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Subject: Re: [PATCH 5/5] f2fs: do not __punch_discard_cmd in lfs mode
To:     Yunlong Song <yunlong.song@huawei.com>, <jaegeuk@kernel.org>,
        <chao@kernel.org>, <yunlong.song@icloud.com>
CC:     <miaoxie@huawei.com>, <bintian.wang@huawei.com>,
        <shengyong1@huawei.com>, <heyunlei@huawei.com>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>
References: <1531408170-45758-1-git-send-email-yunlong.song@huawei.com>
 <1531408170-45758-6-git-send-email-yunlong.song@huawei.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <7049c66a-867a-aef6-a58e-16ade179461e@huawei.com>
Date:   Fri, 13 Jul 2018 11:26:27 +0800
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On 2018/7/12 23:09, Yunlong Song wrote:
> In lfs mode, it is better to submit and wait for discard of the
> new_blkaddr's overall section, rather than punch it which makes
> more small discards and is not friendly with flash alignment. And
> f2fs does not have to wait discard of each new_blkaddr except for the
> start_block of each section with this patch.

For non-zoned block device, unaligned discard can be allowed; and if synchronous
discard is very slow, it will block block allocator here, rather than that, I
prefer just punch 4k lba of discard entry for performance.

If you don't want to encounter this condition, I suggest issue large size
discard more quickly.

