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Date:      Tue, 10 May 2016 15:22:28 -0500
From:      Matthew Grooms <mgrooms@shrew.net>
To:        freebsd-current@freebsd.org
Subject:   Re: Resizing a zpool as a VMware ESXi guest ...
Message-ID:  <157c5d41-41c2-8812-79f1-3cab2c1eb8e5@shrew.net>
In-Reply-To: <565A7906.60106@shrew.net>
References:  <543841B8.4070007@shrew.net> <20141016081016.GA4670@brick.home> <5657F135.6080902@shrew.net> <56581F5A.4010009@digiware.nl> <56589C1A.1020702@shrew.net> <5658A764.5030508@shrew.net> <565906E8.9060005@shrew.net> <565A425C.7020101@shrew.net> <565A7906.60106@shrew.net>

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On 11/28/2015 10:03 PM, Matthew Grooms wrote:
> On 11/28/2015 6:10 PM, Matthew Grooms wrote:
>> On 11/27/2015 7:44 PM, Matthew Grooms wrote:
>>> I spent the day looking over the FreeBSD cam and scsi_da source code.
>>> After sprinkling a bunch of printf's around to see what code paths
>>> were being called, It's obvious that Edward was correct in assuming
>>> that ESXi 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. It's frustrating that the only way to
>>> get the scsci_da code to call reprobe() is by receiving a command
>>> from the device. Would something like this work? ...
>>>
>>> 1) Register a callback using xpt_register_async( daasync,
>>> AC_REPROBE_DEVICE, path ) that calls reprobe()
>>> 2) Implement a new IOCTL in cam_xpt that camcontrol can call with the
>>> bus:target:lun as the argument
>>> 3) have cam_xpt capture the IOCTL request and call xpt_async(
>>> AC_REPROBE_DEVICE, path ) as a result
>>>
>>> This way users would have the option of manually asking cam to
>>> communicate the new size to geom. The only option now is one or more
>>> reboots to gain access to the increased disk capacity. If this sounds
>>> like a reasonable approach, I'll take a stab at implementing it.
>>>
>>
>> Here is a proof of concept patch. I'm a complete noob when it comes to
>> cam, scsi or freebsd kernel development for that matter, so I'm sure
>> it could have been done a better way. In any case, I added a new
>> command to camcontrol that allows you to specify a bus, target and lun
>> as an argument. 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 output shows the
>> size as 32G but geom 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
>>
>> This generates an event that is captured by the scsci da device to
>> forces a reprobe. 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 increase
>> the partition size and grow the fs ...
>>
>> [root@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
>>
>> Sure would be nice to have something like this in the tree. It's
>> really a drag to have to reboot production VMs to increase disk
>> capacity when it could be easily avoided. I'm not sure what the
>> correct IOCTL should look like. Maybe CAMIOCOMMAND is a better way to
>> go? If someone with some experience with the cam/scsi subsystems was
>> willing to give me some direction I'd be willing to try and rewrite
>> the patch in a way that would be commit worthy. I just need some
>> direction.
>>
>
> Ok, last post until I get some feedback. Here's a new version of the
> patch complete with man page updates. It communicates via CAMIOCOMMAND
> instead of introducing a new ioctl value. I tried to model it after the
> device reset option, hopefully with some degree of success. Functionally
> it should be the same as the first patch.
>

The PR 204901 filed for this can be closed now that the author (ahem) 
has committed support for the camcontrol reprobe command ...

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=204901
https://docs.freebsd.org/cgi/getmsg.cgi?fetch=866020+0+current/svn-src-head

-Matthew



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