Bug in swapfs (2.4.0-ac9)

Bug in swapfs (2.4.0-ac9)

[Gregor Jasny]

I think I've found a bug in swapfs:

fstab:
swapfs          /dev/shm        swapfs  defaults 0 0
swapfs         /tmp    swapfs  defaults 0 0

When I hit <enter> on a tar.gz file in Midnight Commander nothing happens. If 
I do a umonut /tmp and hit <enter> again it works as It should (I see the 
archived files).
Nearly the same Problem with the Acrobat Reader pluin for Netscape. It shows 
only a blank page when /tmp is swapfs.

I've noticed that it's possible to mount /tmp more than once. mount shows then
[snip]
swapfs on /dev/shm type swapfs (rw)
swapfs on /tmp type swapfs (rw)
swapfs on /tmp type swapfs (rw)
swapfs on /tmp type swapfs (rw)
swapfs on /tmp type swapfs (rw)

The permissions for /tmp are rwxrwxrwt, and even -omode=777,exec didn't help.

Any Ideas?

-Gregor
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Re: Bug in swapfs (2.4.0-ac9)

[Christoph Rohland]

Hi Gregor,

On Mon, 15 Jan 2001, Gregor Jasny wrote:
> I think I've found a bug in swapfs:
> 
> fstab:
> swapfs          /dev/shm        swapfs  defaults 0 0
> swapfs         /tmp    swapfs  defaults 0 0
> 
> When I hit <enter> on a tar.gz file in Midnight Commander nothing
> happens. If I do a umonut /tmp and hit <enter> again it works as It
> should (I see the archived files).  Nearly the same Problem with the
> Acrobat Reader pluin for Netscape. It shows only a blank page when
> /tmp is swapfs.

Yep, Alan introduced a maxbytes field to the superblock which is not
set in swapfs. So the vfs will always fail with EFBIG. 
I will send out a patch soon.

> I've noticed that it's possible to mount /tmp more than once. mount
> shows then
> [snip]
> swapfs on /dev/shm type swapfs (rw)
> swapfs on /tmp type swapfs (rw)
> swapfs on /tmp type swapfs (rw)
> swapfs on /tmp type swapfs (rw)
> swapfs on /tmp type swapfs (rw)

The vfs allows multiple mount with 2.4, and for swapfs you always get
a fresh instance with its own resource limits. Think anout chroot with
its own swapfs instance. AFAIK the new util-linux will give you some
checking.

> The permissions for /tmp are rwxrwxrwt, and even -omode=777,exec
> didn't help.

Your bootup script sets the mode after mounting? The mode parameter is
functional for me and the default is 777. 1777 has to be done in user
space.

Greetings
		Christoph

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