Date:   Fri, 27 Oct 2017 19:16:35 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: fix to keep backward compatibility of flexible
 inline xattr feature

On 2017/10/27 18:56, Jaegeuk Kim wrote:
> On 10/27, Chao Yu wrote:
>> On 2017/10/26 22:05, Jaegeuk Kim wrote:
>>> On 10/26, Chao Yu wrote:
>>>> On 2017/10/26 19:52, Jaegeuk Kim wrote:
>>>>> On 10/26, Chao Yu wrote:
>>>>>> Hi Jaegeuk,
>>>>>>
>>>>>> On 2017/10/26 18:02, Jaegeuk Kim wrote:
>>>>>>> Hi Chao,
>>>>>>>
>>>>>>> On 10/26, Jaegeuk Kim wrote:
>>>>>>>> On 10/26, Chao Yu wrote:
>>>>>>>>> Hi Jaegeuk,
>>>>>>>>>
>>>>>>>>> On 2017/10/26 16:42, Jaegeuk Kim wrote:
>>>>>>>>>> Hi Chao,
>>>>>>>>>>
>>>>>>>>>> It seems this is a critical problem, so let me integrate this patch with your
>>>>>>>>>> initial patch "f2fs: support flexible inline xattr size".
>>>>>>>>>> Let me know, if you have any other concern.
>>>>>>>>>
>>>>>>>>> Better. ;)
>>>>>>>>>
>>>>>>>>> Please add commit message of this patch into initial patch "f2fs: support
>>>>>>>>> flexible inline xattr size".
>>>>>>>
>>>>>>> BTW, I read the patch again, and couldn't catch the problem actually.
>>>>>>> We didn't assign inline_xattr all the time, instead do if inline_xattr
>>>>>>
>>>>>> But you can see, MAX_INLINE_DATA is calculated as below, in where we will always
>>>>>> reserve F2FS_INLINE_XATTR_ADDRS of 200 bytes, now we will change
>>>>>> F2FS_INLINE_XATTR_ADDRS to F2FS_INLINE_XATTR_ADDRS(inode) which is an flexible
>>>>>> size, so MAX_INLINE_DATA could be calculated to expand 200 bytes than before,
>>>>>
>>>>> That doesn't mean inline_addr is starting after 200 bytes. We're getting the
>>>>> address only if inline_xattr is set, no? The below size seems reserving the
>>>>
>>>> This isn't about inline_xattr_addr, it is about MAX_INLINE_DATA size calculation.
>>>>
>>>> For example, in old image, inode is with inline_{data,dentry} flag, but without
>>>> inline_xattr flag, it will only use 3688 - 200 bytes for storing inline data/dents,
>>>> which means, it reserves 200 bytes.
>>>>
>>>> If we update kernel, get_inline_xattr_addrs will return 0 if inline_xattr flag is not
>>>> set, so MAX_INLINE_DATA will be 3688, then inline_dentry page layout will change.
>>>
>>> Thanks. This makes much clear to me. It seems we need to handle directory only.
>>> Could you please check the dev-test branches in f2fs and f2fs-tools?
>>
>> This is a little complicated, as for non-inline_{data,dentry} inode, we will get
>> addrs number in inode by:
>>
>> static inline unsigned int addrs_per_inode(struct inode *inode)
>> {
>> 	if (f2fs_has_inline_xattr(inode))
>> 		return CUR_ADDRS_PER_INODE(inode) - F2FS_INLINE_XATTR_ADDRS;
>> 	return CUR_ADDRS_PER_INODE(inode);
>> }
>>
>> It only cares about this inode is inline_xattr or not, so, if we reserve 200
>> bytes for dir inode, it will cause incompatibility.
>>
>> So we need add this logic into i_inline_xattr_size calculation? Such as:
>>
>> a. new_inode:
>>
>> 	if (f2fs_sb_has_flexible_inline_xattr(sbi->sb)) {
>> 		f2fs_bug_on(sbi, !f2fs_has_extra_attr(inode));
>> 		if (f2fs_has_inline_xattr)
>> 			xattr_size = sbi->inline_xattr_size;
>> 	} else if (f2fs_has_inline_xattr(inode) ||
>> 			(f2fs_has_inline_dentry(inode) && S_ISDIR(inode->i_mode))) {
> 
> We don't need to check both of them. It'd be enough to check
> f2fs_has_inline_dentry(inode).

Agreed.

