linux-kernel - Re: [PATCH v2] F2FS: invalidate META

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Date:   Tue, 2 Nov 2021 11:37:31 +0800
From:   Chao Yu <chao@...nel.org>
To:     Hyeong-Jun Kim <hj514.kim@...sung.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, guoweichao@...o.com
Subject: Re: [PATCH v2] F2FS: invalidate META_MAPPING before IPU/DIO write

On 2021/11/1 16:46, Hyeong-Jun Kim wrote:
> Encrypted pages during GC are read and cached in META_MAPPING.
> However, due to cached pages in META_MAPPING, there is an issue where
> newly written pages are lost by IPU or DIO writes.
> 
> Thread A - f2fs_gc()            Thread B
> /* phase 3 */
> down_write(i_gc_rwsem)
> ra_data_block()       ---- (a)
> up_write(i_gc_rwsem)
>                                  f2fs_direct_IO() :
>                                   - down_read(i_gc_rwsem)
>                                   - __blockdev_direct_io()
>                                   - get_data_block_dio_write()
>                                   - f2fs_dio_submit_bio()  ---- (b)
>                                   - up_read(i_gc_rwsem)
> /* phase 4 */
> down_write(i_gc_rwsem)
> move_data_block()     ---- (c)
> up_write(i_gc_rwsem)
> 
> (a) In phase 3 of f2fs_gc(), up-to-date page is read from storage and
>      cached in META_MAPPING.
> (b) In thread B, writing new data by IPU or DIO write on same blkaddr as
>      read in (a). cached page in META_MAPPING become out-dated.
> (c) In phase 4 of f2fs_gc(), out-dated page in META_MAPPING is copied to
>      new blkaddr. In conclusion, the newly written data in (b) is lost.
> 
> To address this issue, invalidating pages in META_MAPPING before IPU or
> DIO write.
> 
> Fixes: 6aa58d8ad20a ("f2fs: readahead encrypted block during GC")
> Signed-off-by: Hyeong-Jun Kim <hj514.kim@...sung.com>
> ---
>   fs/f2fs/data.c    | 2 ++
>   fs/f2fs/segment.c | 3 +++
>   2 files changed, 5 insertions(+)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 74e1a350c1d8..9f754aaef558 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1708,6 +1708,8 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
>   		 */
>   		f2fs_wait_on_block_writeback_range(inode,
>   						map->m_pblk, map->m_len);
> +		invalidate_mapping_pages(META_MAPPING(sbi),
> +						map->m_pblk, map->m_pblk);
>   
>   		if (map->m_multidev_dio) {
>   			block_t blk_addr = map->m_pblk;
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 526423fe84ce..f57c55190f9e 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -3652,6 +3652,9 @@ int f2fs_inplace_write_data(struct f2fs_io_info *fio)
>   		goto drop_bio;
>   	}
>   
> +	invalidate_mapping_pages(META_MAPPING(fio->sbi),

There is one more comment from Weichao:

Use sbi instead of fio->sbi?

Thanks,

> +				fio->new_blkaddr, fio->new_blkaddr);
> +
>   	stat_inc_inplace_blocks(fio->sbi);
>   
>   	if (fio->bio && !(SM_I(sbi)->ipu_policy & (1 << F2FS_IPU_NOCACHE)))
>