linux-ext4 - Re: [PATCH] e2fsprogs: Don't report uninit extents past EOF invalid

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Date:	Mon, 12 Aug 2013 18:21:25 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Eric Whitney <enwlinux@...il.com>
CC:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH] e2fsprogs: Don't report uninit extents past EOF invalid

On 7/21/13 3:28 PM, Eric Whitney wrote:
> Commit d3f32c2db8 caused e2fsck misbehavior during xfstests runs.
> It reported that uninitialized extents created by fallocate() at
> the end of file with the FALLOC_FL_KEEP_SIZE flag were invalid.
> Because FALLOC_FL_KEEP_SIZE does not increase the file size when
> an extent is fallocated, an uninitialized extent can legally contain
> blocks past the end of file.
> 
> The information reported by ext2fs_extent_get() and used by the commit
> to determine legal extent ranges is limited by the value of i_size
> (determines end_blk in the root extent index), so block values greater
> than that containing i_size were reported as invalid.
> 
> To fix this, filter out possible invalid extent candidates if they are
> uninitialized and extend past the block containing the end of file.
> 
> Signed-off-by: Eric Whitney <enwlinux@...il.com>
> ---
>  e2fsck/pass1.c      |    4 +++-
>  lib/ext2fs/ext2fs.h |    1 +
>  lib/ext2fs/extent.c |    1 +
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index ba6025b..b84b0d0 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -1892,7 +1892,9 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
>  			problem = PR_1_EXTENT_BAD_START_BLK;
>  		else if (extent.e_lblk < start_block)
>  			problem = PR_1_OUT_OF_ORDER_EXTENTS;
> -		else if (end_block && last_lblk > end_block)
> +		else if ((end_block && last_lblk > end_block) &&
> +			 (!(extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT &&
> +			    last_lblk > info.eof_blk - 1)))
>  			problem = PR_1_EXTENT_END_OUT_OF_BOUNDS;
>  		else if (is_leaf && extent.e_len == 0)
>  			problem = PR_1_EXTENT_LENGTH_ZERO;
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index 311ceda..85f2ac8 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -409,6 +409,7 @@ struct ext2_extent_info {
>  	int		bytes_avail;
>  	blk64_t		max_lblk;
>  	blk64_t		max_pblk;
> +	blk64_t         eof_blk;
>  	__u32		max_len;
>  	__u32		max_uninit_len;
>  };

I just realized, this affects the ABI, doesn't it?  Hm.

As a hack-around, can probably just use ehandle->path[0].end_blk directly
in scan_extent_node and stash eof_blk locally?

-Eric

> diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
> index 65bb099..de54319 100644
> --- a/lib/ext2fs/extent.c
> +++ b/lib/ext2fs/extent.c
> @@ -1572,6 +1572,7 @@ errcode_t ext2fs_extent_get_info(ext2_extent_handle_t handle,
>  	info->max_depth = handle->max_depth;
>  	info->max_lblk = ((__u64) 1 << 32) - 1;
>  	info->max_pblk = ((__u64) 1 << 48) - 1;
> +	info->eof_blk = handle->path[0].end_blk;
>  	info->max_len = (1UL << 15);
>  	info->max_uninit_len = (1UL << 15) - 1;
>  
> 

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