Re: Btrfs check reports errors, filesystem seems fine

[Filippe LeMarchand <gasinvein@gmail.com>]

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Done, files added to same GDrive folder with corresponding names.
If it matters, subvol 4546 is my root filesystem (r/w snapshot created with snapper rollback), and 5134 is its snapshot.

In a letter dated Wednesday, July 12, 2017 15:44:52 MSK user Qu Wenruo wrote:
> 
> On 2017年07月12日 19:12, Filippe LeMarchand wrote:
> >> Maybe something wrong in grep happened which skip "(79177" ?
> > Yes, my bad. Now I used grep -E "\(79177| 79177" pattern, file on GDrive updated.
> 
> It looks much better, thanks.
> 
> > 
> > And btrfs check --mode=lowmem gives this:
> > 
> > checking extents
> > ERROR: extent[1609877700608, 94208] referencer count mismatch (root: 260, owner: 61720, offset: 6742016) wanted: 2, have: 5
> > ERROR: extent[1630301675520, 39583744] referencer count mismatch (root: 260, owner: 5847554, offset: 0) wanted: 36, have: 114
> > ERROR: extent[1658646986752, 10551296] referencer count mismatch (root: 274, owner: 283675, offset: 0) wanted: 2, have: 5
> > ERROR: extent[1672239132672, 84381696] referencer count mismatch (root: 274, owner: 2521382, offset: 0) wanted: 21, have: 25
> > ERROR: errors found in extent allocation tree or chunk allocation
> 
> Looks much like an exposed lowmem mode bug.
> Feel free to ignore these error from extent tree, they are just false 
> alerts.
> 
> > checking free space cache
> > checking fs roots
> > ERROR: root 4546 DIR_ITEM[79177 54846528] relative INODE_REF missing namelen 14 filename deprecated.sxt filetype 1
> 
> The error report is much better than original mode, and that's what I need.
> 
> Now I can wipe out all other noise as we know exactly which tree and 
> which DIR_ITEM/INODE_REF is causing the problem.
> 
> Would you please update the dump result with "-t 4546" passed to 
> btrfs-debug-tree like:
> 
> # btrfs-debug-tree -t 4546 <device>| grep 79177
> 
> Only "-t 4546" is added, to only dump the result of subvolume 4546.
> As always, all 3 grep results (2 "deprecated" and one 79177) need to be 
> updated.
> 
> And it seems that my previous assumption is still right for this case.
> If it's caused by kernel, your dump would definitely help us to locate 
> the problem.
> 
> > ERROR: root 4546 INODE REF[4222342 79177] and DIR_ITEM[79177 54846528] mismatch namelen 14 filename deprecated.txt filetype 1
> > ERROR: root 5134 DIR_ITEM[79177 54846528] relative INODE_REF missing namelen 14 filename deprecated.sxt filetype 1
> 
> Also for root 5134 please.
> 
> Thanks,
> Qu
> 
> > ERROR: errors found in fs roots
> > Checking filesystem on /dev/sda2
> > UUID: 12c84aa3-ce65-4390-807e-a72cc8a7445e
> > found 153429872640 bytes used, error(s) found
> > total csum bytes: 121991672
> > total tree bytes: 1940160512
> > total fs tree bytes: 1683767296
> > total extent tree bytes: 103841792
> > btree space waste bytes: 310722480
> > file data blocks allocated: 842455031808
> >   referenced 159286636544
> > 
> > In a letter from Wednesday, July 12, 2017 10:15:18 MSK user Qu Wenruo wrote:
> >> Sorry for the late reply.
> >>
> >> After investigating the dumps, I found the output is quite strange.
> >>
> >> 1) Mismatching output.
> >> In "btrfs-debug-tree-grep-79177.txt" I found only 79177 as offset for
> >> INODE_REF is here, while 79177 as objectid for DIR_ITEM/DIR_INDEX is not
> >> here at all.
> >>
> >> While in "btrfs-debug-tree-grep-deprecated-txt.txt" there is epected
> >> 79177 DIR_ITEM/DIR_INDEX.
> >>
> >> Maybe something wrong in grep happened which skip "(79177" ?
> >>
> >> 2) Mismatched hash
> >> The main problem I found is that, for key (79177 DIR_ITEM 54846528), the
> >> number 54846528 is the hash(crc32c) of filename, and it contains 2
