[Ocfs2-devel] [PATCH 2/3] ocfs2: add ocfs2_overwrite_io function

[Gang He]

Hello Joseph,


>>> 
> Hi Gang,
> 
> On 17/11/27 17:46, Gang He wrote:
>> Add ocfs2_overwrite_io function, which is used to judge if
>> overwrite allocated blocks, otherwise, the write will bring extra
>> block allocation overhead.
>> 
>> Signed-off-by: Gang He <ghe at suse.com>
>> ---
>>  fs/ocfs2/extent_map.c | 67 
> +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  fs/ocfs2/extent_map.h |  3 +++
>>  2 files changed, 70 insertions(+)
>> 
>> diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
>> index e4719e0..98bf325 100644
>> --- a/fs/ocfs2/extent_map.c
>> +++ b/fs/ocfs2/extent_map.c
>> @@ -832,6 +832,73 @@ int ocfs2_fiemap(struct inode *inode, struct 
> fiemap_extent_info *fieinfo,
>>  	return ret;
>>  }
>>  
>> +/* Is IO overwriting allocated blocks? */
>> +int ocfs2_overwrite_io(struct inode *inode, u64 map_start, u64 map_len,
>> +		       int wait)
>> +{
>> +	int ret = 0, is_last;
>> +	u32 mapping_end, cpos;
>> +	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>> +	struct buffer_head *di_bh = NULL;
>> +	struct ocfs2_extent_rec rec;
>> +
>> +	if (wait)
>> +		ret = ocfs2_inode_lock(inode, &di_bh, 0);
>> +	else
>> +		ret = ocfs2_try_inode_lock(inode, &di_bh, 0);
>> +	if (ret)
>> +		goto out;
>> +
>> +	if (wait)
>> +		down_read(&OCFS2_I(inode)->ip_alloc_sem);
>> +	else {
>> +		if (!down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem)) {
>> +			ret = -EAGAIN;
>> +			goto out_unlock1;
>> +		}
>> +	}
>> +
>> +	if ((OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) &&
>> +	   ((map_start + map_len) <= i_size_read(inode)))
>> +		goto out_unlock2;
>> +
>> +	cpos = map_start >> osb->s_clustersize_bits;
>> +	mapping_end = ocfs2_clusters_for_bytes(inode->i_sb,
>> +					       map_start + map_len);
>> +	is_last = 0;
>> +	while (cpos < mapping_end && !is_last) {
>> +		ret = ocfs2_get_clusters_nocache(inode, di_bh, cpos,
>> +						 NULL, &rec, &is_last);
>> +		if (ret) {
>> +			mlog_errno(ret);
>> +			goto out_unlock2;
>> +		}
>> +
>> +		if (rec.e_blkno == 0ULL)
>> +			break;
>> +
>> +		if (rec.e_flags & OCFS2_EXT_REFCOUNTED)
>> +			break;
>> +
>> +		cpos = le32_to_cpu(rec.e_cpos) +
>> +			le16_to_cpu(rec.e_leaf_clusters);
>> +	}
>> +
>> +	if (cpos < mapping_end)
>> +		ret = 1;
>> +
>> +out_unlock2:
>> +	brelse(di_bh);
>> +
>> +	up_read(&OCFS2_I(inode)->ip_alloc_sem);
>> +
>> +out_unlock1:
> Should brelse(di_bh) be here?
If the code jumps to out_unlock1 directly, the di_bh pointer should be NULL, it is not necessary to release.

> 
>> +	ocfs2_inode_unlock(inode, 0);
>> +
>> +out:
>> +	return (ret ? 0 : 1);
> I don't think EAGAIN and other error code can be handled the same. We
> have to distinguish them.
Ok, I think we can add one line log to report the error in case the error is not EAGAIN. 

> 
> Thanks,
> Joseph
> 
>> +}
>> +
>>  int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int 
> whence)
>>  {
>>  	struct inode *inode = file->f_mapping->host;
>> diff --git a/fs/ocfs2/extent_map.h b/fs/ocfs2/extent_map.h
>> index 67ea57d..fd9e86a 100644
>> --- a/fs/ocfs2/extent_map.h
>> +++ b/fs/ocfs2/extent_map.h
>> @@ -53,6 +53,9 @@ int ocfs2_extent_map_get_blocks(struct inode *inode, u64 
> v_blkno, u64 *p_blkno,
>>  int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>>  		 u64 map_start, u64 map_len);
>>  
>> +int ocfs2_overwrite_io(struct inode *inode, u64 map_start, u64 map_len,
>> +		       int wait);
>> +
>>  int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int 
> origin);
>>  
>>  int ocfs2_xattr_get_clusters(struct inode *inode, u32 v_cluster,
>>