linux-ext4 - Re: [PATCH] ext4,fiemap: Add inode offset for xattr fiemap

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Message-ID: <fcc21a8b-4c53-4755-9747-8e6b83036ecd@huawei.com>
Date: Thu, 18 Dec 2025 09:05:57 +0800
From: "wangjianjian (C)" <wangjianjian3@...wei.com>
To: "Darrick J. Wong" <djwong@...nel.org>
CC: <tytso@....edu>, <linux-ext4@...r.kernel.org>, <wangjianjian0@...mail.com>
Subject: Re: [PATCH] ext4,fiemap: Add inode offset for xattr fiemap

On 2025/12/18 0:35, Darrick J. Wong wrote:
> On Wed, Dec 17, 2025 at 04:47:08PM +0800, Wang Jianjian wrote:
>> For xattr in inode, need add inode offset in this block?
>> Also, there is one problem, if we have xattrs both in inode
>> and block, current implementation will only return xattr inode fiemap.
>> Is this by design?
> 
> I don't think there's much value in reporting the inline xattrs via
> FIEMAP because user programs can't directly access that area anyway.
> The only reason (AFAICT) for reporting the external xattr block is for
> building a map of lost data given a report of localized media failure.
yes, I agree with this. however, current behavior is it will always 
reporting inline xattr first. Do you think we should fix this?
> 
> (FIEMAP only being useful for debugging and after-the-shatter forensics)
> 
>> Signed-off-by: Wang Jianjian <wangjianjian3@...wei.com>
>> ---
>>   fs/ext4/extents.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 2cf5759ba689..a16bfc75345d 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -5043,6 +5043,7 @@ static int ext4_iomap_xattr_fiemap(struct inode *inode, struct iomap *iomap)
>>   		if (error)
>>   			return error;
>>   		physical = (__u64)iloc.bh->b_blocknr << blockbits;
>> +		physical += iloc.offset;
> 
> Also it doesn't make sense to add the address of the external block to
> the inode offset.
IIUC, bh is the buffer head of the inode is in and iloc.offset is its 
offset of this block.
> 
> --D
> 
>>   		offset = EXT4_GOOD_OLD_INODE_SIZE +
>>   				EXT4_I(inode)->i_extra_isize;
>>   		physical += offset;
>> -- 
>> 2.34.1
>>
>>
-- 
Regards