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: sobo...@sippysoft.com [mailto:sobo...@sippysoft.com] On Behalf Of Maxim Sobolev Sent: Friday, July 8, 2016 23:20 To: Dexuan Cui <de...@microsoft.com> Cc: freebsd-geom@freebsd.org; Allan Jude <allanj...@freebsd.org>; ken <k...@freebsd.org>; imp <i...@freebsd.org>; Hongjiang Zhang <honz...@microsoft.com>; Sepherosa Ziehau <sepher...@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 <de...@microsoft.com<mailto:de...@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 _______________________________________________ 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"
