Hello,

When I do a btrfs send, I get the following error code:

    # btrfs send mysnapshot > /dev/null
    ERROR: send ioctl failed with -2: No such file or directory

I get it after 70-100% of the bytes are sent.

    $ uname -a
    Linux nicolas-desktop 4.17.0-rc2_3+ #1 SMP PREEMPT Tue May 8 01:14:47 CEST 2018 x86_64 GNU/Linux 

    $ btrfs --version
    btrfs-progs v4.16.1

    # btrfs fi show
    Label: 'ssd'  uuid: 135e8b6e-c5e5-4d2c-8c1a-62093b41ed1c
          Total devices 1 FS bytes used 178.72GiB
          devid    1 size 238.47GiB used 238.47GiB path /dev/sdb1

    # btrfs fi df /home
    Data, single: total=226.44GiB, used=173.10GiB
    System, single: total=32.00MiB, used=48.00KiB
    Metadata, single: total=12.00GiB, used=5.62GiB
    GlobalReserve, single: total=512.00MiB, used=0.00B

    # sudo btrfs scrub status /home                                                                                                               
    scrub status for 135e8b6e-c5e5-4d2c-8c1a-62093b41ed1c
    scrub started at Mon May  7 02:07:52 2018 and finished after 00:07:23
    total bytes scrubbed: 162.16GiB with 0 errors

For the kernel version, I had the same problem with v4.16.1 so this is
not a regression of the rc.

I use btrbk to automate my snapshots and backups. I only have the
problem with one of my subvolumes while I do the automatic snapshots
with many subvolumes on this drive. Also, all the snapshots of this
subvolume seem affected.

Did anyone encounter a similar issue or can help me investigate it?

I started looking at the kernel code for the send ioctl but was too lazy
to go through the call hierarchy after 3 function calls. I also found a
page on the btrfs wiki how to debug btrfs using user mode linux but I do
not know if it still works considering it is using 2.6.

Thank you.

-- 
Nicolas Porcel