Re: [f2fs-dev] [PATCH] f2fs: limit # of inmemory pages

[Chao Yu]

On 2017/10/19 10:15, Jaegeuk Kim wrote:
> If some abnormal users try lots of atomic write operations, f2fs is able to
> produce pinned pages in the main memory which affects system performance.
> This patch limits that as 20% over total memory size, and if f2fs reaches
> to the limit, it will drop all the inmemory pages.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>

The code looks good to me, but we will fail all atomic writes by telling them
ENOMEM when all atomic write takes 20% memory of total size, but our user may
be confused as there may be lots of free memory, it's hard to let user to
understand this condition...

Atomic commit won't delay much time after atomic writing, so is that due
to incorrect usage of atomic write in application?

Thanks,

> ---
>  fs/f2fs/data.c    |  8 ++++++++
>  fs/f2fs/f2fs.h    |  3 +++
>  fs/f2fs/node.c    |  4 ++++
>  fs/f2fs/node.h    |  1 +
>  fs/f2fs/segment.c | 38 ++++++++++++++++++++++++++++++++++++++
>  fs/f2fs/super.c   |  1 +
>  6 files changed, 55 insertions(+)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 95fdbe3e6cca..7fd09837820a 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1944,6 +1944,12 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
>  
>  	trace_f2fs_write_begin(inode, pos, len, flags);
>  
> +	if (f2fs_is_atomic_file(inode) &&
> +			!available_free_memory(sbi, INMEM_PAGES)) {
> +		err = -ENOMEM;
> +		goto fail;
> +	}
> +
>  	/*
>  	 * We should check this at this moment to avoid deadlock on inode page
>  	 * and #0 page. The locking rule for inline_data conversion should be:
> @@ -2021,6 +2027,8 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
>  fail:
>  	f2fs_put_page(page, 1);
>  	f2fs_write_failed(mapping, pos + len);
> +	if (f2fs_is_atomic_file(inode))
> +		drop_inmem_pages_all(sbi);
>  	return err;
>  }
>  
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index a53fa3dbccf8..e0ef31cb2cc6 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -606,6 +606,7 @@ struct f2fs_inode_info {
>  #endif
>  	struct list_head dirty_list;	/* dirty list for dirs and files */
>  	struct list_head gdirty_list;	/* linked in global dirty list */
> +	struct list_head inmem_ilist;	/* list for inmem inodes */
>  	struct list_head inmem_pages;	/* inmemory pages managed by f2fs */
>  	struct task_struct *inmem_task;	/* store inmemory task */
>  	struct mutex inmem_lock;	/* lock for inmemory pages */
> @@ -971,6 +972,7 @@ enum inode_type {
>  	DIR_INODE,			/* for dirty dir inode */
>  	FILE_INODE,			/* for dirty regular/symlink inode */
>  	DIRTY_META,			/* for all dirtied inode metadata */
> +	ATOMIC_FILE,			/* for all atomic files */
>  	NR_INODE_TYPE,
>  };
>  
> @@ -2556,6 +2558,7 @@ void destroy_node_manager_caches(void);
>   */
>  bool need_SSR(struct f2fs_sb_info *sbi);
>  void register_inmem_page(struct inode *inode, struct page *page);
> +void drop_inmem_pages_all(struct f2fs_sb_info *sbi);
>  void drop_inmem_pages(struct inode *inode);
>  void drop_inmem_page(struct inode *inode, struct page *page);
>  int commit_inmem_pages(struct inode *inode);
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index b95b2784e7d8..ac629d6258ca 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -74,6 +74,10 @@ bool available_free_memory(struct f2fs_sb_info *sbi, int type)
>  				atomic_read(&sbi->total_ext_node) *
>  				sizeof(struct extent_node)) >> PAGE_SHIFT;
>  		res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 1);
> +	} else if (type == INMEM_PAGES) {
> +		/* it allows 20% / total_ram for inmemory pages */
> +		mem_size = get_pages(sbi, F2FS_INMEM_PAGES);
