On Tue, 2016-05-10 at 16:48 +0200, Jinpu Wang wrote: > On Mon, May 9, 2016 at 6:41 PM, Jinpu Wang < > jinpu.wang@xxxxxxxxxxxxxxxx> wrote: > > On Wed, May 4, 2016 at 7:02 PM, Jinpu Wang < > > jinpu.wang@xxxxxxxxxxxxxxxx> wrote: > > > On Mon, May 2, 2016 at 3:44 PM, James Bottomley < > > > jejb@xxxxxxxxxxxxxxxxxx> wrote: > > > > On Mon, 2016-05-02 at 12:05 +0200, Hannes Reinecke wrote: > > > > > On 04/29/2016 02:49 PM, Jinpu Wang wrote: > > > > > > Hi, all > > > > > > > > > > > > We hit IO error on fsync, it turns out was because sd treat > > > > > > succeeded > > > > > > SYNC as error. From what I checked in SBC spec there is no > > > > > > indication > > > > > > we should fail IO in this case, so we create this patch. > > > > > > > > > > > > > > > > > > Best Regards, > > > > > > > > > > > > Jack Wang > > > > > > > > > > > > v2: > > > > > > No change on patch itself, only resend in body as suggested > > > > > > by > > > > > > Bart, > > > > > > still keep the attachment in case mail client break the > > > > > > format. > > > > > > > > > > > > From 5d1f72d9643ce61cd9f3d312377378c43f171d0c Mon Sep 17 > > > > > > 00:00:00 > > > > > > 2001 > > > > > > From: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx> > > > > > > Date: Mon, 25 Apr 2016 12:05:22 +0200 > > > > > > Subject: [PATCH] sd: Don't treat succeeded SYNC as error > > > > > > > > > > > > We hit IO error in our production on multipath devices > > > > > > during > > > > > > resize > > > > > > device on target side, the problem turns out sd driver > > > > > > passes up as > > > > > > IO > > > > > > error when sense data is UNIT_ATTENTION and ASC && ASCQ > > > > > > indicate > > > > > > Capacity data has changed, even storage side sync the data > > > > > > properly. > > > > > > > > > > > > In order to fix this check in sd_done, report success if > > > > > > condition > > > > > > matches. > > > > > > > > > > > > Sebastian Parschauer report/analyze the bug here: > > > > > > https://sourceforge.net/p/scst/mailman/message/34953416/ > > > > > > > > > > > > Signed-off-by: Sebastian Parschauer <s.parschauer@xxxxxx> > > > > > > Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx> > > > > > > --- > > > > > > drivers/scsi/sd.c | 13 +++++++++++++ > > > > > > 1 file changed, 13 insertions(+) > > > > > > > > > > > Well. > > > > > Is there anything which guarantees us that 'capacity data has > > > > > changed' will be the only sense code which we'll be seeing as > > > > > a > > > > > response to SYNCHRONIZE CACHE? > > > > > I sincerely doubt so. > > > > > So why don't you fall back to the default action (ie retry > > > > > the > > > > > command) whenever you hit an UNIT ATTENTION? > > > > > This way we would cove any resulting sense code, _and_ would > > > > > get rid > > > > > of the rather ugly special case here. > > > > > > > > Actually, why are we getting here at all? should we be eating > > > > this > > > > unit attention once we've reported it in scsi_check_sense()? > > > > > > > > I also don't quite understand why the normal retry mechanism in > > > > scsi_io_completion() (called after drv->done()) isn't handling > > > > this. > > > > We set retries on a flush command and we give sd_sync_cache > > > > three > > > > goes. Any one of those should also cause the CC/UA to be > > > > ignored. > > > > > > > > James > > > > > > > > > > > > > > Sorry for delay, I agree safer to retry this command. > > > I checked the code path, in scsi_io_completion, we call > > > __scsi_error_from_host_byte for FLUSH request, > > > and we set error to EIO by default, somehow the code report error > > > directly to user space without retry. > > > [ 647.206270] sd 1:0:0:0: [sdb] tag#0 Send: scmd > > > 0xffff8800b6558480 > > > [ 647.206422] sd 1:0:0:0: [sdb] tag#0 CDB: Synchronize Cache(10) > > > 35 > > > 00 00 00 00 00 00 00 00 00 > > > [ 647.209748] sd 1:0:0:0: