Re: [PATCH] btrfs-progs: repair: Trickle down EEXISTS while freeing

[David Sterba <dsterba@suse.cz>]

On Fri, Oct 28, 2016 at 10:02:06AM -0500, Goldwyn Rodrigues wrote:
> 
> 
> On 10/28/2016 09:42 AM, David Sterba wrote:
> > On Thu, Oct 27, 2016 at 01:05:08PM -0500, Goldwyn Rodrigues wrote:
> >> While deleting pending extents, we insert extents to the
> >> extent_tree. However, because of corruption, this might already
> >> be freed. We trickle the EEXISTS error and let the caller
> >> decide what needs to be done with it. In this case, ignore, so
> >> the repair may proceed.
> >>
> >> The primary motivation of this is to resolve this BUG_ON:
> >> extent-tree.c:2731: alloc_reserved_tree_block: Assertion `ret` failed, value 0
> >>
> >> #2  assert_trace (val=0, line=2728, func=0x489510 <__func__.11558> "alloc_reserved_tree_block", 
> >> 	filename=0x489065 "extent-tree.c", assertion=0x48cfb5 "ret") at kerncompat.h:102
> >> #3  alloc_reserved_tree_block (trans=trans@entry=0x7e7240, root=root@entry=0x6a88a0, root_objectid=2, 
> >> 	generation=175654, flags=0, key=key@entry=0x2bc5c70, level=0, ins=ins@entry=0x7fffffffcf30) at extent-tree.c:2728
> >> #4  finish_current_insert (trans=trans@entry=0x7e7240, extent_root=extent_root@entry=0x6a88a0)
> >>     at extent-tree.c:2108
> >> #5  __free_extent (trans=trans@entry=0x7e7240, root=root@entry=0x6a88a0, bytenr=57127387136, 
> >> 	num_bytes=<optimized out>, parent=parent@entry=0, root_objectid=<optimized out>, owner_objectid=0, 
> >> 	owner_offset=owner_offset@entry=0, refs_to_drop=refs_to_drop@entry=1) at extent-tree.c:2410
> >> #6  del_pending_extents (trans=trans@entry=0x7e7240, extent_root=0x6a88a0) at extent-tree.c:2448
> > 
> > Do you have a reproducer for that?
> 
> I have a corrupt btrfs-image, not a test case though. Should I share
> that? If yes, where should I upload it?

The image should not be large (compressed), if it's about to be stored
in git. Minimizing can take time, I haven't analyzed the trace if
there's an easier way to trigger it (eg corrupting a specific key).
> >> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> > 
> > Applied, thanks.
> > 
> 
> Ahh, just realized. Spell check s/EEXISTS/EEXIST/

Fixed.