On Mon, 2012-09-24 at 11:35 +0400, James Bottomley wrote:
> 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).
Hi James,
Do you mean something like this:
=======
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index de2337f..c1b05a8 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -789,7 +789,6 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
int cmnd_size, int timeout, unsigned sense_bytes)
{
struct scsi_device *sdev = scmd->device;
- struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
struct Scsi_Host *shost = sdev->host;
DECLARE_COMPLETION_ONSTACK(done);
unsigned long timeleft;
@@ -845,8 +844,11 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
scsi_eh_restore_cmnd(scmd, &ses);
- if (sdrv && sdrv->eh_action)
- rtn = sdrv->eh_action(scmd, cmnd, cmnd_size, rtn);
+ if (scmd->request->cmd_type != REQ_TYPE_BLOCK_PC) {
+ struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
+ if (sdrv->eh_action)
+ rtn = sdrv->eh_action(scmd, cmnd, cmnd_size, rtn);
+ }
return rtn;
}
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index ac06cc5..377df4a 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -134,16 +134,7 @@ struct scsi_cmnd {
static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
{
- struct scsi_driver **sdp;
-
- if (!cmd->request->rq_disk)
- return NULL;
-
- sdp = (struct scsi_driver **)cmd->request->rq_disk->private_data;
- if (!sdp)
- return NULL;
-
- return *sdp;
+ return *(struct scsi_driver **)cmd->request->rq_disk->private_data;
}
extern struct scsi_cmnd *scsi_get_command(struct scsi_device *, gfp_t);
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