Re: [PATCH 1/1] block: add default clause for unsupported T10_PI types

["Martin K. Petersen" <martin.petersen@oracle.com>]

Jens,

>> block/t10-pi.c: In function 't10_pi_verify':
>> block/t10-pi.c:62:3: warning: enumeration value 'T10_PI_TYPE0_PROTECTION'
>>                       not handled in switch [-Wswitch]
>>        switch (type) {
>>        ^~~~~~
>
> This commit message is woefully lacking. It doesn't explain
> anything...?  Why aren't we just flagging this as an error? Seems a
> lot saner than adding a BUG().

The fundamental issue is that T10_PI_TYPE0_PROTECTION means "no attached
protection information". So it's a block layer bug if we ever end up in
this function and the protection type is 0.

My main beef with all this is that I don't particularly like introducing
a nonsensical switch case to quiesce a compiler warning. We never call
t10_pi_verify() with a type of 0 and there are lots of safeguards
further up the stack preventing that from ever happening. Adding a Type
0 here gives the reader the false impression that it's valid input to
the function. Which it really isn't.

Arnd: Any ideas how to handle this?

-- 
Martin K. Petersen	Oracle Linux Engineering