linux-ext4 - Re: [PATCH -next] ext4: add an update to i_disksize in ext4_block_page

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Message-ID: <f78e3cf5-41b1-4b84-bb25-dc0de03fd30f@huawei.com>
Date: Mon, 1 Sep 2025 15:01:45 +0800
From: Sun Yongjian <sunyongjian1@...wei.com>
To: <linux-ext4@...r.kernel.org>
CC: <yangerkun@...wei.com>, <yi.zhang@...wei.com>, <libaokun1@...wei.com>,
	<tytso@....edu>, <jack@...e.cz>
Subject: Re: [PATCH -next] ext4: add an update to i_disksize in
 ext4_block_page_mkwrite



在 2025/7/31 22:05, sunyongjian@...weicloud.com 写道:
Gentle ping.
> From: Yongjian Sun <sunyongjian1@...wei.com>
> 
> After running a stress test combined with fault injection,
> we performed fsck -a followed by fsck -fn on the filesystem
> image. During the second pass, fsck -fn reported:
> 
> Inode 131512, end of extent exceeds allowed value
> 	(logical block 405, physical block 1180540, len 2)
> 
> This inode was not in the orphan list. Analysis revealed the
> following call chain that leads to the inconsistency:
> 
>                               ext4_da_write_end()
>                                //does not update i_disksize
>                               ext4_punch_hole()
>                                //truncate folio, keep size
> ext4_page_mkwrite()
>   ext4_block_page_mkwrite()
>    ext4_block_write_begin()
>      ext4_get_block()
>       //insert written extent without update i_disksize
> journal commit
> echo 1 > /sys/block/xxx/device/delete
> 
> da-write path updates i_size but does not update i_disksize. Then
> ext4_punch_hole truncates the da-folio yet still leaves i_disksize
> unchanged. Then ext4_page_mkwrite sees ext4_nonda_switch return 1
> and takes the nodioread_nolock path, the folio about to be written
> has just been punched out, and it’s offset sits beyond the current
> i_disksize. This may result in a written extent being inserted, but
> again does not update i_disksize. If the journal gets committed and
> then the block device is yanked, we might run into this.
> 
> To fix this, we now check in ext4_block_page_mkwrite whether
> i_disksize needs to be updated to cover the newly allocated blocks.
> 
> Signed-off-by: Yongjian Sun <sunyongjian1@...wei.com>
> ---
>   fs/ext4/inode.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index ed54c4d0f2f9..050270b265ae 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6666,8 +6666,18 @@ static int ext4_block_page_mkwrite(struct inode *inode, struct folio *folio,
>   		goto out_error;
>   
>   	if (!ext4_should_journal_data(inode)) {
> +		loff_t disksize = folio_pos(folio) + len;
>   		block_commit_write(folio, 0, len);
>   		folio_mark_dirty(folio);
> +		if (disksize > READ_ONCE(EXT4_I(inode)->i_disksize)) {
> +			down_write(&EXT4_I(inode)->i_data_sem);
> +			if (disksize > EXT4_I(inode)->i_disksize)
> +				EXT4_I(inode)->i_disksize = disksize;
> +			up_write(&EXT4_I(inode)->i_data_sem);
> +			ret = ext4_mark_inode_dirty(handle, inode);
> +			if (ret)
> +				goto out_error;
> +		}
>   	} else {
>   		ret = ext4_journal_folio_buffers(handle, folio, len);
>   		if (ret)