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

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Message-ID: <f9cf5992-0357-4702-be73-881c9997929d@gmail.com>
Date: Wed, 29 Oct 2025 16:09:44 +0800
From: Yongpeng Yang <yangyongpeng.storage@...il.com>
To: Chao Yu <chao@...nel.org>, jaegeuk@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
 Yongpeng Yang <yangyongpeng@...omi.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix to access i_size w/ i_size_read()

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.

Yongpeng,