[Ocfs2-devel] [PATCH] ocfs2: check the metadate alloc before marking extent written

[Joseph Qi]

On 17/12/5 10:36, alex chen wrote:
> Hi Joseph,
> 
> Thanks for your reviews.
> 
> On 2017/12/5 10:21, Joseph Qi wrote:
>>
>>
>> On 17/12/5 09:41, alex chen wrote:
>>> We need to check the free number of the records in each loop to mark
>>> extent written, because the last extent block may be changed through
>>> many times marking extent written and the 'num_free_extents' also be
>>> changed. In the worst case, the 'num_free_extents' may become less
>>> than the beginning of the loop. So we should not estimate the free
>>> number of the records at the beginning of the loop to mark extent
>>> written.
>>>
>>> Reported-by: John Lightsey <john at nixnuts.net>
>>> Signed-off-by: Alex Chen <alex.chen at huawei.com>
>>> Reviewed-by: Jun Piao <piaojun at huawei.com>
>>> ---
>>>  fs/ocfs2/aops.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++---------
>>>  1 file changed, 64 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>>> index d151632..702aebc 100644
>>> --- a/fs/ocfs2/aops.c
>>> +++ b/fs/ocfs2/aops.c
>>> @@ -2272,6 +2272,35 @@ static int ocfs2_dio_wr_get_block(struct inode *inode, sector_t iblock,
>>>  	return ret;
>>>  }
>>>
>>> +static int ocfs2_dio_should_restart(struct ocfs2_extent_tree *et,
>>> +		struct ocfs2_alloc_context *meta_ac, int max_rec_needed)
>>> +{
>>> +	int status = 0, free_extents;
>>> +
>>> +	free_extents = ocfs2_num_free_extents(et);
>>> +	if (free_extents < 0) {
>>> +		status = free_extents;
>>> +		mlog_errno(status);
>>> +		return status;
>>> +	}
>>> +
>>> +	/*
>>> +	 * there are two cases which could cause us to EAGAIN in the
>>> +	 * we-need-more-metadata case:
>>> +	 * 1) we haven't reserved *any*
>>> +	 * 2) we are so fragmented, we've needed to add metadata too
>>> +	 *    many times.
>>> +	 */
>>> +	if (free_extents < max_rec_needed) {
>>> +		if (!meta_ac || (ocfs2_alloc_context_bits_left(meta_ac)
>>> +				< ocfs2_extend_meta_needed(et->et_root_el)))
>>> +			status = 1;
>>> +	}
>>> +
>>> +	return status;
>>> +}
>>> +
>>> +#define OCFS2_MAX_REC_NEEDED_SPLIT 2
>>>  static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  				  struct ocfs2_dio_write_ctxt *dwc,
>>>  				  loff_t offset,
>>> @@ -2281,14 +2310,13 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  	struct ocfs2_extent_tree et;
>>>  	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>>>  	struct ocfs2_inode_info *oi = OCFS2_I(inode);
>>> -	struct ocfs2_unwritten_extent *ue = NULL;
>>> +	struct ocfs2_unwritten_extent *ue = NULL, *tmp_ue;
>>>  	struct buffer_head *di_bh = NULL;
>>>  	struct ocfs2_dinode *di;
>>> -	struct ocfs2_alloc_context *data_ac = NULL;
>>>  	struct ocfs2_alloc_context *meta_ac = NULL;
>>>  	handle_t *handle = NULL;
>>>  	loff_t end = offset + bytes;
>>> -	int ret = 0, credits = 0, locked = 0;
>>> +	int ret = 0, credits = 0, locked = 0, restart = 0;
>>>
>>>  	ocfs2_init_dealloc_ctxt(&dealloc);
>>>
>>> @@ -2330,8 +2358,9 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>
>> Should we restart here?
> 
> OK. we should restart before initialized the inode extent tree.
> 
>>
>>>  	ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);
>>>
>>> -	ret = ocfs2_lock_allocators(inode, &et, 0, dwc->dw_zero_count*2,
>>> -				    &data_ac, &meta_ac);
>>> +restart_all:
>>> +	ret = ocfs2_lock_allocators(inode, &et, 0, OCFS2_MAX_REC_NEEDED_SPLIT,
>>> +				    NULL, &meta_ac);
>>>  	if (ret) {
>>>  		mlog_errno(ret);
>>>  		goto unlock;
>>> @@ -2343,7 +2372,7 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  	if (IS_ERR(handle)) {
>>>  		ret = PTR_ERR(handle);
>>>  		mlog_errno(ret);
>>> -		goto unlock;
>>> +		goto free_ac;
>> I don't think it is a necessary change here.
> 
> we need to free the 'meta_ac' which allocated in ocfs2_lock_allocators() when we
> start transaction failed.
> 
As I described in the last mail, just move the restart check after the
original free meta_ac check.

