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From: STEVE LEUNG <sjleung@shaw.ca>
To: linux-btrfs@vger.kernel.org
Subject: corruption with multi-device btrfs + single bcache, won't mount
Date: Sat, 9 Feb 2019 23:56:31 -0700 (MST)
Message-ID: <1690578645.233565651.1549781791550.JavaMail.zimbra@shaw.ca> (raw)

Hi all,

I decided to try something a bit crazy, and try multi-device raid1 btrfs on
top of dm-crypt and bcache.  That is:

  btrfs -> dm-crypt -> bcache -> physical disks

I have a single cache device in front of 4 disks.  Maybe this wasn't
that good of an idea, because the filesystem went read-only a few
days after setting it up, and now it won't mount.  I'd been running
btrfs on top of 4 dm-crypt-ed disks for some time without any
problems, and only added bcache (taking one device out at a time,
converting it over, adding it back) recently.

This was on Arch Linux x86-64, kernel 4.20.1.

dmesg from a mount attempt (using -o usebackuproot,nospace_cache,clear_cache):

  [  267.355024] BTRFS info (device dm-5): trying to use backup root at mount time
  [  267.355027] BTRFS info (device dm-5): force clearing of disk cache
  [  267.355030] BTRFS info (device dm-5): disabling disk space caching
  [  267.355032] BTRFS info (device dm-5): has skinny extents
  [  271.446808] BTRFS error (device dm-5): parent transid verify failed on 13069706166272 wanted 4196588 found 4196585
  [  271.447485] BTRFS error (device dm-5): parent transid verify failed on 13069706166272 wanted 4196588 found 4196585
  [  271.447491] BTRFS error (device dm-5): failed to read block groups: -5
  [  271.455868] BTRFS error (device dm-5): open_ctree failed

btrfs check:

  parent transid verify failed on 13069706166272 wanted 4196588 found 4196585
  parent transid verify failed on 13069706166272 wanted 4196588 found 4196585
  parent transid verify failed on 13069706166272 wanted 4196588 found 4196585
  parent transid verify failed on 13069706166272 wanted 4196588 found 4196585
  Ignoring transid failure
  ERROR: child eb corrupted: parent bytenr=13069708722176 item=7 parent level=2 child level=0
  ERROR: cannot open file system

Any simple fix for the filesystem?  It'd be nice to recover the data
that's hopefully still intact.  I have some backups that I can dust
off if it really comes down to it, but it's more convenient to
recover the data in-place.

This is complete speculation, but I do wonder if having the single
cache device for multiple btrfs disks triggered the problem.

Thanks for any assistance.

Steve

             reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-10  6:56 STEVE LEUNG [this message]
2019-02-10 10:35 ` Thiago Ramon
2019-02-11  5:22   ` STEVE LEUNG
2019-02-10 13:52 ` Qu Wenruo
2019-02-11  5:25   ` STEVE LEUNG
2019-02-12  6:22   ` Steve Leung
2019-02-12  6:51     ` Qu Wenruo

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