Re: reflink copy now works with nocow?

[Brian Hansen <dulanic@gmail.com>]

Ah I see, so I only have +C set on my temporary directory, but I guess
when the file is moved to the final directory which does not have C
set, it still has it enabled from when it was in the temporary
directory. So I'll need to setup a script to remove C when moving
directories. Unless there is a easier way to deal with this? I have it
download to incomplete then move to a final dir, but it seems to trake
the +C /w it.

------------------ ./archive
------------------ ./radarr
------------------ ./sonarr
------------------ ./autodl
------------------ ./radarr4k
---------------C-- ./incomplete
------------------ ./archive1
------------------ ./temp
------------------ ./freeleech

File was moved from incomplete to radarr4k but it seems to carry the +C.

---------------C--
/mnt/btrfs/downloads/torrent/radarr4k/Spider-Man.Far.from.Home.2019.UHD.BluRay.2160p.TrueHD.Atmos.7.1.HEVC.REMUX-FraMeSToR/Spider-Man.Far.from.Home.2019.UHD.BluRay.2160p.TrueHD.Atmos.7.1.HEVC.REMUX-FraMeSToR.mkv


On Sat, Nov 2, 2019 at 9:36 AM Roman Mamedov <rm@romanrm.net> wrote:
>
> On Sat, 2 Nov 2019 08:49:37 -0500
> Brian Hansen <dulanic@gmail.com> wrote:
>
> > Hello,
> >
> > First time i've sent to this group but I am trying to figure out the
> > cause of this. Normal copy is working fine, but then if I use
> > --reflink it says invalid argument. Not sure how to read some of this,
> > but here is the strace.
> >
> > I'm running kernel v4.15
> >
> > Here is the full output of strace. I ran a strace on normal copy and
> > most looks similar so I'm not able to figure out much here...
> >
> > https://pastebin.com/raw/YmQ8FvCH
>
> At first I was going to say, "oh it's because you are using 'chattr +C', or
> mounted the filesystem as nocow, and reflink copying is prevented by those".
> In fact this article from 2014 confirms that to be the case:
> http://infotinks.com/btrfs-nodatacow-reflink-copies-snapshots/
>
> But then I tested on my machine, and what used to fail, now works:
>
>   # mkdir tmp
>   # chattr +C tmp
>   # echo abc > tmp/a
>   # cp -a --reflink=always tmp/a tmp/b
>   # lsattr tmp/
>   ----------------C-- tmp/a
>   ----------------C-- tmp/b
>
> According to strace, the clone IOCTL succeeds:
>
> ...
>   openat(AT_FDCWD, "tmp/b", O_WRONLY|O_CREAT|O_EXCL, 0600) = 4
>   fstat(4, {st_mode=S_IFREG|0600, st_size=0, ...}) = 0
>   ioctl(4, BTRFS_IOC_CLONE or FICLONE, 3) = 0
> ...
>
> Same on kernels 4.14.151, 4.14.113 and 4.9.189.
>
> So I wonder, is setting nocow via 'chattr +C' getting ignored now, or is there
> an improvement that it no longer prevents reflink copying?
>
> --
> With respect,
> Roman