Timeouts copying large files to a Samba server with Btrfs

[Roman Mamedov <rm@romanrm.net>]

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Hello,

Sometimes when I copy large files (the latest case was with a 13 GB file) to a
Btrfs-residing share on a Samba file server (using Thunar file manager), the
copy process fails around the end with following messages in dmesg on the
client:

[7699154.504380] CIFS VFS: sends on sock ffff88010d41e800 stuck for 15 seconds
[7699154.504440] CIFS VFS: Error -11 sending data on socket to server
[7699215.173469] CIFS VFS: sends on sock ffff88010d41e800 stuck for 15 seconds
[7699215.173533] CIFS VFS: Error -11 sending data on socket to server
[7699317.982262] CIFS VFS: sends on sock ffff88010d41e800 stuck for 15 seconds
[7699317.982319] CIFS VFS: Error -11 sending data on socket to server

Nothing in dmesg on the server.

My guess is that the Samba server process submits too much queued buffers at
once to be written to disk, then blocks on waiting for this, and the whole
operation ends up taking so long, that it doesn't get back to the client in
time.

This also happens much more often is compress-force is enabled on the server.

The server specs are AMD E-350 1.6GHz, 16GB of RAM, client/server network
connection is 1 Gbit. Kernel 4.1.15 on the server, 3.18.21 on the client.

Any idea what to tune so that this doesn't happen? (server/client/Samba/Btrfs?)

-- 
With respect,
Roman

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