Date: Mon, 16 Aug 2010 22:13:34 +0200 (CEST) From: Stefan Richter Subject: firewire: sbp2: fix stall with "Unsolicited response" Fix I/O stalls with some 4-bay RAID enclosures which are based on OXUF936QSE: - Onnto dataTale RSM4QO, old firmware (not anymore with current firmware), - inXtron Hydra Super-S LCM, old as well as current firmware when used in RAID-5 mode, perhaps also in other RAID modes. The stalls happen during heavy or moderate disk traffic in periods that are a multiple of 5 minutes, roughly twice per hour. They are caused by the target responding too late to an ORB_Pointer register write: The target responds after Split_Timeout, hence firewire-core cancels the transaction, and firewire-sbp2 fails the SCSI request. The SCSI core retries the request, that fails again (and again), hence SCSI core calls firewire-sbp2's abort handler (and even the Management_Agent register write in the abort handler has the transaction timeout problem). During all that, the process which issued the I/O is stalled in I/O wait state. Meanwhile, the target actually acts on the first failed SCSI request: It responds to the ORB_Pointer write later (seen in the kernel log as "firewire_core: Unsolicited response") and also finishes the SCSI request with proper status (seen in the kernel log as "firewire_sbp2: status write for unknown orb"). So let's just ignore RCODE_CANCELLED in the transaction callback and wait for the target to complete the ORB nevertheless. This requires a small modification is sbp2_cancel_orbs(); it now needs to call orb->callback() regardless whether fw_cancel_transaction() found the transaction unfinished or finished. A different solution which has been proven to work too is to increase Split_Timeout on the local node. (Tested: 2000ms timeout; maybe 1000ms or something like that works too. 200ms is insufficient. Standard is 100ms.) However, I rather not do this because any software on any node could change the Split_Timeout to something unsuitable. Or such a large Split_Timeout might be undesirable for other purposes. Signed-off-by: Stefan Richter --- drivers/firewire/sbp2.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) Index: b/drivers/firewire/sbp2.c =================================================================== --- a/drivers/firewire/sbp2.c +++ b/drivers/firewire/sbp2.c @@ -472,12 +472,18 @@ static void complete_transaction(struct * So this callback only sets the rcode if it hasn't already * been set and only does the cleanup if the transaction * failed and we didn't already get a status write. + * + * Here we treat RCODE_CANCELLED like RCODE_COMPLETE because some + * OXUF936QSE firmwares occasionally respond after Split_Timeout and + * complete the ORB just fine. Note, we also get RCODE_CANCELLED + * from sbp2_cancel_orbs() if fw_cancel_transaction() == 0. */ spin_lock_irqsave(&card->lock, flags); if (orb->rcode == -1) orb->rcode = rcode; - if (orb->rcode != RCODE_COMPLETE) { + + if (orb->rcode != RCODE_COMPLETE && orb->rcode != RCODE_CANCELLED) { list_del(&orb->link); spin_unlock_irqrestore(&card->lock, flags); @@ -526,8 +532,7 @@ static int sbp2_cancel_orbs(struct sbp2_ list_for_each_entry_safe(orb, next, &list, link) { retval = 0; - if (fw_cancel_transaction(device->card, &orb->t) == 0) - continue; + fw_cancel_transaction(device->card, &orb->t); orb->rcode = RCODE_CANCELLED; orb->callback(orb, NULL);