[maemo-users] Missing space on MMC2

From: Marius Gedminas marius at pov.lt
Date: Fri Jun 27 17:59:27 EEST 2008
On Fri, Jun 27, 2008 at 04:58:47PM +0300, Eero Tamminen wrote:
> ext Marius Gedminas wrote:
> >Still, that doesn't explain the other experiments I did earlier.  I
> >created a 1.7 GB partition (to be really really sure I'm not
> >accidentally trying to make the filesystem larger than the device),
> >formatted it as VFAT and created a single large empty file (dd
> >if=/dev/zero of=/media/mmc2/bigfile), and that caused vfat errors in
> >dmesg and, at least once, caused the *partition table* to get
> >overwritten with zeroes.  See this (short) thread:
> >http://lists.maemo.org/pipermail/maemo-users/2008-March/020492.html
> What if you use the whole card like Windows usually formats them
> i.e. whole card is a single partition without any partition table?
> Does that change anything?

Let me try it now.

First, disable virtual memory in the Control Panel.  Then ssh to the
tablet and become root

  # umount /dev/mmcblk0p1

Let me first see if the problem persists in Diablo

  # sfdisk -l /dev/mmcblk0  

Disk /dev/mmcblk0: 61440 cylinders, 4 heads, 16 sectors/track
Units = cylinders of 32768 bytes, blocks of 1024 bytes, counting from 0
   Device Boot Start     End   #cyls    #blocks   Id  System
/dev/mmcblk0p1          0+  61439   61440-   1966072    b  W95 FAT32
/dev/mmcblk0p2          0       -       0          0    0  Empty
/dev/mmcblk0p3          0       -       0          0    0  Empty
/dev/mmcblk0p4          0       -       0          0    0  Empty

  # mkdosfs -F 32 /dev/mmcblk0p1
  # mount /dev/mmcblk0p1

Aargh, it mounted the fs on /media/mmc1, on top of my external card

  # umount /dev/mmcblk0p1
  # mount /dev/mmcblk0p1 /media/mmc2
  # dd if=/dev/zero of=/media/mmc2/bigfile bs=4K

long wait at 1.7 MB/s, while wondering what these tests do to the life
time of my non-replaceable internal flash memory...

dd: writing '/media/mmc2/bigfile': No space left on device
490555+0 records in
490554+0 records out

  # dmesg|tail

No errors

  # grep mmcblk0p1 /proc/mounts

/dev/mmcblk0p1 /media/mmc2 msdos rw,fmask=0022,dmask=0022,codepage=cp437 0 0

Not remounted read-only.  Although I now see it's mounted as msdos
rather than vfat.

  # umount /media/mmc2
  # mount -t vfat /dev/mmcblk0p1 /media/mmc2
  # cat /media/mmc2/bigfile > /dev/null

4.6 megs per second, according to vmstat.

No errors in dmesg.


So, either it was a bug in Chinook's kernel, or I was doing something
wrong in my tests.

Marius Gedminas
"Linux was made by foreign terrorists to take money from true US companies
like Microsoft." -Some AOL'er.
"To this end we dedicate ourselves..." -Don
(From the sig of "Don" <don at cs.byu.edu>)
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