[Ocfs2-devel] [PATCH] ocfs2: lighten up allocate transaction

[Younger Liu]

On 2013/7/4 23:05, Jeff Liu wrote:
> Hi Yonger,
> 
> On 07/04/2013 09:17 PM, Younger Liu wrote:
> 
>> The issue scenario is as following:
>> When fallocating a very large disk space for a small file,
>> __ocfs2_extend_allocation attempts to get a very large transaction. 
>> For some journal sizes, there may be not enough room for this 
>> transaction, and the fallocate will fail.
>>
>> The patch below extents & restarts the transaction as necessary while
>> allocating space, and should work with even the smallest journal.
>> This patch refers ext4 resize.
>>
>> Test:
>> # mkfs.ocfs2 -b 4K -C 32K -T datafiles /dev/sdc
>> ...(jounral size is 32M)
>> # mount.ocfs2 /dev/sdc /mnt/ocfs2/
>> # touch /mnt/ocfs2/1.log
>> # fallocate -o 0 -l 400G /mnt/ocfs2/1.log
>> fallocate: /mnt/ocfs2/1.log: fallocate failed: Cannot allocate memory
>> # tail -f /var/log/messages
>> [ 7372.278591] JBD: fallocate wants too many credits (2051 > 2048)
>> [ 7372.278597] (fallocate,6438,0):__ocfs2_extend_allocation:709 ERROR: status = -12
>> [ 7372.278603] (fallocate,6438,0):ocfs2_allocate_unwritten_extents:1504 ERROR: status = -12
>> [ 7372.278607] (fallocate,6438,0):__ocfs2_change_file_space:1955 ERROR: status = -12
> 
> Could you please cut down the log length by removing the beginning
> timestamps up to "kernel:"? i.e, only show "[ 7372.....] xxxx" is fine. :)
> 
Thanks for your suggestion.

>> ^C
>>
>> With this patch, the test works well.
>>
>> Signed-off-by: Younger Liu <younger.liu at huawei.com>
>> ---
>>  fs/ocfs2/file.c    |    6 +-----
>>  fs/ocfs2/journal.c |   34 ++++++++++++++++++++++++++++++++++
>>  fs/ocfs2/journal.h |   11 +++++++++++
>>  3 files changed, 46 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
>> index 05c0bb1..4943918 100644
>> --- a/fs/ocfs2/file.c
>> +++ b/fs/ocfs2/file.c
>> @@ -666,11 +666,7 @@ restarted_transaction:
>>  		} else {
>>  			BUG_ON(why != RESTART_TRANS);
>>  
>> -			/* TODO: This can be more intelligent. */
>> -			credits = ocfs2_calc_extend_credits(osb->sb,
>> -							    &fe->id2.i_list,
>> -							    clusters_to_add);
>> -			status = ocfs2_extend_trans(handle, credits);
>> +			status = ocfs2_allocate_extend_trans(handle, 1);
>>  			if (status < 0) {
>>  				/* handle still has to be committed at
>>  				 * this point. */
>> diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
>> index 8eccfab..501b2fe 100644
>> --- a/fs/ocfs2/journal.c
>> +++ b/fs/ocfs2/journal.c
>> @@ -455,6 +455,40 @@ bail:
>>  	return status;
>>  }
>>  
>> +/*
>> + * If we have fewer than thresh credits, extend by OCFS2_MAX_TRANS_DATA.
>> + * If that fails, restart the transaction & regain write access for the
>> + * buffer head which is used for metadata modifications.
>> + * Refer extend_or_restart_transaction() 
> 
>     * Taken from Ext4: extend_or_restart_transaction()
> 
>> + */
>> +int ocfs2_allocate_extend_trans(handle_t *handle, int thresh)
>> +{
>> +	int status;
>> +
>> +	BUG_ON(!handle);
>> +	
>> +	if (handle->h_buffer_credits < thresh)
>> +		return 0;
>> +
> 
> I wonder if we need a particular trace point or not...
> 	old_nblks = handle->h_buffer_credits;
> 	trace_ocfs2_allocate_extend_trans(old_nblks, thresh);
> 
Good point for tracer.
It is conveniently for debugging or analyzing some issues too.
I will resent the patch in a moment. Please help to review it again.
thanks.
					--Younger

>> +	status = jbd2_journal_extend(handle, OCFS2_MAX_TRANS_DATA);
>> +	if (status < 0) {
>> +		mlog_errno(status);
>> +		goto bail;
>> +	}
>> +
>> +	if (status > 0) {
>> +		status = jbd2_journal_restart(handle, OCFS2_MAX_TRANS_DATA);
>> +		if (status < 0) {
>> +			mlog_errno(status);
>> +			goto bail;
>> +		}
> 
> 		if (status < 0)
> 			mlog_errno(status);
> 
> I'll run some further tests tomorrow, thanks for your patch!
> 
> -Jeff
> 
>> +	}
>> +	
>> +bail:
>> +	return status;
>> +}
>> +
>> +
>>  struct ocfs2_triggers {
>>  	struct jbd2_buffer_trigger_type	ot_triggers;
>>  	int				ot_offset;
>> diff --git a/fs/ocfs2/journal.h b/fs/ocfs2/journal.h
>> index a3385b6..62a26bd 100644
>> --- a/fs/ocfs2/journal.h
>> +++ b/fs/ocfs2/journal.h
>> @@ -259,6 +259,17 @@ handle_t		    *ocfs2_start_trans(struct ocfs2_super *osb,
>>  int			     ocfs2_commit_trans(struct ocfs2_super *osb,
>>  						handle_t *handle);
>>  int			     ocfs2_extend_trans(handle_t *handle, int nblocks);
>> +int			     ocfs2_allocate_extend_trans(handle_t *handle,
>> +						int thresh);
>> +
>> +/* 
>> + * Define an arbitrary limit for the amount of data we will anticipate
>> + * writing to any given transaction.  For unbounded transactions such as
>> + * fallocate(2) we can write more than this, but we always
>> + * start off at the maximum transaction size and grow the transaction
>> + * optimistically as we go.
>> + */
>> +#define OCFS2_MAX_TRANS_DATA	64U
>>  
>>  /*
>>   * Create access is for when we get a newly created buffer and we're
> 
> 
> .
>