* [LSF/MM TOPIC] filesystem virtualization
@ 2019-02-06 13:00 Miklos Szeredi
2019-02-06 20:02 ` Amir Goldstein
0 siblings, 1 reply; 2+ messages in thread
From: Miklos Szeredi @ 2019-02-06 13:00 UTC (permalink / raw)
To: lsf-pc
Cc: linux-fsdevel, linux-mm, Vivek Goyal, Stefan Hajnoczi,
Dr. David Alan Gilbert
This is a joint topic proposal with Vivek Goyal.
Discuss remaining issues related to exporting a filesystem from host to
guest (see virtio-fs prototype posting[1] for more background):
* How to provide strong coherency guarantees?
- Fsnotify synchronous post op notification
- Extend lease (delegation) API to userspace
- Multi-component path revalidation
* Issues related to c/m/atime handling:
- Clock synchronization between host and guest (not an fs issue, but fs
has to deal with lack of it)
- Could we have O_NOCMTIME open flag?
* Shared access to file data:
- Use DAX in guest to access host page cache (mmap/munmap sections of
file in guest address space; happens dynamically on a need basis); is
this design reasonable?
- Avoids memory copies and cache duplication, but host page table setup
may have high cost. Can that be improved? (E.g. fault-ahead)
- Too many VMA’s on host per qemu instance?
* File locking:
- Host API for POSIX lock sharing?
* Ideas for the future:
- Buffering directory operations (e.g. "tar xfz ..." with as few
synchronous ops as possible)
[1] https://lore.kernel.org/lkml/20181210171318.16998-1-vgoyal@redhat.com/
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [LSF/MM TOPIC] filesystem virtualization
2019-02-06 13:00 [LSF/MM TOPIC] filesystem virtualization Miklos Szeredi
@ 2019-02-06 20:02 ` Amir Goldstein
0 siblings, 0 replies; 2+ messages in thread
From: Amir Goldstein @ 2019-02-06 20:02 UTC (permalink / raw)
To: Miklos Szeredi
Cc: lsf-pc, linux-fsdevel, Linux MM, Vivek Goyal, Stefan Hajnoczi,
Dr. David Alan Gilbert
On Wed, Feb 6, 2019 at 3:06 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> This is a joint topic proposal with Vivek Goyal.
>
> Discuss remaining issues related to exporting a filesystem from host to
> guest (see virtio-fs prototype posting[1] for more background):
>
> * How to provide strong coherency guarantees?
>
> - Fsnotify synchronous post op notification
> - Extend lease (delegation) API to userspace
There are some commonalities here with userspace networking
file servers. I am interested in samba in particular and things
that we can do to improve Linux interfaces for samba.
SMB3 directory leases for example.
Thanks,
Amir.
> - Multi-component path revalidation
>
> * Issues related to c/m/atime handling:
>
> - Clock synchronization between host and guest (not an fs issue, but fs
> has to deal with lack of it)
>
> - Could we have O_NOCMTIME open flag?
>
> * Shared access to file data:
>
> - Use DAX in guest to access host page cache (mmap/munmap sections of
> file in guest address space; happens dynamically on a need basis); is
> this design reasonable?
>
> - Avoids memory copies and cache duplication, but host page table setup
> may have high cost. Can that be improved? (E.g. fault-ahead)
>
> - Too many VMA’s on host per qemu instance?
>
> * File locking:
>
> - Host API for POSIX lock sharing?
>
> * Ideas for the future:
>
> - Buffering directory operations (e.g. "tar xfz ..." with as few
> synchronous ops as possible)
>
> [1] https://lore.kernel.org/lkml/20181210171318.16998-1-vgoyal@redhat.com/
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-02-06 20:02 ` Amir Goldstein
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