6.1-stable review patch. If anyone has any objections, please let me know.
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From: Peter Oberparleiter oberpar@linux.ibm.com
commit 5ef1dc40ffa6a6cb968b0fdc43c3a61727a9e950 upstream.
The s390 common I/O layer (CIO) returns an unexpected -EBUSY return code when drivers try to start I/O while a path-verification (PV) process is pending. This can lead to failed device initialization attempts with symptoms like broken network connectivity after boot.
Fix this by replacing the -EBUSY return code with a deferred condition code 1 reply to make path-verification handling consistent from a driver's point of view.
The problem can be reproduced semi-regularly using the following process, while repeating steps 2-3 as necessary (example assumes an OSA device with bus-IDs 0.0.a000-0.0.a002 on CHPID 0.02):
1. echo 0.0.a000,0.0.a001,0.0.a002 >/sys/bus/ccwgroup/drivers/qeth/group 2. echo 0 > /sys/bus/ccwgroup/devices/0.0.a000/online 3. echo 1 > /sys/bus/ccwgroup/devices/0.0.a000/online ; \ echo on > /sys/devices/css0/chp0.02/status
Background information:
The common I/O layer starts path-verification I/Os when it receives indications about changes in a device path's availability. This occurs for example when hardware events indicate a change in channel-path status, or when a manual operation such as a CHPID vary or configure operation is performed.
If a driver attempts to start I/O while a PV is running, CIO reports a successful I/O start (ccw_device_start() return code 0). Then, after completion of PV, CIO synthesizes an interrupt response that indicates an asynchronous status condition that prevented the start of the I/O (deferred condition code 1).
If a PV indication arrives while a device is busy with driver-owned I/O, PV is delayed until after I/O completion was reported to the driver's interrupt handler. To ensure that PV can be started eventually, CIO reports a device busy condition (ccw_device_start() return code -EBUSY) if a driver tries to start another I/O while PV is pending.
In some cases this -EBUSY return code causes device drivers to consider a device not operational, resulting in failed device initialization.
Note: The code that introduced the problem was added in 2003. Symptoms started appearing with the following CIO commit that causes a PV indication when a device is removed from the cio_ignore list after the associated parent subchannel device was probed, but before online processing of the CCW device has started:
2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
During boot, the cio_ignore list is modified by the cio_ignore dracut module [1] as well as Linux vendor-specific systemd service scripts[2]. When combined, this commit and boot scripts cause a frequent occurrence of the problem during boot.
[1] https://github.com/dracutdevs/dracut/tree/master/modules.d/81cio_ignore [2] https://github.com/SUSE/s390-tools/blob/master/cio_ignore.service
Cc: stable@vger.kernel.org # v5.15+ Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers") Tested-By: Thorsten Winkler twinkler@linux.ibm.com Reviewed-by: Thorsten Winkler twinkler@linux.ibm.com Signed-off-by: Peter Oberparleiter oberpar@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/s390/cio/device_ops.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/s390/cio/device_ops.c +++ b/drivers/s390/cio/device_ops.c @@ -202,7 +202,8 @@ int ccw_device_start_timeout_key(struct return -EINVAL; if (cdev->private->state == DEV_STATE_NOT_OPER) return -ENODEV; - if (cdev->private->state == DEV_STATE_VERIFY) { + if (cdev->private->state == DEV_STATE_VERIFY || + cdev->private->flags.doverify) { /* Remember to fake irb when finished. */ if (!cdev->private->flags.fake_irb) { cdev->private->flags.fake_irb = FAKE_CMD_IRB; @@ -214,8 +215,7 @@ int ccw_device_start_timeout_key(struct } if (cdev->private->state != DEV_STATE_ONLINE || ((sch->schib.scsw.cmd.stctl & SCSW_STCTL_PRIM_STATUS) && - !(sch->schib.scsw.cmd.stctl & SCSW_STCTL_SEC_STATUS)) || - cdev->private->flags.doverify) + !(sch->schib.scsw.cmd.stctl & SCSW_STCTL_SEC_STATUS))) return -EBUSY; ret = cio_set_options (sch, flags); if (ret)