Bug#603944: retry mounting of root

["Serge E. Hallyn" <serge.hallyn@canonical.com>]

Package: initramfs-tools
Version: 0.98

When using multipath, it is possible that mountroot() will race with
udev's renaming of /dev/disk/by-uuid/{rootfs-uuid} from /dev/sd?? to
/dev/mapper/something.  After multipath has grabbed the /dev/sd?? and
until udev completes the rename, mounting
/dev/disk/by-uuid/{rootfs-uuid} will fail with -EBUSY.

Here is a patch I've been using successfully for awhile.  Colin Watson
has suggested that:

> A poll/retry loop is generally a suboptimal way to do this kind of
> thing; what we really want is to wait for udev to tell us that it has
> finished with the event that triggered renaming of the device.

which does seem cleaner.

thanks,
-serge

diff -Nru initramfs-tools-0.98ubuntu2/debian/changelog initramfs-tools-0.98ubuntu3/debian/changelog
--- initramfs-tools-0.98ubuntu2/debian/changelog	2010-08-20 03:48:58.000000000 -0500
+++ initramfs-tools-0.98ubuntu3/debian/changelog	2010-08-24 22:31:31.000000000 -0500
@@ -1,3 +1,14 @@
+initramfs-tools (0.98ubuntu3) maverick; urgency=low
+
+  * Add retries to mountroot().  This is particularly needed when we
+    use multipath, because it is possible that mountroot() will race
+    with udev's renaming of /dev/disk/by-uuid/{rootfs-uuid} from
+    /dev/sd?? to /dev/mapper/something.  After multipath has grabbed
+    the /dev/sd?? and until udev completes the rename, mounting
+    /dev/disk/by-uuid/{rootfs-uuid} will fail with -EBUSY.
+
+ -- Serge Hallyn <serge.hallyn@canonical.com>  Tue, 24 Aug 2010 22:17:57 -0500
+
 initramfs-tools (0.98ubuntu2) maverick; urgency=low
 
   * The ramzswap device changed its interface so that the disk size needs to
diff -Nru initramfs-tools-0.98ubuntu2/scripts/local initramfs-tools-0.98ubuntu3/scripts/local
--- initramfs-tools-0.98ubuntu2/scripts/local	2010-08-20 03:48:58.000000000 -0500
+++ initramfs-tools-0.98ubuntu3/scripts/local	2010-08-24 22:16:17.000000000 -0500
@@ -86,10 +86,19 @@
 	# FIXME This has no error checking
 	[ -n "${FSTYPE}" ] && modprobe ${FSTYPE}
 
-	# FIXME This has no error checking
 	# Mount root
-	mount ${roflag} ${FSTYPE:+-t ${FSTYPE} }${ROOTFLAGS} ${ROOT} ${rootmnt}
-	mountroot_status="$?"
+	tries=0
+	ret=1
+	while [ $tries -lt 10 -a $ret -ne 0 ]; do
+		mount ${roflag} ${FSTYPE:+-t ${FSTYPE} }${ROOTFLAGS} ${ROOT} ${rootmnt}
+		ret=$?
+		if [ $ret -ne 0 ]; then
+			echo "failed attempt $tries to mount $ROOT as root"
+			sleep 1
+			tries=$((tries+1))
+		fi
+	done
+	mountroot_status=$ret
 	if [ "$LOOP" ]; then
 		if [ "$mountroot_status" != 0 ]; then
 			if [ ${FSTYPE} = ntfs ] || [ ${FSTYPE} = vfat ]; then