Capacity data has changed > > > [ 647.209896] sd 1:0:0:0: [sdb] tag#0 Done: SUCCESS Result: > > > hostbyte=DID_OK driverbyte=DRIVER_OK > > > [ 647.210157] sd 1:0:0:0: [sdb] tag#0 CDB: Synchronize Cache(10) > > > 35 > > > 00 00 00 00 00 00 00 00 00 > > > [ 647.210419] sd 1:0:0:0: [sdb] tag#0 Sense Key : Unit Attention > > > [current] > > > [ 647.210567] sd 1:0:0:0: [sdb] tag#0 Add. Sense: Capacity data > > > has changed > > > [ 647.210741] sd 1:0:0:0: [sdb] tag#0 scsi host busy 1 failed 0 > > > [ 647.210888] sd 1:0:0:0: Notifying upper driver of completion > > > (result 8000002) > > > [ 647.211035] sd 1:0:0:0: [sdb] tag#0 sd_done: completed 0 of 0 > > > bytes > > > [ 647.211182] sd 1:0:0:0: [sdb] tag#0 0 sectors total, 0 bytes > > > done, error -5 > > > [ 647.211330] blk_update_request: I/O error, dev sdb, sector 0 > > > > > > Will figure out why retry doesn't work. > > > > > > Thanks James and Hannes for all your input. > > > > > > Regards, > > > Jack > > > > Hi James, Hannes and all, > > > > I find out it's code below which report error directly back to user > > space without any retry. > > 913 /* > > 914 * If we finished all bytes in the request we are done > > now. > > 915 */ > > 916 if (!scsi_end_request(req, error, good_bytes, 0)) > > 917 return; > > > > But not sure, what's the best way to fix the behavior to let it > > retry, > > maybe add condition with sense key && asc && ascq direct go to > > requeue before line 913? > > > > Thanks > > Jack > > > Hi James , Hannes and all, > > I created a patch below, I did basic test on my test machines. Please > share your comments! > > Thanks, > Jack > From 72ab860811e14e37db81fb409abf0fa7e7fe32cb Mon Sep 17 00:00:00 > 2001 > From: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx> > Date: Tue, 10 May 2016 10:10:59 +0200 > Subject: [PATCH] scsi: requeue command on capacity data has changed > > We hit IO error in our production on multipath devices during resize > device on target side, the problem turns out scsi driver passes up as > IO > error when sense data is UNIT_ATTENTION and ASC && ASCQ indicate > Capacity data has changed, even storage side sync the data properly. > > To fix this, when condition met, we simply requeue the command. > > Reported-by: Sebastian Parschauer <s.parschauer@xxxxxx> > Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx> > --- > drivers/scsi/scsi_lib.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index 8106515..b00310f 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -910,6 +910,11 @@ void scsi_io_completion(struct scsi_cmnd *cmd, > unsigned int good_bytes) > error = 0; > } > > + if (sense_valid && (sshdr.sense_key == UNIT_ATTENTION)) { > + if ((sshdr.asc == 0x2a && sshdr.ascq == 0x09)) > + goto requeue; > + } > + Actually, I think this is symptomatic of a much bigger problem. Now that the FS can send zero length non BLOCK_PC request, we're not treating failure correctly. blk_update_request() will always finish them becuase they have no bytes outstanding (not having any in the first case). So I think we need a special exception for all zero length commands which complete with a failure to allow them to retry (if required). James --- diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 8106515..5a97866 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -911,9 +911,12 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) } /* - * If we finished all bytes in the request we are done now. + * special case: failed zero length commands always need to + * drop down into the retry code. Otherwise, if we finished + * all bytes in the request we are done now. */ - if (!scsi_end_request(req, error, good_bytes, 0)) + if (!(good_bytes == 0 && blk_rq_bytes(req) == 0 && result != 0) && + !scsi_end_request(req, error, good_bytes, 0)) return; /* -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
