Messages in this thread | | | Subject | Re: [RFC PATCH] scsi: libsas: fix WARN on device removal | From | John Garry <> | Date | Mon, 21 Nov 2016 15:16:26 +0000 |
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>>>> @Maintainers, would you be willing to accept this patch as an interim fix >>>> for the dastardly WARN while we try to fix the flutter issue? >>> >>> >>> To me this adds a bug to quiet a benign, albeit noisy, warning. >>> >> >> What is the bug which is being added? > > The bug where we queue a port teardown, but see a port formation event > in the meantime.
As I understand, this vulnerability already exists: http://marc.info/?l=linux-scsi&m=143801026028006&w=2
I actually don't understand how libsas dealt with flutter (which I take to mean a burst of up and down events) before these changes, as it can only queue simultaneously one up and one down event per port. So, if we get a flutter, then the events are lost and we get indeterminate state.
> >> And it's a very noisy warning, as in 6K lines on the console when an >> expander is unplugged. > > Does something like this modulate the failure? > > diff --git a/drivers/scsi/scsi_transport_sas.c > b/drivers/scsi/scsi_transport_sas.c index > 60b651bfaa01..11401e5c88ba 100644 > --- a/drivers/scsi/scsi_transport_sas.c > +++ b/drivers/scsi/scsi_transport_sas.c > @@ -262,9 +262,10 @@ static void sas_bsg_remove(struct Scsi_Host > *shost, struct sas_rphy *rphy > { > struct request_queue *q; > > - if (rphy) > + if (rphy) { > q = rphy->q; > - else > + rphy->q = NULL; > + } else > q = to_sas_host_attrs(shost)->q; > > if (!q) > > . >
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