[Ocfs2-devel] [PATCH] ocfs2: Try to free truncate log when meeting ENOSPC in write.

[Tao Ma <tao.ma@oracle.com>]

On 11/04/2010 09:46 AM, Joel Becker wrote:
> On Tue, Oct 26, 2010 at 03:29:08PM +0800, Tao Ma wrote:
>> Recently, one of our colleagues meet with a problem that if we
>> write/delete a 32mb files repeatly, we will get an ENOSPC in
>> the end. And the corresponding bug is 1288.
>> http://oss.oracle.com/bugzilla/show_bug.cgi?id=1288
>>
>> The real problem is that although we have freed the clusters,
>> they are in truncate log and they will be summed up so that
>> we can free them once in a whole.
>>
>> So this patch just try to resolve it. In case we see -ENOSPC
>> in ocfs2_write_begin_no_lock, we will check whether the truncate
>> log has enough clusters for our need, if yes, we will try to
>> flush the truncate log at that point and try again. This method
>> is inspired by Mark Fasheh<mfasheh@suse.com>. Thanks.
>
> 	Ok, this is more like what I was thinking about.  I guess I wish
> we could do it inside the allocation routines, but I think we have too
> many locks at that point.
yeah, the locks are really the biggest problem for us.
>  This patch doesn't help any place that
> allocates other than write() and mmap().  Is this something that could
> be added to extending truncate and unwritten allocation?
I haven't tried in other cases. but in general it could be possible 
since all the work is done in ocfs2_try_to_free_truncate_log. We may try 
it in other place after thinking carefully of the lock there. But I 
guess we can let it in first to see how it works. If it is right and 
robust, I can generate another patch for them later. :)
> 	I agree that we only care to have one pass.  Have you run it
> against the test case from
> http://oss.oracle.com/bugzilla/show_bug.cgi?id=1288?  If so, modulo
> any cleanups you did after others commented, I'm happy ;-)
yes, I have run the test case overnight and didn't hit ENOSPC any more. 
So do you think of accepting it? If yes, I will regenerate the patch for 
your merge.
>
>> diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
>> index d840821..de06558 100644
>> --- a/fs/ocfs2/ocfs2.h
>> +++ b/fs/ocfs2/ocfs2.h
>> @@ -439,6 +439,8 @@ struct ocfs2_super
>>   	/* rb tree root for refcount lock. */
>>   	struct rb_root	osb_rf_lock_tree;
>>   	struct ocfs2_refcount_tree *osb_ref_tree_lru;
>> +
>> +	unsigned int truncated_clusters;
>
> 	Make sure you comment what lock is needed to access
> truncated_clusters.
OK, I will add comment for it.

Regards,
Tao