|
When scsi_dh_activate returns SCSI_DH_NOSYS the H/W
handler callback is not called, pg_init_done is not called in the multipath layer and pending I/O is requeued
forever; this situation causes all userland processes currently performing I/O on the device to I/O hang. A similar situation
occurs when the device has transitioned to SDEV_CANCEL/SDEV_DEL and the device handler data had not yet been deleted. The easiest way to reproduce this is in an ISCSI
environment: dd if=/dev/dm-0 of=/dev/zero bs=8k
count=1000000 & /etc/init.d/iscsi stop In this example, dd will I/O hang forever and the
only way to release it will be to reboot the machine This patch calls pg_init_done directly from the
mpath code when the scsi_dh_activate returns a non SCSI_DH_OK error. Note: The patch is over RHEL5.5. When running an upstream kernel, the above scenario
may not occur because the request queue is aborted in dm-mpath.c:fail_path. This patch makes sure the problem does not occur at
all, rather than handling it when it does. In addition, it seems too risky to
apply request queue abort functionality on RHEL5 at this
stage. diff -r -U 2 a/drivers/md/dm-mpath.c
b/drivers/md/dm-mpath.c --- a/drivers/md/dm-mpath.c 2010-12-13
09:16:31.358858000 +0200 +++ b/drivers/md/dm-mpath.c 2010-12-13
09:16:31.796998000 +0200 @@ -1190,4 +1190,5 @@ case SCSI_DH_OK: break; + case SCSI_DH_DEV_OFFLINED: case SCSI_DH_NOSYS: if
(!m->hw_handler_name) { @@ -1252,7 +1253,15 @@ { struct pgpath *pgpath
= (struct pgpath *) data; + int err; - scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev), + err =
scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev), pg_init_done,
&pgpath->path); + + /* + * If error is not
SCSI_DH_OK, we have not entered the scsi_dh H/W handler and did not call
pg_init_done - + * need to call
pg_init_done directly. + */ + if (err) + pg_init_done(&pgpath->path,
err); } diff -r -U 2 a/drivers/scsi/device_handler/scsi_dh.c
b/drivers/scsi/device_handler/scsi_dh.c --- a/drivers/scsi/device_handler/scsi_dh.c 2010-12-13
09:16:31.616554000 +0200 +++ b/drivers/scsi/device_handler/scsi_dh.c 2010-12-13
09:16:31.878170000 +0200 @@ -443,4 +443,9 @@ spin_unlock_irqrestore(q->queue_lock,
flags); + if (sdev->sdev_state ==
SDEV_CANCEL || +
sdev->sdev_state == SDEV_DEL || +
sdev->sdev_state == SDEV_OFFLINE) + err
= SCSI_DH_DEV_OFFLINED; + if (err) return
err; diff -r -U 2
a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c --- a/drivers/scsi/device_handler/scsi_dh_rdac.c 2010-12-13
09:16:31.747755000 +0200 +++ b/drivers/scsi/device_handler/scsi_dh_rdac.c 2010-12-13
09:16:31.912827000 +0200 @@ -665,4 +665,5 @@ if (fn) fn(data,
err); + return 0; } Menny Hamburger Engineer Dell | IDC office +972 97698789, fax +972 97698889 Dell IDC. 4 Hacharoshet St, Raanana 43657, Israel |
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