Re: /dev/loop* devices not appearing in /dev (at least since2.6.22-rc3*)
From: Paolo Ornati
Date: Thu Jun 14 2007 - 11:23:16 EST
On Thu, 14 Jun 2007 16:10:44 +0200
Matthew <jackdachef@xxxxxxxxx> wrote:
> I just tried out
> modprobe loop max_loop=32
> output of dmesg is:
> [ 457.607575] loop: the max_loop option is obsolete and will be
> removed in March 2008
> [ 457.607578] loop: module loaded
> but there are NO loop devices in /dev:
> ls -l /dev/ | grep loop
> still shows nothing, strange ...
it's not strange, with your kernel version "max_loop" will just limit
the max number of loop devices at most.
This is what happens with the mentioned patch (-rc5 and later):
+ * loop module now has a feature to instantiate underlying device
+ * structure on-demand, provided that there is an access dev node.
+ * However, this will not work well with user space tool that doesn't
+ * know about such "feature". In order to not break any existing
+ * tool, we do the following:
+ * (1) if max_loop is specified, create that many upfront, and this
+ * also becomes a hard limit.
+ * (2) if max_loop is not specified, create 8 loop device on module
+ * load, user can further extend loop device by create dev node
+ * themselves and have kernel automatically instantiate actual
+ * device on-demand.
So with this patch "max_loop=32" will create 32 loop devices... but
then it doesn't allow more of them.
Without options it creates 8 and you (or some userspace tool) can add
Linux 2.6.22-rc4-cfs-v16-g47932c49 on x86_64
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