Re: [PATCH] f2fs: add a modify discard command function

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 02/27, Yunlei He wrote:
> This patch add a function to modify discard command if one segment
> reuse before discard. Split this segment from multi-segments discard
> range, and discard the left bigger range.

Now MAX_DISCARD_BLOCKS() is set to section size, so there will be no
multi-sections discard range. Am I missing some cases?

Thanks,

> 
> 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 9006d8e..5af736b 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 __modify_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 (dc->lstart - blkaddr < dc->lstart + dc->len - end_block) {
> +		dc->lstart = end_block;
> +		dc->len -= (end_block - dc->lstart);
> +	} 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)
>  {
> @@ -699,7 +715,7 @@ void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
>  			if (dc->state == D_SUBMIT)
>  				wait_for_completion_io(&dc->wait);
>  			else
> -				__remove_discard_cmd(sbi, dc);
> +				__modify_discard_cmd(sbi, dc, blkaddr);
>  		}
>  	}
>  	blk_finish_plug(&plug);
> -- 
> 2.10.1

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