linux-kernel - Re: [PATCH v2 2/4] ext4: fix incorrect punch max

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Message-ID: <a40b2f88-8590-485b-9542-3a7b120a1b17@huawei.com>
Date: Tue, 6 May 2025 15:39:27 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Zhang Yi <yi.zhang@...weicloud.com>
CC: <linux-ext4@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <tytso@....edu>, <adilger.kernel@...ger.ca>,
	<jack@...e.cz>, <wanghaichi0403@...il.com>, <yi.zhang@...wei.com>,
	<yukuai3@...wei.com>, <yangerkun@...wei.com>
Subject: Re: [PATCH v2 2/4] ext4: fix incorrect punch max_end

On 2025/5/6 9:20, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
>
> For the extents based inodes, the maxbytes should be sb->s_maxbytes
> instead of sbi->s_bitmap_maxbytes. Additionally, for the calculation of
> max_end, the -sb->s_blocksize operation is necessary only for
> indirect-block based inodes. Correct the maxbytes and max_end value to
> correct the behavior of punch hole.
>
> Fixes: 2da376228a24 ("ext4: limit length to bitmap_maxbytes - blocksize in punch_hole")
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
Looks good to me.

Reviewed-by: Baokun Li <libaokun1@...wei.com>
> ---
>   fs/ext4/inode.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 4ec4a80b6879..5691966a19e1 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4006,7 +4006,7 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
>   	struct inode *inode = file_inode(file);
>   	struct super_block *sb = inode->i_sb;
>   	ext4_lblk_t start_lblk, end_lblk;
> -	loff_t max_end = EXT4_SB(sb)->s_bitmap_maxbytes - sb->s_blocksize;
> +	loff_t max_end = sb->s_maxbytes;
>   	loff_t end = offset + length;
>   	handle_t *handle;
>   	unsigned int credits;
> @@ -4015,14 +4015,20 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
>   	trace_ext4_punch_hole(inode, offset, length, 0);
>   	WARN_ON_ONCE(!inode_is_locked(inode));
>   
> +	/*
> +	 * For indirect-block based inodes, make sure that the hole within
> +	 * one block before last range.
> +	 */
> +	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
> +		max_end = EXT4_SB(sb)->s_bitmap_maxbytes - sb->s_blocksize;
> +
>   	/* No need to punch hole beyond i_size */
>   	if (offset >= inode->i_size || offset >= max_end)
>   		return 0;
>   
>   	/*
>   	 * If the hole extends beyond i_size, set the hole to end after
> -	 * the page that contains i_size, and also make sure that the hole
> -	 * within one block before last range.
> +	 * the page that contains i_size.
>   	 */
>   	if (end > inode->i_size)
>   		end = round_up(inode->i_size, PAGE_SIZE);