1) When I tested this problem, deleting the device set it temporarily to SDEV_DEL (sometimes SDEV_CANCEL) state. So the main issue should be solved with the function returning SCSI_DH_NOSYS. Failing to the default on offline is OK with me since there is no issue with !mw_handler_name because the device still exists. 2) Aborting the request queue does not obviate the need for this patch, it's just that in a system where abort queue exists, the I/O hang will not occur. Another way to say this is that the abort queue functionality (if it worked OK - which it doesn't) hides the problem from the user experience by forcing all the queues to be flushed. My preference was always to make sure a problem (in this case the I/O hang) does not occur in the first place rather than take actions when it does. Hope this answers your questions. Menny -----Original Message----- From: Mike Snitzer [mailto:snitzer@xxxxxxxxxx] Sent: 16 December, 2010 17:30 To: Hamburger, Menny Cc: dm-devel@xxxxxxxxxx; Thomas, Rob; Dar, Itay Subject: [PATCH v2][SCSI] scsi_dh: propagate SCSI device deletion On Thu, Dec 16 2010 at 9:21am -0500, Menny_Hamburger@xxxxxxxx <Menny_Hamburger@xxxxxxxx> wrote: > Mike, > > What I meant is that removing the dm-mpath change from the patch makes > the operation path go into an area that I did not test (the default > case). > I know it's only a !hw_handler_name and a printk (as I said before - > this might sound superstitious), however I did my tests with the > dm-mpath part, and I prefer to send a 100% tested patch then to add > something I did not test. > My suggestion was to supply a scsi_dh only patch that goes through the > same operation path as the one I tested - via the SCSI_DH_NOSYS case > in pg_init_done. In addition, the separation of offline from > cancel/del also seems the correct way to do this. I see, my misunderstanding. - But you're still returning SCSI_DH_DEV_OFFLINED; so if dm mpath's pg_init_done isn't updated to explicitly handle it it'll just fail_path() via the default case. Are you OK with that? - In your initial patch you said: "When running an upstream kernel, the above scenario may not occur because the request queue is aborted when the multipath fails the path." I'm missing _why_ fail_path's call to blk_abort_queue() would obviate the need for this patch. blk_abort_queue() is only called from fail_path(). But I thought the problem is fail_path() isn't called in this case where the device is SCSI_DH_NOSYS or SCSI_DH_DEV_OFFLINED? -- due to the missing call to activate_complete callback (pg_init_done) (again, I'm very interested in this because we'll be reverting DM mpath's call to blk_abort_queue in the near future). But this would be the revised scsi_dh patch (I'm not sending to linux-scsi until I have an answer for the above concerns): From: Menny Hamburger <Menny_Hamburger@xxxxxxxx> When the scsi_dh_activate returns SCSI_DH_NOSYS the activate_complete callback is not called and the error is not propagated to DM mpath. When a SCSI device attached to a device handler is deleted, userland processes currently performing I/O on the device will have their I/O hang forever. - Set SCSI_DH_NOSYS error when the handler is in the process of being deleted (e.g. the SCSI device is in a SDEV_CANCEL or SDEV_DEL state). - Set SCSI_DH_DEV_OFFLINED error when device is in SDEV_OFFLINE state. - Call the activate_complete callback function directly from scsi_dh_activate if an error has been set (when either the scsi_dh internal data has already been deleted or is in the process of being deleted). The patch was tested in an ISCSI environment, RDAC H/W handler and multipath. In the following reproduction process, dd will I/O hang forever and the only way to release it will be to reboot the machine: 1) Perform I/O on a multipath device: dd if=/dev/dm-0 of=/dev/zero bs=8k count=1000000 & 2) Delete all slave SCSI devices contained in the mpath device: I) In an ISCSI environment, the easiest way to do this is by stopping ISCSI: /etc/init.d/iscsi stop II) Another way to delete the devices is by applying the following bash scriptlet: dm_devs=$(ls /sys/block/ | grep dm- | xargs) for dm_dev in $dm_devs; do devices=$(ls /sys/block/$dm_dev/slaves) for device in $devices; do echo 1 > /sys/block/$device/device/delete done done NOTE: when DM mpath uses blk_abort_queue this scsi_dh change isn't required. However, DM mpath's call to blk_abort_queue has proven to be unsafe due to a race (between blk_abort_queue and scsi_request_fn) that can lead to list corruption. Therefore we cannot rely on blk_abort_queue (dm mpath's blk_abort_queue call will be reverted and will only be restored once the race with scsi_request_fn is fixed). Signed-off-by: Menny Hamburger <Menny_Hamburger@xxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> --- drivers/scsi/device_handler/scsi_dh.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c index 6fae3d2..b0c56f6 100644 --- a/drivers/scsi/device_handler/scsi_dh.c +++ b/drivers/scsi/device_handler/scsi_dh.c @@ -442,12 +442,19 @@ int scsi_dh_activate(struct request_queue *q, activate_complete fn, void *data) sdev = q->queuedata; if (sdev && sdev->scsi_dh_data) scsi_dh = sdev->scsi_dh_data->scsi_dh; - if (!scsi_dh || !get_device(&sdev->sdev_gendev)) + if (!scsi_dh || !get_device(&sdev->sdev_gendev) || + sdev->sdev_state == SDEV_CANCEL || + sdev->sdev_state == SDEV_DEL) err = SCSI_DH_NOSYS; + if (sdev->sdev_state == SDEV_OFFLINE) + err = SCSI_DH_DEV_OFFLINED; spin_unlock_irqrestore(q->queue_lock, flags); - if (err) + if (err) { + if (fn) + fn(data, err); return err; + } if (scsi_dh->activate) err = scsi_dh->activate(sdev, fn, data); -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
