Date: Sat, 9 Jul 2016 02:20:54 +0000 From: Dexuan Cui <decui@microsoft.com> To: Maxim Sobolev <sobomax@freebsd.org> Cc: "freebsd-geom@freebsd.org" <freebsd-geom@freebsd.org>, Allan Jude <allanjude@freebsd.org>, ken <ken@freebsd.org>, imp <imp@freebsd.org>, Hongjiang Zhang <honzhan@microsoft.com>, Sepherosa Ziehau <sepherosa@gmail.com> Subject: RE: How to force GEOM to recalculate the free space after the disk is resized? Message-ID: <CO2PR03MB2182D0D7BB893795EA14F85DBF3D0@CO2PR03MB2182.namprd03.prod.outlook.com> In-Reply-To: <CAH7qZfsov93YC3_tS=NZ1142zh4-WhdVYN2jnhaPshLqKPbx1A@mail.gmail.com> References: <CO2PR03MB2182532200F6E92F110EBAA1BF3C0@CO2PR03MB2182.namprd03.prod.outlook.com> <CAH7qZfsov93YC3_tS=NZ1142zh4-WhdVYN2jnhaPshLqKPbx1A@mail.gmail.com>
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Yes, this is also my suspicion.
Here with “diskinfo /dev/da1”, geom can already detect the new disk capacity but it just doesn’t update its internal structure for new free space.
I think I’ll have to locate the related code and ask geom to re-probe free space on disk capacity change.
It would be great if somebody can point out the exact code I need to dig into.
-- Dexuan
From: sobomax@sippysoft.com [mailto:sobomax@sippysoft.com] On Behalf Of Maxim Sobolev
Sent: Friday, July 8, 2016 23:20
To: Dexuan Cui <decui@microsoft.com>
Cc: freebsd-geom@freebsd.org; Allan Jude <allanjude@freebsd.org>; ken <ken@freebsd.org>; imp <imp@freebsd.org>; Hongjiang Zhang <honzhan@microsoft.com>; Sepherosa Ziehau <sepherosa@gmail.com>
Subject: Re: How to force GEOM to recalculate the free space after the disk is resized?
Smells like a bug in the geom_part where it supposed to re-read the partitions and update its internal structures. The reason why it works when you open dev/da1 for writing is because the geom_part provider that is attached to that disk is destroyed and created anew when you close the fd.
-Maxim
On Fri, Jul 8, 2016 at 5:19 AM, Dexuan Cui <decui@microsoft.com<mailto:decui@microsoft.com>> wrote:
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
help
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