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Date:   Thu, 3 Feb 2022 22:16:24 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: add a way to limit roll forward
 recovery time
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On 02/04, Chao Yu wrote:
> On 2022/2/4 1:42, Jaegeuk Kim wrote:
> > On 02/03, Chao Yu wrote:
> > > On 2022/2/3 8:34, 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.
> > > > Default value doesn't enforce the limitation which is same as before.
> > > > 
> > > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > > > ---
> > > > v2 from v1:
> > > >    - make the default w/o enforcement
> > > > 
> > > >    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                      | 4 ++++
> > > >    fs/f2fs/sysfs.c                         | 2 ++
> > > >    7 files changed, 21 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 (NM_I(sbi)->max_rf_node_blocks)
> > > 	percpu_counter_inc(&sbi->rf_node_block_count);
> > 
> > I think we can just count this and adjust right away once sysfs is changed.
> 
> Since this long recovery latency issue is a corner case, I guess we can avoid this
> to save cpu time...

I think we can show this in debugfs, as it won't give huge overhead.

> 
> BTW, shouldn't we account all warn dnode blocks? as we will traverse all blocks there
> in warn node list.

I thought we don't need to track the whole bunch of chains, but would be enough
to record # of fsync calls roughly.

> 
> Thanks,
> 
> > 
> > > 
> > > Thanks,
> > > 
> > > >    				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..4c1d34bfea78 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			0
> > > > +
> > > >    /* 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..1c8041fd854e 100644
> > > > --- a/fs/f2fs/recovery.c
> > > > +++ b/fs/f2fs/recovery.c
> > > > @@ -53,9 +53,13 @@ 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 (NM_I(sbi)->max_rf_node_blocks &&
> > > > +			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),