Thanks,

> 
> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> ---
>  fs/f2fs/segment.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
>  fs/f2fs/segment.h |  7 ++++-
>  2 files changed, 75 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index f6c20e0..bce321a 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -893,7 +893,19 @@ static void __remove_discard_cmd(struct f2fs_sb_info *sbi,
>  static void f2fs_submit_discard_endio(struct bio *bio)
>  {
>  	struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
> +	struct f2fs_sb_info *sbi = F2FS_SB(dc->bdev->bd_super);
>  
> +	if (test_opt(sbi, LFS)) {
> +		unsigned int segno = GET_SEGNO(sbi, dc->lstart);
> +		unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
> +		int cnt = (dc->len >> sbi->log_blocks_per_seg) /
> +				sbi->segs_per_sec;
> +
> +		while (cnt--) {
> +			set_bit(secno, FREE_I(sbi)->discard_secmap);
> +			secno++;
> +		}
> +	}
>  	dc->error = blk_status_to_errno(bio->bi_status);
>  	dc->state = D_DONE;
>  	complete_all(&dc->wait);
> @@ -1349,8 +1361,15 @@ static void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
>  	dc = (struct discard_cmd *)f2fs_lookup_rb_tree(&dcc->root,
>  							NULL, blkaddr);
>  	if (dc) {
> -		if (dc->state == D_PREP) {
> +		if (dc->state == D_PREP && !test_opt(sbi, LFS))
>  			__punch_discard_cmd(sbi, dc, blkaddr);
> +		else if (dc->state == D_PREP && test_opt(sbi, LFS)) {
> +			struct discard_policy dpolicy;
> +
> +			__init_discard_policy(sbi, &dpolicy, DPOLICY_FORCE, 1);
> +			__submit_discard_cmd(sbi, &dpolicy, dc);
> +			dc->ref++;
> +			need_wait = true;
>  		} else {
>  			dc->ref++;
>  			need_wait = true;
> @@ -2071,9 +2090,10 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
>  	unsigned int hint = GET_SEC_FROM_SEG(sbi, *newseg);
>  	unsigned int old_zoneno = GET_ZONE_FROM_SEG(sbi, *newseg);
>  	unsigned int left_start = hint;
> -	bool init = true;
> +	bool init = true, check_discard = test_opt(sbi, LFS) ? true : false;
>  	int go_left = 0;
>  	int i;
> +	unsigned long *free_secmap;
>  
>  	spin_lock(&free_i->segmap_lock);
>  
> @@ -2084,11 +2104,25 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
>  			goto got_it;
>  	}
>  find_other_zone:
> -	secno = find_next_zero_bit(free_i->free_secmap, MAIN_SECS(sbi), hint);
> +	if (check_discard) {
> +		int entries = f2fs_bitmap_size(MAIN_SECS(sbi)) / sizeof(unsigned long);
> +
> +		free_secmap = free_i->tmp_secmap;
> +		for (i = 0; i < entries; i++)
> +			free_secmap[i] = (!(free_i->free_secmap[i] ^
> +				free_i->discard_secmap[i])) | free_i->free_secmap[i];
> +	} else
> +		free_secmap = free_i->free_secmap;
> +
> +	secno = find_next_zero_bit(free_secmap, MAIN_SECS(sbi), hint);
>  	if (secno >= MAIN_SECS(sbi)) {
>  		if (dir == ALLOC_RIGHT) {
> -			secno = find_next_zero_bit(free_i->free_secmap,
> +			secno = find_next_zero_bit(free_secmap,
>  							MAIN_SECS(sbi), 0);
> +			if (secno >= MAIN_SECS(sbi) && check_discard) {
> +				check_discard = false;
> +				goto find_other_zone;
> +			}
>  			f2fs_bug_on(sbi, secno >= MAIN_SECS(sbi));
>  		} else {
>  			go_left = 1;
> @@ -2098,13 +2132,17 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
>  	if (go_left == 0)
>  		goto skip_left;
>  
> -	while (test_bit(left_start, free_i->free_secmap)) {
> +	while (test_bit(left_start, free_secmap)) {
>  		if (left_start > 0) {
>  			left_start--;
>  			continue;
>  		}
> -		left_start = find_next_zero_bit(free_i->free_secmap,
> +		left_start = find_next_zero_bit(free_secmap,
>  							MAIN_SECS(sbi), 0);
> +		if (left_start >= MAIN_SECS(sbi) && check_discard) {
> +			check_discard = false;
> +			goto find_other_zone;
> +		}
>  		f2fs_bug_on(sbi, left_start >= MAIN_SECS(sbi));
>  		break;
>  	}
> @@ -2719,7 +2757,18 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
>  
>  	*new_blkaddr = NEXT_FREE_BLKADDR(sbi, curseg);
>  
> -	f2fs_wait_discard_bio(sbi, *new_blkaddr);
> +	if (test_opt(sbi, LFS)) {
> +		unsigned int start_segno, secno;
> +
> +		secno = GET_SEC_FROM_SEG(sbi, curseg->segno);
> +		start_segno = secno * sbi->segs_per_sec;
> +		if (*new_blkaddr == START_BLOCK(sbi, start_segno) &&
> +				!test_bit(secno, FREE_I(sbi)->discard_secmap))
> +			f2fs_wait_discard_bio(sbi, *new_blkaddr);
> +		f2fs_bug_on(sbi, !test_bit(secno, FREE_I(sbi)->discard_secmap));
> +	}
> +	else
> +		f2fs_wait_discard_bio(sbi, *new_blkaddr);
>  
>  	/*
>  	 * __add_sum_entry should be resided under the curseg_mutex
> @@ -3648,10 +3697,21 @@ static int build_free_segmap(struct f2fs_sb_info *sbi)
>  	if (!free_i->free_secmap)
>  		return -ENOMEM;
>  
> +	free_i->discard_secmap = f2fs_kvmalloc(sbi, sec_bitmap_size, GFP_KERNEL);
> +	if (!free_i->discard_secmap)
> +		return -ENOMEM;
> +
> +	free_i->tmp_secmap = f2fs_kvmalloc(sbi, sec_bitmap_size, GFP_KERNEL);
> +	if (!free_i->tmp_secmap)
> +		return -ENOMEM;
> +
>  	/* set all segments as dirty temporarily */
>  	memset(free_i->free_segmap, 0xff, bitmap_size);
>  	memset(free_i->free_secmap, 0xff, sec_bitmap_size);
>  
> +	/* set all sections as discarded temporarily */
> +	memset(free_i->discard_secmap, 0xff, sec_bitmap_size);
> +
>  	/* init free segmap information */
>  	free_i->start_segno = GET_SEGNO_FROM_SEG0(sbi, MAIN_BLKADDR(sbi));
>  	free_i->free_segments = 0;
> @@ -4047,6 +4107,8 @@ static void destroy_free_segmap(struct f2fs_sb_info *sbi)
>  	SM_I(sbi)->free_info = NULL;
>  	kvfree(free_i->free_segmap);
>  	kvfree(free_i->free_secmap);
> +	kvfree(free_i->discard_secmap);
> +	kvfree(free_i->tmp_secmap);
>  	kfree(free_i);
>  }
>  
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 5049551..b37a909 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -259,6 +259,8 @@ struct free_segmap_info {
>  	spinlock_t segmap_lock;		/* free segmap lock */
>  	unsigned long *free_segmap;	/* free segment bitmap */
>  	unsigned long *free_secmap;	/* free section bitmap */
> +	unsigned long *discard_secmap;	/* discard section bitmap */
> +	unsigned long *tmp_secmap;	/* bitmap for temporal use */
>  };
>  
>  /* Notice: The order of dirty type is same with CURSEG_XXX in f2fs.h */
> @@ -453,8 +455,11 @@ static inline void __set_test_and_free(struct f2fs_sb_info *sbi,
>  		next = find_next_bit(free_i->free_segmap,
>  				start_segno + sbi->segs_per_sec, start_segno);
>  		if (next >= start_segno + sbi->segs_per_sec) {
> -			if (test_and_clear_bit(secno, free_i->free_secmap))
> +			if (test_and_clear_bit(secno, free_i->free_secmap)) {
>  				free_i->free_sections++;
> +				if (test_opt(sbi, LFS))
> +					clear_bit(secno, free_i->discard_secmap);
> +			}
>  		}
>  	}
>  skip_free:
>