Date:   Sat, 28 Jul 2018 18:33:51 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH v5 1/2] f2fs: fix to avoid broken of dnode block list

On 07/28, Chao Yu wrote:
> f2fs recovery flow is relying on dnode block link list, it means fsynced
> file recovery depends on previous dnode's persistence in the list, so
> during fsync() we should wait on all regular inode's dnode writebacked
> before issuing flush.
> 
> By this way, we can avoid dnode block list being broken by out-of-order
> IO submission due to IO scheduler or driver.
> 
> Sheng Yong helps to do the test with this patch:
> 
> Target:/data (f2fs, -)
> 64MB / 32768KB / 4KB / 8
> 
> 1 / PERSIST / Index
> 
> Base:
> 	SEQ-RD(MB/s)	SEQ-WR(MB/s)	RND-RD(IOPS)	RND-WR(IOPS)	Insert(TPS)	Update(TPS)	Delete(TPS)
> 1	867.82		204.15		41440.03	41370.54	680.8		1025.94		1031.08
> 2	871.87		205.87		41370.3		40275.2		791.14		1065.84		1101.7
> 3	866.52		205.69		41795.67	40596.16	694.69		1037.16		1031.48
> Avg	868.7366667	205.2366667	41535.33333	40747.3		722.21		1042.98		1054.753333
> 
> After:
> 	SEQ-RD(MB/s)	SEQ-WR(MB/s)	RND-RD(IOPS)	RND-WR(IOPS)	Insert(TPS)	Update(TPS)	Delete(TPS)
> 1	798.81		202.5		41143		40613.87	602.71		838.08		913.83
> 2	805.79		206.47		40297.2		41291.46	604.44		840.75		924.27
> 3	814.83		206.17		41209.57	40453.62	602.85		834.66		927.91
> Avg	806.4766667	205.0466667	40883.25667	40786.31667	603.3333333	837.83		922.0033333
> 
> Patched/Original:
> 	0.928332713	0.999074239	0.984300676	1.000957528	0.835398753	0.803303994	0.874141189

I expect Sheng will provide more test results tho, at least it seems SEQ-RD
in Base shows better than two After results, even if it doesn't matter with
the issue. Please confirm it first in order for anybody to say there is no
regression.

> 
> It looks like atomic write will suffer performance regression.
> 
> I suspect that the criminal is that we forcing to wait all dnode being in
> storage cache before we issue PREFLUSH+FUA.
> 
> BTW, will commit ("f2fs: don't need to wait for node writes for atomic write")
> cause the problem: we will lose data of last transaction after SPO, even if
> atomic write return no error:
> 
> - atomic_open();
> - write() P1, P2, P3;
> - atomic_commit();
>  - writeback data: P1, P2, P3;
>  - writeback node: N1, N2, N3;  <--- If N1, N2 is not writebacked, N3 with fsync_mark is
> writebacked, In SPOR, we won't find N3 since node chain is broken, turns out that losing
> last transaction.
>  - preflush + fua;
> - power-cut
> 
> If we don't wait dnode writeback for atomic_write:
> 
> 	SEQ-RD(MB/s)	SEQ-WR(MB/s)	RND-RD(IOPS)	RND-WR(IOPS)	Insert(TPS)	Update(TPS)	Delete(TPS)
> 1	779.91		206.03		41621.5		40333.16	716.9		1038.21		1034.85
> 2	848.51		204.35		40082.44	39486.17	791.83		1119.96		1083.77
> 3	772.12		206.27		41335.25	41599.65	723.29		1055.07		971.92
> Avg	800.18		205.55		41013.06333	40472.99333	744.0066667	1071.08		1030.18
> 
> Patched/Original:
> 	0.92108464	1.001526693	0.987425886	0.993268102	1.030180511	1.026942031	0.976702294
> 
> SQLite's performance recovers.
> 
> Jaegeuk:
> "Practically, I don't see db corruption becase of this. We can excuse to lose
> the last transaction."
> 
> Finally, we decide to keep original implementation of atomic write interface
> sematics that we don't wait all dnode writeback before preflush+fua submission.
> 
> Tested-by: Sheng Yong <shengyong1@...wei.com>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> v5:
> - add missing Tested-by.
> - fix f2fs_reset_fsync_node_info() to reset sbi->fsync_seg_id correctly.
>  fs/f2fs/checkpoint.c |   2 +
>  fs/f2fs/data.c       |   2 +
>  fs/f2fs/f2fs.h       |  21 ++++++-
>  fs/f2fs/file.c       |   5 +-
>  fs/f2fs/node.c       | 144 +++++++++++++++++++++++++++++++++++--------
>  fs/f2fs/super.c      |   4 ++
>  6 files changed, 150 insertions(+), 28 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 581710760ba6..2136430f9f0d 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1410,6 +1410,8 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>  
>  	f2fs_release_ino_entry(sbi, false);
>  
> +	f2fs_reset_fsync_node_info(sbi);
> +
>  	clear_sbi_flag(sbi, SBI_IS_DIRTY);
>  	clear_sbi_flag(sbi, SBI_NEED_CP);
>  	__set_cp_next_pack(sbi);
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 6b8ca5011bfd..572c91e43337 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -177,6 +177,8 @@ static void f2fs_write_end_io(struct bio *bio)
>  					page->index != nid_of_node(page));
>  
>  		dec_page_count(sbi, type);
> +		if (f2fs_in_warm_node_list(sbi, page))
> +			f2fs_del_fsync_node_entry(sbi, page);
>  		clear_cold_data(page);
>  		end_page_writeback(page);
>  	}
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 0374f069520c..6627fef9ae38 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -228,6 +228,12 @@ struct inode_entry {
>  	struct inode *inode;	/* vfs inode pointer */
>  };
>  
> +struct fsync_node_entry {
> +	struct list_head list;	/* list head */
> +	struct page *page;	/* warm node page pointer */
> +	unsigned int seq_id;	/* sequence id */
> +};
> +
>  /* for the bitmap indicate blocks to be discarded */
>  struct discard_entry {
>  	struct list_head list;	/* list head */
> @@ -1156,6 +1162,11 @@ struct f2fs_sb_info {
>  
>  	struct inode_management im[MAX_INO_ENTRY];      /* manage inode cache */
>  
> +	spinlock_t fsync_node_lock;		/* for node entry lock */
> +	struct list_head fsync_node_list;	/* node list head */
> +	unsigned int fsync_seg_id;		/* sequence id */
> +	unsigned int fsync_node_num;		/* number of node entries */
> +
>  	/* for orphan inode, use 0'th array */
>  	unsigned int max_orphans;		/* max orphan inodes */
>  
> @@ -2822,6 +2833,10 @@ struct node_info;
>  
>  int f2fs_check_nid_range(struct f2fs_sb_info *sbi, nid_t nid);
>  bool f2fs_available_free_memory(struct f2fs_sb_info *sbi, int type);
> +bool f2fs_in_warm_node_list(struct f2fs_sb_info *sbi, struct page *page);
> +void f2fs_init_fsync_node_info(struct f2fs_sb_info *sbi);
> +void f2fs_del_fsync_node_entry(struct f2fs_sb_info *sbi, struct page *page);
> +void f2fs_reset_fsync_node_info(struct f2fs_sb_info *sbi);
>  int f2fs_need_dentry_mark(struct f2fs_sb_info *sbi, nid_t nid);
>  bool f2fs_is_checkpointed_node(struct f2fs_sb_info *sbi, nid_t nid);
>  bool f2fs_need_inode_block_update(struct f2fs_sb_info *sbi, nid_t ino);
> @@ -2831,7 +2846,8 @@ pgoff_t f2fs_get_next_page_offset(struct dnode_of_data *dn, pgoff_t pgofs);
>  int f2fs_get_dnode_of_data(struct dnode_of_data *dn, pgoff_t index, int mode);
>  int f2fs_truncate_inode_blocks(struct inode *inode, pgoff_t from);
>  int f2fs_truncate_xattr_node(struct inode *inode);
> -int f2fs_wait_on_node_pages_writeback(struct f2fs_sb_info *sbi, nid_t ino);
