Re: 2.4 bug: fifo-write causes diskwrites to read-only fs !

[Richard B. Johnson]

On Wed, 28 May 2003, Rob van Nieuwkerk wrote:

>
> I wrote:
> > It turns out that Linux is updating inode timestamps of fifos (named
> > pipes) that are written to while residing on a read-only filesystem.
> > It is not only updating in-ram info, but it will issue *physical*
> > writes to the read-only fs on the disk !
> 	.
> 	.
> 	.
> > Sysinfo:
> > --------
> > - various 2.4 kernels including RH-2.4.20-13.9,
> >   but also straight 2.4(ac) ones.
> > - CompactFlash (= IDE disk)
> > - Geode GX1 CPU (i586 compatible)
>
> Forgot to mention: I use an ext2 fs, but maybe it's a generic,
> fs-independant problem.
>
> 	greetings,
> 	Rob van Nieuwkerk

How does it 'know' it's a R/O file-system? Have you mounted it
R/O, mounted it noatime, or just taken whatever you get when
you boot from a ramdisk?

FYI, I created a FIFO with mkfifo, remounted the file-system
R/O, executed `cat` with it's input coming from the FIFO, and
then waited for a few minutes. I then wrote to the FIFO.
The atime did not change with 2.4.20.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.