linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: fix to access i_size w/ i_size

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Message-ID: <130dbea7-01fc-44dd-927e-197badf57450@gmail.com>
Date: Wed, 29 Oct 2025 19:12:45 +0800
From: Yongpeng Yang <yangyongpeng.storage@...il.com>
To: Chao Yu <chao@...nel.org>, Yongpeng Yang
 <yangyongpeng.storage@...il.com>, jaegeuk@...nel.org
Cc: Yongpeng Yang <yangyongpeng@...omi.com>, linux-kernel@...r.kernel.org,
 linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix to access i_size w/ i_size_read()

On 10/29/25 17:41, Chao Yu via Linux-f2fs-devel wrote:
> On 10/29/25 16:09, Yongpeng Yang wrote:
>> On 10/29/25 14:31, Chao Yu via Linux-f2fs-devel wrote:
>>> It recommends to use i_size_{read,write}() to access and update i_size,
>>> otherwise, we may get wrong tearing value due to high 32-bits value
>>> and low 32-bits value of i_size field are not updated atomically in
>>> 32-bits archicture machine.
>>>
>>> Signed-off-by: Chao Yu <chao@...nel.org>
>>> ---
>>>    include/trace/events/f2fs.h | 8 ++++----
>>>    1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
>>> index edbbd869078f..e1fae78d64a5 100644
>>> --- a/include/trace/events/f2fs.h
>>> +++ b/include/trace/events/f2fs.h
>>> @@ -204,7 +204,7 @@ DECLARE_EVENT_CLASS(f2fs__inode,
>>>            __entry->pino    = F2FS_I(inode)->i_pino;
>>>            __entry->mode    = inode->i_mode;
>>>            __entry->nlink    = inode->i_nlink;
>>> -        __entry->size    = inode->i_size;
>>> +        __entry->size    = i_size_read(inode);
>>>            __entry->blocks    = inode->i_blocks;
>>>            __entry->advise    = F2FS_I(inode)->i_advise;
>>>        ),
>>> @@ -353,7 +353,7 @@ TRACE_EVENT(f2fs_unlink_enter,
>>>        TP_fast_assign(
>>>            __entry->dev    = dir->i_sb->s_dev;
>>>            __entry->ino    = dir->i_ino;
>>> -        __entry->size    = dir->i_size;
>>> +        __entry->size    = i_size_read(dir);
>>>            __entry->blocks    = dir->i_blocks;
>>>            __assign_str(name);
>>>        ),
>>> @@ -433,7 +433,7 @@ DECLARE_EVENT_CLASS(f2fs__truncate_op,
>>>        TP_fast_assign(
>>>            __entry->dev    = inode->i_sb->s_dev;
>>>            __entry->ino    = inode->i_ino;
>>> -        __entry->size    = inode->i_size;
>>> +        __entry->size    = i_size_read(inode);
>>>            __entry->blocks    = inode->i_blocks;
>>>            __entry->from    = from;
>>>        ),
>>> @@ -1006,7 +1006,7 @@ TRACE_EVENT(f2fs_fallocate,
>>>            __entry->mode    = mode;
>>>            __entry->offset    = offset;
>>>            __entry->len    = len;
>>> -        __entry->size    = inode->i_size;
>>> +        __entry->size    = i_size_read(inode);
>>>            __entry->blocks = inode->i_blocks;
>>>            __entry->ret    = ret;
>>>        ),
>>
>> inode->i_size usage in fs/f2fs/ also needs to be updated. For example in f2fs_need_verity(), which may not protected by inode_lock.
> 
> Accessing i_size directly in f2fs_need_verity() should be fine? Because fsverity
> actived inode should be readonly.

Yes, it's fine.>
> Do you see any other cases which are not covered by inode_lock()?

I checked again, no other cases.:)>
> Thanks,
> 
>>
>> Yongpeng,
> 
> 
> 
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> Linux-f2fs-devel@...ts.sourceforge.net
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