[PATCH] staging: erofs: support bmap

[Chao Yu]

Hi Xiang,

On 2019/7/16 15:19, Gao Xiang wrote:
> Hi Chao,
> 
> On 2019/7/16 15:05, Chao Yu wrote:
>> Add erofs_bmap() to support FIBMAP ioctl on flatmode inode.
>>
>> Signed-off-by: Chao Yu <yuchao0 at huawei.com>
>> ---
>>  drivers/staging/erofs/data.c | 29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/drivers/staging/erofs/data.c b/drivers/staging/erofs/data.c
>> index fbce71403d87..03da57f04347 100644
>> --- a/drivers/staging/erofs/data.c
>> +++ b/drivers/staging/erofs/data.c
>> @@ -308,9 +308,38 @@ static int erofs_raw_access_readpages(struct file *filp,
>>  	return iomap_readpages(mapping, pages, nr_pages, &erofs_iomap_ops);
>>  }
>>  
>> +static int erofs_get_block(struct inode *inode, sector_t iblock,
>> +			   struct buffer_head *bh, int create)
>> +{
>> +	struct erofs_map_blocks map = {
>> +		.m_la = iblock << 9,
>> +	};
>> +	int err;
>> +
>> +	err = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
>> +	if (err)
>> +		return err;
>> +
>> +	if (map.m_flags & EROFS_MAP_MAPPED)
>> +		bh->b_blocknr = erofs_blknr(map.m_pa);
>> +
>> +	return err;
>> +}
>> +
>> +static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
>> +{
>> +	struct inode *inode = mapping->host;
>> +
>> +	if (is_inode_flat_inline(inode))
>> +		return 0;
> 
> could we support flat_inline as well? some difficulty on this?

I think we can support partial of this on inline inode, e.g.:

[0, 4k] mapped
[4k, 5k] inline

We can find and return the physical block address for first block, but for last
block locating in metadata, we should just return 0 (0 indicate bmap has failed
to get mapped block address).

Thanks,

> (I have no idea return 0 is suitable for us since we have tail-end packing...)
> 
> Thanks,
> Gao Xiang
> 
>> +
>> +	return generic_block_bmap(mapping, block, erofs_get_block);
>> +}
>> +
>>  /* for uncompressed (aligned) files and raw access for other files */
>>  const struct address_space_operations erofs_raw_access_aops = {
>>  	.readpage = erofs_raw_access_readpage,
>>  	.readpages = erofs_raw_access_readpages,
>> +	.bmap = erofs_bmap,
>>  };
>>  
>>
> .
>