linux-ext4 - Re: [PATCH v2 3/5] ext4: fix wrong m_len value after unwritten extent conversion

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Date:	Thu, 07 Mar 2013 19:42:35 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Zheng Liu <gnehzuil.liu@...il.com>, linux-ext4@...r.kernel.org
Cc:	Zheng Liu <wenqing.lz@...bao.com>, Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH v2 3/5] ext4: fix wrong m_len value after unwritten extent conversion

On Wed,  6 Mar 2013 22:17:13 +0800, Zheng Liu <gnehzuil.liu@...il.com> wrote:
> From: Zheng Liu <wenqing.lz@...bao.com>
> 
> We always assume that the return value of ext4_ext_map_blocks is equal
> to map->m_len but when we try to convert an unwritten extent 'm_len'
> value will break this assumption.  It is harmless until we use status
> tree as a extent cache because we need to update status tree according
> to 'm_len' value.
> 
> Meanwhile this commit marks EXT4_MAP_MAPPED flag after unwritten extent
> conversion.  It shouldn't cause a bug because we update status tree
> according to checking EXT4_MAP_UNWRITTEN flag.  But it should be fixed.
> 
> After applied this commit, the following error message from self-testing
> infrastructure disappears.
> 
>     ...
>     kernel: ES len assertation failed for inode: 230 retval 1 !=
>     map->m_len 3 in ext4_map_blocks (allocation)
>     ...
Ok. fill free to add Reviewed-by: Dmitry Monakhov <dmonakhov@...nvz.org>
> 
> Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
> Cc: "Theodore Ts'o" <tytso@....edu>
> Cc: Dmitry Monakhov <dmonakhov@...nvz.org>
> ---
>  fs/ext4/extents.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 25c86aa..110e85a 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3650,6 +3650,10 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
>  						 path, map->m_len);
>  		} else
>  			err = ret;
> +		map->m_flags |= EXT4_MAP_MAPPED;
> +		if (allocated > map->m_len)
> +			allocated = map->m_len;
> +		map->m_len = allocated;
>  		goto out2;
>  	}
>  	/* buffered IO case */
> -- 
> 1.7.12.rc2.18.g61b472e
> 
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