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From: Li Zhong <zhong@linux.vnet.ibm.com>
To: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-scsi@vger.kernel.org,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH scsi] Add NULL checking of return value from scsi_cmd_to_driver()
Date: Mon, 24 Sep 2012 15:03:30 +0800	[thread overview]
Message-ID: <1348470210.2475.47.camel@ThinkPad-T420> (raw)
In-Reply-To: <1348465493.2467.3.camel@dabdike>

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. 

Thanks, Zhong

> James
> 
> 



  reply	other threads:[~2012-09-24  7:03 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-24  5:30 [PATCH scsi] Add NULL checking of return value from scsi_cmd_to_driver() Li Zhong
2012-09-24  5:44 ` James Bottomley
2012-09-24  7:03   ` Li Zhong [this message]
2012-09-24  7:35     ` James Bottomley
2012-09-24  9:25       ` Li Zhong
2012-09-24  9:33         ` James Bottomley
2012-09-27  2:02       ` Martin K. Petersen
2012-09-27  4:44         ` James Bottomley
2012-09-27  9:51           ` [PATCH scsi] Short the path length of scsi_cmd_to_driver() Li Zhong
2012-09-27 17:43             ` Martin K. Petersen
2012-09-28  7:13               ` Li Zhong
2012-09-28  7:45               ` James Bottomley
2012-09-27 17:41           ` [PATCH scsi] Add NULL checking of return value from scsi_cmd_to_driver() Martin K. Petersen
2012-09-28  7:48             ` James Bottomley
2012-09-29  4:23               ` [PATCH v2 scsi] Short the path length of scsi_cmd_to_driver() Li Zhong
2012-10-02 22:22                 ` Martin K. Petersen

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