Hi, I have a FreeBSD virtual machine (VM) running on Hyper-V and I'm testing
Hyper-V's Disk Online Resizing feature. The feature can expand or shrink the
(virtual) disk capacity of a VM when the VM is running.
There is an issue with gpart or GEOM: after the disk capacity is expanded (or
shrunk), gpart/GEOM can detect the new bigger capacity, but the free space
displayed by gpart remained the same unless I open the disk dev file for
writing, e.g.,
[root@decui-bsd11 ~]# gpart create -s MBR /dev/da1
da1 created
[root@decui-bsd11 ~]# gpart show /dev/da1
=> 63 83886017 da1 MBR (40G)
63 83886017 - free - (40G)
[root@decui-bsd11 ~]# diskinfo /dev/da1
/dev/da1 512 42949672960 83886080 4096 0 5221
255 63
Now I expand the disk from 40GB to 50GB by Hyper-V management tool.
Next, I get the below, i.e., gpart/GEOM detects the new disk capacity, but the
free space remains the same.
(Note: the first diskinfo failure should be expected: Hyper-V only notifies the
VM of the capacity change on the VM's next read or write request, and in the VM
it seems there is a race condition between the ioctl and the handling of
capacity change. I'll see how this can be fixed.)
[root@decui-bsd11 ~]# diskinfo /dev/da1
diskinfo: /dev/da1: ioctl(DIOCGMEDIASIZE) failed, probably not a disk.
[root@decui-bsd11 ~]# diskinfo /dev/da1
/dev/da1 512 53687091200 104857600 4096 0 6527
255 63
[root@decui-bsd11 ~]# gpart show /dev/da1
=> 63 83886017 da1 MBR (50G)
63 83886017 - free - (40G)
Now, if I run a program that only does
"openat(AT_FDCWD,"/dev/da1",O_WRONLY|O_CREAT,0644);", GEOM will detect that the
free space is 50GB now and GEOM will pass this info to gpart:
[root@decui-bsd11 ~]# gpart show /dev/da1
=> 63 104857537 da1 MBR (50G)
63 104857537 - free - (50G)
I'm not familiar with GEOM.
Can somebody please explain the behavior?
I don't know who exactly maintains GEOM , so I just picked some names from "git
log geom/" and put you to Cc. Sorry if this mail bothers you. :-)
Thanks,
-- Dexuan
_______________________________________________
freebsd-geom@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-geom
To unsubscribe, send any mail to "freebsd-geom-unsubscr...@freebsd.org"
