bugfindutils - Bugs: bug #50859, fstype btrfs isn't supported


bug #50859: fstype btrfs isn't supported

Submitted by:  Tavian Barnes <tavianator>
Submitted on:  Sun 23 Apr 2017 02:44:50 PM UTC  
Category:  find Severity:  3 - Normal
Item Group:  Wrong result Status:  None
Privacy:  Public Assigned to:  Bernhard Voelker <berny>
Originator Name:  Open/Closed:  Open
Release:  4.6.0 Fixed Release:  None

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Sun 23 Apr 2017 09:48:39 PM UTC, comment #2: 

Ah okay, you're actually parsing the device number out of /proc/self/mountinfo?  When I implemented -fstype for bfs, I didn't bother getting it from there, as it's not returned by getmntent().  I just stat() the mount point itself, which obviously works.

Tavian Barnes <tavianator>
Sun 23 Apr 2017 09:34:23 PM UTC, comment #1: 

find(1) supports BTRFS like any other file system type: there
is nothing special implemented in the code.  Instead, it looks
at the entries in "/proc/self/mountinfo" to find the device id.

Thus, "find -fstype btrfs" works ... as long as you search in
the root of an BTRFS file system: the underlying stat() system
call returns a different device number for BTRFS snaphots and
BTRFS subvolumes, and these can not be found in the above
mentioned mountinfo file:

  $ stat -c "%d %n" /mnt /mnt/_subvol /mnt/.snapshot
  38 /mnt
  40 /mnt/_subvol
  41 /mnt/.snapshot

See also https://savannah.gnu.org/bugs/?50326
Also other tools like "df -T" are not able to display the
file system type.

  $ df --output=fstype,target /mnt /mnt/_subvol /mnt/.snapshot
  Type  Mounted on
  btrfs /mnt
  -     /mnt/_subvol
  -     /mnt/.snapshot

Now, we could only add a workaround for this BTRFS - let's
call it - "anomaly" to find(1): if it doesn't find a file system
type for a given path, and the next one higher in the hierarchy
is a BTRFS, then it could assume that the current entry is on a
BTRFS snapshot or BTRFS subvolume.
I have such a hack in my local git tree, but didn't publish it
yet (as I usually do not use BTRFS at all, thus lacking tests).
What do others think about such a (hacky?) workaround?

Bernhard Voelker <berny>
Project AdministratorIn charge of this item.
Sun 23 Apr 2017 02:44:50 PM UTC, original submission:  

On a btrfs file system, find -fstype btrfs doesn't find any files, and find -printf '%p %F\n' prints

. unknown
./.git unknown
./.git/refs unknown

Tavian Barnes <tavianator>


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