writable mmap doesn't work (was Re: [Encfs-users] straw doesn't work)

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writable mmap doesn't work (was Re: [Encfs-users] straw doesn't work)

Valient Gough
On Thursday 29 September 2005 12:38, Ruben Porras wrote:

> I've also problems with mmap and programs that use mono, as an example:
>
> ~$ LC_ALL=C monodevelop
>
> ** (./MonoDevelop.exe:7718): CRITICAL **: _wapi_shm_attach: mmap error:
> No such device
>
> ** ERROR **: file handles.c: line 125 (shared_init): assertion failed:
> (_wapi_shared_layout != NULL)
> aborting...
> Abortado

I created an account which has its home directory under a FUSE filesystem
(encfs), and I can confirm that programs running under the mono virtual
machine do not work (at least MonoDevelop).  

Mono dies after getting an error trying to create a mmap with PROT_WRITE
permission.  I think this is a FUSE issue (see
http://thread.gmane.org/gmane.comp.file-systems.fuse.devel/1207 for one of
many discussions of writable mmap & fuse)..

So, I don't think there is anything I can do from within encfs that will help.

>> the problem is getting really annoying :(


--
Valient



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Re: writable mmap doesn't work (was Re: [Encfs-users] straw doesn't work)

neuron
Valient Gough wrote:

> On Thursday 29 September 2005 12:38, Ruben Porras wrote:
>
>>I've also problems with mmap and programs that use mono, as an example:
>>
>>~$ LC_ALL=C monodevelop
>>
>>** (./MonoDevelop.exe:7718): CRITICAL **: _wapi_shm_attach: mmap error:
>>No such device
>>
>>** ERROR **: file handles.c: line 125 (shared_init): assertion failed:
>>(_wapi_shared_layout != NULL)
>>aborting...
>>Abortado
>
>
> I created an account which has its home directory under a FUSE filesystem
> (encfs), and I can confirm that programs running under the mono virtual
> machine do not work (at least MonoDevelop).  

I've had this problem too, and it's not just monodevelop, it's any mono
app, or most likely any app using mmap the way mono does.

>
> Mono dies after getting an error trying to create a mmap with PROT_WRITE
> permission.  I think this is a FUSE issue (see
> http://thread.gmane.org/gmane.comp.file-systems.fuse.devel/1207 for one of
> many discussions of writable mmap & fuse)..
>
> So, I don't think there is anything I can do from within encfs that will help.
>
>
>>>the problem is getting really annoying :(
>
>
>
> --
> Valient
>
>
>
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Re: writable mmap doesn't work (was Re: [Encfs-users] straw doesn't work)

Miklos Szeredi
In reply to this post by Valient Gough
> > I've also problems with mmap and programs that use mono, as an example:
> >
> > ~$ LC_ALL=C monodevelop
> >
> > ** (./MonoDevelop.exe:7718): CRITICAL **: _wapi_shm_attach: mmap error:
> > No such device
> >
> > ** ERROR **: file handles.c: line 125 (shared_init): assertion failed:
> > (_wapi_shared_layout != NULL)
> > aborting...
> > Abortado
>
> I created an account which has its home directory under a FUSE filesystem
> (encfs), and I can confirm that programs running under the mono virtual
> machine do not work (at least MonoDevelop).  
>
> Mono dies after getting an error trying to create a mmap with PROT_WRITE
> permission.  I think this is a FUSE issue (see
> http://thread.gmane.org/gmane.comp.file-systems.fuse.devel/1207 for one of
> many discussions of writable mmap & fuse)..
>
> So, I don't think there is anything I can do from within encfs that will help.
>
> >> the problem is getting really annoying :(

Hmm, it's not easy to fix though.

A respected filesystem expert (Al Viro) has the opinion, that
applications which can't fall back read/write are broken:

  http://marc.theaimsgroup.com/?l=linux-fsdevel&m=111489310208909&w=2

It's not impossible, that at some time FUSE _will_ support writable
mmaps, but it's not at all clear when, and if at all.

So, if it's an important issue, it's best to contact the mono team.

Thanks,
Miklos




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