> >> items, one for "deprecated.txt" and one for "deprecated.sxt".
> >>
> >> But we found that 54846528 only matches the hash for "deprecated.txt",
> >> not "deprecated.sxt".
> >>
> >> I think that's the main problem.
> >>
> >> BTW, would you please try "btrfs check --mode=lowmem" to see if lowmem
> >> mode reports similar (well, output may differ) error?
> >>
> >> If lowmem mode also reports error on such DIR_ITEM, I'm pretty sure
> >> that's the problem.
> >>
> >> However it may take some time before we can fix it in repair mode.
> >>
> >> Thanks,
> >> Qu
> >>
> >>
> >>
> >> 在 2017年07月04日 21:24, Filippe LeMarchand 写道:
> >>> Sure, here it is:
> >>> https://drive.google.com/drive/folders/0B1ax9Am81gx9YjJBVVA0LXRHeGc
> >>>
> >>> In a letter dated Tuesday, July 4, 2017 16:16:36 MSK user Lu Fengqi wrote:
> >>>> On Mon, Jul 03, 2017 at 08:34:52AM +0800, Qu Wenruo wrote:
> >>>>>
> >>>>>
> >>>>> At 07/01/2017 07:59 PM, Filippe LeMarchand wrote:
> >>>>>> Hello everyone.
> >>>>>>
> >>>>>> I have an btrfs root partition on Intel 530 ssd, which mounts without errors and seem to work fine,
> >>>>>> but `btrfs check` gives me foloowing output (and --repair doesn't remove errors):
> >>>>>>
> >>>>>> enabling repair mode
> >>>>>> Checking filesystem on /dev/sda2
> >>>>>> UUID: 12c84aa3-ce65-4390-807e-a72cc8a7445e
> >>>>>> checking extents
> >>>>>> Fixed 0 roots.
> >>>>>> checking free space cache
> >>>>>> cache and super generation don't match, space cache will be invalidated
> >>>>>> checking fs roots
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>
> >>>>> This means that in dir whose inode number is 79177, it has a child inode
> >>>>> pointer pointing to depercated.sxt.
> >>>>>
> >>>>> But it doesn't have dir index and corresponding inode ref, which is breaking
> >>>>> the cross reference rule of btrfs.
> >>>>>
> >>>>> Would you please run the following command to dump needed info for us to
> >>>>> debug?
> >>>>>
> >>>>> # btrfs-debug-tree /dev/sda2 | grep 79177 -C 10
> >>>>>
> >>>>> and
> >>>>>
> >>>>> # btrfs-debug-tree /dev/sda2 | grep deprecated.sxt -C 10
> >>>>>
> >>>>> and
> >>>>>
> >>>>> # btrfs-debug-tree /dev/sda2 | grep deprecated.txt -C 10
> >>>>>
> >>>>>
> >>>>> Considering the output has both .txt and .sxt, I think that's the problem.
> >>>>> But such bit-flip should be detected by tree block csum.
> >>>>> I'm not sure what's wrong with it.
> >>>>>
> >>>>> Thanks,
> >>>>> Qu
> >>>>>
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> 	unresolved ref dir 79177 index 0 namelen 14 name deprecated.sxt filetype 1 errors 6, no dir index, no inode ref
> >>>>>> 	unresolved ref dir 79177 index 417 namelen 14 name deprecated.txt filetype 1 errors 1, no dir item
> >>>>>> checking csums
> >>>>>> checking root refs
> >>>>>> found 23421812736 bytes used err is 0
> >>>>>> total csum bytes: 21531608
> >>>>>> total tree bytes: 776650752
> >>>>>> total fs tree bytes: 711278592
> >>>>>> total extent tree bytes: 36798464
> >>>>>> btree space waste bytes: 116002036
> >>>>>> file data blocks allocated: 850546470912
> >>>>>>     referenced 27611987968
> >>>>>>
> >>>>>> Is it dangerous and what should I do about it?
> >>>>>>
> >>>>>> I also tried --clear-space-cache, but it just removes the line about space cache.
> >>>>>>
> >>>>>
> >>>>>
> >>>>> --
> >>>>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> >>>>> the body of a message to majordomo@vger.kernel.org
> >>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>>>
> >>>> I'm afraid that your mail may be rejected because the attachment size
> >>>> exceeds the allowable limit(100kB) of btrfs mailing list. Could you
> >>>> share the attachment by google drive?
> >>>>
> >>>> Lastly, while Qu's timing is too tight, I will assist you on this issue.
> >>>>
> 

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