> Thanks,
> Alex
>>
>>>  	}
>>>  	ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
>>>  				      OCFS2_JOURNAL_ACCESS_WRITE);
>>> @@ -2352,7 +2381,17 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  		goto commit;
>>>  	}
>>>
>>> -	list_for_each_entry(ue, &dwc->dw_zero_list, ue_node) {
>>> +	list_for_each_entry_safe(ue, tmp_ue, &dwc->dw_zero_list, ue_node) {
>>> +		ret = ocfs2_dio_should_restart(&et, meta_ac,
>>> +				OCFS2_MAX_REC_NEEDED_SPLIT * 2);
>>> +		if (ret < 0) {
>>> +			mlog_errno(ret);
>>> +			break;
>>> +		} else if (ret == 1) {
>>> +			restart = 1;
>>> +			break;
>>> +		}
>>> +
>>>  		ret = ocfs2_mark_extent_written(inode, &et, handle,
>>>  						ue->ue_cpos, 1,
>>>  						ue->ue_phys,
>>> @@ -2361,24 +2400,37 @@ static int ocfs2_dio_end_io_write(struct inode *inode,
>>>  			mlog_errno(ret);
>>>  			break;
>>>  		}
>>> +
>>> +		dwc->dw_zero_count--;
>>> +		list_del_init(&ue->ue_node);
>>> +		spin_lock(&oi->ip_lock);
>>> +		list_del_init(&ue->ue_ip_node);
>>> +		spin_unlock(&oi->ip_lock);
>>> +		kfree(ue);
>>>  	}
>>>
>>> -	if (end > i_size_read(inode)) {
>>> +	if (!restart && end > i_size_read(inode)) {
>>>  		ret = ocfs2_set_inode_size(handle, inode, di_bh, end);
>>>  		if (ret < 0)
>>>  			mlog_errno(ret);
>>>  	}
>>> +
>>>  commit:
>>>  	ocfs2_commit_trans(osb, handle);
>>> +free_ac:
>>> +	if (meta_ac) {
>>> +		ocfs2_free_alloc_context(meta_ac);
>>> +		meta_ac = NULL;
>>> +	}
>>> +	if (restart) {
>>> +		restart = 0;
>>> +		goto restart_all;
>>> +	}
>>>  unlock:
>>>  	up_write(&oi->ip_alloc_sem);
>>>  	ocfs2_inode_unlock(inode, 1);
>>>  	brelse(di_bh);
>>>  out:
>>> -	if (data_ac)
>>> -		ocfs2_free_alloc_context(data_ac);
>> Agree to cleanup the unused data_ac.
>>
>>> -	if (meta_ac)
>>> -		ocfs2_free_alloc_context(meta_ac);
Just move the restart logic down is enough.
>>
>> Thanks,
>> Joseph
>>
>>>  	ocfs2_run_deallocs(osb, &dealloc);
>>>  	if (locked)
>>>  		inode_unlock(inode);
>>>
>>
>> .
>>
>