linux-ext4 - Re: [PATCH] ext4: Do not zeroout extents beyond i

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Date:   Tue, 31 Mar 2020 15:34:10 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org,
        Dmitry Monakhov <dmonakhov@...nvz.org>, stable@...r.kernel.org
Subject: Re: [PATCH] ext4: Do not zeroout extents beyond i_disksize

On Tue, Mar 31, 2020 at 12:50:16PM +0200, Jan Kara wrote:
> We do not want to create initialized extents beyond end of file because
> for e2fsck it is impossible to distinguish them from a case of corrupted
> file size / extent tree and so it complains like:
> 
> Inode 12, i_size is 147456, should be 163840.  Fix? no
> 
> Code in ext4_ext_convert_to_initialized() and
> ext4_split_convert_extents() try to make sure it does not create
> initialized extents beyond inode size however they check against
> inode->i_size which is wrong. They should instead check against
> EXT4_I(inode)->i_disksize which is the current inode size on disk.
> That's what e2fsck is going to see in case of crash before all dirty
> data is written. This bug manifests as generic/456 test failure (with
> recent enough fstests where fsx got fixed to properly pass
> FALLOC_KEEP_SIZE_FL flags to the kernel) when run with dioread_lock
> mount option.

Makes sense, thanks.

Reviewed-by: Lukas Czerner <lczerner@...hat.com>

-Lukas

> 
> CC: stable@...r.kernel.org
> Fixes: 21ca087a3891 ("ext4: Do not zero out uninitialized extents beyond i_size")
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/extents.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 954013d6076b..c5e190fd4589 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3532,8 +3532,8 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  		(unsigned long long)map->m_lblk, map_len);
>  
>  	sbi = EXT4_SB(inode->i_sb);
> -	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
> -		inode->i_sb->s_blocksize_bits;
> +	eof_block = (EXT4_I(inode)->i_disksize + inode->i_sb->s_blocksize - 1)
> +			>> inode->i_sb->s_blocksize_bits;
>  	if (eof_block < map->m_lblk + map_len)
>  		eof_block = map->m_lblk + map_len;
>  
> @@ -3785,8 +3785,8 @@ static int ext4_split_convert_extents(handle_t *handle,
>  		  __func__, inode->i_ino,
>  		  (unsigned long long)map->m_lblk, map->m_len);
>  
> -	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
> -		inode->i_sb->s_blocksize_bits;
> +	eof_block = (EXT4_I(inode)->i_disksize + inode->i_sb->s_blocksize - 1)
> +			>> inode->i_sb->s_blocksize_bits;
>  	if (eof_block < map->m_lblk + map->m_len)
>  		eof_block = map->m_lblk + map->m_len;
>  	/*
> -- 
> 2.16.4
>