> +int f2fs_wait_on_node_pages_writeback(struct f2fs_sb_info *sbi,
> +					unsigned int seq_id);
>  int f2fs_remove_inode_page(struct inode *inode);
>  struct page *f2fs_new_inode_page(struct inode *inode);
>  struct page *f2fs_new_node_page(struct dnode_of_data *dn, unsigned int ofs);
> @@ -2840,7 +2856,8 @@ struct page *f2fs_get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid);
>  struct page *f2fs_get_node_page_ra(struct page *parent, int start);
>  void f2fs_move_node_page(struct page *node_page, int gc_type);
>  int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
> -			struct writeback_control *wbc, bool atomic);
> +			struct writeback_control *wbc, bool atomic,
> +			unsigned int *seq_id);
>  int f2fs_sync_node_pages(struct f2fs_sb_info *sbi,
>  			struct writeback_control *wbc,
>  			bool do_balance, enum iostat_type io_type);
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 8f9ab66858ca..7bd2412a8c37 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -213,6 +213,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>  		.nr_to_write = LONG_MAX,
>  		.for_reclaim = 0,
>  	};
> +	unsigned int seq_id = 0;
>  
>  	if (unlikely(f2fs_readonly(inode->i_sb)))
>  		return 0;
> @@ -275,7 +276,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>  	}
>  sync_nodes:
>  	atomic_inc(&sbi->wb_sync_req[NODE]);
> -	ret = f2fs_fsync_node_pages(sbi, inode, &wbc, atomic);
> +	ret = f2fs_fsync_node_pages(sbi, inode, &wbc, atomic, &seq_id);
>  	atomic_dec(&sbi->wb_sync_req[NODE]);
>  	if (ret)
>  		goto out;
> @@ -301,7 +302,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>  	 * given fsync mark.
>  	 */
>  	if (!atomic) {
> -		ret = f2fs_wait_on_node_pages_writeback(sbi, ino);
> +		ret = f2fs_wait_on_node_pages_writeback(sbi, seq_id);
>  		if (ret)
>  			goto out;
>  	}
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 9d9f4c9750c4..e109c671cd84 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -28,6 +28,7 @@
>  static struct kmem_cache *nat_entry_slab;
>  static struct kmem_cache *free_nid_slab;
>  static struct kmem_cache *nat_entry_set_slab;
> +static struct kmem_cache *fsync_node_entry_slab;
>  
>  /*
>   * Check whether the given nid is within node id range.
> @@ -264,6 +265,72 @@ static unsigned int __gang_lookup_nat_set(struct f2fs_nm_info *nm_i,
>  							start, nr);
>  }
>  
> +bool f2fs_in_warm_node_list(struct f2fs_sb_info *sbi, struct page *page)
> +{
> +	return NODE_MAPPING(sbi) == page->mapping &&
> +			IS_DNODE(page) && is_cold_node(page);
> +}
> +
> +void f2fs_init_fsync_node_info(struct f2fs_sb_info *sbi)
> +{
> +	spin_lock_init(&sbi->fsync_node_lock);
> +	INIT_LIST_HEAD(&sbi->fsync_node_list);
> +	sbi->fsync_seg_id = 0;
> +	sbi->fsync_node_num = 0;
> +}
> +
> +static unsigned int f2fs_add_fsync_node_entry(struct f2fs_sb_info *sbi,
> +							struct page *page)
> +{
> +	struct fsync_node_entry *fn;
> +	unsigned long flags;
> +	unsigned int seq_id;
> +
> +	fn = f2fs_kmem_cache_alloc(fsync_node_entry_slab, GFP_NOFS);
> +
> +	get_page(page);
> +	fn->page = page;
> +	INIT_LIST_HEAD(&fn->list);
> +
> +	spin_lock_irqsave(&sbi->fsync_node_lock, flags);
> +	list_add_tail(&fn->list, &sbi->fsync_node_list);
> +	fn->seq_id = sbi->fsync_seg_id++;
> +	seq_id = fn->seq_id;
> +	sbi->fsync_node_num++;
> +	spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
> +
> +	return seq_id;
> +}
> +
