Re: losetuping files in tmpfs fails?

Andrew Morton
2002-01-03T23:17:25Z

Andy Gaynor wrote:
>
> Whilst trying to figure out why my dang stripes won't persist (a separate
> but worrisome issue), I wrote a dittie which creates a couple junk files in
> /tmp (tmpfs), associates loop devices with them, whoops, losetup craps out.
>
> ...
> /tmp# mount | grep tmp # Filesystem is ...
> tmpfs on /tmp type tmpfs (rw) # tmpfs
> /tmp# echo foo > foo # Create file foo
> /tmp# losetup /dev/loop/5 foo # Give foo to /dev/loop/5
> ioctl: LOOP_SET_FD: Invalid argument # DISCO!!! <o > <o >

Yup, tmpfs doesn't provide some of the facilities which the
loop driver requires. Specifically, prepare_write() and
commit_write().

Probably it's not too hard to change loop to use generic_file_write(),
and it will then permit tmpfs file-backed loop mounts.

It's not obvious that there's a burning need to support loop-on-tmpfs
though, is there?

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