Re: Incremental receive completes succesfully despite missing files

From: Chris Murphy <lists@colorremedies.com>
To: Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Cc: Dennis K <dennisk@netspace.net.au>,
	Andrei Borzenkov <arvidjaar@gmail.com>
Subject: Re: Incremental receive completes succesfully despite missing files
Date: Mon, 21 Jan 2019 21:54:19 -0700	[thread overview]
Message-ID: <CAJCQCtScPtJ=agTJbunPG9GT4hQg5VQWMOEM_JAyLseNKraqNw@mail.gmail.com> (raw)
In-Reply-To: <CAJCQCtSOBcK=MXLUFVZk6YCrFx60UEH7PgOtPYbcRkfjG0XDyQ@mail.gmail.com>

On Mon, Jan 21, 2019 at 3:23 PM Chris Murphy <lists@colorremedies.com> wrote:

> If <parent> has a UUID of 54321, I expect that <subvol> must have
> Parent UUID of 54321, or the send command should fail.

OK I think the following is a reproducible bug.

# btrfs sub create 1
# btrfs sub create 2
# touch 1/one
# touch 2/two
# btrfs sub snap -r 1 1.ro1
# btrfs sub snap -r 2 2.ro1
# touch 1/oneone
# touch 2/twotwo
# btrfs sub snap -r 1 1.ro2
# btrfs sub snap -r 2 2.ro2
# btrfs send 1.ro1 | ssh chris@fnuc.local "sudo btrfs receive /srv/scratch/"
At subvol 1.ro1
At subvol 1.ro1
# btrfs send 2.ro1 | ssh chris@fnuc.local "sudo btrfs receive /srv/scratch/"
At subvol 2.ro1
At subvol 2.ro1
# btrfs send -p 1.ro1 2.ro2 | ssh chris@fnuc.local "sudo btrfs receive
/srv/scratch/"
At subvol 2.ro2
At snapshot 2.ro2
#

I expect the last command to fail because 1.ro1 is not the parent of
2.ro2. The command completes, and 2.ro2 is on the destination, and at
least in this simple example it contains the expected files. However
'btrfs show' indicates that the "parent UUID" of 2.ro2 is the "UUID"
of 1.ro1, which is definitely wrong. So it's a legit bug, not just a
cosmetic problem due to lack of error checking.

$ ls -l 1.ro1
total 0
-rw-rw-r--. 1 chris chris 0 Jan 21 21:41 one
$ ls -l 2.ro1
total 0
-rw-rw-r--. 1 chris chris 0 Jan 21 21:41 two
$ ls -l 2.ro2
total 0
-rw-rw-r--. 1 chris chris 0 Jan 21 21:41 two
-rw-rw-r--. 1 chris chris 0 Jan 21 21:41 twotwo
$

  fnuc.local  chris  /  srv  scratch  sudo btrfs sub show 1.ro1
scratch/1.ro1
    Name:             1.ro1
    UUID:             eb0bb290-3f7d-d34d-94c3-1ed9da96f2fa
    Parent UUID:         -
    Received UUID:         b965a4b6-e77d-714b-af0e-83e15e734fd5
    Creation time:         2019-01-21 21:43:04 -0700
    Subvolume ID:         3107
    Generation:         25788
    Gen at creation:     25782
    Parent ID:         2039
    Top level ID:         2039
    Flags:             readonly
    Snapshot(s):
                scratch/2.ro2
  fnuc.local  chris  /  srv  scratch  sudo btrfs sub show 1.ro2
ERROR: cannot find real path for '1.ro2': No such file or directory
  fnuc.local  chris  /  srv  scratch  sudo btrfs sub show 2.ro1
scratch/2.ro1
    Name:             2.ro1
    UUID:             ce0d762a-d4ea-6448-aa71-1573d70fe60e
    Parent UUID:         -
    Received UUID:         d382f4f9-23c9-394e-852d-ecbe9a95fa75
    Creation time:         2019-01-21 21:43:15 -0700
    Subvolume ID:         3108
    Generation:         25786
    Gen at creation:     25785
    Parent ID:         2039
    Top level ID:         2039
    Flags:             readonly
    Snapshot(s):
  fnuc.local  chris  /  srv  scratch  sudo btrfs sub show 2.ro2
scratch/2.ro2
    Name:             2.ro2
    UUID:             165a4a66-0600-3b49-80aa-edae8fd850d9
    Parent UUID:         eb0bb290-3f7d-d34d-94c3-1ed9da96f2fa
    Received UUID:         b8343d21-882f-bf47-ac61-b59e53b126a4
    Creation time:         2019-01-21 21:43:38 -0700
    Subvolume ID:         3109
    Generation:         25789
    Gen at creation:     25788
    Parent ID:         2039
    Top level ID:         2039
    Flags:             readonly
    Snapshot(s):
  fnuc.local  chris  /  srv  scratch 

-- 
Chris Murphy