[patch 7/9] unprivileged mounts: allow unprivileged fuse mounts
nigel at nigel.suspend2.net
Wed Jan 9 01:29:24 PST 2008
Miklos Szeredi wrote:
>>>> On Tue 2008-01-08 12:35:09, Miklos Szeredi wrote:
>>>>> From: Miklos Szeredi <mszeredi at suse.cz>
>>>>> Use FS_SAFE for "fuse" fs type, but not for "fuseblk".
>>>>> FUSE was designed from the beginning to be safe for unprivileged users. This
>>>>> has also been verified in practice over many years. In addition unprivileged
>>>> Eh? So 'kill -9 no longer works' and 'suspend no longer works' is not
>>>> considered important enough to even mention?
>>> No. Because in practice they don't seem to matter. Also because
>>> there's no way in which fuse could be done differently to address
>>> these issues.
>> Could you clarify, please? I hope I'm getting the wrong end of the stick
>> - it sounds to me like you and Pavel are saying that this patch breaks
>> suspending to ram (and hibernating?) but you want to push it anyway
>> because you haven't been able to produce an instance, don't think
>> suspending or hibernating matter and couldn't fix fuse anyway?
> This patch has nothing to do with suspend or hibernate. What this
> patchset does, is help get rid of fusermount, a suid-root mount
> helper. It also opens up new possibilities, which are not fuse
That's what I thought. So what was Pavel talking about with "kill -9 no
longer works" and "suspend no longer works" above? I couldn't understand
it from the context.
> Fuse has bad interactions with the freezer, theoretically. In
> practice, I remember just one bug report (that sparked off this whole
> "do we need freezer, or don't we" flamefest), that actually got fixed
> fairly quickly, ...maybe. Rafael probably remembers better.
I think they just gave up and considered it unsolvable. I'm not sure it is.
>>> The 'kill -9' thing is basically due to VFS level locking not being
>>> interruptible. It could be changed, but I'm not sure it's worth it.
>>> For the suspend issue, there are also no easy solutions.
>> What are the non-easy solutions?
> The ability to freeze tasks in uninterruptible sleep, or more
> generally at any preempt point (except when drivers are poking
Couldn't some sort of scheduler based solution deal with the
uninterruptible sleeping case?
> I know this doesn't play well with userspace hibernate, and I don't
> think it can be resolved without going the kexec way.
I can see the desirability of kexec when it comes to avoiding the
freezer, but comes with its own problems too - having the original
context usable is handy, not having to set aside a large amount of space
for a second kernel is also desirable and there are still greater issues
of transferring information backwards and forwards between the two kernels.
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