> +void f2fs_del_fsync_node_entry(struct f2fs_sb_info *sbi, struct page *page)
> +{
> +	struct fsync_node_entry *fn;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&sbi->fsync_node_lock, flags);
> +	list_for_each_entry(fn, &sbi->fsync_node_list, list) {
> +		if (fn->page == page) {
> +			list_del(&fn->list);
> +			sbi->fsync_node_num--;
> +			spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
> +			kmem_cache_free(fsync_node_entry_slab, fn);
> +			put_page(page);
> +			return;
> +		}
> +	}
> +	spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
> +	f2fs_bug_on(sbi, 1);
> +}
> +
> +void f2fs_reset_fsync_node_info(struct f2fs_sb_info *sbi)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&sbi->fsync_node_lock, flags);
> +	sbi->fsync_seg_id = 0;
> +	spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
> +}
> +
>  int f2fs_need_dentry_mark(struct f2fs_sb_info *sbi, nid_t nid)
>  {
>  	struct f2fs_nm_info *nm_i = NM_I(sbi);
> @@ -1384,7 +1451,7 @@ static struct page *last_fsync_dnode(struct f2fs_sb_info *sbi, nid_t ino)
>  
>  static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>  				struct writeback_control *wbc, bool do_balance,
> -				enum iostat_type io_type)
> +				enum iostat_type io_type, unsigned int *seq_id)
>  {
>  	struct f2fs_sb_info *sbi = F2FS_P_SB(page);
>  	nid_t nid;
> @@ -1401,6 +1468,7 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>  		.io_type = io_type,
>  		.io_wbc = wbc,
>  	};
> +	unsigned int seq;
>  
>  	trace_f2fs_writepage(page, NODE);
>  
> @@ -1442,6 +1510,13 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
>  
>  	set_page_writeback(page);
>  	ClearPageError(page);
> +
> +	if (f2fs_in_warm_node_list(sbi, page)) {
> +		seq = f2fs_add_fsync_node_entry(sbi, page);
> +		if (seq_id)
> +			*seq_id = seq;
> +	}
> +
>  	fio.old_blkaddr = ni.blk_addr;
>  	f2fs_do_write_node_page(nid, &fio);
>  	set_node_addr(sbi, &ni, fio.new_blkaddr, is_fsync_dnode(page));
> @@ -1489,7 +1564,7 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>  			goto out_page;
>  
>  		if (__write_node_page(node_page, false, NULL,
> -					&wbc, false, FS_GC_NODE_IO))
> +					&wbc, false, FS_GC_NODE_IO, NULL))
>  			unlock_page(node_page);
>  		goto release_page;
>  	} else {
> @@ -1506,11 +1581,13 @@ void f2fs_move_node_page(struct page *node_page, int gc_type)
>  static int f2fs_write_node_page(struct page *page,
>  				struct writeback_control *wbc)
>  {
> -	return __write_node_page(page, false, NULL, wbc, false, FS_NODE_IO);
> +	return __write_node_page(page, false, NULL, wbc, false,
> +						FS_NODE_IO, NULL);
>  }
>  
>  int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
> -			struct writeback_control *wbc, bool atomic)
> +			struct writeback_control *wbc, bool atomic,
> +			unsigned int *seq_id)
>  {
>  	pgoff_t index;
>  	pgoff_t last_idx = ULONG_MAX;
> @@ -1591,7 +1668,7 @@ int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>  			ret = __write_node_page(page, atomic &&
>  						page == last_page,
>  						&submitted, wbc, true,
> -						FS_NODE_IO);
> +						FS_NODE_IO, seq_id);
>  			if (ret) {
>  				unlock_page(page);
>  				f2fs_put_page(last_page, 0);
> @@ -1708,7 +1785,7 @@ int f2fs_sync_node_pages(struct f2fs_sb_info *sbi,
>  			set_dentry_mark(page, 0);
>  
>  			ret = __write_node_page(page, false, &submitted,
> -						wbc, do_balance, io_type);
> +						wbc, do_balance, io_type, NULL);
