On Mon, Jan 18, 2021 at 3:07 AM Qu Wenruo <quwenruo.bt...@gmx.com> wrote: > On 2021/1/18 下午6:33, Erik Jensen wrote: > > I ended up having other priorities occupying my time since 2019, and the > > "solution" of exporting the individual drives on my NAS using NBD and > > mounting them on my desktop worked, even if it wasn't pretty. > > > > However, I am currently looking into Syncthing, which I would like to > > run on the NAS directly. That would, of course, require accessing the > > filesystem directly on the NAS rather than just exporting the raw > > devices, which means circling back to this issue. > > > > After updating my NAS, I have determined that the issue still occurs > > with Linux 5.8. > > > > What's the next best step for debugging the issue? Ideally, I'd like to > > help track down the issue to find a proper fix, rather than just trying > > to bypass the issue. I wasn't sure if the suggestion to comment out > > btrfs_verify_dev_extents() was more geared toward the former or the latter. > > After rewinding my memory on this case, the problem is really that the > ARM btrfs kernel is reading garbage, while X86 or ARM user space tool > works as expected. > > Can you recompile your kernel on the ARM board to add extra debugging > messages? > If possible, we can try to add some extra debug points to bombarding > your dmesg. > > Or do you have other ARM boards to test the same fs? > > > Thanks, > Qu
It's pretty easy to build a kernel with custom patches applied, though the actual building takes a while, so I'd be happy to add whatever debug messages would be useful. I also have an old Raspberry Pi (original model B) I can dig out and try to get going, tomorrow. I can't hook it up to the drives directly, but I should be able to access them via NBD like I was doing from my desktop. If I can't get that going for whatever reason, I could also try running an emulated ARM system with QEMU. > > > > On Fri, Jun 28, 2019 at 1:15 AM Qu Wenruo <quwenruo.bt...@gmx.com > > <mailto:quwenruo.bt...@gmx.com>> wrote: > > > > > > > > On 2019/6/28 下午4:00, Erik Jensen wrote: > > >> So it's either the block layer reading some wrong from the disk > > or btrfs > > >> layer doesn't do correct endian convert. > > > > > > My ARM board is running in little endian mode, so it doesn't seem > > like > > > endianness should be an issue. (It is 32-bits versus my desktop's 64, > > > though.) I've also tried exporting the drives via NBD to my x86_64 > > > system, and that worked fine, so if the problem is under btrfs, it > > > would have to be in the encryption layer, but fsck succeeding on the > > > ARM board would seem to rule that out, as well. > > > > > >> Would you dump the following data (X86 and ARM should output the > > same > > >> content, thus one output is enough). > > >> # btrfs ins dump-tree -b 17628726968320 /dev/dm-3 > > >> # btrfs ins dump-tree -b 17628727001088 /dev/dm-3 > > > > > > Attached, and also 17628705964032, since that's the block > > mentioned in > > > my most recent mount attempt (see below). > > > > The trees are completely fine. > > > > So it should be something else causing the problem. > > > > > > > >> And then, for the ARM system, please apply the following diff, > > and try > > >> mount again. > > >> The diff adds extra debug info, to exam the vital members of a > > tree block. > > >> > > >> Correct fs should output something like: > > >> BTRFS error (device dm-4): bad tree block start, want 30408704 > > have 0 > > >> tree block gen=4 owner=5 nritems=2 level=0 > > >> csum: > > >> > > a304e483-0000-0000-0000-00000000000000000000-0000-0000-0000-000000000000 > > >> > > >> The csum one is the most important one, if there aren't so many > > zeros, > > >> it means at that timing, btrfs just got a bunch of garbage, thus we > > >> could do further debug. > > > > > > [ 131.725573] BTRFS info (device dm-1): disk space caching is > > enabled > > > [ 131.731884] BTRFS info (device dm-1): has skinny extents > > > [ 133.046145] BTRFS error (device dm-1): bad tree block start, want > > > 17628705964032 have 2807793151171243621 > > > [ 133.055775] tree block gen=7888986126946982446 > > > owner=11331573954727661546 nritems=4191910623 level=112 > > > [ 133.065661] csum: > > > > > 416a456c-1e68-dbc3-185d-aaad410beaef5493ab3f-3cb9-4ba1-2214-b41cba9656fc > > > > Completely garbage here, so I'd say the data we got isn't what we want. > > > > > [ 133.108383] BTRFS error (device dm-1): bad tree block start, want > > > 17628705964032 have 2807793151171243621 > > > [ 133.117999] tree block gen=7888986126946982446 > > > owner=11331573954727661546 nritems=4191910623 level=112 > > > [ 133.127756] csum: > > > > > 416a456c-1e68-dbc3-185d-aaad410beaef5493ab3f-3cb9-4ba1-2214-b41cba9656fc > > > > But strangely, the 2nd try still gives us the same result, if it's > > really some garbage, we should get some different result. > > > > > [ 133.136241] BTRFS error (device dm-1): failed to verify dev > > extents > > > against chunks: -5 > > > > You can try to skip the dev extents verification by commenting out the > > btrfs_verify_dev_extents() call in disk-io.c::open_ctree(). > > > > It may fail at another location though. > > > > The more strange part is, we have the device tree root node read out > > without problem. > > > > Thanks, > > Qu > > > > > [ 133.166165] BTRFS error (device dm-1): open_ctree failed > > > > > > I copied some files over last time I had it mounted on my desktop, > > > which may be why it's now failing at a different block. > > > > > > Thanks! > > > > >
