From f18e083bf8ce0c0d1997002f9986122be6d4ebe8 Mon Sep 17 00:00:00 2001
From: George Wilson <george.wilson@delphix.com>
Date: Thu, 2 Feb 2023 18:11:35 -0500
Subject: [PATCH] rootdelay on zfs should be adaptive

The 'rootdelay' boot option currently pauses the boot for a specified
amount of time. The original intent was to ensure that slower
configurations would have ample time to enumerate the devices to make
importing the root pool successful. This, however, causes unnecessary
boot delay for environments like Azure which set this parameter by
default.

This commit changes the initramfs logic to pause until it can
successfully load the 'zfs' module. The timeout specified by
'rootdelay' now becomes the maximum amount of time that initramfs will
wait before failing the boot.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Prakash Surya <prakash.surya@delphix.com>
Signed-off-by: George Wilson <gwilson@delphix.com>
Closes #14430
---
 contrib/initramfs/scripts/zfs | 54 +++++++++++++++++++++++------------
 1 file changed, 35 insertions(+), 19 deletions(-)

diff --git a/contrib/initramfs/scripts/zfs b/contrib/initramfs/scripts/zfs
index c724f0c2c..41a4d96f8 100644
--- a/contrib/initramfs/scripts/zfs
+++ b/contrib/initramfs/scripts/zfs
@@ -272,30 +272,46 @@ import_pool()
 # with more logging etc.
 load_module_initrd()
 {
-	[ -n "$ROOTDELAY" ] && ZFS_INITRD_PRE_MOUNTROOT_SLEEP="$ROOTDELAY"
+	ZFS_INITRD_PRE_MOUNTROOT_SLEEP=${ROOTDELAY:-0}
 
-	if [ "$ZFS_INITRD_PRE_MOUNTROOT_SLEEP" -gt 0 ] 2>/dev/null
-	then
-		if [ "$quiet" != "y" ]; then
-			zfs_log_begin_msg "Sleeping for" \
-				"$ZFS_INITRD_PRE_MOUNTROOT_SLEEP seconds..."
+	if [ "$ZFS_INITRD_PRE_MOUNTROOT_SLEEP" -gt 0 ]; then
+		[ "$quiet" != "y" ] && zfs_log_begin_msg "Delaying for up to '${ZFS_INITRD_PRE_MOUNTROOT_SLEEP}' seconds."
+	fi
+
+	START=$(/bin/date -u +%s)
+	END=$((START+ZFS_INITRD_PRE_MOUNTROOT_SLEEP))
+	while true; do
+
+		# Wait for all of the /dev/{hd,sd}[a-z] device nodes to appear.
+		if command -v wait_for_udev > /dev/null 2>&1 ; then
+			wait_for_udev 10
+		elif command -v wait_for_dev > /dev/null 2>&1 ; then
+			wait_for_dev
 		fi
-		sleep "$ZFS_INITRD_PRE_MOUNTROOT_SLEEP"
+
+		#
+		# zpool import refuse to import without a valid
+		# /proc/self/mounts
+		#
+		[ ! -f /proc/self/mounts ] && mount proc /proc
+
+		# Load the module
+		if load_module "zfs"; then
+			ret=0
+			break
+		else
+			ret=1
+		fi
+
+		[ "$(/bin/date -u +%s)" -gt "$END" ] && break
+		sleep 1
+
+	done
+	if [ "$ZFS_INITRD_PRE_MOUNTROOT_SLEEP" -gt 0 ]; then
 		[ "$quiet" != "y" ] && zfs_log_end_msg
 	fi
 
-	# Wait for all of the /dev/{hd,sd}[a-z] device nodes to appear.
-	if command -v wait_for_udev > /dev/null 2>&1 ; then
-		wait_for_udev 10
-	elif command -v wait_for_dev > /dev/null 2>&1 ; then
-		wait_for_dev
-	fi
-
-	# zpool import refuse to import without a valid /proc/self/mounts
-	[ ! -f /proc/self/mounts ] && mount proc /proc
-
-	# Load the module
-	load_module "zfs" || return 1
+	[ "$ret" -ne 0 ] && return 1
 
 	if [ "$ZFS_INITRD_POST_MODPROBE_SLEEP" -gt 0 ] 2>/dev/null
 	then