[Ocfs2-tools-devel] [PATCH 17/20] fsck.ocfs2: Make pass0 aware of discontig block group.

[Tao Ma]

On 07/18/2010 03:45 AM, Joel Becker wrote:
> On Sat, Jul 17, 2010 at 10:40:51PM +0800, Tao Ma wrote:
>> yes, I knew that and actually my discontiguous block group will also
>> be set in the
>> global bitmap in mark_group_used.
>
> 	Yes, which is great.  I just worried if l_next_free_rec was
> bogus, we might walk of the end or something.  That can't happen with a
> contig bg because we just count cpg from an already validated bg_blkno.
>
>> So let me describe what I think we need for discontiguous block group check:
>> 1. do some sanity check for the extent list. includes
>> l_tree_depth(should always be 0),
>>    l_count and l_next_free_rec.
>> 2. for each extent_record, check whether we have a valid e_cpos.
>> 3. for the whole extent list, check whether the total clusters number = cpg.
>> If there is any error during the check, just remove the whole group.
>
> 	I think this sounds pretty reasonable.  If an extent has a bad
> e_cpos, we can't really fix that.  However, I think that l_tree_depth
> can be fixed to 0, l_count can be fixed to extent_recs_per_gd and
> l_next_free_rec can even be fixed in the trivial case.
yes, l_tree_depth, l_count is easy to fix.
> 	How would one figure l_next_free_rec?  Well, if you walk the
> extents and discover that N extents add up to exactly cpg, doesn't that
> have to be the l_next_free_rec?  If you run into a zero extent before
> counting cpg, the whole group has to be removed, of course.
So we will trust the extent record in the list and change 
l_next_free_rec accordingly? maybe it works, let us wait and see the 
result. ;)
> 	What about fixing a bad e_leaf_clusters?  I don't think we can
> handle all the possible combinations, but if we find an e_leaf_clusters
> that would clearly go past the cpg, I think we can check the remaining
> extents and see via subtraction what it should have been.
OK, so I will generate a separate patch for this whole bunch of stuff. 
Thanks for the advice.

Regards,
Tao