linux-ext4 - Re: [PATCH] ext4: swap i_disksize when swaping the boot loader inode

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Date:   Wed, 8 Mar 2023 14:15:49 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     Theodore Ts'o <tytso@....edu>, <bugzilla-daemon@...nel.org>
CC:     <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: swap i_disksize when swaping the boot loader inode

Hi Ted,

> The following patch fixes the reported issue.
> 
>>>From f4e156cef119f3ffcc56874da4fb9299cc14f68e Mon Sep 17 00:00:00 2001
> From: Theodore Ts'o <tytso@....edu>
> Date: Tue, 7 Mar 2023 23:06:59 -0500
> Subject: [PATCH] ext4: swap i_disksize when swaping the boot loader inode
> 
> Normally well-behaved of EXT4_IOC_SWAP_BOOT won't actually try to
> write to the either inode after using the ioctl, but if they do, the
> fact that we're not swapping ei->i_disksize as well as inode->i_size
> can trigger warnings.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217159
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
>   fs/ext4/ioctl.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index 2e8c34036313..e552c5db0c95 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -329,9 +329,13 @@ static void swap_inode_data(struct inode *inode1, struct inode *inode2)

Shall we drop the redundant assignments 'swap(ei1->i_disksize, 
ei2->i_disksize);' ?

>   	ext4_es_remove_extent(inode1, 0, EXT_MAX_BLOCKS);
>   	ext4_es_remove_extent(inode2, 0, EXT_MAX_BLOCKS);
>   
> -	isize = i_size_read(inode1);
> -	i_size_write(inode1, i_size_read(inode2));
> -	i_size_write(inode2, isize);
> +	/*
> +	 * Both inodes are locked, so we don't need to fool around
> +	 * with i_size_read() and i_size_write().
> +	 */
> +	isize = inode1->i_size;
> +	inode1->i_size = ei1->i_disksize = inode2->i_size;
> +	inode2->i_size = ei2->i_disksize = isize;
>   }
>   
>   void ext4_reset_inode_seed(struct inode *inode)
>