Re: [PATCH] exofs: exofs_file_fsync correctness

[Boaz Harrosh <bharrosh@panasas.com>]

On 06/01/2010 06:47 PM, Christoph Hellwig wrote:
> On Tue, Jun 01, 2010 at 06:40:46PM +0300, Boaz Harrosh wrote:
>>>> +	struct writeback_control wbc = {
>>>> +		.sync_mode = WB_SYNC_ALL,
>>>> +		.nr_to_write = LONG_MAX,
>>>
>>> By setting a nr_to_write you still write out data (at least in theory).
>>>
>>
>> So when do I also sync the data? is that done for me at the VFS layer?
> 
> You never have to.  vfs_fsync_range does the data writeout for you.
> 
>>> I'd recommend just copying the code from generic_file_fsync..
>>>
>>
>> I was actually mimicking the code from nfs/write.c which has similar
>> semantics as mine.
> 
> nfs code has no good reason to do that, at least when called from
> ->fsync.
> 
>> And if so then I'll need to not reuse the above in .flush
> 
> I would recommend keeping the ->flush code separate.

OK, ... I think I got it this time. (I hope)

And you are totally right. The ->flush code is called without any
locks and the ->fsync is called with i_mutex held. So the previous
code was totally racy for ->flush.

Boaz