>  			if (ret)
>  				unlock_page(page);
>  			else if (submitted)
> @@ -1739,35 +1816,46 @@ int f2fs_sync_node_pages(struct f2fs_sb_info *sbi,
>  	return ret;
>  }
>  
> -int f2fs_wait_on_node_pages_writeback(struct f2fs_sb_info *sbi, nid_t ino)
> +int f2fs_wait_on_node_pages_writeback(struct f2fs_sb_info *sbi,
> +						unsigned int seq_id)
>  {
> -	pgoff_t index = 0;
> -	struct pagevec pvec;
> +	struct fsync_node_entry *fn;
> +	struct page *page;
> +	struct list_head *head = &sbi->fsync_node_list;
> +	unsigned long flags;
> +	unsigned int cur_seq_id = 0;
>  	int ret2, ret = 0;
> -	int nr_pages;
>  
> -	pagevec_init(&pvec);
> +	while (seq_id && cur_seq_id < seq_id) {
> +		spin_lock_irqsave(&sbi->fsync_node_lock, flags);
> +		if (list_empty(head)) {
> +			spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
> +			break;
> +		}
> +		fn = list_first_entry(head, struct fsync_node_entry, list);
> +		if (fn->seq_id > seq_id) {
> +			spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
> +			break;
> +		}
> +		cur_seq_id = fn->seq_id;
> +		page = fn->page;
> +		get_page(page);
> +		spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
>  
> -	while ((nr_pages = pagevec_lookup_tag(&pvec, NODE_MAPPING(sbi), &index,
> -				PAGECACHE_TAG_WRITEBACK))) {
> -		int i;
> +		f2fs_wait_on_page_writeback(page, NODE, true);
> +		if (TestClearPageError(page))
> +			ret = -EIO;
>  
> -		for (i = 0; i < nr_pages; i++) {
> -			struct page *page = pvec.pages[i];
> +		put_page(page);
>  
> -			if (ino && ino_of_node(page) == ino) {
> -				f2fs_wait_on_page_writeback(page, NODE, true);
> -				if (TestClearPageError(page))
> -					ret = -EIO;
> -			}
> -		}
> -		pagevec_release(&pvec);
> -		cond_resched();
> +		if (ret)
> +			break;
>  	}
>  
>  	ret2 = filemap_check_errors(NODE_MAPPING(sbi));
>  	if (!ret)
>  		ret = ret2;
> +
>  	return ret;
>  }
>  
> @@ -2982,8 +3070,15 @@ int __init f2fs_create_node_manager_caches(void)
>  			sizeof(struct nat_entry_set));
>  	if (!nat_entry_set_slab)
>  		goto destroy_free_nid;
> +
> +	fsync_node_entry_slab = f2fs_kmem_cache_create("fsync_node_entry",
> +			sizeof(struct fsync_node_entry));
> +	if (!fsync_node_entry_slab)
> +		goto destroy_nat_entry_set;
>  	return 0;
>  
> +destroy_nat_entry_set:
> +	kmem_cache_destroy(nat_entry_set_slab);
>  destroy_free_nid:
>  	kmem_cache_destroy(free_nid_slab);
>  destroy_nat_entry:
> @@ -2994,6 +3089,7 @@ int __init f2fs_create_node_manager_caches(void)
>  
>  void f2fs_destroy_node_manager_caches(void)
>  {
> +	kmem_cache_destroy(fsync_node_entry_slab);
>  	kmem_cache_destroy(nat_entry_set_slab);
>  	kmem_cache_destroy(free_nid_slab);
>  	kmem_cache_destroy(nat_entry_slab);
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 0eff4637fe55..cb1ba9f18353 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -1030,6 +1030,8 @@ static void f2fs_put_super(struct super_block *sb)
>  	 */
>  	f2fs_release_ino_entry(sbi, true);
>  
> +	f2fs_bug_on(sbi, sbi->fsync_node_num);
> +
>  	f2fs_leave_shrinker(sbi);
>  	mutex_unlock(&sbi->umount_mutex);
>  
> @@ -2923,6 +2925,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  
>  	f2fs_init_ino_entry_info(sbi);
>  
> +	f2fs_init_fsync_node_info(sbi);
> +
>  	/* setup f2fs internal modules */
>  	err = f2fs_build_segment_manager(sbi);
>  	if (err) {
> -- 
> 2.18.0.rc1

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