Re: Killing process in D state on mount to dead NFS server.

[NeilBrown <neilb@suse.de>]

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On Wed, 13 Aug 2014 08:42:34 -0700 Ben Greear <greearb@candelatech.com> wrote:

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> Hello!
> 
> Did you get a chance to look at the stacks below?

Yes I did, and I replied on Date: Fri, 1 Aug 2014 07:50:53 +1000

The problem is that "fsync" and related functions are not killable.
I think it is generally agreed that this is a bug, and that a fix would
probably be accepted.
I started working on one the other day but haven't got very hard yet (lots of
other things to work on).

NeilBrown

> 
> Thanks,
> Ben
> 
> 
> On 07/31/2014 02:20 PM, Ben Greear wrote:
> > On 07/31/2014 01:42 PM, NeilBrown wrote:
> >> On Thu, 31 Jul 2014 11:00:35 -0700 Ben Greear <greearb@candelatech.com> wrote:
> > 
> >>> So, this has been asked all over the interweb for years and years, but the best answer I can find is to reboot the system or create a fake NFS server 
> >>> somewhere with the same IP as the gone-away NFS server.
> >>> 
> >>> The problem is:
> >>> 
> >>> I have some mounts to an NFS server that no longer exists (crashed/powered down).
> >>> 
> >>> I have some processes stuck trying to write to files open on these mounts.
> >>> 
> >>> I want to kill the process and unmount.
> >>> 
> >>> umount -l will make the mount go a way, sort of.  But process is still hung. umount -f complains: umount2:  Device or resource busy umount.nfs:
> >>> /mnt/foo: device is busy
> >>> 
> >>> kill -9 does not work on process.
> > 
> >> Kill -1 should work (since about 2.6.25 or so).
> > 
> > That is -[ONE], right?  Assuming so, it did not work for me.
> > 
> > Kernel is 3.14.4+, with some of extra patches, but probably nothing that influences this particular behaviour.
> > 
> > [root@lf1005-14010010 ~]# cat /proc/3805/stack [<ffffffff811371ba>] sleep_on_page+0x9/0xd [<ffffffff8113738e>] wait_on_page_bit+0x71/0x78 
> > [<ffffffff8113769a>] filemap_fdatawait_range+0xa2/0x16d [<ffffffff8113780e>] filemap_write_and_wait_range+0x3b/0x77 [<ffffffffa0f04734>]
> > nfs_file_fsync+0x37/0x83 [nfs] [<ffffffff811a8d32>] vfs_fsync_range+0x19/0x1b [<ffffffff811a8d4b>] vfs_fsync+0x17/0x19 [<ffffffffa0f05305>]
> > nfs_file_flush+0x6b/0x6f [nfs] [<ffffffff81183e46>] filp_close+0x3f/0x71 [<ffffffff8119c8ae>] __close_fd+0x80/0x98 [<ffffffff81183de5>]
> > SyS_close+0x1c/0x3e [<ffffffff815c55f9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff [root@lf1005-14010010 ~]# kill -1 3805 
> > [root@lf1005-14010010 ~]# cat /proc/3805/stack [<ffffffff811371ba>] sleep_on_page+0x9/0xd [<ffffffff8113738e>] wait_on_page_bit+0x71/0x78 
> > [<ffffffff8113769a>] filemap_fdatawait_range+0xa2/0x16d [<ffffffff8113780e>] filemap_write_and_wait_range+0x3b/0x77 [<ffffffffa0f04734>]
> > nfs_file_fsync+0x37/0x83 [nfs] [<ffffffff811a8d32>] vfs_fsync_range+0x19/0x1b [<ffffffff811a8d4b>] vfs_fsync+0x17/0x19 [<ffffffffa0f05305>]
> > nfs_file_flush+0x6b/0x6f [nfs] [<ffffffff81183e46>] filp_close+0x3f/0x71 [<ffffffff8119c8ae>] __close_fd+0x80/0x98 [<ffffffff81183de5>]
> > SyS_close+0x1c/0x3e [<ffffffff815c55f9>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff
> > 
> > Thanks, Ben
> > 
> >> If it doesn't please report the kernel version and cat /proc/$PID/stack
> > 
> >> for some processes that cannot be killed.
> > 
> >> NeilBrown
> > 
> >>> 
> >>> 
> >>> Aside from bringing a fake NFS server back up on the same IP, is there any other way to get these mounts unmounted and the processes killed without 
> >>> rebooting?
> >>> 
> >>> Thanks, Ben
> >>> 
> > 
> > 
> > 
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> 
> - -- 
> Ben Greear <greearb@candelatech.com>
> Candela Technologies Inc  http://www.candelatech.com
> 
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