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

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Date:	Mon, 12 Aug 2013 18:35:47 -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 8/12/13 6:28 PM, Eric Sandeen wrote:
> On 8/12/13 6:21 PM, Eric Sandeen wrote:
>> 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?
> 
> Nope, we can't crack an extent handle, it's an opaque type.
> 
> Ned some V2 interfaces now?  :(
> 

or maybe just:

+       eof_blk = (EXT2_I_SIZE(pctx->inode) + ctx->fs->blocksize - 1) >>
+                  EXT2_BLOCK_SIZE_BITS(ctx->fs->super);

unless that's too ugly.

-Eric (done replying to himself for now)

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