> 
>> 		xattr = DEFAULT_INLINE_XATTR_ADDRS
>> 	}
>> 	F2FS_I(inode)->i_inline_xattr_size = xattr_size;
>>
>> b. do_read_inode
>>
>> 	if (f2fs_sb_has_flexible_inline_xattr(sbi->sb)) {
>> 		f2fs_bug_on(sbi, !f2fs_has_extra_attr(inode));
>> 		fi->i_inline_xattr_size = le16_to_cpu(ri->i_inline_xattr_size);
>> 	} else if (f2fs_has_inline_xattr(inode) ||
>> 			(f2fs_has_inline_dentry(inode) && S_ISDIR(inode->i_mode)) {
> 
> Ditto.
> 
> I merged the change in dev-test, so could you check that out again? ;)
> 
> Thanks,
> 
>> 		fi->i_inline_xattr_size = DEFAULT_INLINE_XATTR_ADDRS;
>> 	} else {
>> 		/*
>> 		 * Previous inline_data always reserved 200 bytes, even if
>> 		 * inline_xattr is disabled. But only inline_data is safe

Minor thing, how about:

	/*
	 * Previous inline data or directory always reserved 200 bytes in
	 * inode layout, even if inline_xattr is disabled, in order to
	 * stablize inline dentry's structure for backward compatibility,
	 * we only get back reserved space for inline data.
	 */

Otherwise code in dev-test looks good to me. ;)

