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Date:   Sat, 29 Jan 2022 16:20:57 +0800
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Subject: Re: [f2fs-dev] [PATCH] f2fs: add a way to limit roll forward recovery
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To:     Jaegeuk Kim <jaegeuk@kernel.org>, linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
References: <20220127214102.2040254-1-jaegeuk@kernel.org>
From:   Chao Yu <chao@kernel.org>
In-Reply-To: <20220127214102.2040254-1-jaegeuk@kernel.org>
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On 2022/1/28 5:41, Jaegeuk Kim wrote:
> This adds a sysfs entry to call checkpoint during fsync() in order to avoid
> long elapsed time to run roll-forward recovery when booting the device.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>   Documentation/ABI/testing/sysfs-fs-f2fs | 6 ++++++
>   fs/f2fs/checkpoint.c                    | 1 +
>   fs/f2fs/f2fs.h                          | 3 +++
>   fs/f2fs/node.c                          | 2 ++
>   fs/f2fs/node.h                          | 3 +++
>   fs/f2fs/recovery.c                      | 3 +++
>   fs/f2fs/sysfs.c                         | 2 ++
>   7 files changed, 20 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index 87d3884c90ea..ce8103f522cb 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -567,3 +567,9 @@ Contact:	"Daeho Jeong" <daehojeong@google.com>
>   Description:	You can set the trial count limit for GC urgent high mode with this value.
>   		If GC thread gets to the limit, the mode will turn back to GC normal mode.
>   		By default, the value is zero, which means there is no limit like before.
> +
> +What:		/sys/fs/f2fs/<disk>/max_roll_forward_node_blocks
> +Date:		January 2022
> +Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
> +Description:	Controls max # of node block writes to be used for roll forward
> +		recovery. This can limit the roll forward recovery time.
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index deeda95688f0..57a2d9164bee 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1543,6 +1543,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>   	/* update user_block_counts */
>   	sbi->last_valid_block_count = sbi->total_valid_block_count;
>   	percpu_counter_set(&sbi->alloc_valid_block_count, 0);
> +	percpu_counter_set(&sbi->rf_node_block_count, 0);
>   
>   	/* Here, we have one bio having CP pack except cp pack 2 page */
>   	f2fs_sync_meta_pages(sbi, META, LONG_MAX, FS_CP_META_IO);
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 63c90416364b..6ddb98ff0b7c 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -913,6 +913,7 @@ struct f2fs_nm_info {
>   	nid_t max_nid;			/* maximum possible node ids */
>   	nid_t available_nids;		/* # of available node ids */
>   	nid_t next_scan_nid;		/* the next nid to be scanned */
> +	nid_t max_rf_node_blocks;	/* max # of nodes for recovery */
>   	unsigned int ram_thresh;	/* control the memory footprint */
>   	unsigned int ra_nid_pages;	/* # of nid pages to be readaheaded */
>   	unsigned int dirty_nats_ratio;	/* control dirty nats ratio threshold */
> @@ -1684,6 +1685,8 @@ struct f2fs_sb_info {
>   	atomic_t nr_pages[NR_COUNT_TYPE];
>   	/* # of allocated blocks */
>   	struct percpu_counter alloc_valid_block_count;
> +	/* # of node block writes as roll forward recovery */
> +	struct percpu_counter rf_node_block_count;
>   
>   	/* writeback control */
>   	atomic_t wb_sync_req[META];	/* count # of WB_SYNC threads */
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 93512f8859d5..0d9883457579 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1782,6 +1782,7 @@ int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>   
>   			if (!atomic || page == last_page) {
>   				set_fsync_mark(page, 1);
> +				percpu_counter_inc(&sbi->rf_node_block_count);
>   				if (IS_INODE(page)) {
>   					if (is_inode_flag_set(inode,
>   								FI_DIRTY_INODE))
> @@ -3218,6 +3219,7 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
>   	nm_i->ram_thresh = DEF_RAM_THRESHOLD;
>   	nm_i->ra_nid_pages = DEF_RA_NID_PAGES;
>   	nm_i->dirty_nats_ratio = DEF_DIRTY_NAT_RATIO_THRESHOLD;
> +	nm_i->max_rf_node_blocks = DEF_RF_NODE_BLOCKS;
>   
>   	INIT_RADIX_TREE(&nm_i->free_nid_root, GFP_ATOMIC);
>   	INIT_LIST_HEAD(&nm_i->free_nid_list);
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index 18b98cf0465b..fe56fd29c0d3 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -31,6 +31,9 @@
>   /* control total # of nats */
>   #define DEF_NAT_CACHE_THRESHOLD			100000
>   
> +/* control total # of node writes used for roll-fowrad recovery */
> +#define DEF_RF_NODE_BLOCKS			100

Will we suffer performance regression issue in some scenarios in where user triggers
fsync/fdatasync frequently? e.g. performance test.

If this issue is a corner case, it's better to increase DEF_RF_NODE_BLOCKS to
avoid affecting common case AMSP?

Thanks,

> +
>   /* vector size for gang look-up from nat cache that consists of radix tree */
>   #define NATVEC_SIZE	64
>   #define SETVEC_SIZE	32
> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> index 10d152cfa58d..f69b685fb2b2 100644
> --- a/fs/f2fs/recovery.c
> +++ b/fs/f2fs/recovery.c
> @@ -53,9 +53,12 @@ extern struct kmem_cache *f2fs_cf_name_slab;
>   bool f2fs_space_for_roll_forward(struct f2fs_sb_info *sbi)
>   {
>   	s64 nalloc = percpu_counter_sum_positive(&sbi->alloc_valid_block_count);
> +	u32 rf_node = percpu_counter_sum_positive(&sbi->rf_node_block_count);
>   
>   	if (sbi->last_valid_block_count + nalloc > sbi->user_block_count)
>   		return false;
> +	if (rf_node >= NM_I(sbi)->max_rf_node_blocks)
> +		return false;
>   	return true;
>   }
>   
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index 281bc0133ee6..47efcf233afd 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -732,6 +732,7 @@ F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ssr_sections, min_ssr_sections);
>   F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, ram_thresh, ram_thresh);
>   F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, ra_nid_pages, ra_nid_pages);
>   F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, dirty_nats_ratio, dirty_nats_ratio);
> +F2FS_RW_ATTR(NM_INFO, f2fs_nm_info, max_roll_forward_node_blocks, max_rf_node_blocks);
>   F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, max_victim_search, max_victim_search);
>   F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, migration_granularity, migration_granularity);
>   F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, dir_level, dir_level);
> @@ -855,6 +856,7 @@ static struct attribute *f2fs_attrs[] = {
>   	ATTR_LIST(ram_thresh),
>   	ATTR_LIST(ra_nid_pages),
>   	ATTR_LIST(dirty_nats_ratio),
> +	ATTR_LIST(max_roll_forward_node_blocks),
>   	ATTR_LIST(cp_interval),
>   	ATTR_LIST(idle_interval),
>   	ATTR_LIST(discard_idle_interval),