changes are enforcing the behavioral changes that 
we want.  I thought this might be a good stabilizer to the rest of the 
delayed attr series.  Because chasing this bug back up through the log 
replay is a much bigger PITA than catching it here.  Thoughts?

>>>       if (error)
>>>           goto out_trans_cancel;
>>> @@ -545,6 +553,10 @@ xfs_attr_remove(
>>>        */
>>>       xfs_trans_ijoin(args.trans, dp, 0);
>>> +    error = xfs_has_attr(&args);
>>> +    if (error != -EEXIST)
>>> +        goto out;
>>> +
Here too:
ASSERT(error != -EEXIST)

Let me know what folks think.  Thanks!

Allison

>>>       error = xfs_attr_remove_args(&args);
>>>       if (error)
>>>           goto out;
>>> -- 
>>> 2.7.4
>>>