Re: OOM & [OT] util-linux-2.12e

DervishD
2004-09-20T12:10:07Z

Hi Paulo :)

* Paulo Marques <pmarques@grupopie.com> dixit:
> >>>>- fix all broken apps that still rely on mtab. like GNU df(1)
> >>>df does not rely on /etc/mtab. It relies on getmntent.
> >> Then my GNU df has any problem :???
> >No, if any then getmntent.
> I don't get this. From "man getmntent" it seems that getmntent is just a
> parser for /etc/mtab, and that you must call "setmntent" with the
> filename you want to parse.

From the code of coreutils 5.2.1, lib/mountlist.c, df uses the
default name for the mounted filesystems table. Under glibc, it uses
_PATH_MOUNTED that is, effectively, "/etc/mtab". BTW, 'MOUNTED' is
shown in glibc headers as a deprecated alias.

> So if you do "setmntent("/etc/mtab",...)" you're explicitly saying
> that you want getmntent to use /etc/mtab. This is just a open/read
> in disguise.
> Am I missing something?

Maybe: df (well, lib/mountlist.c) shouldn't try to 'detect' which
kernel are you running, if one with /etc/mtab or a newer one that
only supports /proc/mounts (which needs procfs support, BTW, and that
can be a problem too). Is glibc who should do all that, and try to
open /etc/mtab and /proc/mounts, in that order. Being a userspace
app, df should not mess with kernel interface changes. In the worst
case, it *could* try to open /etc/mtab (with setmntent, I mean) and
if that fails, open /proc/mounts if the operating system is Linux
(which can be easily decided at './configure' time).

I'm really not sure about what should be fixed. IMHO, getmntent
should only try to open _PATH_MOUNTED. Any other desired behaviour
should be set using setmntent. Just my 0,02 EUR.

Raúl Núñez de Arenas Coronado

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