Re: [PATCH 1/6] f2fs: support issuing/waiting discard in range

[Jaegeuk Kim]

On 09/19, Chao Yu wrote:
> From: Chao Yu <yuchao0@xxxxxxxxxx>
> 
> Fstrim intends to trim invalid blocks of filesystem only with specified
> range and granularity, but actually, it will issue all previous cached
> discard commands which may be out-of-range and be with unmatched
> granularity, it's unneeded.
> 
> In order to fix above issues, this patch introduces new helps to support
> to issue and wait discard in range and adds a new fstrim_list for tracking
> in-flight discard from ->fstrim.
> 
> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
> ---
>  fs/f2fs/f2fs.h    |   1 +
>  fs/f2fs/segment.c | 125 +++++++++++++++++++++++++++++++++++++++++++++---------
>  2 files changed, 106 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 89b4927dcd79..cb13c7df6971 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -249,6 +249,7 @@ struct discard_cmd_control {
>  	struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
>  	unsigned char pend_list_tag[MAX_PLIST_NUM];/* tag for pending entries */
>  	struct list_head wait_list;		/* store on-flushing entries */
> +	struct list_head fstrim_list;		/* in-flight discard from fstrim */
>  	wait_queue_head_t discard_wait_queue;	/* waiting queue for wake-up */
>  	unsigned int discard_wake;		/* to wake up discard thread */
>  	struct mutex cmd_lock;
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index dedf0209d820..088936c61905 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -845,9 +845,11 @@ void __check_sit_bitmap(struct f2fs_sb_info *sbi,
>  
>  /* this function is copied from blkdev_issue_discard from block/blk-lib.c */
>  static void __submit_discard_cmd(struct f2fs_sb_info *sbi,
> -				struct discard_cmd *dc)
> +				struct discard_cmd *dc, bool fstrim)
>  {
>  	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +	struct list_head *wait_list = fstrim ? &(dcc->fstrim_list) :
> +							&(dcc->wait_list);
>  	struct bio *bio = NULL;
>  
>  	if (dc->state != D_PREP)
> @@ -869,7 +871,7 @@ static void __submit_discard_cmd(struct f2fs_sb_info *sbi,
>  			bio->bi_end_io = f2fs_submit_discard_endio;
>  			bio->bi_opf |= REQ_SYNC;
>  			submit_bio(bio);
> -			list_move_tail(&dc->list, &dcc->wait_list);
> +			list_move_tail(&dc->list, wait_list);
>  			__check_sit_bitmap(sbi, dc->start, dc->start + dc->len);
>  
>  			f2fs_update_iostat(sbi, FS_DISCARD, 1);
> @@ -1054,6 +1056,68 @@ static int __queue_discard_cmd(struct f2fs_sb_info *sbi,
>  	return 0;
>  }
>  
> +static void __issue_discard_cmd_range(struct f2fs_sb_info *sbi,
> +					unsigned int start, unsigned int end,
> +					unsigned int granularity)
> +{
> +	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +	struct discard_cmd *prev_dc = NULL, *next_dc = NULL;
> +	struct rb_node **insert_p = NULL, *insert_parent = NULL;
> +	struct discard_cmd *dc;
> +	struct blk_plug plug;
> +	int issued;
> +
> +next:
> +	issued = 0;
> +
> +	mutex_lock(&dcc->cmd_lock);
> +	f2fs_bug_on(sbi, !__check_rb_tree_consistence(sbi, &dcc->root));
> +
> +	dc = (struct discard_cmd *)__lookup_rb_tree_ret(&dcc->root,
> +					NULL, start,
> +					(struct rb_entry **)&prev_dc,
> +					(struct rb_entry **)&next_dc,
