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

[alex chen <alex.chen@huawei.com>]

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@nixnuts.net>
>> Signed-off-by: Alex Chen <alex.chen@huawei.com>
>> Reviewed-by: Jun Piao <piaojun@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.

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);
>>
> 
> .
>