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<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>When scsi_dh_activate returns SCSI_DH_NOSYS the H/W
handler callback is not called, pg_init_done is not called in <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>the multipath layer and pending I/O is requeued
forever; this situation causes all userland processes currently performing I/O<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>on the device to I/O hang. A similar situation
occurs when the device has transitioned to SDEV_CANCEL/SDEV_DEL and the device<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>handler data had not yet been deleted.<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>The easiest way to reproduce this is in an ISCSI
environment:<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> dd if=/dev/dm-0 of=/dev/zero bs=8k
count=1000000 &<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> /etc/init.d/iscsi stop<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>In this example, dd will I/O hang forever and the
only way to release it will be to reboot the machine<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>This patch calls pg_init_done directly from the
mpath code when the scsi_dh_activate returns a non SCSI_DH_OK error.<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>Note:<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>The patch is over RHEL5.5.<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>When running an upstream kernel, the above scenario
may not occur because the request queue is aborted in dm-mpath.c:fail_path.<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>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 <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>request queue abort functionality on RHEL5 at this
stage.<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>diff -r -U 2 a/drivers/md/dm-mpath.c
b/drivers/md/dm-mpath.c<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>--- a/drivers/md/dm-mpath.c 2010-12-13
09:16:31.358858000 +0200<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+++ b/drivers/md/dm-mpath.c 2010-12-13
09:16:31.796998000 +0200<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>@@ -1190,4 +1190,5 @@<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> case SCSI_DH_OK:<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> break;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ case SCSI_DH_DEV_OFFLINED:<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> case SCSI_DH_NOSYS:<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> if
(!m->hw_handler_name) {<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>@@ -1252,7 +1253,15 @@<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> {<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> struct pgpath *pgpath
= (struct pgpath *) data;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ int err;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>- scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ err =
scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> pg_init_done,
&pgpath->path);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ /*<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ * If error is not
SCSI_DH_OK, we have not entered the scsi_dh H/W handler and did not call
pg_init_done - <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ * need to call
pg_init_done directly.<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ */<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ if (err) <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ pg_init_done(&pgpath->path,
err);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> }<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>diff -r -U 2 a/drivers/scsi/device_handler/scsi_dh.c
b/drivers/scsi/device_handler/scsi_dh.c<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>--- a/drivers/scsi/device_handler/scsi_dh.c 2010-12-13
09:16:31.616554000 +0200<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+++ b/drivers/scsi/device_handler/scsi_dh.c 2010-12-13
09:16:31.878170000 +0200<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>@@ -443,4 +443,9 @@<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> spin_unlock_irqrestore(q->queue_lock,
flags);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> <o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ if (sdev->sdev_state ==
SDEV_CANCEL ||<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+
sdev->sdev_state == SDEV_DEL ||<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+
sdev->sdev_state == SDEV_OFFLINE)<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+ err
= SCSI_DH_DEV_OFFLINED;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> if (err)<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> return
err;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>diff -r -U 2
a/drivers/scsi/device_handler/scsi_dh_rdac.c b/drivers/scsi/device_handler/scsi_dh_rdac.c<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>--- a/drivers/scsi/device_handler/scsi_dh_rdac.c 2010-12-13
09:16:31.747755000 +0200<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+++ b/drivers/scsi/device_handler/scsi_dh_rdac.c 2010-12-13
09:16:31.912827000 +0200<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>@@ -665,4 +665,5 @@<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> if (fn)<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> fn(data,
err);<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'>+<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> return 0;<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'> }<o:p></o:p></span></p>
<p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Trebuchet MS","sans-serif";
color:#444444'>Menny Hamburger</span></b><span style='font-size:8.0pt;
font-family:"Trebuchet MS","sans-serif";color:#444444'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";
color:#444444'>Engineer<o:p></o:p></span></p>
<p class=MsoNormal><b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";
color:#0085C3'>Dell</span></b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";
color:#444444'> | IDC<b><o:p></o:p></b></span></p>
<p class=MsoNormal><b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";
color:#444444'>office </span></b><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";
color:#444444'>+972 97698789<b>, fax </b>+972 97698889<b><o:p></o:p></b></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Trebuchet MS","sans-serif";
color:#444444'>Dell IDC. 4 Hacharoshet St, Raanana 43657, Israel</span><span
style='color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
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