Re: Using loop devices in Debian

[David <bouncingcats@gmail.com>]

On 26 January 2014 02:53, Zenaan Harkness <zen@freedbms.net> wrote:
>
> OK, loopback mounting:

I wish people would clearly distinguish "loop" devices from "loopback" devices.

The word loopback appears nowhere in 'man losetup', nor in any actual
command for a loop device, but somehow it has come into widespread
use.

Looback devices are part of the network system.
Loop devices are part of the file system.

"Loopback devices" are so named because they return data back up the
network stack. See
Linux/drivers/net/loopback.c

"Loop devices" are so named because the filesystem driver accesses a
higher level of the filesystem before descending again. As far as I am
aware, there is no loop in data flow, only in the access path to it.
As far as I am aware, there is no closed loop, only a return to a
higher access level before descending again somewhere else. They are
implemented by Linux/drivers/block/loop.c

I am aware this usage is widespread. It has even infected loop.c

$ uname -r
3.2.0-4-686-pae
$ grep -i loopback loop.c | wc -l
1
$ grep -i loop loop.c | wc -l
322

However it feels quite wrong to me to not distinguish the two, because
they are totally different things, with almost nothing in common. It
is easily achieved.

If I am overlooking something, please do feel free to correct me.