Re: [PATCH 1/3] f2fs: turn off atomic writes when deteting abnormal behaviors

[Chao Yu <yuchao0@huawei.com>]

On 2018/7/15 9:11, Jaegeuk Kim wrote:
> In order to prevent abusing atomic writes by abnormal users, we've added a
> threshold, 20% over memory footprint, which disallows further atomic writes.
> Previously, however, SQLite doesn't know the files became normal, so that
> it could write stale data and commit on revoked normal database file.
> 
> Once f2fs detects such the abnormal behavior, this patch simply disables
> all the atomic operations such as:
> - write_begin() gives EINVAL to avoid stale data writes, and SQLite will call
>   F2FS_IOC_ABORT_VOLATILE_WRITE to notify aborting the transaction,
> - F2FS_IOC_START_ATOMIC_WRITE gives EINVAL for SQLite to fall back normal
>   journal_mode,
> - F2FS_IOC_COMMIT_ATOMIC_WRITE gives EINVAL, if the file was revoked, so that
>   Framework retries to submit the transaction given propagated SQLite error.
> 
> Note that, this patch also turns off atomic operations, if foreground GC tries
> to move atomic files too frequently.

Well, how about just keeping original implementation: shutdown atomic write for
those files which are really affect fggc? Since intention of the original
behavior is targeting to abnormal atomic write usage, e.g. open atomic_write
file for very long time, then fggc will be blocked each time when moving its
block. So shutdown it, fggc will recover.

