Re: [PATCH RFC] mnt: umount mounts one by one in umount_tree()

[Eric W. Biederman]

Ian Kent <raven@xxxxxxxxxx> writes:

> On Fri, 2017-05-12 at 00:08 -0700, Andrei Vagin wrote:
>> With this patch, we don't try to umount all mounts of a tree together.
>> Instead of this we umount them one by one. In this case, we see a significant
>> improvement in performance for the worsÐ case.
>
> Indeed, umount has been very slow for a while now.
> Even a moderately large number of mounts (~10000) become painfully slow.
>
> Re you still perusing this?
> Anything I can do to help?
>
> Eric, what are your thoughts on this latest attempt?

I have something slightly more recent.  Please checkout my for-next
branch of my userns tree:

git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git for-next

There is one open area of semantics that I looking at with Ram Pai in
the hopes we can drive consensus before we take any patches for
better checkpoint-restart support.

Eric