[Bug 204901] GEOM doesn't see new disk capacity after VMDK resize without a reboot

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=204901

            Bug ID: 204901
           Summary: GEOM doesn't see new disk capacity after VMDK resize
                    without a reboot
           Product: Base System
           Version: 11.0-CURRENT
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: mgrooms at shrew.net

Created attachment 163665
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=163665&action=edit
patch that adds camcontrol reprobe device command

ESXi allows the user to resize a VMDK attached to a running VM. Unfortunately
it doesn't return any 'Unit Attention' sense information in response to a 'Read
Capacity' request. This kinda makes sense as ESXi emulates SCSI-2 disk devices
and, as far as I can tell, the 0x2A/0x09 ASC/ASCQ sense code that denotes
'Capacity Data Has Changed' wasn't defined until the SCSCI-3 spec.

I am attaching a patch that allows an admin to request that a device be
re-probed via camcontrol. The new command sends a CCB message that creates an
async event. The event is captured by scsi_da which calls reprobe() on the
peripheral, the same code that is executed when the 'Unit Attention' 'Capacity
Data Has Changed' sense code is received from the device. For example ...

# camcontrol readcap da1 -h
Device Size: 32 G, Block Length: 512 bytes

# gpart show da1
=>      40  58720176  da1  GPT  (28G)
        40  58720176    1  freebsd-ufs  (28G)

Note, I resized the VMDK disk in ESXi. The camcontrol readcap output shows the
size as 32G but geom still thinks its 28G.

# camcontrol devlist
<NECVMWar VMware IDE CDR10 1.00>   at scbus1 target 0 lun 0 (cd0,pass0)
<VMware Virtual disk 1.0>          at scbus2 target 0 lun 0 (pass1,da0)
<VMware Virtual disk 1.0>          at scbus2 target 1 lun 0 (pass2,da1)
<FREEBSD CTLDISK 0001>             at scbus3 target 0 lun 0 (da2,pass3)

# camcontrol reprobe 2:1:0

The kernel output looks almost identical to when the 'Unit Attention' sense
data is received ...

Nov 28 17:46:13 iscsi-i kernel: (da1:mpt0:0:1:0): Re-probe requested
Nov 28 17:46:13 iscsi-i kernel: GEOM_PART: da1 was automatically resized.
Nov 28 17:46:13 iscsi-i kernel: Use `gpart commit da1` to save changes or
`gpart undo da1` to revert them.

Now that geom knows about the increased disk capacity, I can resize the
partition and grow the fs ...

[root at iscsi-i /home/mgrooms]# gpart show da1
=>      40  67108784  da1  GPT  (32G)
        40  58720176    1  freebsd-ufs  (28G)
  58720216   8388608       - free -  (4.0G)

# gpart resize -i 1 da1
da1p1 resized

# growfs da1p1
Device is mounted read-write; resizing will result in temporary write
suspension for /var/data1.
It's strongly recommended to make a backup before growing the file system.
OK to grow filesystem on /dev/da1p1, mounted on /var/data1, from 28GB to 32GB?
[Yes/No] Yes
super-block backups (for fsck_ffs -b #) at:
 58983232, 60265472, 61547712, 62829952, 64112192, 65394432, 66676672

# df -h
Filesystem    Size    Used   Avail Capacity  Mounted on
/dev/da0p3     18G    5.3G     12G    31%    /
devfs         1.0K    1.0K      0B   100%    /dev
/dev/da1p1     31G     32M     28G     0%    /var/data1
/dev/da2p1     15G     32M     14G     0%    /var/data2

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