[PATCH] dracut-module-setup.sh: check whether to include multipath-hostonly or not

[Pingfan Liu]

Due to the following commit in dracut, which splits out hostonly modules
commit 5ce7cc7337a4c769b223152c083914f2052aa348
Author: Harald Hoyer 
Date:   Mon Jul 10 13:28:40 2017 +0200

add 90multipath-hostonly module

hardcoding the wwid of the drives in the initramfs causes problems
    when the drives are cloned to a system with the same hardware, but
    different disk wwid's

https://bugzilla.redhat.com/show_bug.cgi?id=1457311

So kdump should decide whether to include the hostonly module.
The multipath-hostonly can help kdump to include only the needed mpath device,
in order to use less memory by 2nd kernel.

---- The performance -----
before this patch
[root@localhost ~]# time kdumpctl start
Detected change(s) in the following file(s):

/etc/kdump.conf
Rebuilding /boot/initramfs-4.13.9-300.fc27.x86_64kdump.img
kexec: loaded kdump kernel
Starting kdump: [OK]

real    0m12.485s
user    0m10.096s
sys     0m1.887s

after this patch

root@localhost ~]# time kdumpctl start
Detected change(s) in the following file(s):

/etc/kdump.conf
Rebuilding /boot/initramfs-4.13.9-300.fc27.x86_64kdump.img
kexec: loaded kdump kernel
Starting kdump: [OK]

real    0m15.839s
user    0m13.015s
sys     0m1.853s

Signed-off-by: Pingfan Liu 
---
 dracut-module-setup.sh | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
index 256d315..2c6de14 100755
--- a/dracut-module-setup.sh
+++ b/dracut-module-setup.sh
@@ -7,6 +7,13 @@ if ! [[ -d "${initdir}/tmp" ]]; then
     mkdir -p "${initdir}/tmp"
 fi

+is_mpath() {
+    local _dev=$1
+    [ -e /sys/dev/block/$_dev/dm/uuid ] || return 1
+    [[ $(cat /sys/dev/block/$_dev/dm/uuid) =~ mpath- ]] && return 0
+    return 1
+}
+
 check() {
     [[ $debug ]] && set -x
     #kdumpctl sets this explicitly
@@ -28,6 +35,7 @@ depends() {
         _dep="$_dep network"
     fi

+    for_each_host_dev_and_slaves is_mpath && _dep="$_dep multipath-hostonly"
     echo $_dep
     return 0
 }

[Dave Young]

On 11/23/17 at 10:17am, Pingfan Liu wrote:
> Due to the following commit in dracut, which splits out hostonly modules
> commit 5ce7cc7337a4c769b223152c083914f2052aa348
> Author: Harald Hoyer 
> Date:   Mon Jul 10 13:28:40 2017 +0200
> add 90multipath-hostonly module
>
> hardcoding the wwid of the drives in the initramfs causes problems
> when the drives are cloned to a system with the same hardware, but
> different disk wwid's
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1457311
>
> So kdump should decide whether to include the hostonly module.
> The multipath-hostonly can help kdump to include only the needed mpath device,
> in order to use less memory by 2nd kernel.
>
> ---- The performance -----
> before this patch
> [root@localhost ~]# time kdumpctl start
> Detected change(s) in the following file(s):
>
> /etc/kdump.conf
> Rebuilding /boot/initramfs-4.13.9-300.fc27.x86_64kdump.img
> kexec: loaded kdump kernel
> Starting kdump: [OK]
>
> real    0m12.485s
> user    0m10.096s
> sys     0m1.887s
>
> after this patch
>
> root@localhost ~]# time kdumpctl start
> Detected change(s) in the following file(s):
>
> /etc/kdump.conf
> Rebuilding /boot/initramfs-4.13.9-300.fc27.x86_64kdump.img
> kexec: loaded kdump kernel
> Starting kdump: [OK]
>
> real    0m15.839s
> user    0m13.015s
> sys     0m1.853s

I think you were testing in F27 instead of rawhide, in my rawhide
without multpath, it is nearly same with the additional for_each loop. 
But since we have to add this or we will have regression, thus
Acked-by: Dave Young

In the future it can be improved in dracut.
> Signed-off-by: Pingfan Liu
>
> dracut-module-setup.sh | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
> index 256d315..2c6de14 100755
> --- a/dracut-module-setup.sh
> +++ b/dracut-module-setup.sh
> @@ -7,6 +7,13 @@ if ! [[ -d "${initdir}/tmp" ]]; then
>      mkdir -p "${initdir}/tmp"
>  fi
>
> +is_mpath() {
> local _dev=$1
> [ -e /sys/dev/block/$_dev/dm/uuid ] || return 1
> [[ $(cat /sys/dev/block/$_dev/dm/uuid) =~ mpath- ]] && return 0
> return 1
>
> +}
>
> check() {
>      [[ $debug ]] && set -x
>      #kdumpctl sets this explicitly
> @@ -28,6 +35,7 @@ depends() {
>          _dep="$_dep network"
>      fi
> for_each_host_dev_and_slaves is_mpath && _dep="$_dep multipath-hostonly"
> echo $_dep
> return 0
> }
>
> 2.7.4
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