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

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Date: Thu, 28 Dec 2023 23:33:37 +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 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);

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