[Stgt-devel] [PATCH] Make changes so that VTL stuff works properly ...

[Richard Sharpe]

On Mon, Jul 28, 2008 at 7:49 PM, Mark Harvey <markh794 at gmail.com> wrote:
> Richard Sharpe wrote:
>>>
>>> From a16d368a29298170df2c21fd19d8490c248f06b1 Mon Sep 17 00:00:00 2001
>>
>> From: Richard Sharpe <realrichardsharpe at gmail.com>
>> Date: Mon, 28 Jul 2008 14:34:12 -0700
>> Subject: [PATCH] Make changes so that VTL stuff works properly ...
>> Signed-off-by: Richard Sharpe <realrichardsharpe at gmail.com>
>>
>> There are three changes here.
>>
>> In target.h I expose device_lookup for use by the smc.c code.
>>
>> In target.h I modify tgt_device_path_update so that we can call it to
>> both open and close a file that has been allocated to a
>> data_transfer_station.
>>
>> In smc.c I modified set_slot_full and set_slot_empty to call the
>> modified tgt_device_path_update to achieve my goals. We call
>> device_lookup to figure out the device we are interested in.
>>
>> I have tested this by loading and unloading tapes and DVDs, doing tar
>> to the drive and using cdrecord on the device, and verifying with lsof
>> that the tgtd has the files open when they are in the transfer station
>> and does not have them open when the station has been unloaded.
>>
>> It all seems to work. I have attached the patch as well because gmail
>> seems to kill patches ... I hope the attached patch is OK.
>
> Sorry, I don't quite understand the reason for this patch.
>
> The smc already calls a non-static dtd_load_unload() which performs a
> similar function to tgt_device_path_update() but with different args.
>
> int dtd_load_unload(int tid, uint64_t lun, int load, char *file)
> vs
> int tgt_device_path_update(struct target *target, struct scsi_lu *lu, char
> *path)
>
> i.e. dtd_load_unload calls __device_lookup() and then opens/closes the
> backing store.
>
> All this patch seems to do is call the 'open' or 'close' backing store
> twice.
>
>
> Perhaps 'fixing' dtd_load_unload() so it then calls tgt_device_path_update()
> if this function is not correct.
>
> FWIW: dtd_load_unload == Data Transfer Device load/unload
>
> At the time this function was added, the tgt_device_path_update() did not
> exist.

All I know is that the current code segfaults when you ask for a tape
to be loaded into the transfer station.

It segfaults because the appropriate bs_open method has not been
called (which initializes some lists and such).

tgt_device_path_update calls the bs_open routine (through the dev structure) ...