Re: [fuse-devel] fusermount reports "Device or resource busy" but unmounts it anyway

Re: [fuse-devel] fusermount reports "Device or resource busy" but unmounts it anyway

[Miklos Szeredi]

[CCs added]

On Tue, May 12, 2015 at 11:34 AM, Richard W.M. Jones <rjones@redhat.com> wrote:
>
> Has something changed in FUSE / the kernel in the past few months so
> that 'fusermount -u /mp' reports the error:
>
>   fusermount: failed to unmount /mp: Device or resource busy
>

That's from the umount2() syscall, and most likely not a fuse issue.

> and returns a non-zero exit code, but the mountpoint is unmounted
> anyway?

Is this in 4.1-rc?  If so, then the recent fs/namespace.c patches from
Eric Biederman would be suspect.

Thanks,
Miklos


>
> We have a fusermount wrapper which relies on the fact that fusermount
> either succeeds & unmounts; or reports an error & doesn't unmount --
> the wrapper retries in this case.
>
> Rich.
>

Re: [fuse-devel] fusermount reports "Device or resource busy" but unmounts it anyway

[Richard W.M. Jones]

On Wed, May 13, 2015 at 10:27:09AM +0200, Miklos Szeredi wrote:
> [CCs added]
> 
> On Tue, May 12, 2015 at 11:34 AM, Richard W.M. Jones <rjones@redhat.com> wrote:
> >
> > Has something changed in FUSE / the kernel in the past few months so
> > that 'fusermount -u /mp' reports the error:
> >
> >   fusermount: failed to unmount /mp: Device or resource busy
> >
> 
> That's from the umount2() syscall, and most likely not a fuse issue.
> 
> > and returns a non-zero exit code, but the mountpoint is unmounted
> > anyway?
> 
> Is this in 4.1-rc?  If so, then the recent fs/namespace.c patches from
> Eric Biederman would be suspect.

Yes, this is reproducible with:

kernel-4.1.0-0.rc2.git3.1.fc23.x86_64 (from Fedora Rawide)
fuse-2.9.3-4.fc22.x86_64

I will see if I can make a small reproducer and get back.

Rich.

-- 
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Re: [fuse-devel] fusermount reports "Device or resource busy" but unmounts it anyway

[Eric W. Biederman]

"Richard W.M. Jones" <rjones@redhat.com> writes:

> On Wed, May 13, 2015 at 10:27:09AM +0200, Miklos Szeredi wrote:
>> [CCs added]
>> 
>> On Tue, May 12, 2015 at 11:34 AM, Richard W.M. Jones <rjones@redhat.com> wrote:
>> >
>> > Has something changed in FUSE / the kernel in the past few months so
>> > that 'fusermount -u /mp' reports the error:
>> >
>> >   fusermount: failed to unmount /mp: Device or resource busy
>> >
>> 
>> That's from the umount2() syscall, and most likely not a fuse issue.
>> 
>> > and returns a non-zero exit code, but the mountpoint is unmounted
>> > anyway?
>> 
>> Is this in 4.1-rc?  If so, then the recent fs/namespace.c patches from
>> Eric Biederman would be suspect.
>
> Yes, this is reproducible with:
>
> kernel-4.1.0-0.rc2.git3.1.fc23.x86_64 (from Fedora Rawide)
> fuse-2.9.3-4.fc22.x86_64
>
> I will see if I can make a small reproducer and get back.

I will be happy to look at this if there is a reasonably small reproducer.
I don't think I changed anything that could cause that kind of failure,
but I have touched a fair amount of that code recently and at the very
least I will be familiar with it.

The only case I can imagine is the mount point being deleted.

Eric