gfs2-utils: Fix hang on withdraw

Issuing a withdraw on a gfs2 filesystem causes a hang. When gfs_controld was removed, the userspace functionality that completes a withdraw operation went away. This causes gfs2 kernel to hang waiting for a withdraw completion ack from userspace.

This patchset introduces a uevent-based shell script to do the job that gfs_controld used to do on withdraw. An 'offline' uevent triggers the execution of this script. This script suspends the device associated with the filesystem and signals a completed withdraw to the kernel.

Resolves: rhbz#1225634

Signed-off-by Abhi Das <[email protected]>

---
  gfs2/scripts/82-gfs2-withdraw.rules |  2 ++
  gfs2/scripts/gfs2_wd_udev.sh        | 30 ++++++++++++++++++++++++++++++
  2 files changed, 32 insertions(+)

create mode 100644 gfs2/scripts/82-gfs2-withdraw.rules create mode 100755 gfs2/scripts/gfs2_wd_udev.sh

gfs2/scripts/82-gfs2-withdraw.rules new file +1 -0

+

gfs2/scripts/gfs2_wd_udev.sh new file +30 -0

new file mode 100755
index 0000000..ac3ce35
@@ -0,0 +1,30 @@
+#!/bin/sh
+#
+# Do not run this script manually. This script is called by udev on a gfs2
+# withdraw uevent and is used to complete the withdraw action and notify the
+# kernel.
+#
+
+# Sanity checks
+if [ "$SUBSYSTEM" != "gfs2" ] || [ "$LOCKPROTO" != "lock_dlm" ] ||
+       [ -z "$DEVPATH" ] || [ "$ACTION" != "offline" ]
+then
+    exit 1 # Nothing to do here
+fi
+
+# Try and suspend the device
+SYSFS_TOPDIR="/sys"$DEVPATH
+DM_NAME=$(cat "$SYSFS_TOPDIR/device/dm/name")
+DM_DEV="/dev/mapper/"$DM_NAME
+
+if [ -z "$DM_DEV" ]
+then
+    /usr/bin/dmsetup suspend $DM_DEV
+fi
+
+# Signal completion of withdraw
+WD_ACK="$SYSFS_TOPDIR/lock_module/withdraw"
+if [ -f "$WD_ACK" ]
+then
+    echo "1" > $WD_ACK
+fi

From: "Andrew Price" <[email protected]>
To: "Abhijith Das" <[email protected]>, "cluster-devel" <[email protected]>
Sent: Tuesday, August 4, 2015 6:06:16 AM
Subject: Re: [Cluster-devel] [GFS2 PATCH] gfs2-utils: Fix hang on withdraw

Hi Abhi,

Quoted 12 lines · Abhijith Das

Issuing a withdraw on a gfs2 filesystem causes a hang. When gfs_controld was removed, the userspace functionality that completes a withdraw operation went away. This causes gfs2 kernel to hang waiting for a withdraw completion ack from userspace.

This patchset introduces a uevent-based shell script to do the job that gfs_controld used to do on withdraw. An 'offline' uevent triggers the execution of this script. This script suspends the device associated with the filesystem and signals a completed withdraw to the kernel.

Quoted 8 lines

Resolves: rhbz#1225634

Signed-off-by Abhi Das <[email protected]>

---
  gfs2/scripts/82-gfs2-withdraw.rules |  2 ++
  gfs2/scripts/gfs2_wd_udev.sh        | 30 ++++++++++++++++++++++++++++++
  2 files changed, 32 insertions(+)

create mode 100644 gfs2/scripts/82-gfs2-withdraw.rules create mode 100755 gfs2/scripts/gfs2_wd_udev.sh

Even if they're not getting installed in 'make install' the build system will need to know about them, in gfs2/scripts/Makefile.am:

noinst_SCRIPTS = \
	82-gfs2-withdraw.rules \
	gfs2_wd_udev.sh

I think some documentation in README.build would be useful too, so that package maintainers know why and where to install them.

gfs2/scripts/82-gfs2-withdraw.rules line 1

Quoted 8 lines

gfs2/scripts/82-gfs2-withdraw.rules new file +1 -0

new file mode 100644
index 0000000..c1ab02b
@@ -0,0 +1,2 @@
+SUBSYSTEM=="gfs2", ACTION=="offline", RUN+="/bin/sh /sbin/gfs2_wd_udev.sh"

Perhaps that should be /usr/sbin instead of /sbin, after the whole "UsrMove" thing.