Re: [PATCH scsi] Add NULL checking of return value from scsi_cmd_to_driver()

On Mon, 2012-09-24 at 09:44 +0400, James Bottomley wrote:

On Mon, 2012-09-24 at 13:30 +0800, Li Zhong wrote:

quoted

Just noticed that after commit 919f797, it is possible that 
scsi_cmd_to_driver() returns NULL. This patch adds the NULL checking for drv 
returned from the above function. 

Maybe it is not possible at run time, but from the code itself, we'd better
have this check?  

There's not much point having a check that never trips, unless it's an
assert, in which case a NULL deref does that.  All it does is add
pointless instructions to the critical path.  only REQ_TYPE_BLOCK_PC
commands can be submitted without a driver, so the check above would
seem to preclude that.

Hi James, 

Thank you, it sounds reasonable to me. Let's drop it. 

Thanks, Zhong

James