Thanks,

>> 		 * to get back the space.
>> 		 */
>> 		fi->i_inline_xattr_size = 0;
>> 	}
>>
>> How about this? IMO, it's better to keep codes similar in between new_inode
>> and do_read_inode. :)
>>
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Thanks,
>>>>
>>>>> last 200 bytes which we just didn't use fully before.
>>>>>
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>> It is okay for regular or symlink inode generated in old kernel to enlarge
>>>>>> MAX_INLINE_DATA in new kernel, as reserved 200 bytes in inode are zero all the
>>>>>> time, for directory, it will be problematic because our layout of inline
>>>>>> dentry page is fixed and calculated according to MAX_INLINE_DATA, so if
>>>>>> MAX_INLINE_DATA is enlarged, fields offset in dentry structure will relocate,
>>>>>> result in incompatibility.
>>>>>>
>>>>>> #define MAX_INLINE_DATA(inode)	(sizeof(__le32) * \
>>>>>> 				(CUR_ADDRS_PER_INODE(inode) - \
>>>>>> 				DEF_INLINE_RESERVED_SIZE - \
>>>>>> 				F2FS_INLINE_XATTR_ADDRS))
>>>>>>
>>>>>>> is set. Have you done some tests with this? I'm failing tests with these
>>>>>>> changes.
>>>>>>
>>>>>> Oh, sorry, I just tested with this patch without the modification of f2fs-tools,
>>>>>> fstest didn't report any errors so far.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>>
>>>>>>>>>
>>>>>>>>> And please fix related issue in f2fs-tools with below diff code:
>>>>>>>>
>>>>>>>> Okay, merged.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>>>
>>>>>>>>> ---
>>>>>>>>>  include/f2fs_fs.h | 9 ++++++---
>>>>>>>>>  1 file changed, 6 insertions(+), 3 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
>>>>>>>>> index 2db7495804fd..a0e15ba85d97 100644
>>>>>>>>> --- a/include/f2fs_fs.h
>>>>>>>>> +++ b/include/f2fs_fs.h
>>>>>>>>> @@ -1047,11 +1047,14 @@ static inline int __get_extra_isize(struct f2fs_inode *inode)
>>>>>>>>>  extern struct f2fs_configuration c;
>>>>>>>>>  static inline int get_inline_xattr_addrs(struct f2fs_inode *inode)
>>>>>>>>>  {
>>>>>>>>> -	if (!(inode->i_inline & F2FS_INLINE_XATTR))
>>>>>>>>> +	if ((c.feature & cpu_to_le32(F2FS_FEATURE_EXTRA_ATTR)) &&
>>>>>>>>> +		(c.feature & cpu_to_le32(F2FS_FEATURE_FLEXIBLE_INLINE_XATTR)))
>>>>>>>>> +		return le16_to_cpu(inode->i_inline_xattr_size);
>>>>>>>>> +	else if (!(inode->i_inline & F2FS_INLINE_XATTR) &&
>>>>>>>>> +		(S_ISREG(inode->i_mode) || S_ISLNK(inode->i_mode)))
>>>>>>>>>  		return 0;
>>>>>>>>> -	if (!(c.feature & cpu_to_le32(F2FS_FEATURE_FLEXIBLE_INLINE_XATTR)))
>>>>>>>>> +	else
>>>>>>>>>  		return DEFAULT_INLINE_XATTR_ADDRS;
>>>>>>>>> -	return le16_to_cpu(inode->i_inline_xattr_size);
>>>>>>>>>  }
>>>>>>>>>
>>>>>>>>>  #define get_extra_isize(node)	__get_extra_isize(&node->i)
>>>>>>>>> -- 
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>>
>>>>>>>>>> On 10/25, Chao Yu wrote:
>>>>>>>>>>> Previously, in inode layout, we will always reserve 200 bytes for inline
>>>>>>>>>>> xattr space no matter the inode enables inline xattr feature or not, due
>>>>>>>>>>> to this reason, max inline size of inode is fixed, but now, if inline
>>>>>>>>>>> xattr is not enabled, max inline size of inode will be enlarged by 200
>>>>>>>>>>> bytes, for regular and symlink inode, it will be safe to reuse resevered
>>>>>>>>>>> space as they are all zero, but for directory, we need to keep the
>>>>>>>>>>> reservation for stablizing directory structure.
>>>>>>>>>>>
>>>>>>>>>>> Reported-by: Sheng Yong <shengyong1@...wei.com>
>>>>>>>>>>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>>>>>>>>>>> ---
>>>>>>>>>>>  fs/f2fs/f2fs.h  |  5 +----
>>>>>>>>>>>  fs/f2fs/inode.c | 15 ++++++++++++---
>>>>>>>>>>>  fs/f2fs/namei.c |  2 ++
>>>>>>>>>>>  3 files changed, 15 insertions(+), 7 deletions(-)
>>>>>>>>>>>
>>>>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>>>>>> index 2af1d31ae74b..7ddd0d085e3b 100644
>>>>>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>>>>>> @@ -2393,10 +2393,7 @@ static inline int get_extra_isize(struct inode *inode)
>>>>>>>>>>>  static inline int f2fs_sb_has_flexible_inline_xattr(struct super_block *sb);
>>>>>>>>>>>  static inline int get_inline_xattr_addrs(struct inode *inode)
>>>>>>>>>>>  {
>>>>>>>>>>> -	if (!f2fs_has_inline_xattr(inode))
>>>>>>>>>>> -		return 0;
>>>>>>>>>>> -	if (!f2fs_sb_has_flexible_inline_xattr(F2FS_I_SB(inode)->sb))
>>>>>>>>>>> -		return DEFAULT_INLINE_XATTR_ADDRS;
>>>>>>>>>>> +
>>>>>>>>>>>  	return F2FS_I(inode)->i_inline_xattr_size;
>>>>>>>>>>>  }
>>>>>>>>>>>  
>>>>>>>>>>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>>>>>>>>>>> index bb876737e653..7f31b22c9efa 100644
>>>>>>>>>>> --- a/fs/f2fs/inode.c
>>>>>>>>>>> +++ b/fs/f2fs/inode.c
>>>>>>>>>>> @@ -232,10 +232,19 @@ static int do_read_inode(struct inode *inode)
>>>>>>>>>>>  	fi->i_extra_isize = f2fs_has_extra_attr(inode) ?
>>>>>>>>>>>  					le16_to_cpu(ri->i_extra_isize) : 0;
>>>>>>>>>>>  
>>>>>>>>>>> -	if (!f2fs_has_inline_xattr(inode))
>>>>>>>>>>> -		fi->i_inline_xattr_size = 0;
>>>>>>>>>>> -	else if (f2fs_sb_has_flexible_inline_xattr(sbi->sb))
>>>>>>>>>>> +	/*
>>>>>>>>>>> +	 * Previously, we will always reserve DEFAULT_INLINE_XATTR_ADDRS size
>>>>>>>>>>> +	 * space for inline xattr datas, if inline xattr is not enabled, we
>>>>>>>>>>> +	 * can expect all zero in reserved area, so for regular or symlink,
>>>>>>>>>>> +	 * it will be safe to reuse reserved area, but for directory, we
>>>>>>>>>>> +	 * should keep the reservation for stablizing directory structure.
>>>>>>>>>>> +	 */
>>>>>>>>>>> +	if (f2fs_has_extra_attr(inode) &&
>>>>>>>>>>> +		f2fs_sb_has_flexible_inline_xattr(sbi->sb))
>>>>>>>>>>>  		fi->i_inline_xattr_size = le16_to_cpu(ri->i_inline_xattr_size);
>>>>>>>>>>> +	else if (!f2fs_has_inline_xattr(inode) &&
>>>>>>>>>>> +		(S_ISREG(inode->i_mode) || S_ISLNK(inode->i_mode)))
>>>>>>>>>>> +		fi->i_inline_xattr_size = 0;
>>>>>>>>>>>  	else
>>>>>>>>>>>  		fi->i_inline_xattr_size = DEFAULT_INLINE_XATTR_ADDRS;
>>>>>>>>>>>  
>>>>>>>>>>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
>>>>>>>>>>> index e6f86d5d97b9..a1c56a14c191 100644
>>>>>>>>>>> --- a/fs/f2fs/namei.c
>>>>>>>>>>> +++ b/fs/f2fs/namei.c
>>>>>>>>>>> @@ -91,6 +91,8 @@ static struct inode *f2fs_new_inode(struct inode *dir, umode_t mode)
>>>>>>>>>>>  		f2fs_sb_has_flexible_inline_xattr(sbi->sb) &&
>>>>>>>>>>>  		f2fs_has_inline_xattr(inode))
>>>>>>>>>>>  		F2FS_I(inode)->i_inline_xattr_size = sbi->inline_xattr_size;
>>>>>>>>>>> +	else
>>>>>>>>>>> +		F2FS_I(inode)->i_inline_xattr_size = 0;
>>>>>>>>>>>  
>>>>>>>>>>>  	if (test_opt(sbi, INLINE_DATA) && f2fs_may_inline_data(inode))
>>>>>>>>>>>  		set_inode_flag(inode, FI_INLINE_DATA);
>>>>>>>>>>> -- 
>>>>>>>>>>> 2.13.1.388.g69e6b9b4f4a9
>>>>>>>>>>
>>>>>>>>>> .
>>>>>>>>>>
>>>
>>> .
>>>

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