Re: [PATCH] fix id computation in scsi_eh_target_reset()

James Bottomley
2010-10-26T23:09:35Z

On Tue, 2010-10-26 at 18:07 -0500, Mike Christie wrote:
> On 10/25/2010 03:53 PM, James Bottomley wrote:
> >
> > diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> > index 1de30eb..484b128 100644
> > --- a/drivers/scsi/scsi_error.c
> > +++ b/drivers/scsi/scsi_error.c
> > @@ -1156,51 +1156,40 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
> > struct list_head *work_q,
> > struct list_head *done_q)
> > {
> > - struct scsi_cmnd *scmd, *tgtr_scmd, *next;
> > - unsigned int id = 0;
> > - int rtn;
> > + LIST_HEAD(tmp_list);
> >
> > - do {
> > - tgtr_scmd = NULL;
> > - list_for_each_entry(scmd, work_q, eh_entry) {
> > - if (id == scmd_id(scmd)) {
> > - tgtr_scmd = scmd;
> > - break;
> > - }
> > - }
> > - if (!tgtr_scmd) {
> > - /* not one exactly equal; find the next highest */
> > - list_for_each_entry(scmd, work_q, eh_entry) {
> > - if (scmd_id(scmd)> id&&
> > - (!tgtr_scmd ||
> > - scmd_id(tgtr_scmd)> scmd_id(scmd)))
> > - tgtr_scmd = scmd;
> > - }
> > - }
> > - if (!tgtr_scmd)
> > - /* no more commands, that's it */
> > - break;
> > + list_splice(work_q,&tmp_list);
>
>
> I think I am hitting multiple bugs. One might be with this patch, but
> strangely they both hit __list_add bugs in the scsi eh. I think this
> needs to be list_splice_init().

I think that's exactly right ... I keep getting tripped up by the _init
requirements for reusing lists (and list_heads).

> > + list_for_each_entry_safe(scmd, next,&tmp_list, eh_entry) {
> > + if (scmd_id(scmd) != id)
> > + continue;
> > +
> > + if ((rtn == SUCCESS || rtn == FAST_IO_FAIL)
> > + && (!scsi_device_online(scmd->device) ||
> > + rtn == FAST_IO_FAIL || !scsi_eh_tur(scmd)))
> > + scsi_eh_finish_cmd(scmd, done_q);
>
> Because if the target resets work and move all the commands to the
> done_q here.
>
>
> > + else
> > + /* push back on work queue for further processing */
> > + list_move(&scmd->eh_entry, work_q);
> > + }
> >
> > return list_empty(work_q);
> > }
>
>
> Then this work_q is showing garbage in it from the splice I think.
> Without the list_splice_init I get that trace I cut and pasted in the
> other mail when I just force the scsi eh to run the target reset code.
>
> In the test, the target reset succeeds. The scsi_eh_finish_cmd call
> above moves all the cmds to the done_q. But the work_q still has junk in
> it, and so we return that we need to do more work and eventually we end
> up running scsi_eh_offline_sdevs which calls scsi_eh_finish_cmd on a
> command we already moved to the done_q.

So does changing to the _init version fix at least the junk done_q
problem?

James