df /usr stats all mounted filesystems

[jsc]

Hi,

When I "df /usr", the command hangs for about 2-3 seconds, and error
messages appear in /var/log/messages about supermounted filesystems
(cdrom, zip, floppy).  Basically, it seems that "df /usr" is calling stat
on all filesystems in /etc/mtab.

I am using df version 4.1 from the fileutils-4.1-5mdk rpm.

I'm not sure if it is a bug with df, or just a messed up linux setup.  It
suddenly appeared when I upgraded my kernel from 2.4.3 to 2.4.13 and also
installed devfs.  I am running a Mandrake Linux distro.

# excerpt from cat /proc/mounts

none /mnt/cdrom supermount ro 0 0
none /mnt/floppy supermount rw 0 0
none /mnt/zip supermount rw 0 0

# excerpt from strace df /usr

....
stat64("/mnt/cdrom", {st_mode=S_IFDIR|0777, st_size=0, ...}) = 0
stat64("/mnt/floppy", {st_mode=S_IFDIR|0777,st_size=0, ...}) = 0
stat64("/mnt/zip", {st_mode=S_IFDIR|0777, st_size=0, ...}) = 0
stat64("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0


Anyhow, I'm not that comfortable with the low-level stuff like this, but
after discussion with someone on alt.os.mandrake.linux (Thread: error
messages and devfs), he also reproduced it.

It's only an annoyance for me; however, "df" (of all filesystems) now
takes about 30 seconds to complete.

Thanks,

-jsc