On Mon, 2012-09-24 at 15:03 +0800, Li Zhong wrote: > On Mon, 2012-09-24 at 09:44 +0400, James Bottomley wrote: > > On Mon, 2012-09-24 at 13:30 +0800, Li Zhong wrote: > > > 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. Well, there is another thing you might do: The path length of scsi_cmd_to_driver() increased a lot thanks to 18a4d0a22ed6 it might be worth getting it back to what it was (this looks to be doable with the same != REQ_TYPE_BLOCK_PC test in the error handler. Plus, I think it fixes a bug where you get different behaviours from REQ_TYPE_BLOCK_PC commands when a driver is and isn't attached (I've cc'd Martin to see what he thinks). James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
