Re: [PATCH 0/4] Dump core correctly to the bind mounted target

[Minfei Huang]

On 03/09/15 at 01:59pm, Dave Young wrote:
> On 03/04/15 at 01:07am, Minfei Huang wrote:
> > Enhance kdump to support bind mounted target, since kdump cann't parse
> > the bind mounted path.
> >
> > Following is the testcases which kdump can generate the core sucessfully.
> > rootfs, default path / specified path
> > rootfs with bind mounted path which is in the rootfs device
> >    # cat /etc/kdump | grep ^path
> >    path /var/crash
> >    # mount -o bind /var/crash /mnt/crash
> > rootfs with bind mounted path which is not in the rootfs device
> >    # cat /etc/kdump | grep ^path
> >    path /var/crash
> >    # mount /dev/vdb /mnt
> >    # mount -o bind /var/crash /mnt/crash
> > no-rootfs
> > no-rootfs with bind mounted path which is in the same device
> > no-rootfs with bind mounted path which is not in the same device
> > nfs
> > nfs with bind mounted path which is under the nfs mount point path
> >    # cat /etc/kdump | grep ^nfs
> >    nfs 192.168.122.134:/opt/crash
> >    # cat /etc/kdump | grep ^path
> >    path /var/crash
> >    # mount.nfs 192.168.122.134:/opt/crash /mnt/nfs
> >    # mount -o bind /mnt/nfs/var/crash /mnt/nfs/dump
> > nfs with bind mounted path which is not under the nfs mount point path
> >    # cat /etc/kdump | grep ^nfs
> >    nfs 192.168.122.134:/opt/crash
> >    # cat /etc/kdump | grep ^path
> >    path /var/crash
> >    # mount.nfs 192.168.122.134:/opt/crash /mnt/nfs
> >    # mount -o bind /mnt/nfs/var/crash /mnt/dump
> > nfs which don't specify the nfs option in the /etc/kdump, with bind mounted path which is under the nfs mount point path 
> >    # cat /etc/kdump | grep ^nfs
> >    # mount.nfs 192.168.122.134:/opt/crash /mnt/nfs
> >    # cat /etc/kdump | grep ^path
> >    path /mnt/nfs/var/crash
> >    # mount -o bind /mnt/nfs/var/crash /mnt/nfs/dump
> > nfs which don't specify the nfs option in the /etc/kdump, with bind mounted path which is not under the nfs mount point path 
> >    # cat /etc/kdump | grep ^nfs
> >    # mount.nfs 192.168.122.134:/opt/crash /mnt/nfs
> >    # cat /etc/kdump | grep ^path
> >    path /mnt/nfs/var/crash
> >    # mount -o bind /mnt/nfs/var/crash /mnt/dump
> > ext4
> > ext4 with bind mounted path which is under the ext4 mount point path
> > ext4 with bind mounted path which is not under the ext4 mount point path
> > btrfs
> > btrfs with subvolume which mounts under mount point path
> > btrfs with subvolume which does not mount under mount point path
> >
> > Minfei Huang (4):
> >   kdump-lib: Add new function to cut out the substring
> >   kdump-lib: Add the new function to enhance bind mounted judgement
> >   kdump-lib: Get the mount point correctly, if the device has several
> >     mount point
> >   dracut-module-setup: Fix the incorrect dumping target, if the path is
> >     bind mounted
> >
> > dracut-module-setup.sh | 49 +++++++++++++++++++++++++++++++++++-----
> >  kdump-lib.sh           | 61 +++++++++++++++++++++++++++++++++++++++++++++++++-
> >  mkdumprd               | 32 +++++++++++++++++++-------
> >  3 files changed, 128 insertions(+), 14 deletions(-)
>
> There's some problems ie. umount original directory and only keep bind mounted one.

Hi, Dave.
Since the complicated testcases, we can hold on this patchset, if we are
requested to support bind mounted someday.
> The cases looks complicated, I agree with Bao that it increases code complexity
> dramaticlly so how about do it like below:
> document that we do not support bind mount
> for atomic, two ways to resolve the problem:
> *) they can pack a different kdump.conf with different default path 
> *) we can fix it by conditionally set default path for atomic

Agreed. I think the Atomic should be setted a default path, which points
to the /var/crash. And the dumping target never be permitted to change,
if the customer wants to dump core correctly.

Thanks
Minfei
> Thanks
> Dave