Re: [PATCH v2] f2fs: add a punch discard command function

[Jaegeuk Kim <jaegeuk@kernel.org>]

Hi Yunlei,

On 03/02, Yunlei He wrote:
> This patch add a function to punch discard command if one segment
> reuse before discard. Split this segment from multi-segments discard
> range, and discard the left bigger range.
> 
> Signed-off-by: Yunlei He <heyunlei@huawei.com>
> ---
>  fs/f2fs/segment.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 4bd7a8b..1e1d5d3 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -672,6 +672,22 @@ static void __remove_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *d
>  	kmem_cache_free(discard_cmd_slab, dc);
>  }
>  
> +static void __punch_discard_cmd(struct f2fs_sb_info *sbi, struct discard_cmd *dc, block_t blkaddr)
> +{
> +	block_t end_block = START_BLOCK(sbi, GET_SEGNO(sbi, blkaddr) + 1);
> +
> +	if (dc->lstart + dc->len <= end_block) {
> +		__remove_discard_cmd(sbi, dc);
> +		return;
> +	}
> +
> +	if (blkaddr - dc->lstart < dc->lstart + dc->len - end_block) {
> +		dc->lstart = end_block;
> +		dc->len -= (end_block - dc->lstart);

I just missed one thing which we already have a bio to submit later. So, in
order to do this, we should manage dc->bio as well.
Let me think about whole flow again.

Thanks,

> +	} else
> +		dc->len = blkaddr - dc->lstart;
> +}
> +
>  /* This should be covered by global mutex, &sit_i->sentry_lock */
>  void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
>  {
> @@ -708,7 +724,7 @@ void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
>  	if (blkaddr == NULL_ADDR) {
>  		list_for_each_entry_safe(dc, tmp, wait_list, list) {
>  			wait_for_completion_io(&dc->wait);
> -			__remove_discard_cmd(sbi, dc);
> +			__punch_discard_cmd(sbi, dc, blkaddr);
>  		}
>  	}
>  	mutex_unlock(&dcc->cmd_lock);
> -- 
> 2.10.1

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