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

[Chao Yu]

On 2018/7/23 21:03, Jaegeuk Kim wrote:
> On 07/16, Chao Yu wrote:
>> 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 - F2FS_IOC_COMMIT_ATOMIC_WRITE gives EINVAL, if the file was revoked, so that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.
> 
> The point here is stopping sqlite to keep going wrong data writes even after
> we already revoked blocks.

Yes, that's correct, what I mean is that if we can do that with smaller
granularity like just revoke blocks for file which is blocking fggc, it will
affect system/sqlite flow much less than forcing closing all atomic_write.

Thanks,

> 
> Thanks,
> 
>>
>> Thanks,
>>
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
>>> ---
>>>  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);
>>>  }
>>>  
>>>
> 
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