Re: [PATCH v4 00/13] btrfs-progs:fsck: Add inode nlink mismatch and

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

-------- Original Message --------
Subject: Re: [PATCH v4 00/13] btrfs-progs:fsck: Add inode nlink mismatch and
From: Filipe David Manana <fdmanana@gmail.com>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: 2014年12月11日 19:07
> On Thu, Dec 11, 2014 at 12:50 AM, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>> -------- Original Message --------
>> Subject: Re: [PATCH v4 00/13] btrfs-progs:fsck: Add inode nlink mismatch and
>> From: David Sterba <dsterba@suse.cz>
>> To: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> Date: 2014年12月10日 20:37
>>> On Tue, Dec 09, 2014 at 04:27:19PM +0800, Qu Wenruo wrote:
>>>> The patchset introduce two new repair function and some helpers to
>>>> archive a huge goal:
>>>>     Repair btrfs whose fs tree's non-root leaf/node is corrupted when no
>>>>     duplication is valid.
>>>>
>>>> The two new repair functions are:
>>>>     repair_inode_nlinks():
>>>>       Repair any inode nlink related problem.
>>>>       From fixing the nlink number and related
>>>>       inode_ref/dir_index/dir_item to recovering file name and file type
>>>>       and salvage them into the lost+found dir.
>>>>       This does not only fix a case that some users reported but also
>>>>       cooperate with repair_inode_no_item() function to salvaged heavily
>>>>       damaged inode to lost+found dir.
>>>>
>>>>     repair_inode_no_item():
>>>>       Repair case for inode_item missing case, which is quite common when
>>>>       fs tree leaf/node is missing.
>>>>       This only does the inode item rebuild. Later recovery like move it
>>>>       to lost+found dir is done by repair_inode_nlinks().
>>>>
>>>> The main helper is the repair_btree() function, which will drops the
>>>> corrupted non-root leaf/node and rebalance the tree to keep the
>>>> correctness of the btree.
>>> Sounds a bit intrusive, but under the circumstances I don't see anything
>>> better to do.
>> Better non-destructive but less generic method may be introduced later.
>> My dream is to inspect each key and its item to rebuild each member, but it
>> would takes a long long time
>> to implement.
>>>
>>>> With this patchset, even a non-root leaf/node is corrupted and no
>>>> duplication survived, btrfsck can still repair it to a mountable status.
>>>> (And normal rw should also be OK,)
>>>>
>>>> The remaining unfixable problems will be inode nbytes error with file
>>>> extent discounts error, which may be fixed in next patchset.
>>>>
>>>> Cc David:
>>>> Sorry for the huge change in the patchset and merge the old inode nlink
>>>> repair with new inode item rebuild patchset.
>>> No problem, the incremental changelogs helped a lot.
>>>
>>>> Since when developing inode item rebuild patchset, I found the old nlink
>>>> cooperated very bad with item rebuild and there is some duplicated codes
>>>> between the two patchset, no to mention the math lib introduced by nlink
>>>> repair patch.
>>>> So I decided to somewhat rebase the nlink repair patchset to provide
>>>> better generality.
>>> Great, the patchset looks good for merge, I'm adding it to 3.18. From
>>> now on please send only incremental changes and not the whole patchset.
>>> Thanks.
>> Thanks, this should be the last large update patchset.
>> Later work will focus on file extent recovery and should not interfere with
>> this patch.
>>
>> Thanks.
>> Qu
> Can we please get some tests too?
> Add some broken fs images, document what is broken and the expected
> result after running the repair code (besides verifying the repair
> worked for every single inode of course)...
>
> thanks
Tests are definitely needed, I tested this by randomly corrupt a leaf of 
fstree, which contains contents of my /etc,
and run repair.

But the problem is that, we can't add tests like other btrfsck using 
btrfs-image dump, since it will fail to dump
a btree-broken btrfs.
And if we add test image directly, it may takes up several MB as a 
binary image dump.

Any good idea about how to add test case without btrfs-image support?

Thanks,
Qu
>
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