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On Sat, Oct 14, 2017 at 01:40:45AM +0200, Marek Marczykowski-Górecki wrote:
> On Sat, Oct 14, 2017 at 01:21:58AM +0200, Wojtek Porczyk wrote:
> > On Sat, Oct 14, 2017 at 01:20:13AM +0200, Marek Marczykowski-Górecki wrote:
> > > You can't reload partition table while it is used (something from there
> > > is mounted). At least Linux doesn't support it.
> >
> > Just tested with loop device, fdisk, and ext4. Looks like it works. Unless
> > it
> > works only with loop?
>
> No, it doesn't work, at least not directly:
>
> [root@testvm user]# truncate -s 10G test.img
> [root@testvm user]# losetup -f -P --show test.img
> /dev/loop0
> [root@testvm user]# fdisk /dev/loop0
> (...)
> Created a new partition 1 of type 'Linux' and of size 10 GiB.
>
> Command (m for help): w
> The partition table has been altered.
> Syncing disks.
>
> [root@testvm user]# blockdev --rereadpt /dev/loop0
> [root@testvm user]# mkfs /dev/loop0p1
> (...)
> [root@testvm user]# mount /dev/loop0p1 /mnt
> [root@testvm user]# truncate -s 20G test.img
> [root@testvm user]# losetup -c /dev/loop0
> [root@testvm user]# fdisk /dev/loop0
> (...)
> Command (m for help): p
> Disk /dev/loop0: 20 GiB, 21474836480 bytes, 41943040 sectors
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: dos
> Disk identifier: 0x75e36dce
>
> Device Boot Start End Sectors Size Id Type
> /dev/loop0p1 2048 41943039 41940992 20G 83 Linux
>
> Command (m for help): w
> The partition table has been altered.
> Calling ioctl() to re-read partition table.
> Re-reading the partition table failed.: Device or resource busy
>
> The kernel still uses the old table. The new table will be used at the
> next reboot or after you run partprobe(8) or kpartx(8).
>
> I wonder on what conditions partprobe would work. And how would mounted
> filesystem react for it.
I'm calling bullshit on that. Coredump follows:
- -- >8 --
Command (m for help): n
Partition type
p primary (2 primary, 0 extended, 2 free)
e extended (container for logical partitions)
Select (default p):
Using default response p.
Partition number (3,4, default 3):
First sector (43008-195311, default 43008):
Last sector, +sectors or +size{K,M,G,T,P} (43008-195311, default 195311): +50M
Created a new partition 3 of type 'Linux' and of size 50 MiB.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: Invalid argument
The kernel still uses the old table. The new table will be used at the next
reboot or after you run partprobe(8) or kpartx(8).
[root@qubes-dev tmp]# partprobe /dev/loop0
[root@qubes-dev tmp]# ls -ld /dev/loop0*
brw-rw---- 1 root disk 7, 0 Oct 14 01:16 /dev/loop0
brw-rw---- 1 root disk 259, 0 Oct 14 01:16 /dev/loop0p1
brw-rw---- 1 root disk 259, 1 Oct 14 01:16 /dev/loop0p2
brw-rw---- 1 root disk 259, 2 Oct 14 01:16 /dev/loop0p3
[root@qubes-dev tmp]# blockdev --getsize64 /dev/loop0p3
52428800
[root@qubes-dev tmp]# resize2fs /dev/loop0p3
resize2fs 1.43.3 (04-Sep-2016)
Filesystem at /dev/loop0p3 is mounted on /mnt; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/loop0p3 is now 51200 (1k) blocks long.