> +					&insert_p, &insert_parent, true);
> +	if (!dc)
> +		dc = next_dc;
> +
> +	blk_start_plug(&plug);
> +
> +	while (dc && dc->lstart <= end) {
> +		struct rb_node *node;
> +
> +		if (dc->len < granularity)
> +			goto skip;
> +
> +		if (dc->state != D_PREP) {
> +			list_move_tail(&dc->list, &dcc->fstrim_list);
> +			goto skip;
> +		}
> +
> +		__submit_discard_cmd(sbi, dc, true);
> +
> +		if (++issued >= DISCARD_ISSUE_RATE) {
> +			start = dc->lstart + dc->len;
> +
> +			blk_finish_plug(&plug);
> +			mutex_unlock(&dcc->cmd_lock);
> +
> +			schedule();
> +
> +			goto next;
> +		}
> +skip:
> +		node = rb_next(&dc->rb_node);
> +		dc = rb_entry_safe(node, struct discard_cmd, rb_node);
> +
> +		if (fatal_signal_pending(current))
> +			break;
> +	}
> +
> +	blk_finish_plug(&plug);
> +	mutex_unlock(&dcc->cmd_lock);
> +}
> +
>  static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>  {
>  	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> @@ -1076,22 +1140,19 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, bool issue_cond)
>  
>  			/* Hurry up to finish fstrim */
>  			if (dcc->pend_list_tag[i] & P_TRIM) {
> -				__submit_discard_cmd(sbi, dc);
> +				__submit_discard_cmd(sbi, dc, false);
>  				issued++;
> -
> -				if (fatal_signal_pending(current))
> -					break;

Where did you move this in the change? Or, we don't need this at all?

>  				continue;
>  			}
>  
>  			if (!issue_cond) {
> -				__submit_discard_cmd(sbi, dc);
> +				__submit_discard_cmd(sbi, dc, false);
>  				issued++;
>  				continue;
>  			}
>  
>  			if (is_idle(sbi)) {
> -				__submit_discard_cmd(sbi, dc);
> +				__submit_discard_cmd(sbi, dc, false);
>  				issued++;
>  			} else {
>  				io_interrupted = true;
> @@ -1145,10 +1206,14 @@ static void __wait_one_discard_bio(struct f2fs_sb_info *sbi,
>  	mutex_unlock(&dcc->cmd_lock);
>  }
>  
> -static void __wait_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
> +static void __wait_discard_cmd_range(struct f2fs_sb_info *sbi, bool wait_cond,
> +						block_t start, block_t end,
> +						unsigned int granularity,
> +						bool fstrim)
>  {
>  	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> -	struct list_head *wait_list = &(dcc->wait_list);
> +	struct list_head *wait_list = fstrim ? &(dcc->fstrim_list) :
> +							&(dcc->wait_list);
>  	struct discard_cmd *dc, *tmp;
>  	bool need_wait;
>  
> @@ -1157,6 +1222,10 @@ static void __wait_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
>  
>  	mutex_lock(&dcc->cmd_lock);
>  	list_for_each_entry_safe(dc, tmp, wait_list, list) {
> +		if (dc->lstart + dc->len <= start || end <= dc->lstart)
> +			continue;
> +		if (dc->len < granularity)
> +			continue;
>  		if (!wait_cond || (dc->state == D_DONE && !dc->ref)) {
>  			wait_for_completion_io(&dc->wait);
>  			__remove_discard_cmd(sbi, dc);
> @@ -1174,6 +1243,11 @@ static void __wait_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
>  	}
>  }
>  
> +static void __wait_all_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
> +{
> +	__wait_discard_cmd_range(sbi, wait_cond, 0, UINT_MAX, 1, false);
> +}
> +
>  /* This should be covered by global mutex, &sit_i->sentry_lock */
>  void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
