On 2016/05/19 at 16:13, Dave Young wrote:
On 05/19/16 at 03:45pm, Xunlei Pang wrote:
> There are some complaints about nfs kdump that users must mount
> nfs beforehand, which may cause some overhead to nfs server.
> For example, there're thounsands of clients deployed with kdump
> diskless boot, each time the client is boot up, it will trigger
> kdump rebuilding so will mount nfs, thus resulting in thousands
> of nfs request concurrently imposed on the same nfs server.
>
> We introduce a new way of specifying mount information via the
> already-existent "dracut_args" directive, we will skip all the
> filesystem mounting and checking things for it. So it can be used
> in the above-mentioned nfs scenario and avoid creating severe nfs
> server overhead.
>
> Specifically, if there is any "--mount" information specifed via
> "dracut_args" in /etc/kdump.conf, always use it as the final mount
> without any check(users are expected to ensure its correctness),
> it overrides any target specified in /etc/kdump.conf.
>
> As an example:
> dracut_args --mount "192.168.1.1:/test test nfs defaults,x-initrd.mount"
Could also update the kdump howto to define the valid format of --mount?
Sure
and give an example. Should we limit it to nfs only or for all fs
types?
The approach itself is a general implementation, I personally perfer it for all fs types.
> NOTE:
> 1)Only one mount information can be specified via "dracut_args".
> 2)Dracut will create <mountpoint> if it doesn't exist in kdump kernel.
>
> Suggested-by: Dave Young <dyoung(a)redhat.com>
> Signed-off-by: Xunlei Pang <xlpang(a)redhat.com>
> ---
> v1->v2:
> -Consider "dracut_args" in is_user_configured_dump_target().
> -Add dracut "nfs" module properly.
> -Prohibit specifying multiple mount information via "dracut_args".
>
> kdump-lib.sh | 25 ++++++++++++++++++++++++-
> kdumpctl | 8 +++++++-
> mkdumprd | 9 +++++++++
> 3 files changed, 40 insertions(+), 2 deletions(-)
>
> diff --git a/kdump-lib.sh b/kdump-lib.sh
> index fc2c036..e90fe4c 100755
> --- a/kdump-lib.sh
> +++ b/kdump-lib.sh
> @@ -45,7 +45,8 @@ is_fs_dump_target()
>
> is_user_configured_dump_target()
> {
> - return $(is_ssh_dump_target || is_nfs_dump_target || is_raw_dump_target ||
is_fs_dump_target)
> + return $(is_ssh_dump_target || is_nfs_dump_target || is_raw_dump_target \
> + || is_fs_dump_target || dracut_args_contains_mount)
> }
>
> strip_comments()
> @@ -279,3 +280,25 @@ is_hostname()
> fi
> echo $1 | grep -q "[a-zA-Z]"
> }
> +
> +# If "dracut_args" contains "--mount" information, use it
> +# directly without any check(users are expected to ensure
> +# its correctness). It overrides any target specified in
> +# /etc/kdump.conf.
> +dracut_args_contains_mount()
> +{
> + return $(grep ^dracut_args /etc/kdump.conf | grep -q "\-\-mount")
> +}
> +
> +get_fstype_from_dracut_args()
> +{
> + local user_dracut_args fstype
> +
> + user_dracut_args=$(grep ^dracut_args /etc/kdump.conf | grep "\-\-mount |
head -1")
> + if [[ -n "$user_dracut_args" ]]; then
> + fstype=$(echo $user_dracut_args | awk -F "--mount \""
'{print $2}' | cut -d' ' -f3)
> + fi
> +
> + echo $fstype
> +}
> +
> diff --git a/kdumpctl b/kdumpctl
> index fcc9ad0..4e9d6a4 100755
> --- a/kdumpctl
> +++ b/kdumpctl
> @@ -236,7 +236,8 @@ check_config()
> {
> local nr
>
> - nr=$(awk 'BEGIN{cnt=0}
/^raw|^ssh[[:blank:]]|^nfs|^ext[234]|^xfs|^btrfs|^minix/{cnt++} END{print cnt}'
$KDUMP_CONFIG_FILE)
> + nr=$(awk 'BEGIN{cnt=0} /^raw|^ssh[[:blank:]]|^nfs|^ext[234]|^xfs|^btrfs|^minix|
\
> + ^dracut_args .*\-\-mount/{cnt++} END{print cnt}' $KDUMP_CONFIG_FILE)
> [ $nr -gt 1 ] && {
> echo "More than one dump targets specified."
> return 1
> @@ -365,6 +366,11 @@ check_dump_fs_modified()
> local _new_dev _new_mntpoint _new_fstype
> local _target _path _dracut_args
>
> + # No need to check in case of mount target specified via "dracut_args".
> + if dracut_args_contains_mount; then
> + return 0
> + fi
> +
> # No need to check in case of raw target.
> # Currently we do not check also if ssh/nfs target is specified
> if is_ssh_dump_target || is_nfs_dump_target || is_raw_dump_target; then
> diff --git a/mkdumprd b/mkdumprd
> index 78afb1a..2156be6 100644
> --- a/mkdumprd
> +++ b/mkdumprd
> @@ -497,6 +497,12 @@ do
> extra_modules="$extra_modules $config_val"
> ;;
> ext[234]|xfs|btrfs|minix|nfs)
> + # Use the mount information in "dracut_args" specifed by users
> + # in /etc/kdump.conf, skip further parsing.
> + if dracut_args_contains_mount; then
> + continue
Do we allow one specify fs dump here at the same time, if no a warning here
is good to tell that we will use --mount instead.
I'm a little worried about multiple "--mount" passed to dracut, at least
one
I can think of now is Pratyush's recent force_rebuild patchset, it relys on
the first "--mount" to get the old target, old mountpoint, old fstype.
That's why I prohibit multiple "--mount" and skip "target" in the
patch.
Regards,
Xunlei
> + fi
> +
> if ! findmnt $config_val >/dev/null; then
> perror_exit "Dump target $config_val is probably not
mounted."
> fi
> @@ -544,6 +550,9 @@ do
> verify_core_collector "$config_val"
> ;;
> dracut_args)
> + if [[ $(get_fstype_from_dracut_args) = nfs* ]]; then
> + add_dracut_module "nfs"
> + fi
> add_dracut_arg $config_val
> ;;
> *)
> --
> 1.8.3.1
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