[root@qubes-dev tmp]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/dmroot 9.5G 4.6G 4.5G 51% /
/dev/xvdd 477M 227M 226M 51%
/usr/lib/modules/4.9.45-21.pvops.qubes.x86_64
devtmpfs 145M 0 145M 0% /dev
tmpfs 1.0G 0 1.0G 0% /dev/shm
tmpfs 153M 616K 152M 1% /run
tmpfs 153M 0 153M 0% /sys/fs/cgroup
tmpfs 1.0G 76M 949M 8% /tmp
/dev/xvdb 197G 168G 30G 85% /rw
tmpfs 31M 12K 31M 1% /run/user/1000
/dev/loop0p3 48M 650K 45M 2% /mnt
[root@qubes-dev tmp]# truncate -s 1G hda1
[root@qubes-dev tmp]# losetup -c /dev/loop0
[root@qubes-dev tmp]# blockdev --getsize64 /dev/loop0
1073741824
[root@qubes-dev tmp]# fdisk /dev/loop0
Welcome to fdisk (util-linux 2.28.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): p
Disk /dev/loop0: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x75b4ec65
Device Boot Start End Sectors Size Id Type
/dev/loop0p1 2048 22527 20480 10M 83 Linux
/dev/loop0p2 22528 43007 20480 10M 83 Linux
/dev/loop0p3 43008 145407 102400 50M 83 Linux
Command (m for help): d
Partition number (1-3, default 3):
Partition 3 has been deleted.
Command (m for help): n
Partition type
p primary (2 primary, 0 extended, 2 free)
e extended (container for logical partitions)
Select (default p):
Using default response p.
Partition number (3,4, default 3):
First sector (43008-2097151, default 43008):
Last sector, +sectors or +size{K,M,G,T,P} (43008-2097151, default 2097151):
Created a new partition 3 of type 'Linux' and of size 1003 MiB.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: Invalid argument
The kernel still uses the old table. The new table will be used at the next
reboot or after you run partprobe(8) or kpartx(8).
[root@qubes-dev tmp]# partprobe /dev/loop0
[root@qubes-dev tmp]# echo $?
0
[root@qubes-dev tmp]# resize2fs /dev/loop0p3
resize2fs 1.43.3 (04-Sep-2016)
Filesystem at /dev/loop0p3 is mounted on /mnt; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 8
The filesystem on /dev/loop0p3 is now 1027072 (1k) blocks long.
[root@qubes-dev tmp]# cat /etc/os-release
NAME=Fedora
VERSION="25 (Twenty Five)"
ID=fedora
VERSION_ID=25
PRETTY_NAME="Fedora 25 (Twenty Five)"
ANSI_COLOR="0;34"
CPE_NAME="cpe:/o:fedoraproject:fedora:25"
HOME_URL="https://fedoraproject.org/";
SUPPORT_URL="https://fedoraproject.org/wiki/Communicating_and_getting_help";
BUG_REPORT_URL="https://bugzilla.redhat.com/";
REDHAT_BUGZILLA_PRODUCT="Fedora"
REDHAT_BUGZILLA_PRODUCT_VERSION=25
REDHAT_SUPPORT_PRODUCT="Fedora"
REDHAT_SUPPORT_PRODUCT_VERSION=25
PRIVACY_POLICY_URL=https://fedoraproject.org/wiki/Legal:PrivacyPolicy
[root@qubes-dev tmp]# uname -a
Linux qubes-dev 4.9.45-21.pvops.qubes.x86_64 #1 SMP Tue Aug 29 14:50:28 UTC
2017 x86_64 x86_64 x86_64 GNU/Linux
[root@qubes-dev tmp]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/dmroot 9.5G 4.6G 4.5G 51% /
/dev/xvdd 477M 227M 226M 51%
/usr/lib/modules/4.9.45-21.pvops.qubes.x86_64
devtmpfs 145M 0 145M 0% /dev
tmpfs 1.0G 0 1.0G 0% /dev/shm
tmpfs 153M 616K 152M 1% /run
tmpfs 153M 0 153M 0% /sys/fs/cgroup
tmpfs 1.0G 75M 950M 8% /tmp
/dev/xvdb 197G 168G 30G 85% /rw
tmpfs 31M 12K 31M 1% /run/user/1000
/dev/loop0p3 976M 1.7M 943M 1% /mnt
[root@qubes-dev tmp]#
- -- >8 --
- --
pozdrawiam / best regards _.-._
Wojtek Porczyk .-^' '^-.
Invisible Things Lab |'-.-^-.-'|
| | | |
I do not fear computers, | '-.-' |
I fear lack of them. '-._ : ,-'
-- Isaac Asimov `^-^-_>
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