From: Andrei Borzenkov <arvidjaar@gmail.com>
To: Vladimir Panteleev <thecybershadow@gmail.com>
Cc: Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: "kernel BUG" and segmentation fault with "device delete"
Date: Fri, 5 Jul 2019 12:42:16 +0300 [thread overview]
Message-ID: <CAA91j0W+UhJ2O+K1SJs3JaOfzkCnRhWgGjfFxXju5_sUsCj18A@mail.gmail.com> (raw)
In-Reply-To: <966f5562-1993-2a4f-0d6d-5cea69d6e1c6@gmail.com>
On Fri, Jul 5, 2019 at 7:45 AM Vladimir Panteleev
<thecybershadow@gmail.com> wrote:
>
> Hi,
>
> I'm trying to convert a data=RAID10,metadata=RAID1 (4 disks) array to
> RAID1 (2 disks). The array was less than half full, and I disconnected
> two parity drives,
btrfs does not have dedicated parity drives; it is quite possible that
some chunks had their mirror pieces on these two drives, meaning you
effectively induced data loss. You had to perform "btrfs device
delete" *first*, then disconnect unused drive after this process has
completed.
I suspect at this point the only possibility to salvage data is "btrfs restore".
> leaving two that contained one copy of all data.
>
> After stubbing out btrfs_check_rw_degradable (because btrfs currently
> can't realize when it has all drives needed for RAID10), I've
> successfully mounted rw+degraded, balance-converted all RAID10 data to
> RAID1, and then btrfs-device-delete-d one of the missing drives. It
> fails at deleting the second.
>
> The process reached a point where the last missing device shows as
> containing 20 GB of RAID1 metadata. At this point, attempting to delete
> the device causes the operation to shortly fail with "No space left",
> followed by a "kernel BUG at fs/btrfs/relocation.c:2499!", and the
> "btrfs device delete" command to crash with a segmentation fault.
>
> Here is the information about the filesystem:
>
> https://dump.thecybershadow.net/55d558b4d0a59643e24c6b4ee9019dca/04%3A28%3A23-upload.txt
>
> And here is the dmesg output (with enospc_debug):
>
> https://dump.thecybershadow.net/9d3811b85d078908141a30886df8894c/04%3A28%3A53-upload.txt
>
> Attempting to unmount the filesystem causes another warning:
>
> https://dump.thecybershadow.net/6d6f2353cd07cd8464ece7e4df90816e/04%3A30%3A30-upload.txt
>
> The umount command then hangs indefinitely.
>
> Linux 5.1.15-arch1-1-ARCH, btrfs-progs v5.1.1
>
> --
> Best regards,
> Vladimir
next prev parent reply other threads:[~2019-07-05 9:42 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-05 4:39 "kernel BUG" and segmentation fault with "device delete" Vladimir Panteleev
2019-07-05 7:01 ` Vladimir Panteleev
2019-07-05 9:42 ` Andrei Borzenkov [this message]
2019-07-05 10:20 ` Vladimir Panteleev
2019-07-05 21:48 ` Chris Murphy
2019-07-05 22:04 ` Chris Murphy
2019-07-05 21:43 ` Chris Murphy
2019-07-06 0:05 ` Vladimir Panteleev
2019-07-06 2:38 ` Chris Murphy
2019-07-06 3:37 ` Vladimir Panteleev
2019-07-06 17:36 ` Chris Murphy
2019-07-06 5:01 ` Qu Wenruo
2019-07-06 5:13 ` Vladimir Panteleev
2019-07-06 5:51 ` Qu Wenruo
2019-07-06 15:09 ` Vladimir Panteleev
2019-07-20 10:59 ` Vladimir Panteleev
2019-08-08 20:40 ` Vladimir Panteleev
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