linux-ext4 - Re: [PATCH v2 3/4] ext4: don't return error if huge

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Date:   Thu, 19 Aug 2021 12:26:14 +0200
From:   Jan Kara <jack@...e.cz>
To:     Zhang Yi <yi.zhang@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, yukuai3@...wei.com
Subject: Re: [PATCH v2 3/4] ext4: don't return error if huge_file feature
 mismatch

On Thu 19-08-21 14:57:03, Zhang Yi wrote:
> In ext4_inode_blocks_set(), huge_file feature should exist when setting
> i_blocks beyond a 32 bit variable could be represented, return EFBIG if
> not. This error should never happen in theory since sb->s_maxbytes should
> not have allowed this, and we have already init sb->s_maxbytes according
> to this feature in ext4_fill_super(). So switch to use WARN_ON_ONCE
> instead.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
> ---

One comment below:

> @@ -4918,10 +4918,15 @@ static int ext4_inode_blocks_set(handle_t *handle,
>  		raw_inode->i_blocks_lo   = cpu_to_le32(i_blocks);
>  		raw_inode->i_blocks_high = 0;
>  		ext4_clear_inode_flag(inode, EXT4_INODE_HUGE_FILE);
> -		return 0;
> +		return;
>  	}
> -	if (!ext4_has_feature_huge_file(sb))
> -		return -EFBIG;
> +
> +	/*
> +	 * This should never happen since sb->s_maxbytes should not have
> +	 * allowed this, which was set according to the huge_file feature
> +	 * in ext4_fill_super().
> +	 */
> +	WARN_ON_ONCE(!ext4_has_feature_huge_file(sb));

Thinking about this a bit more, this could also happen due to fs
corruption. So we probably need to call ext4_error_inode() here instead of
WARN_ON_ONCE(). Also it will result in properly marking fs as having
errors. But since we hold i_raw_lock at this call site we need to
keep the error bail out from ext4_inode_blocks_set() and in
ext4_do_update_inode() finish updating inode and then call
ext4_error_inode() after dropping i_raw_lock.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR