Re: [f2fs-dev] [RFC PATHC 2/2] f2fs: apply write hints to select the type of segment for direct write

[Hyunchul Lee]

On 11/13/2017 10:24 AM, Chao Yu wrote:
> On 2017/11/13 8:07, Hyunchul Lee wrote:
>> On 11/11/2017 09:38 AM, Chao Yu wrote:
>>> On 2017/11/9 13:51, Hyunchul Lee wrote:
>>>> From: Hyunchul Lee <cheol.lee@xxxxxxx>
>>>>
>>>> Select the type of the segment using write hints, when blocks are
>>>> allocated for direct write.
>>>>
>>>> There are unhandled corner cases. Hints are not applied in
>>>> in-place update.  And if the blocks of a file is not pre-allocated
>>>> because of the invalid user buffer, CURSEG_WARM_DATA segment will
>>>> be selected.
>>>>
>>>> Signed-off-by: Hyunchul Lee <cheol.lee@xxxxxxx>
>>>> ---
>>>>  fs/f2fs/data.c | 101 ++++++++++++++++++++++++++++++++++-----------------------
>>>>  fs/f2fs/f2fs.h |   1 +
>>>>  2 files changed, 61 insertions(+), 41 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>> index 36b5352..d06048a 100644
>>>> --- a/fs/f2fs/data.c
>>>> +++ b/fs/f2fs/data.c
>>>> @@ -783,7 +783,7 @@ struct page *get_new_data_page(struct inode *inode,
>>>>  	return page;
>>>>  }
>>>>  
>>>> -static int __allocate_data_block(struct dnode_of_data *dn)
>>>> +static int __allocate_data_block(struct dnode_of_data *dn, int seg_type)
>>>>  {
>>>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
>>>>  	struct f2fs_summary sum;
>>>> @@ -808,7 +808,7 @@ static int __allocate_data_block(struct dnode_of_data *dn)
>>>>  	set_summary(&sum, dn->nid, dn->ofs_in_node, ni.version);
>>>>  
>>>>  	allocate_data_block(sbi, NULL, dn->data_blkaddr, &dn->data_blkaddr,
>>>> -					&sum, CURSEG_WARM_DATA, NULL, false);
>>>> +					&sum, seg_type, NULL, false);
>>>>  	set_data_blkaddr(dn);
>>>>  
>>>>  	/* update i_size */
>>>> @@ -827,42 +827,6 @@ static inline bool __force_buffered_io(struct inode *inode, int rw)
>>>>  			F2FS_I_SB(inode)->s_ndevs);
>>>>  }
>>>>  
>>>> -int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>>>> -{
>>>> -	struct inode *inode = file_inode(iocb->ki_filp);
>>>> -	struct f2fs_map_blocks map;
>>>> -	int err = 0;
>>>> -
>>>> -	if (is_inode_flag_set(inode, FI_NO_PREALLOC))
>>>> -		return 0;
>>>> -
>>>> -	map.m_lblk = F2FS_BLK_ALIGN(iocb->ki_pos);
>>>> -	map.m_len = F2FS_BYTES_TO_BLK(iocb->ki_pos + iov_iter_count(from));
>>>> -	if (map.m_len > map.m_lblk)
>>>> -		map.m_len -= map.m_lblk;
>>>> -	else
>>>> -		map.m_len = 0;
>>>> -
>>>> -	map.m_next_pgofs = NULL;
>>>> -
>>>> -	if (iocb->ki_flags & IOCB_DIRECT) {
>>>> -		err = f2fs_convert_inline_inode(inode);
>>>> -		if (err)
>>>> -			return err;
>>>> -		return f2fs_map_blocks(inode, &map, 1,
>>>> -			__force_buffered_io(inode, WRITE) ?
>>>> -				F2FS_GET_BLOCK_PRE_AIO :
>>>> -				F2FS_GET_BLOCK_PRE_DIO);
>>>> -	}
>>>> -	if (iocb->ki_pos + iov_iter_count(from) > MAX_INLINE_DATA(inode)) {
>>>> -		err = f2fs_convert_inline_inode(inode);
>>>> -		if (err)
>>>> -			return err;
>>>> -	}
>>>> -	if (!f2fs_has_inline_data(inode))
>>>> -		return f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_AIO);
>>>> -	return err;
>>>> -}
>>>>  
>>>>  static inline void __do_map_lock(struct f2fs_sb_info *sbi, int flag, bool lock)
>>>>  {
>>>> @@ -888,8 +852,8 @@ static inline void __do_map_lock(struct f2fs_sb_info *sbi, int flag, bool lock)
>>>>   *     b. do not use extent cache for better performance
>>>>   *     c. give the block addresses to blockdev
>>>>   */
>>>> -int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>>>> -						int create, int flag)
>>>> +static int __f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>>>> +				int create, int flag, int seg_type)
>>>>  {
>>>>  	unsigned int maxblocks = map->m_len;
>>>>  	struct dnode_of_data dn;
>>>> @@ -957,7 +921,12 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>>>>  					last_ofs_in_node = dn.ofs_in_node;
>>>>  				}
>>>>  			} else {
>>>> -				err = __allocate_data_block(&dn);
>>>> +				/* if this inode is marked with FI_NO_PREALLOC,
>>>> +				 * @seg_type is NO_CHECK_TYPE