>  {
> @@ -1209,12 +1283,12 @@ void stop_discard_thread(struct f2fs_sb_info *sbi)
>  	}
>  }
>  
> -/* This comes from f2fs_put_super and f2fs_trim_fs */
> +/* This comes from f2fs_put_super */
>  void f2fs_wait_discard_bios(struct f2fs_sb_info *sbi)
>  {
>  	__issue_discard_cmd(sbi, false);
>  	__drop_discard_cmd(sbi);
> -	__wait_discard_cmd(sbi, false);
> +	__wait_all_discard_cmd(sbi, false);
>  }
>  
>  static void mark_discard_range_all(struct f2fs_sb_info *sbi)
> @@ -1258,7 +1332,7 @@ static int issue_discard_thread(void *data)
>  
>  		issued = __issue_discard_cmd(sbi, true);
>  		if (issued) {
> -			__wait_discard_cmd(sbi, true);
> +			__wait_all_discard_cmd(sbi, true);
>  			wait_ms = DEF_MIN_DISCARD_ISSUE_TIME;
>  		} else {
>  			wait_ms = DEF_MAX_DISCARD_ISSUE_TIME;
> @@ -1569,6 +1643,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>  			dcc->pend_list_tag[i] |= P_ACTIVE;
>  	}
>  	INIT_LIST_HEAD(&dcc->wait_list);
> +	INIT_LIST_HEAD(&dcc->fstrim_list);
>  	mutex_init(&dcc->cmd_lock);
>  	atomic_set(&dcc->issued_discard, 0);
>  	atomic_set(&dcc->issing_discard, 0);
> @@ -2196,7 +2271,8 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>  {
>  	__u64 start = F2FS_BYTES_TO_BLK(range->start);
>  	__u64 end = start + F2FS_BYTES_TO_BLK(range->len) - 1;
> -	unsigned int start_segno, end_segno;
> +	unsigned int start_segno, end_segno, cur_segno;
> +	block_t start_block, end_block;
>  	struct cp_control cpc;
>  	int err = 0;
>  
> @@ -2217,12 +2293,17 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>  	start_segno = (start <= MAIN_BLKADDR(sbi)) ? 0 : GET_SEGNO(sbi, start);
>  	end_segno = (end >= MAX_BLKADDR(sbi)) ? MAIN_SEGS(sbi) - 1 :
>  						GET_SEGNO(sbi, end);
> +
> +	start_block = START_BLOCK(sbi, start_segno);
> +	end_block = START_BLOCK(sbi, end_segno + 1);
> +
>  	cpc.reason = CP_DISCARD;
>  	cpc.trim_minlen = max_t(__u64, 1, F2FS_BYTES_TO_BLK(range->minlen));
>  
>  	/* do checkpoint to issue discard commands safely */
> -	for (; start_segno <= end_segno; start_segno = cpc.trim_end + 1) {
> -		cpc.trim_start = start_segno;
> +	for (cur_segno = start_segno; cur_segno <= end_segno;
> +					cur_segno = cpc.trim_end + 1) {
> +		cpc.trim_start = cur_segno;
>  
>  		if (sbi->discard_blks == 0)
>  			break;
> @@ -2230,7 +2311,7 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>  			cpc.trim_end = end_segno;
>  		else
>  			cpc.trim_end = min_t(unsigned int,
> -				rounddown(start_segno +
> +				rounddown(cur_segno +
>  				BATCHED_TRIM_SEGMENTS(sbi),
>  				sbi->segs_per_sec) - 1, end_segno);
>  
> @@ -2242,9 +2323,13 @@ int f2fs_trim_fs(struct f2fs_sb_info *sbi, struct fstrim_range *range)
>  
>  		schedule();
>  	}
> -	/* It's time to issue all the filed discards */
> -	mark_discard_range_all(sbi);
> -	f2fs_wait_discard_bios(sbi);
> +
> +	start_block = START_BLOCK(sbi, start_segno);
> +	end_block = START_BLOCK(sbi, min(cur_segno, end_segno) + 1);
> +
> +	__issue_discard_cmd_range(sbi, start_block, end_block, cpc.trim_minlen);
> +	__wait_discard_cmd_range(sbi, false, start_block, end_block,
> +						cpc.trim_minlen, true);
>  out:
>  	range->len = F2FS_BLK_TO_BYTES(cpc.trimmed);
>  	return err;
> -- 
> 2.14.1.145.gb3622a4ee