Thanks,

> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/data.c    |  7 ++++---
>  fs/f2fs/f2fs.h    |  4 ++--
>  fs/f2fs/file.c    |  6 +++++-
>  fs/f2fs/gc.c      |  4 +---
>  fs/f2fs/segment.c | 21 +++++++++++----------
>  5 files changed, 23 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 5e53d210e222..c9e75aa61c24 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2247,8 +2247,9 @@ 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) &&
> -			!f2fs_available_free_memory(sbi, INMEM_PAGES)) {
> -		err = -ENOMEM;
> +			(is_sbi_flag_set(sbi, SBI_DISABLE_ATOMIC_WRITE) ||
> +			!f2fs_available_free_memory(sbi, INMEM_PAGES))) {
> +		err = -EINVAL;
>  		drop_atomic = true;
>  		goto fail;
>  	}
> @@ -2331,7 +2332,7 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
>  	f2fs_put_page(page, 1);
>  	f2fs_write_failed(mapping, pos + len);
>  	if (drop_atomic)
> -		f2fs_drop_inmem_pages_all(sbi, false);
> +		f2fs_disable_atomic_write(sbi);
>  	return err;
>  }
>  
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 4d8b1de83143..1d5c8d543eda 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -621,7 +621,6 @@ enum {
>  
>  enum {
>  	GC_FAILURE_PIN,
> -	GC_FAILURE_ATOMIC,
>  	MAX_GC_FAILURE
>  };
>  
> @@ -1066,6 +1065,7 @@ enum {
>  	SBI_POR_DOING,				/* recovery is doing or not */
>  	SBI_NEED_SB_WRITE,			/* need to recover superblock */
>  	SBI_NEED_CP,				/* need to checkpoint */
> +	SBI_DISABLE_ATOMIC_WRITE,		/* turn off atomic write */
>  };
>  
>  enum {
> @@ -2833,7 +2833,7 @@ void f2fs_destroy_node_manager_caches(void);
>   */
>  bool f2fs_need_SSR(struct f2fs_sb_info *sbi);
>  void f2fs_register_inmem_page(struct inode *inode, struct page *page);
> -void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi, bool gc_failure);
> +void f2fs_disable_atomic_write(struct f2fs_sb_info *sbi);
>  void f2fs_drop_inmem_pages(struct inode *inode);
>  void f2fs_drop_inmem_page(struct inode *inode, struct page *page);
>  int f2fs_commit_inmem_pages(struct inode *inode);
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 6880c6f78d58..b029a4ed3bb0 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1682,6 +1682,9 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
>  	if (!S_ISREG(inode->i_mode))
>  		return -EINVAL;
>  
> +	if (is_sbi_flag_set(F2FS_I_SB(inode), SBI_DISABLE_ATOMIC_WRITE))
> +		return -EINVAL;
> +
>  	ret = mnt_want_write_file(filp);
>  	if (ret)
>  		return ret;
> @@ -1750,7 +1753,6 @@ static int f2fs_ioc_commit_atomic_write(struct file *filp)
>  		ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true);
>  		if (!ret) {
>  			clear_inode_flag(inode, FI_ATOMIC_FILE);
> -			F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
>  			stat_dec_atomic_write(inode);
>  		}
>  	} else {
> @@ -1853,6 +1855,8 @@ static int f2fs_ioc_abort_volatile_write(struct file *filp)
>  		ret = f2fs_do_sync_file(filp, 0, LLONG_MAX, 0, true);
>  	}
>  
> +	clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> +
>  	inode_unlock(inode);
>  
>  	mnt_drop_write_file(filp);
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 9093be6e7a7d..6d762f3cdfc7 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -629,7 +629,6 @@ static void move_data_block(struct inode *inode, block_t bidx,
>  		goto out;
>  
>  	if (f2fs_is_atomic_file(inode)) {
> -		F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>  		F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>  		goto out;
>  	}
> @@ -745,7 +744,6 @@ static void move_data_page(struct inode *inode, block_t bidx, int gc_type,
>  		goto out;
>  
>  	if (f2fs_is_atomic_file(inode)) {
> -		F2FS_I(inode)->i_gc_failures[GC_FAILURE_ATOMIC]++;
>  		F2FS_I_SB(inode)->skipped_atomic_files[gc_type]++;
>  		goto out;
>  	}
> @@ -1100,7 +1098,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
>  		if (has_not_enough_free_secs(sbi, sec_freed, 0)) {
>  			if (skipped_round > MAX_SKIP_ATOMIC_COUNT &&
>  				skipped_round * 2 >= round)
> -				f2fs_drop_inmem_pages_all(sbi, true);
> +				f2fs_disable_atomic_write(sbi);
>  			segno = NULL_SEGNO;
>  			goto gc_more;
>  		}
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 9efce174c51a..05877a2f1894 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -274,11 +274,14 @@ static int __revoke_inmem_pages(struct inode *inode,
>  	return err;
>  }
>  
> -void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi, bool gc_failure)
> +void f2fs_disable_atomic_write(struct f2fs_sb_info *sbi)
>  {
>  	struct list_head *head = &sbi->inode_list[ATOMIC_FILE];
>  	struct inode *inode;
>  	struct f2fs_inode_info *fi;
> +
> +	/* just turn it off */
> +	set_sbi_flag(sbi, SBI_DISABLE_ATOMIC_WRITE);
>  next:
>  	spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
>  	if (list_empty(head)) {
> @@ -290,17 +293,16 @@ void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi, bool gc_failure)
>  	spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>  
>  	if (inode) {
> -		if (gc_failure) {
> -			if (fi->i_gc_failures[GC_FAILURE_ATOMIC])
> -				goto drop;
> -			goto skip;
> +		inode_lock(inode);
> +		/* need to check whether it was already revoked */
> +		if (f2fs_is_atomic_file(inode)) {
> +			f2fs_drop_inmem_pages(inode);
> +			set_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
>  		}
> -drop:
> -		set_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> -		f2fs_drop_inmem_pages(inode);
> +		inode_unlock(inode);
>  		iput(inode);
>  	}
> -skip:
> +
>  	congestion_wait(BLK_RW_ASYNC, HZ/50);
>  	cond_resched();
>  	goto next;
> @@ -320,7 +322,6 @@ void f2fs_drop_inmem_pages(struct inode *inode)
>  	mutex_unlock(&fi->inmem_lock);
>  
>  	clear_inode_flag(inode, FI_ATOMIC_FILE);
> -	fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
>  	stat_dec_atomic_write(inode);
>  }
>  
>