> +		res = mem_size < (val.totalram / 5);
>  	} else {
>  		if (!sbi->sb->s_bdi->wb.dirty_exceeded)
>  			return true;
> diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> index e91b08b4a51a..0ee3e5ff49a3 100644
> --- a/fs/f2fs/node.h
> +++ b/fs/f2fs/node.h
> @@ -140,6 +140,7 @@ enum mem_type {
>  	DIRTY_DENTS,	/* indicates dirty dentry pages */
>  	INO_ENTRIES,	/* indicates inode entries */
>  	EXTENT_CACHE,	/* indicates extent cache */
> +	INMEM_PAGES,	/* indicates inmemory pages */
>  	BASE_CHECK,	/* check kernel status */
>  };
>  
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index bfbcff8339c5..049bbeb8ebff 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -186,6 +186,7 @@ bool need_SSR(struct f2fs_sb_info *sbi)
>  
>  void register_inmem_page(struct inode *inode, struct page *page)
>  {
> +	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>  	struct f2fs_inode_info *fi = F2FS_I(inode);
>  	struct inmem_pages *new;
>  
> @@ -204,6 +205,10 @@ void register_inmem_page(struct inode *inode, struct page *page)
>  	mutex_lock(&fi->inmem_lock);
>  	get_page(page);
>  	list_add_tail(&new->list, &fi->inmem_pages);
> +	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> +	if (list_empty(&fi->inmem_ilist))
> +		list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
> +	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>  	inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
>  	mutex_unlock(&fi->inmem_lock);
>  
> @@ -262,12 +267,41 @@ static int __revoke_inmem_pages(struct inode *inode,
>  	return err;
>  }
>  
> +void drop_inmem_pages_all(struct f2fs_sb_info *sbi)
> +{
> +	struct list_head *head = &sbi->inode_list[ATOMIC_FILE];
> +	struct inode *inode;
> +	struct f2fs_inode_info *fi;
> +next:
> +	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> +	if (list_empty(head)) {
> +		spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> +		return;
> +	}
> +	fi = list_first_entry(head, struct f2fs_inode_info, inmem_ilist);
> +	inode = igrab(&fi->vfs_inode);
> +	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> +
> +	if (inode) {
> +		drop_inmem_pages(inode);
> +		iput(inode);
> +	}
> +	congestion_wait(BLK_RW_ASYNC, HZ/50);
> +	cond_resched();
> +	goto next;
> +}
> +
>  void drop_inmem_pages(struct inode *inode)
>  {
> +	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>  	struct f2fs_inode_info *fi = F2FS_I(inode);
>  
>  	mutex_lock(&fi->inmem_lock);
>  	__revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
> +	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> +	if (!list_empty(&fi->inmem_ilist))
> +		list_del_init(&fi->inmem_ilist);
> +	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>  	mutex_unlock(&fi->inmem_lock);
>  
>  	clear_inode_flag(inode, FI_ATOMIC_FILE);
> @@ -399,6 +433,10 @@ int commit_inmem_pages(struct inode *inode)
>  		/* drop all uncommitted pages */
>  		__revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>  	}
> +	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> +	if (!list_empty(&fi->inmem_ilist))
> +		list_del_init(&fi->inmem_ilist);
> +	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>  	mutex_unlock(&fi->inmem_lock);
>  
>  	clear_inode_flag(inode, FI_ATOMIC_COMMIT);
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 840a0876005b..fc3b74e53670 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -651,6 +651,7 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
>  	init_rwsem(&fi->i_sem);
>  	INIT_LIST_HEAD(&fi->dirty_list);
>  	INIT_LIST_HEAD(&fi->gdirty_list);
> +	INIT_LIST_HEAD(&fi->inmem_ilist);
>  	INIT_LIST_HEAD(&fi->inmem_pages);
>  	mutex_init(&fi->inmem_lock);
>  	init_rwsem(&fi->dio_rwsem[READ]);
>