linux-kernel - Re: [PATCH 5/6] f2fs: fix to restrict condition of compress inode conversion

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Message-ID: <f63d88a2-bc51-4383-a713-09063ec84d99@kernel.org>
Date: Thu, 11 Jan 2024 11:07:24 +0800
From: Chao Yu <chao@...nel.org>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] f2fs: fix to restrict condition of compress inode
 conversion

On 2024/1/3 6:54, Jaegeuk Kim wrote:
> On 12/28, Chao Yu wrote:
>> On 2023/12/13 6:21, Jaegeuk Kim wrote:
>>> On 12/12, Chao Yu wrote:
>>>> On 2023/12/12 6:11, Jaegeuk Kim wrote:
>>>>> On 12/10, Chao Yu wrote:
>>>>>> This patch adds i_size check during compress inode conversion in order
>>>>>> to avoid .page_mkwrite races w/ conversion.
>>>>>
>>>>> Which race condition do you see?
>>>>
>>>> Something like:
>>>>
>>>> - f2fs_setflags_common
>>>>    - check S_ISREG && F2FS_HAS_BLOCKS
>>>> 					- mkwrite
>>>> 					 - f2fs_get_block_locked
>>>> 					  : update metadata in old inode's disk layout
>>>
>>> Don't we need to prevent setting this for mmapped file?
>>
>> Oh, we have used i_sem lock to prevent such race case, however
>> we missed f2fs_disable_compressed_file():
>>
>> - f2fs_disable_compressed_file
>>   - check inode_has_data
>> 						- f2fs_file_mmap
>> 						- mkwrite
>> 						 - f2fs_get_block_locked
>> 						 : update metadata in compressed
>> 						   inode's disk layout
>>   - fi->i_flags &= ~F2FS_COMPR_FL
>>   - clear_inode_flag(inode, FI_COMPRESSED_FILE);
> 
> So, needing i_sem for disabling it on mmapped file? It seems i_size would not
> be enough?

Agreed, let me update the patch.

Thanks,

> 
>>
>> Thanks,
>>
>>>
>>>>    - set_compress_context
>>>>
>>>> Thanks,
>>>>
>>>>>
>>>>>>
>>>>>> Fixes: 4c8ff7095bef ("f2fs: support data compression")
>>>>>> Signed-off-by: Chao Yu <chao@...nel.org>
>>>>>> ---
>>>>>>     fs/f2fs/f2fs.h | 8 +++++++-
>>>>>>     fs/f2fs/file.c | 5 ++---
>>>>>>     2 files changed, 9 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>> index 65294e3b0bef..c9b8a1953913 100644
>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>> @@ -4397,13 +4397,19 @@ static inline int set_compress_context(struct inode *inode)
>>>>>>     #endif
>>>>>>     }
>>>>>> +static inline bool inode_has_data(struct inode *inode)
>>>>>> +{
>>>>>> +	return (S_ISREG(inode->i_mode) &&
>>>>>> +		(F2FS_HAS_BLOCKS(inode) || i_size_read(inode)));
>>>>>> +}
>>>>>> +
>>>>>>     static inline bool f2fs_disable_compressed_file(struct inode *inode)
>>>>>>     {
>>>>>>     	struct f2fs_inode_info *fi = F2FS_I(inode);
>>>>>>     	if (!f2fs_compressed_file(inode))
>>>>>>     		return true;
>>>>>> -	if (S_ISREG(inode->i_mode) && F2FS_HAS_BLOCKS(inode))
>>>>>> +	if (inode_has_data(inode))
>>>>>>     		return false;
>>>>>>     	fi->i_flags &= ~F2FS_COMPR_FL;
>>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>>> index 1a3c29a9a6a0..8af4b29c3e1a 100644
>>>>>> --- a/fs/f2fs/file.c
>>>>>> +++ b/fs/f2fs/file.c
>>>>>> @@ -1922,8 +1922,7 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
>>>>>>     			f2fs_down_write(&F2FS_I(inode)->i_sem);
>>>>>>     			if (!f2fs_may_compress(inode) ||
>>>>>> -					(S_ISREG(inode->i_mode) &&
>>>>>> -					F2FS_HAS_BLOCKS(inode))) {
>>>>>> +					inode_has_data(inode)) {
>>>>>>     				f2fs_up_write(&F2FS_I(inode)->i_sem);
>>>>>>     				return -EINVAL;
>>>>>>     			}
>>>>>> @@ -3996,7 +3995,7 @@ static int f2fs_ioc_set_compress_option(struct file *filp, unsigned long arg)
>>>>>>     		goto out;
>>>>>>     	}
>>>>>> -	if (F2FS_HAS_BLOCKS(inode)) {
>>>>>> +	if (inode_has_data(inode)) {
>>>>>>     		ret = -EFBIG;
>>>>>>     		goto out;
>>>>>>     	}
>>>>>> -- 
>>>>>> 2.40.1