Date:   Fri, 27 Oct 2017 10:13:47 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>
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 2017/10/26 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))) {
		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)) {
		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
		 * 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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