>>>> +				 */
>>>> +				if (seg_type == NO_CHECK_TYPE)
>>>> +					seg_type = CURSEG_WARM_DATA;
>>>> +				err = __allocate_data_block(&dn, seg_type);
>>>
>>> We need to use inode.i_write_hint instead of ki_hint passed from file.f_write_hint?
>>>
>>
>> The following commit says to use file.f_write_hint if it is available. 
>> "c75b1d9 fs: add fcntl() interface for setting/getting write life time hints"
> 
> Oh, yes, f_write_hint is recommended. So, I'm OK with this.
> 
> One left question as below.
> 
>>
>> And ki_hint is assiged to file.f_write_hint or inode.i_write_hint 
>> by file_write_hint() in init_sync_kiocb().
>> So, I think we need to use ki_hint instead of inode.i_write_hint.
>>
>> Thanks
>>
>>> Thanks,
>>>
>>>>  				if (!err)
>>>>  					set_inode_flag(inode, FI_APPEND_WRITE);
>>>>  			}
>>>> @@ -1048,6 +1017,51 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>>>>  	return err;
>>>>  }
>>>>  
>>>> +int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>>>> +						int create, int flag)
>>>> +{
>>>> +	return __f2fs_map_blocks(inode, map, create, flag, NO_CHECK_TYPE);
>>>> +}
>>>> +
>>>> +int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>>>> +{
>>>> +	struct inode *inode = file_inode(iocb->ki_filp);
>>>> +	struct f2fs_map_blocks map;
>>>> +	int err = 0;
>>>> +
>>>> +	if (is_inode_flag_set(inode, FI_NO_PREALLOC))
>>>> +		return 0;
>>>> +
>>>> +	map.m_lblk = F2FS_BLK_ALIGN(iocb->ki_pos);
>>>> +	map.m_len = F2FS_BYTES_TO_BLK(iocb->ki_pos + iov_iter_count(from));
>>>> +	if (map.m_len > map.m_lblk)
>>>> +		map.m_len -= map.m_lblk;
>>>> +	else
>>>> +		map.m_len = 0;
>>>> +
>>>> +	map.m_next_pgofs = NULL;
>>>> +
>>>> +	if (iocb->ki_flags & IOCB_DIRECT) {
>>>> +		err = f2fs_convert_inline_inode(inode);
>>>> +		if (err)
>>>> +			return err;
>>>> +		return __f2fs_map_blocks(inode, &map, 1,
>>>> +			__force_buffered_io(inode, WRITE) ?
>>>> +				F2FS_GET_BLOCK_PRE_AIO :
>>>> +				F2FS_GET_BLOCK_PRE_DIO,
>>>> +				rw_hint_to_seg_type(iocb->ki_hint));
>>>> +	}
>>>> +	if (iocb->ki_pos + iov_iter_count(from) > MAX_INLINE_DATA(inode)) {
>>>> +		err = f2fs_convert_inline_inode(inode);
>>>> +		if (err)
>>>> +			return err;
>>>> +	}
>>>> +	if (!f2fs_has_inline_data(inode))
>>>> +		return f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_AIO);
>>>> +
>>>> +	return err;
>>>> +}
>>>> +
>>>>  static int __get_data_block(struct inode *inode, sector_t iblock,
>>>>  			struct buffer_head *bh, int create, int flag,
>>>>  			pgoff_t *next_pgofs)
>>>> @@ -2082,6 +2096,11 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>>>>  
>>>>  	trace_f2fs_direct_IO_enter(inode, offset, count, rw);
>>>>  
>>>> +	/* This is for avoiding the situation that the data of a segment is
>>>> +	 * passed down to devices with different hints
>>>> +	 */
>>>> +	iocb->ki_hint = WRITE_LIFE_NOT_SET;
> 
> Why we need to change this? I'm not sure this will be used later in somewhere,
> if it's not necessary, how about keeping it as it is?
> 

blkdev_direct_IO will pass down this hint to block layer. But we need to control
the hint before this.
So I think that after we implement this control, passing down the hint is better. 

iocb->ki_hint needs to be re-assigned to the orignal hint after the write.
I will handle this.

Thanks

> Thanks,
> 
>>>> +
>>>>  	down_read(&F2FS_I(inode)->dio_rwsem[rw]);
>>>>  	err = blockdev_direct_IO(iocb, inode, iter, get_data_block_dio);
>>>>  	up_read(&F2FS_I(inode)->dio_rwsem[rw]);
>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>> index 4b4a72f..9be5658 100644
>>>> --- a/fs/f2fs/f2fs.h
>>>> +++ b/fs/f2fs/f2fs.h
>>>> @@ -2562,6 +2562,7 @@ int lookup_journal_in_cursum(struct f2fs_journal *journal, int type,
>>>>  void destroy_segment_manager(struct f2fs_sb_info *sbi);
>>>>  int __init create_segment_manager_caches(void);
>>>>  void destroy_segment_manager_caches(void);
>>>> +int rw_hint_to_seg_type(enum rw_hint hint);
>>>>  
>>>>  /*
>>>>   * checkpoint.c
>>>>
>>>
>>
>> .
>>
> 
>