* Unmounting a busy RO-Filesystem
@ 2002-12-17 1:06 Bourne
2002-12-16 18:03 ` Denis Vlasenko
0 siblings, 1 reply; 3+ messages in thread
From: Bourne @ 2002-12-17 1:06 UTC (permalink / raw)
To: linux-kernel
I have 3 partitions. /dev/hda3 for '/' , /dev/hda1 for /boot and
/dev/hda2 for swap.
I boot & then i do a CTRL+ALT+SYSRQ+U. '/' and '/boot' are now
remounted ReadOnly.
1) cd '/boot'
2) umount /boot ----> This gives me an error "Device Busy"
3) cd /
4) umount / -------> No error
5) echo $? -----> outputs '0' indicating success. !!!!!!!!
When i do the above by skipping the Sysrq part, i get the usual expected
errors.
So is the above behaviour expected ? I tried this on 2.4.19 & 2.5.51.
Same results.
I am subscribed to the list
TIA
Bourne
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Unmounting a busy RO-Filesystem
2002-12-17 1:06 Unmounting a busy RO-Filesystem Bourne
@ 2002-12-16 18:03 ` Denis Vlasenko
2002-12-16 18:17 ` Steven Dake
0 siblings, 1 reply; 3+ messages in thread
From: Denis Vlasenko @ 2002-12-16 18:03 UTC (permalink / raw)
To: Bourne, linux-kernel
On 16 December 2002 23:06, Bourne wrote:
> I have 3 partitions. /dev/hda3 for '/' , /dev/hda1 for /boot and
> /dev/hda2 for swap.
>
> I boot & then i do a CTRL+ALT+SYSRQ+U. '/' and '/boot' are now
> remounted ReadOnly.
>
> 1) cd '/boot'
> 2) umount /boot ----> This gives me an error "Device Busy"
How do you imagine unmounting a directory when you are in it? ;)
> 3) cd /
> 4) umount / -------> No error
This is special case: "umount /" == "mount -o remount,ro /"
> 5) echo $? -----> outputs '0' indicating success. !!!!!!!!
>
> When i do the above by skipping the Sysrq part, i get the usual
> expected errors.
Without SysRq,
# mount -o remount,ro /
fails 'coz you have files open for writing.
You might ask how kernel can do that ro remount with SysRq?
It cheats! ;)
--
vda
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Unmounting a busy RO-Filesystem
2002-12-16 18:03 ` Denis Vlasenko
@ 2002-12-16 18:17 ` Steven Dake
0 siblings, 0 replies; 3+ messages in thread
From: Steven Dake @ 2002-12-16 18:17 UTC (permalink / raw)
To: vda; +Cc: Bourne, linux-kernel
Denis Vlasenko wrote:
>On 16 December 2002 23:06, Bourne wrote:
>
>
>>I have 3 partitions. /dev/hda3 for '/' , /dev/hda1 for /boot and
>>/dev/hda2 for swap.
>>
>>I boot & then i do a CTRL+ALT+SYSRQ+U. '/' and '/boot' are now
>>remounted ReadOnly.
>>
>>1) cd '/boot'
>>2) umount /boot ----> This gives me an error "Device Busy"
>>
>>
>
>How do you imagine unmounting a directory when you are in it? ;)
>
>
This is possible with a kernel patch called forced unmount. It will
blow away the mount point even if there are files open in it or not.
The best part is it properly closes the superblock so the filesystem
doesn't have to be fsck'ed.
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2002-12-17 1:06 Unmounting a busy RO-Filesystem Bourne
2002-12-16 18:03 ` Denis Vlasenko
2002-12-16 18:17 ` Steven Dake
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