Re: [PATCH] f2fs: fix to avoid use SSR allocate when do defragment

[Chao Yu]

On 2024/5/29 16:19, Zhiguo Niu wrote:
> SSR allocate mode will be used when doing file defragment
> if ATGC is working at the same time, that is because
> set_page_private_gcing may make CURSEG_ALL_DATA_ATGC segment
> type got in f2fs_allocate_data_block when defragment page
> is writeback, which may cause file fragmentation is worse.
>
> A file with 2 fragmentations is changed as following after defragment:
>
> ----------------file info-------------------
> sensorsdata :
> --------------------------------------------
> dev       [254:48]
> ino       [0x    3029 : 12329]
> mode      [0x    81b0 : 33200]
> nlink     [0x       1 : 1]
> uid       [0x    27e6 : 10214]
> gid       [0x    27e6 : 10214]
> size      [0x  242000 : 2367488]
> blksize   [0x    1000 : 4096]
> blocks    [0x    1210 : 4624]
> --------------------------------------------
>
> file_pos   start_blk     end_blk        blks
>         0    11361121    11361207          87
>    356352    11361215    11361216           2
>    364544    11361218    11361218           1
>    368640    11361220    11361221           2
>    376832    11361224    11361225           2
>    385024    11361227    11361238          12
>    434176    11361240    11361252          13
>    487424    11361254    11361254           1
>    491520    11361271    11361279           9
>    528384     3681794     3681795           2
>    536576     3681797     3681797           1
>    540672     3681799     3681799           1
>    544768     3681803     3681803           1
>    548864     3681805     3681805           1
>    552960     3681807     3681807           1
>    557056     3681809     3681809           1
>
> A new FI flag FI_DEFRAG_IN_PROGRESS is introduced to avoid
> this scenarios.
>
> Signed-off-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
> ---
>   fs/f2fs/f2fs.h    | 1 +
>   fs/f2fs/file.c    | 2 ++
>   fs/f2fs/segment.c | 3 ++-
>   3 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 4044e67..9281c5e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -803,6 +803,7 @@ enum {
>   	FI_COW_FILE,		/* indicate COW file */
>   	FI_ATOMIC_COMMITTED,	/* indicate atomic commit completed except disk sync */
>   	FI_ATOMIC_REPLACE,	/* indicate atomic replace */
> +	FI_DEFRAG_IN_PROGRESS,	/* indicate file was defragmenting */
>   	FI_MAX,			/* max flag, never be used */
>   };
>   
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 5c0b281..93d2767 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -2717,6 +2717,7 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
>   		goto out;
>   	}
>   
> +	set_inode_flag(inode, FI_DEFRAG_IN_PROGRESS);
>   	map.m_lblk = pg_start;
>   	map.m_len = pg_end - pg_start;
>   	total = 0;
> @@ -2772,6 +2773,7 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
>   clear_out:
>   	clear_inode_flag(inode, FI_SKIP_WRITES);
>   out:
> +	clear_inode_flag(inode, FI_DEFRAG_IN_PROGRESS);
>   	clear_inode_flag(inode, FI_OPU_WRITE);
>   unlock_out:
>   	inode_unlock(inode);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 7caf20a..dd6f8ac 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -3482,7 +3482,8 @@ static int __get_segment_type_6(struct f2fs_io_info *fio)
>   		if (page_private_gcing(fio->page)) {
>   			if (fio->sbi->am.atgc_enabled &&
>   				(fio->io_type == FS_DATA_IO) &&
> -				(fio->sbi->gc_mode != GC_URGENT_HIGH))
> +				(fio->sbi->gc_mode != GC_URGENT_HIGH) &&
> +				!is_inode_flag_set(inode, FI_DEFRAG_IN_PROGRESS))

How about checking FI_OPU_WRITE flag?

Thanks,

>   				return CURSEG_ALL_DATA_ATGC;
>   			else
>   				return CURSEG_COLD_DATA;